# Morphological and Physiological Characterization of Cassava Genotypes on Dry Land of Ultisol Soil in Indonesia

Authors: Ridwan Diaguna; Suwarto; Edi Santosa; Arief Hartono; Gatot Pramuhadi; Nunung Nuryartono; Roza Yusfiandayani; Tri Prartono
Journal: International Journal of Agronomy
 (2022)

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## Abstract

Indonesia has a large cassava diversity, but the tolerant cultivars on drought areas have not been well recorded. Candidate mapping can begin with morphological and physiological characterization. This study aimed to map cassava’s genetic diversity, determining the key phenotype to distinguish genotypes, physiological adaptation, and high-yield candidates under environmental stress. A total of 29 genotypes were clustered into 5 groups. A specific group for genotype from same site was not found. The differences and relations among genotypes were very clear, demonstrating cassava’s genetic diversity in Indonesia. The key group characteristics are upward petiole orientation (G1), nine lobes (G2), prominent foliar scars (G3), winding lobe (G4), and elliptic-lanceolate (G5). A total of 19 genotypes had a number of storage root >10 storage roots, 20 genotypes had a weight of storage root >2 kg/plant, and 3 genotypes had >4 kg/plant. Morphological and physiological trait determination is relevant to contribute to high-yield cassava breeding in dry areas. The morphological characteristics of well-adapted plants were plant height, lobe characteristics, and petiole orientation, while the physiological traits were chlorophyll index, transpiration rate, and photosynthesis rate.


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## Body

## 1. Introduction

Cassava is an important food source in Indonesia. It is cultivated on over 1.3 million hectares, both on mono and mixed crops [1], gradually spreading into the less densely populated areas in Indonesia [2]. Cassava tubers have a high nutritional content, mostly from carbohydrates, which varies depending on the specific plant part (root or leaves), geographic location, variety, plant age, and environmental conditions [3]. Carbohydrates comprise about 32%–35% of its fresh weight and 80%–90% when dry. Starch is composed of 80% carbohydrates, 3% amylopectin, and about 17% amylose, although it also contains low quantities of sucrose, glucose, fructose, and maltose [4].So far, cassava production is dominated by small farmers with low productivity because of the low use of improved cultivars and fertilization in areas which are not always environmentally apt. In addition, climatic changes such as water deficit present looming challenges to food production, even when cassava is considered tolerant to water deficits [5].Adaptable cultivars are an opportunity to produce high-yield cassava despite these conditions. Indonesia has a large cassava diversity, both in farmer-cultivated land and research fields. However, this diversity has not been well explored to find high-yield cultivar candidates in dry areas. This mapping of potential candidate can begin with the morphological and physiological characterization of cassava genotypes, as already shown for genetic clustering [6–8]. Morphological characteristics are important attributes that contribute to gas exchange and plant metabolism, physiological characteristics, that can increase the yield. Therefore, morphological, physiological, and yield characteristics are important selection criteria in breeding programs [9].The present study aimed to characterize the genetic diversity of cassava in Indonesia, pinpoint the key phenotype to distinguish among genotypes and physiological adaptation signal to environmental stress, and determine a high-yield candidate in environmental stress conditions.


## 2. Materials and Methods

### 2.1. Site and Climate

The research was conducted in Jonggol Teaching and Research Farm, Department of Agronomy and Horticulture, Faculty of Agriculture, Bogor Agricultural University. The site is located at 6˚28ʹ12″S 107˚01ʹ47″E. Figure1 shows the climatic conditions during the research. The monthly averages of temperature and relative humidity were 21.4°C and 86.3%, respectively.Figure 1
Climatic conditions during the research.


### 2.2. Experimental Design

The field experiment was arranged in randomized complete block design with five replications, and the factor, i.e., cassava genotypes, consisted of 29 genotypes. Cassava genotypes were collected from both farmers and Indonesia Legumes and Tuber Crops Research Institute (ILETRI) (Table1).Table 1
Cassava genotyping materials.
GenotypeSourceSeed classC5Farmer, JonggolNot certifiedIRFarmer, JonggolNot certifiedVati 2ILETRI, MalangBreeder seedUK 1ILETRI, MalangBreeder seedMalang 4ILETRI, MalangBreeder seedAdira 4ILETRI, MalangBreeder seedVati 1ILETRI, MalangBreeder seedDarul HidayahILETRI, MalangBreeder seedAdira 1ILETRI, MalangBreeder seedMalang 1ILETRI, MalangBreeder seedUJ 3Farmer, LampungNot certifiedGenjah BayamFarmer, LampungNot certifiedBarokahFarmer, LampungNot certifiedRanduFarmer, LampungNot certifiedUJ 5Farmer, LampungNot certifiedGenjah UrangFarmer, LampungNot certifiedUbi KetanFarmer, LampungNot certifiedDaplang TFarmer, TubanNot certifiedDaplang GurehFarmer, TubanNot certifiedJegrekFarmer, TubanNot certifiedKuningFarmer, TubanNot certifiedKetanFarmer, TubanNot certifiedManalagiFarmer, TubanNot certifiedKunirFarmer, TubanNot certifiedDaplang GFarmer, GresikNot certifiedMangu BFarmer, BogorNot certifiedGajahFarmer, BogorNot certifiedKubarFarmer, BogorNot certifiedMangu LFarmer, BogorNot certified


### 2.3. Agronomy Management

A stem cutting (20 cm) was planted at 1 × 0.5 m spacing. Organic manure (about 5 ton ha−1) was laid down before planting. Chemical fertilizers, such as urea, SP-36, KCl, or NPK, were applied 2 weeks after planting, at 300 kg ha−1, 200 kg ha−1, 150 kg ha−1, and 150 kg ha−1, respectively.


### 2.4. Morphological Characterizations

Twenty-three agromorphological characteristics including 14 qualitative and 9 quantitative characteristics were observed (Table2) as described by [10].Table 2
Quantitative and qualitative characteristics used to characterize cassava genotypes.
Character descriptor1Score codeSampling timeQualitative characteristicColor of apical leaves3 = light green, 5 = dark green, 7 = purplish green, 9 = purple3 MAP2Pubescence on apical leaves0 = absent, 1 = present3 MAPLeaf retention1 = very poor retention, 2 = less than average retention, 3 = average leaf retention, 4 = better than average retention, 5 = outstanding leaf retention6 MAPShape of central leaflet1 = ovoid, 2 = elliptic-lanceolate, 3 = obovate-lanceolate, 4 = oblong-lanceolate, 5 = lanceolate, 6 = straight or linear, 7 = pandurate, 8 = linear-pyramidal, 9 = linear-pandurate, 10 = linear-hostatilobalate6 MAPPetiole color1 = yellowish green, 2 = green, 3 = reddish green, 5 = greenish red, 7 = red, 9 = purple6 MAPLeaf color3 = light green, 5 = dark green, 7 = purple-green, 9 = purple6 MAPLobe margins3 = smooth, 7 = winding6 MAPColor of leaf vein3 = green, 5 = reddish green in less than half of the lobe, 7 = reddish green in more than half of the lobe, 9 = all red6 MAPPetiole orientation1 = inclined upwards, 3 = horizontal, 5 = inclined downwards, 7 = irregular6 MAPProminence of foliar scars3 = semiprominent, 5 = prominent6 MAPColor of stem exterior3 = orange, 4 = greenish-yellowish, 5 = golden, 6 = light brown, 7 = silver, 8 = gray, 9 = dark brown6 MAPDistance between leaf scars3 = short ≤8 cm, 5 = medium 8–15 cm, 7 = long ≥15 cm6 MAPStem growth1 = straight, 2 = zigzag6 MAPNumber of leaf lobes3 = three lobes, 5 = five lobes, 7 = seven lobes, 9 = nine lobes, 11 = eleven lobes6 MAPQuantitative characteristicLength of 2nd leaf lobeDirect, meter rule6 MAPWidth of 1st leaf lobeDirect, meter rule6 MAPWidth of 2nd leaf lobeDirect, meter rule6 MAPRatio of 1st leaf lobeDirect, meter rule6 MAPRatio of 2nd leaf lobeDirect, meter rule6 MAPPetiole length of 1st leaf sampleDirect, meter rule6 MAPPetiole length of 2nd leaf sampleDirect, meter rule6 MAPPlant heightDirect, meter ruleHarvestHeight of first branchingDirect, meter ruleHarvest1CAL, color of apical leaves; PAL, pubescence on apical leaves; LR, leaf retention; SCL, shape of central leaflet; PC, petiole color; LC, leaf color; LM, lobe margins; CLV, color of leaf vein; OP, orientation of petiole; PFS, prominence of foliar scars; CSE, color of stem exterior; DLS, distance between leaf scars; GHS, growth habit of stem; NLL, number of leaf lobes; L2LL, length of second leaf lobe; W1LL, width of first leaf lobe; W2LL, width of second leaf lobe; R1LL, ratio of first leaf lobe; R2LL, ratio of second leaf lobe; PL1LS, petiole length of first leaf sample; PL2LS, petiole length of second leaf sample; HP, height of plant; H1B, height of first branching;2MAP, month after planting.


### 2.5. Photosynthesis Rate Measurement

The photosynthetic rate was estimated using LI-COR (LI-6400XT Portable Photosynthesis System, LI-COR Inc., Lincoln, NE, USA). The estimation was conducted to the tenth leaf from shot, five plants per genotype, and measured between 10:00 and 12:00 am.


### 2.6. Chlorophyll Content Measurement

Chlorophyll content was estimated using the chlorophyll content meter (CCM-200 plus, Opti-Sciences Inc.). The measurement was conducted on the tenth leaf from shoot on the tagged plant, five plant per genotypes, and measured between 10:00 and 12:00 am.


### 2.7. Data Analysis

Before data analysis, data were separated into a vegetative and a generative dataset and examined for outliers. Data are expressed as the mean ± standard error and were analyzed statistically using Minitab® Statistical Software Ver.18. Cluster analysis was performed using PBSTAT (http://www.pbstat.com/). The cluster analysis for plant genetic diversity used both quantitative and qualitative data. Clustering used Gower dissimilarity mode and neighbor joining clustering method. The correlation among characteristics was analyzed using the Pearson correlation using opensource R statistic (0.05).


## 2.1. Site and Climate

The research was conducted in Jonggol Teaching and Research Farm, Department of Agronomy and Horticulture, Faculty of Agriculture, Bogor Agricultural University. The site is located at 6˚28ʹ12″S 107˚01ʹ47″E. Figure1 shows the climatic conditions during the research. The monthly averages of temperature and relative humidity were 21.4°C and 86.3%, respectively.Figure 1
Climatic conditions during the research.


## 2.2. Experimental Design

The field experiment was arranged in randomized complete block design with five replications, and the factor, i.e., cassava genotypes, consisted of 29 genotypes. Cassava genotypes were collected from both farmers and Indonesia Legumes and Tuber Crops Research Institute (ILETRI) (Table1).Table 1
Cassava genotyping materials.
GenotypeSourceSeed classC5Farmer, JonggolNot certifiedIRFarmer, JonggolNot certifiedVati 2ILETRI, MalangBreeder seedUK 1ILETRI, MalangBreeder seedMalang 4ILETRI, MalangBreeder seedAdira 4ILETRI, MalangBreeder seedVati 1ILETRI, MalangBreeder seedDarul HidayahILETRI, MalangBreeder seedAdira 1ILETRI, MalangBreeder seedMalang 1ILETRI, MalangBreeder seedUJ 3Farmer, LampungNot certifiedGenjah BayamFarmer, LampungNot certifiedBarokahFarmer, LampungNot certifiedRanduFarmer, LampungNot certifiedUJ 5Farmer, LampungNot certifiedGenjah UrangFarmer, LampungNot certifiedUbi KetanFarmer, LampungNot certifiedDaplang TFarmer, TubanNot certifiedDaplang GurehFarmer, TubanNot certifiedJegrekFarmer, TubanNot certifiedKuningFarmer, TubanNot certifiedKetanFarmer, TubanNot certifiedManalagiFarmer, TubanNot certifiedKunirFarmer, TubanNot certifiedDaplang GFarmer, GresikNot certifiedMangu BFarmer, BogorNot certifiedGajahFarmer, BogorNot certifiedKubarFarmer, BogorNot certifiedMangu LFarmer, BogorNot certified


## 2.3. Agronomy Management

A stem cutting (20 cm) was planted at 1 × 0.5 m spacing. Organic manure (about 5 ton ha−1) was laid down before planting. Chemical fertilizers, such as urea, SP-36, KCl, or NPK, were applied 2 weeks after planting, at 300 kg ha−1, 200 kg ha−1, 150 kg ha−1, and 150 kg ha−1, respectively.


## 2.4. Morphological Characterizations

Twenty-three agromorphological characteristics including 14 qualitative and 9 quantitative characteristics were observed (Table2) as described by [10].Table 2
Quantitative and qualitative characteristics used to characterize cassava genotypes.
Character descriptor1Score codeSampling timeQualitative characteristicColor of apical leaves3 = light green, 5 = dark green, 7 = purplish green, 9 = purple3 MAP2Pubescence on apical leaves0 = absent, 1 = present3 MAPLeaf retention1 = very poor retention, 2 = less than average retention, 3 = average leaf retention, 4 = better than average retention, 5 = outstanding leaf retention6 MAPShape of central leaflet1 = ovoid, 2 = elliptic-lanceolate, 3 = obovate-lanceolate, 4 = oblong-lanceolate, 5 = lanceolate, 6 = straight or linear, 7 = pandurate, 8 = linear-pyramidal, 9 = linear-pandurate, 10 = linear-hostatilobalate6 MAPPetiole color1 = yellowish green, 2 = green, 3 = reddish green, 5 = greenish red, 7 = red, 9 = purple6 MAPLeaf color3 = light green, 5 = dark green, 7 = purple-green, 9 = purple6 MAPLobe margins3 = smooth, 7 = winding6 MAPColor of leaf vein3 = green, 5 = reddish green in less than half of the lobe, 7 = reddish green in more than half of the lobe, 9 = all red6 MAPPetiole orientation1 = inclined upwards, 3 = horizontal, 5 = inclined downwards, 7 = irregular6 MAPProminence of foliar scars3 = semiprominent, 5 = prominent6 MAPColor of stem exterior3 = orange, 4 = greenish-yellowish, 5 = golden, 6 = light brown, 7 = silver, 8 = gray, 9 = dark brown6 MAPDistance between leaf scars3 = short ≤8 cm, 5 = medium 8–15 cm, 7 = long ≥15 cm6 MAPStem growth1 = straight, 2 = zigzag6 MAPNumber of leaf lobes3 = three lobes, 5 = five lobes, 7 = seven lobes, 9 = nine lobes, 11 = eleven lobes6 MAPQuantitative characteristicLength of 2nd leaf lobeDirect, meter rule6 MAPWidth of 1st leaf lobeDirect, meter rule6 MAPWidth of 2nd leaf lobeDirect, meter rule6 MAPRatio of 1st leaf lobeDirect, meter rule6 MAPRatio of 2nd leaf lobeDirect, meter rule6 MAPPetiole length of 1st leaf sampleDirect, meter rule6 MAPPetiole length of 2nd leaf sampleDirect, meter rule6 MAPPlant heightDirect, meter ruleHarvestHeight of first branchingDirect, meter ruleHarvest1CAL, color of apical leaves; PAL, pubescence on apical leaves; LR, leaf retention; SCL, shape of central leaflet; PC, petiole color; LC, leaf color; LM, lobe margins; CLV, color of leaf vein; OP, orientation of petiole; PFS, prominence of foliar scars; CSE, color of stem exterior; DLS, distance between leaf scars; GHS, growth habit of stem; NLL, number of leaf lobes; L2LL, length of second leaf lobe; W1LL, width of first leaf lobe; W2LL, width of second leaf lobe; R1LL, ratio of first leaf lobe; R2LL, ratio of second leaf lobe; PL1LS, petiole length of first leaf sample; PL2LS, petiole length of second leaf sample; HP, height of plant; H1B, height of first branching;2MAP, month after planting.


## 2.5. Photosynthesis Rate Measurement

The photosynthetic rate was estimated using LI-COR (LI-6400XT Portable Photosynthesis System, LI-COR Inc., Lincoln, NE, USA). The estimation was conducted to the tenth leaf from shot, five plants per genotype, and measured between 10:00 and 12:00 am.


## 2.6. Chlorophyll Content Measurement

Chlorophyll content was estimated using the chlorophyll content meter (CCM-200 plus, Opti-Sciences Inc.). The measurement was conducted on the tenth leaf from shoot on the tagged plant, five plant per genotypes, and measured between 10:00 and 12:00 am.


## 2.7. Data Analysis

Before data analysis, data were separated into a vegetative and a generative dataset and examined for outliers. Data are expressed as the mean ± standard error and were analyzed statistically using Minitab® Statistical Software Ver.18. Cluster analysis was performed using PBSTAT (http://www.pbstat.com/). The cluster analysis for plant genetic diversity used both quantitative and qualitative data. Clustering used Gower dissimilarity mode and neighbor joining clustering method. The correlation among characteristics was analyzed using the Pearson correlation using opensource R statistic (0.05).


## 3. Results and Discussion

### 3.1. Morphological Characteristics

This morphological characterization aimed to highlight the variations and identify germplasms for plant breeding [11]. Table 3 provides the details of 14 morphological characteristics, including the color, pattern, and shape for leaf, petiole, lobe, and stem for 29 cassava genotypes. The corresponding data were interpreted on frequency (%; number genotypes/29 genotypes; Table 4). Generally, leaf characteristics were light green color apical leaves, absent pubescence on apical leaves, average leaf retention, lanceolate and elliptic-lanceolate shape of central leaflet, light green leaf color, and green color leaf vein. Color of apical leaves was recorded light green (65.5%), purplish (6.9%), and dark green (27.6%). No genotype showed pubescence on apical leaves. The leaf retentions were average (72.4%) and better than average (27.6%). The shapes of central leaflet were elliptic-lanceolate (37.9%), obovate-lanceolate (13.8%), and lanceolate (48.3%), while the leaf colors were light green (65.5%), dark green (17.3%), and purple-green (17.2%), and color of leaf vein was green (93.1%), reddish green in less than half of the lobe (3.4%), and all red (3.4%).Table 3
Phenotype of cassava genotype in Indonesia.
GenotypesCharacteristics1CALPALLRSCLPCLCLMCLVOPPFSCSEDLSGHSNLLGenjah Bayam31359539157517Malang 131352333157517Adira 431355333357519UJ 331359533357519UK 131359373357319Mangu L71329333354317Darul Hidayah31329333157319Daplang Gureh31329333137519Malang 431359333157519Daplang Tuban51329333357519Mangu B31329333154319Gajah31329335354319Kuning51359333336517Barokah31459333335517Manalagi51455373354517Adira 151459533353517Daplang G71439573354517Kunir31359573334517Vati 131459773357327Jegrek51355773354519IR Jonggol31332773354317C5 Jonggol31332773354319UJ 531432773337319Vati 231452333154317Randu51427333357717Genjah Urang31329373156317Ubi Ketan51329333357727Ketan31325333339517Kubar513293333543171CAL, color of apical leaves; PAL, pubescence on apical leaves; LR, leaf retention; SCL, shape of central leaflet; PC, petiole color; LC, leaf color; LM, lobe margins; CLV, color of leaf vein; OP, orientation of petiole; PFS, prominence of foliar scars; CSE, color of stem exterior; DLS, distance between leaf scars; GHS, growth habit of stem; NLL, number of leaf lobes.Table 4
Genotypic frequency of cassava in Indonesia.
Characteristics1PhenotypesNumberFrequency (%)CALLight green1965.5Dark green827.6Purplish26.9Purple00.0PALAbsent29100.0Present00.0LRVery poor retention00.0Less than average retention00.0Average leaf retention2172.4Better than average retention827.6Outstanding leaf retention00.0SCLOvoid00.0Elliptic-lanceolate1137.9Obovate-lanceolate413.8Oblong-lanceolate00.0Lanceolate1448.3Straight or linear00.0Pandurate00.0Linear-pyramidal00.0Linear-pandurate00.0Linear-hostatilobalate00.0PCYellowish green00.0Green517.2Reddish green00.0Greenish red413.8Red13.4Purple1965.5LCLight green1965.5Dark green517.3Purple-green517.2Purple00.0LMSmooth1965.5Winding1034.5CLVGreen2793.1Reddish green in less than half of the lobe13.4Reddish green in more than half of the lobe00.0All red13.4OPInclined upwards827.6Horizontal2172.4Inclined downwards00.0Irregular00.0PFSSemiprominent620.7Prominent2379.3CSEOrange13.4Greenish-yellowish1137.9Golden13.4Light brown26.9Silver1344.8Gray00.0Dark brown13.4DLSShort1241.4Medium1551.7Long26.9GHSStraight2793.1Zigzag26.9NLLThree lobes00.0Five lobes00.0Seven lobes1758.6Nine lobes1241.4Eleven lobes00.01CAL, color of apical leaves; PAL, pubescence on apical leaves; LR, leaf retention; SCL, shape of central leaflet; PC, petiole color; LC, leaf color; LM, lobe margins; CLV, color of leaf vein; OP, orientation of petiole; PFS, prominence of foliar scars; CSE, color of stem exterior; DLS, distance between leaf scars; GHS, growth habit of stem; NLL, number of leaf lobes.Almost all genotypes had purple petiole color and horizontal orientation, smooth lobe margin, and seven lobes. The petiole color distribution was purple (65.5%), yellowish green (17.2%), greenish red (13.8%), and red (3.4%), while the orientation of petiole is both horizontal (72.4%) and inclined upwards (27.6%). The lobe margin was smooth (65.5%) and winding (34.5%), while the number of leaf lobes was seven lobes (58.6%) and nine lobes (41.4%). Stem phenotypes are large, prominent of foliar scars, silver and green-yellowish stem exterior, medium-long distance between leaf scars, and straight kinds of growth habit. Prominence of foliar scars was both prominent (79.3%) and semiprominent (20.7%). The color of stem exterior was silver (44.8%), green-yellowish (37.9%), and others. The distribution of distance between leaf scars was short (41.4%), medium (51.7%), and long (6.9%), while the kinds of growth habit were straight (93.1%) and zigzag (6.9%).Table5 provides the quantitative evaluation of the characteristics of the 29 genotypes. Malang 1 and UJ 5 were the tallest that are about 280 and 270 cm, respectively. In contrast, the smallest, about 160 cm, was identified on Barokah. Twenty genotypes have a plant height of more than 2 m, while about 9 genotypes have height of less than 2 m. Ten genotypes were recorded with no branching, while 19 genotypes were recorded to have branching. The height of first branching range about 0.2–2 m, whereas the highest first branching was recorded on Adira 1 about 2 m, followed by Kubar about 1.1 m, and other genotypes height of first branching mostly were obtained about 0.2–0.6 m. The shortest petiole length was recorded on Kunir, Genjah Urang, and Vati 2 (about 27 cm). In contrast, the longest petiole length was recorded on Malang 4, Daplang Gureh, and Mangu (about 44 cm). Leaf lobe characteristics including length, width, and ratio were recorded as about 17–25 cm, 4–7 cm, and 3–5 cm, respectively.Table 5
Quantitative characteristics of 29 cassava genotypes in Indonesia at 6 months after planting.
GenotypesHeight of plant (cm)Height of first branching (m)Petiole length (cm)Length of leaf lobe (cm)Width of leaf lobe (cm)Ratio of leaf lobeC52000.4031.1624.075.094.73IR2000.2534.9817.875.823.07Vati 22300.5427.8316.294.373.73UK 12000.0043.8521.715.933.66Malang 42000.0044.4422.425.983.75Adira 42000.0037.5322.485.344.21Vati 12500.2038.9721.485.523.89Darul Hidayah2000.2540.6121.615.753.76Adira 12102.0029.2121.025.523.81Malang 12800.2540.3224.966.743.70UJ 32300.0035.5320.395.943.44Genjah Bayam1700.0036.0322.245.234.26Barokah1600.0043.5225.414.945.15Randu2000.0033.3623.056.553.52UJ 52700.3039.7425.806.174.18Genjah Urang1800.2527.2618.715.153.64Ubi Ketan1700.6030.1617.705.013.53Daplang Tuban2000.0039.1221.355.953.59Daplang Gureh2200.0044.0627.027.173.77Jegrek2100.2536.7121.865.723.82Kuning2000.3542.0727.966.044.64Ketan1900.1632.0219.156.113.14Manalagi2000.2535.3123.025.933.88Kunir1800.0027.0320.114.954.07Daplang G1700.2329.1520.904.924.25Mangu B1900.1043.0620.325.873.46Gajah2400.1043.1721.106.083.47Kubar1901.1028.8219.855.353.71Mangu L2200.4344.0920.166.043.34


### 3.2. Genotype Clustering

Morphological classification is important in plant breeding to emphasize the variability and relationships between genetic lines. Accessions sharing many similarities are closely related [11]. Conversely, accessions showing many differences show distant relationships [12]. The characterization of genetic diversity by morphological characteristic is a cheap and proven method [6,7] that also shows a significant correlation to agronomic traits that could be used to evaluate the potential production and can be used in plant breeding [8].Similarity analysis showed that the genotypes were clustered on five groups (Figure2, Table 6). G1 consists of two genotypes, i.e., Genjah Bayam and Malang 1, while G2 consists of ten genotypes, i.e., Adira 4, UJ 3, UK 1, Mangu L, Darul Hidayah, Daplang Gureh, Malang 4, Daplang Tuban, Mangu B, and Gajah. G3 consists of two genotypes, i.e., Kuning and Barokah. G4 clusters nine genotypes, namely, Manalagi, Adira 1, Daplang Gresik, Kunir, Vati 1, Jegrek, IR Jonggol, C5 Jonggol, and UJ 5. G5 consists of six genotypes, namely, Ubi Ketan, Kubar, Genjah Urang, Vati 2, Ketan, and Randu.Figure 2
A dendrogram cluster of 29 cassava genotypes.Table 6
Genotype groups of cassava based on 24 qualitative and quantitative characteristics.
GroupTotalGenotypesG12Genjah Bayam and Malang 1G210Adira 4, UJ 3, UK 1, Mangu L, Darul Hidayah, Daplang Gureh, Malang 4, Daplang Tuban, Mangu B, and GajahG32Kuning and BarokahG49Manalagi, Adira 1, Daplang Gresik, Kunir, Vati 1, Jegrek, IR Jonggol, C5 Jonggol, and UJ 5G56Ubi kayu Putih (Ubi Ketan), Kubar, Genjah Urang, Vati 2, Ketan, and RanduGroup 1 showed similarity on most qualitative characteristics, except for PC, LC, and CLV. Similarly, group 2 showed similarity on most qualitative characteristics, except CSE, DLS, CAL, SCL, and OP. Group 3 shared all qualitative characteristics, except CAL, LR, and CSE. In contrast, in group 4, similarities were found only for PAL, CLV, and OP characteristics and in group 5 on PAL, LC, CLV, GHS, and NLL. To distinguish among groups, ≥1 characteristics need to be used. However, the number of leaf lobes could be a specific characteristic to differentiate for group 2, prominence of foliar scars for group 3, petiole orientation for group 1, lobe margin for group 4, and shape of central leaflet for group 5.Despite the lack of specific groups in same site genotypes, differences and relationships among genotypes were clear, indicating the genetic diversity of cassava germplasm in Indonesia. Nevertheless, lobe characteristics, prominence of stem, and petiole orientation can distinguish the genotypes in each group. The key characteristics of groups include inclined upward orientation of petiole (G1), nine lobes (G2), prominent foliar scars (G3), winding lobe (G4), and elliptic-lanceolate (G5). The large variations of quantitative characteristics were evaluated among the genotypes. The environmental and genetic effect was suspected to lead their variations. The effect of both interactions was important to cassava traits [13].


### 3.3. Physiological Characteristics: Chlorophyll Index and Photosynthetic Rate

Chlorophyll index (CI), photosynthesis rate, and transpiration rate (TR) among genotypes were varied (Figure3, Table 7). Adira 1 had the highest CI (46.5), whereas Mangu L had the lowest (10.0). Among the groups, the highest CI was recorded in G5 and the lowest in G3, whereas CI in groups G1, G2, and G4 was 36.2, 27.7, and 27.0, respectively. Gas exchange activity was identified by photosynthetic and transpiration rates. G5 also showed the highest photosynthetic rate (33.4), while G2 was the lowest (27.8), whereas photosynthetic rate of groups G1, G3, and G4 was 31.7, 28.1, and 28.1, respectively. Mangu L had the lowest photosynthetic rate (22.6), while Genjah Bayam (32.6) had the highest. TR did not differ much among groups, i.e., G1 (6.4), G2 (6.2), G3 (5.7), G4 (5.8), and G5 (5.7). Daplang Gureh and Vati 2 showed the highest transpiration rate and Ubi Ketan the lowest.Figure 3
Photosynthesis rate and chlorophyll index of 29 cassava genotypes in Indonesia. PR, photosynthetic rate; CI, chlorophyll index; TR, transpiration rate.Table 7
Photosynthetic rate and chlorophyll index pattern of cassava groups.
GroupNChlorophyll indexPhotosynthesis rate (μmol m−2 s−1)Transpiration rate (mmol H2Om−2 s−1)G12Min30.929.24.9Max4633.57.1Average36.2 ± 5.1231.7 ± 1.66.4 ± 0.7G210Min6.517.53.7Max67.734.87.4Average27.7 ± 13.227.8 ± 4.56.2 ± 0.8G32Min8.7233.7Max33.6307.2Average24.6 ± 8.228.1 ± 2.05.7 ± 1.2G49Min9.717.33.6Max67.733.57.4Average27.0 ± 11.028.1 ± 3.95.8 ± 1.0G56Min420.63.3Max48.133.47.4Average48.1 ± 11.233.4 ± 3.85.7 ± 0.9Physiological changes follow morphological changes in plants responding to environmental stress [14]. As reported by [15], CI can serve as adaptation indicator to environmental stress. CI is involved in gas exchange functions such as photosynthesis and transpiration, and [16] considered it as a possible indirect indicator of photosynthetic capacity. Environmental stress could significantly decrease CI, indicating impaired photosynthesis [17]. It is difficult for plant to escape the environment in which they are currently growing, so they must passively adapt to changing or even adverse conditions; therefore, evolution can occur in the process of their long-term adaptation [18].


### 3.4. Yield Characteristics

Yield characteristics consider both storage units and storage root weight. Figure4 shows both characteristics for all genotypes. The highest weight corresponded to UK 1 (5 kg) and the lowest to Manalagi (1.1 kg), while Darul Hidayah (14) had the highest number of storage roots and Daplang G (6) the lowest. Eight genotypes had a storage root weight >3.5 kg plant−1, namely, Ketan, IR, Kunir, Mangu B, UK 1, UJ 3, Malang 1, and Genjah Bayam. More than half of all genotypes (19) had >10 storage roots (Table 8). G2 showed the highest weight and biggest number of storage roots, i.e., 3.1 kg plant−1 and 11.5 storage root plant−1, respectively. G4 showed the lowest weight of storage root (1.1 kg plant−1) and G3 the lowest number of storage roots (8.5 plant−1). NSR/P did not significantly differ among groups.Figure 4
Yield characteristics of genotypes cassava in Indonesia. NSR/P, number of storage root/plant; WSR/P, weight of storage root/plant.Table 8
Yield characteristics of genotype groups.
GroupNWSR/PNSR/PRangeAverageRangeAverageG123.5  –  3.62.1 ± 0.111.7 – 14.011.0 ± 1.6G2101.4 – 5.03.1 ± 1.15.7 – 13.011.5 ± 2.5G321.2 – 1.82.2 ± 0.411.3 – 11.78.5 ± 0.2G491.1 – 3.92.5 ± 0.97.3 – 14.310.2 ± 2.5G561.5 – 3.62.8 ± 0.98.7 – 13.711.0 ± 1.9NSR/P, number of storage root/plant; WSR/P, weight of storage root/plant.The number and weight of storage root yield attributes regulate the sink capacity. Nineteen genotypes had >10 storage roots. This indicates that some genotypes can be potential candidates for dry land conditions. Under water deficit conditions, almost all cassava genotypes resulted in <10 storage roots and about 5–8 root storage plant−1 [19]. In addition, 20 genotypes had >2 kg plant−1 storage root, with 3 having >4 kg plant−1. Since, the weight of storage root of cassava in dry land is usually 1–1.8 kg plant−1 [19]. This result shows the characteristic candidates of high production in dry land.


### 3.5. Correlation among Characteristics

The correlation among characteristics was analyzed to determine relationships between characteristics. Two signs are positively correlated if one increases quantitatively and other decreases quantitatively or if both decrease [12]. The correlation among characteristics was low to moderate (Figure 5). Moderate correlations were found for HP∗PL, HP∗PR, CI∗PR, CI∗WSR/P, and NSR/P∗WSR/P, while low correlations were identified for HP∗TR, PL∗TR, PL∗CI, PL∗NSR/P, PL∗WSR/P, CI∗TR, and CI∗WSR/P. Vegetative growth as indicated by both HP and PL affects photosynthesis and transpiration, whereas higher plant will increase photosynthesis, and a longer petiole would increase transpiration. Since CI affects photosynthetic, TRs further support to increase the weight of storage root. Negative correlations between transpiration rate and yield and photosynthesis rate and NSR/P were found as well.Figure 5
Correlation among characteristics of cassava genotypes in Indonesia. Positive correlations are displayed in blue, and negative correlations are displayed in red. Color intensity and circle size are proportional to the correlation coefficients. PR, photosynthetic rate; CI, chlorophyll index; TR, transpiration rates; HP, height of plant; PL, petiole length; NSR/P, number of storage root/plant; WSR/P, weight of storage root/plant.Positive and moderate correlations among CI, photosynthesis rate, transpiration rate, and storage root weight could be considered storage root accumulations. The correlation of plant growth to physiological activities [20], plant growth to yield characteristics [21], and physiological activities to yield [22], among yield characteristics [23], had been reported. Morphological and physiological description is an important first step for successful high-yield cassava breeding for dry areas. The morphological characteristics of well-adapted plants were plant height, lobe characteristics, and petiole orientation, and the physiological traits were CI, TR, and photosynthesis rate.


## 3.1. Morphological Characteristics

This morphological characterization aimed to highlight the variations and identify germplasms for plant breeding [11]. Table 3 provides the details of 14 morphological characteristics, including the color, pattern, and shape for leaf, petiole, lobe, and stem for 29 cassava genotypes. The corresponding data were interpreted on frequency (%; number genotypes/29 genotypes; Table 4). Generally, leaf characteristics were light green color apical leaves, absent pubescence on apical leaves, average leaf retention, lanceolate and elliptic-lanceolate shape of central leaflet, light green leaf color, and green color leaf vein. Color of apical leaves was recorded light green (65.5%), purplish (6.9%), and dark green (27.6%). No genotype showed pubescence on apical leaves. The leaf retentions were average (72.4%) and better than average (27.6%). The shapes of central leaflet were elliptic-lanceolate (37.9%), obovate-lanceolate (13.8%), and lanceolate (48.3%), while the leaf colors were light green (65.5%), dark green (17.3%), and purple-green (17.2%), and color of leaf vein was green (93.1%), reddish green in less than half of the lobe (3.4%), and all red (3.4%).Table 3
Phenotype of cassava genotype in Indonesia.
GenotypesCharacteristics1CALPALLRSCLPCLCLMCLVOPPFSCSEDLSGHSNLLGenjah Bayam31359539157517Malang 131352333157517Adira 431355333357519UJ 331359533357519UK 131359373357319Mangu L71329333354317Darul Hidayah31329333157319Daplang Gureh31329333137519Malang 431359333157519Daplang Tuban51329333357519Mangu B31329333154319Gajah31329335354319Kuning51359333336517Barokah31459333335517Manalagi51455373354517Adira 151459533353517Daplang G71439573354517Kunir31359573334517Vati 131459773357327Jegrek51355773354519IR Jonggol31332773354317C5 Jonggol31332773354319UJ 531432773337319Vati 231452333154317Randu51427333357717Genjah Urang31329373156317Ubi Ketan51329333357727Ketan31325333339517Kubar513293333543171CAL, color of apical leaves; PAL, pubescence on apical leaves; LR, leaf retention; SCL, shape of central leaflet; PC, petiole color; LC, leaf color; LM, lobe margins; CLV, color of leaf vein; OP, orientation of petiole; PFS, prominence of foliar scars; CSE, color of stem exterior; DLS, distance between leaf scars; GHS, growth habit of stem; NLL, number of leaf lobes.Table 4
Genotypic frequency of cassava in Indonesia.
Characteristics1PhenotypesNumberFrequency (%)CALLight green1965.5Dark green827.6Purplish26.9Purple00.0PALAbsent29100.0Present00.0LRVery poor retention00.0Less than average retention00.0Average leaf retention2172.4Better than average retention827.6Outstanding leaf retention00.0SCLOvoid00.0Elliptic-lanceolate1137.9Obovate-lanceolate413.8Oblong-lanceolate00.0Lanceolate1448.3Straight or linear00.0Pandurate00.0Linear-pyramidal00.0Linear-pandurate00.0Linear-hostatilobalate00.0PCYellowish green00.0Green517.2Reddish green00.0Greenish red413.8Red13.4Purple1965.5LCLight green1965.5Dark green517.3Purple-green517.2Purple00.0LMSmooth1965.5Winding1034.5CLVGreen2793.1Reddish green in less than half of the lobe13.4Reddish green in more than half of the lobe00.0All red13.4OPInclined upwards827.6Horizontal2172.4Inclined downwards00.0Irregular00.0PFSSemiprominent620.7Prominent2379.3CSEOrange13.4Greenish-yellowish1137.9Golden13.4Light brown26.9Silver1344.8Gray00.0Dark brown13.4DLSShort1241.4Medium1551.7Long26.9GHSStraight2793.1Zigzag26.9NLLThree lobes00.0Five lobes00.0Seven lobes1758.6Nine lobes1241.4Eleven lobes00.01CAL, color of apical leaves; PAL, pubescence on apical leaves; LR, leaf retention; SCL, shape of central leaflet; PC, petiole color; LC, leaf color; LM, lobe margins; CLV, color of leaf vein; OP, orientation of petiole; PFS, prominence of foliar scars; CSE, color of stem exterior; DLS, distance between leaf scars; GHS, growth habit of stem; NLL, number of leaf lobes.Almost all genotypes had purple petiole color and horizontal orientation, smooth lobe margin, and seven lobes. The petiole color distribution was purple (65.5%), yellowish green (17.2%), greenish red (13.8%), and red (3.4%), while the orientation of petiole is both horizontal (72.4%) and inclined upwards (27.6%). The lobe margin was smooth (65.5%) and winding (34.5%), while the number of leaf lobes was seven lobes (58.6%) and nine lobes (41.4%). Stem phenotypes are large, prominent of foliar scars, silver and green-yellowish stem exterior, medium-long distance between leaf scars, and straight kinds of growth habit. Prominence of foliar scars was both prominent (79.3%) and semiprominent (20.7%). The color of stem exterior was silver (44.8%), green-yellowish (37.9%), and others. The distribution of distance between leaf scars was short (41.4%), medium (51.7%), and long (6.9%), while the kinds of growth habit were straight (93.1%) and zigzag (6.9%).Table5 provides the quantitative evaluation of the characteristics of the 29 genotypes. Malang 1 and UJ 5 were the tallest that are about 280 and 270 cm, respectively. In contrast, the smallest, about 160 cm, was identified on Barokah. Twenty genotypes have a plant height of more than 2 m, while about 9 genotypes have height of less than 2 m. Ten genotypes were recorded with no branching, while 19 genotypes were recorded to have branching. The height of first branching range about 0.2–2 m, whereas the highest first branching was recorded on Adira 1 about 2 m, followed by Kubar about 1.1 m, and other genotypes height of first branching mostly were obtained about 0.2–0.6 m. The shortest petiole length was recorded on Kunir, Genjah Urang, and Vati 2 (about 27 cm). In contrast, the longest petiole length was recorded on Malang 4, Daplang Gureh, and Mangu (about 44 cm). Leaf lobe characteristics including length, width, and ratio were recorded as about 17–25 cm, 4–7 cm, and 3–5 cm, respectively.Table 5
Quantitative characteristics of 29 cassava genotypes in Indonesia at 6 months after planting.
GenotypesHeight of plant (cm)Height of first branching (m)Petiole length (cm)Length of leaf lobe (cm)Width of leaf lobe (cm)Ratio of leaf lobeC52000.4031.1624.075.094.73IR2000.2534.9817.875.823.07Vati 22300.5427.8316.294.373.73UK 12000.0043.8521.715.933.66Malang 42000.0044.4422.425.983.75Adira 42000.0037.5322.485.344.21Vati 12500.2038.9721.485.523.89Darul Hidayah2000.2540.6121.615.753.76Adira 12102.0029.2121.025.523.81Malang 12800.2540.3224.966.743.70UJ 32300.0035.5320.395.943.44Genjah Bayam1700.0036.0322.245.234.26Barokah1600.0043.5225.414.945.15Randu2000.0033.3623.056.553.52UJ 52700.3039.7425.806.174.18Genjah Urang1800.2527.2618.715.153.64Ubi Ketan1700.6030.1617.705.013.53Daplang Tuban2000.0039.1221.355.953.59Daplang Gureh2200.0044.0627.027.173.77Jegrek2100.2536.7121.865.723.82Kuning2000.3542.0727.966.044.64Ketan1900.1632.0219.156.113.14Manalagi2000.2535.3123.025.933.88Kunir1800.0027.0320.114.954.07Daplang G1700.2329.1520.904.924.25Mangu B1900.1043.0620.325.873.46Gajah2400.1043.1721.106.083.47Kubar1901.1028.8219.855.353.71Mangu L2200.4344.0920.166.043.34


## 3.2. Genotype Clustering

Morphological classification is important in plant breeding to emphasize the variability and relationships between genetic lines. Accessions sharing many similarities are closely related [11]. Conversely, accessions showing many differences show distant relationships [12]. The characterization of genetic diversity by morphological characteristic is a cheap and proven method [6,7] that also shows a significant correlation to agronomic traits that could be used to evaluate the potential production and can be used in plant breeding [8].Similarity analysis showed that the genotypes were clustered on five groups (Figure2, Table 6). G1 consists of two genotypes, i.e., Genjah Bayam and Malang 1, while G2 consists of ten genotypes, i.e., Adira 4, UJ 3, UK 1, Mangu L, Darul Hidayah, Daplang Gureh, Malang 4, Daplang Tuban, Mangu B, and Gajah. G3 consists of two genotypes, i.e., Kuning and Barokah. G4 clusters nine genotypes, namely, Manalagi, Adira 1, Daplang Gresik, Kunir, Vati 1, Jegrek, IR Jonggol, C5 Jonggol, and UJ 5. G5 consists of six genotypes, namely, Ubi Ketan, Kubar, Genjah Urang, Vati 2, Ketan, and Randu.Figure 2
A dendrogram cluster of 29 cassava genotypes.Table 6
Genotype groups of cassava based on 24 qualitative and quantitative characteristics.
GroupTotalGenotypesG12Genjah Bayam and Malang 1G210Adira 4, UJ 3, UK 1, Mangu L, Darul Hidayah, Daplang Gureh, Malang 4, Daplang Tuban, Mangu B, and GajahG32Kuning and BarokahG49Manalagi, Adira 1, Daplang Gresik, Kunir, Vati 1, Jegrek, IR Jonggol, C5 Jonggol, and UJ 5G56Ubi kayu Putih (Ubi Ketan), Kubar, Genjah Urang, Vati 2, Ketan, and RanduGroup 1 showed similarity on most qualitative characteristics, except for PC, LC, and CLV. Similarly, group 2 showed similarity on most qualitative characteristics, except CSE, DLS, CAL, SCL, and OP. Group 3 shared all qualitative characteristics, except CAL, LR, and CSE. In contrast, in group 4, similarities were found only for PAL, CLV, and OP characteristics and in group 5 on PAL, LC, CLV, GHS, and NLL. To distinguish among groups, ≥1 characteristics need to be used. However, the number of leaf lobes could be a specific characteristic to differentiate for group 2, prominence of foliar scars for group 3, petiole orientation for group 1, lobe margin for group 4, and shape of central leaflet for group 5.Despite the lack of specific groups in same site genotypes, differences and relationships among genotypes were clear, indicating the genetic diversity of cassava germplasm in Indonesia. Nevertheless, lobe characteristics, prominence of stem, and petiole orientation can distinguish the genotypes in each group. The key characteristics of groups include inclined upward orientation of petiole (G1), nine lobes (G2), prominent foliar scars (G3), winding lobe (G4), and elliptic-lanceolate (G5). The large variations of quantitative characteristics were evaluated among the genotypes. The environmental and genetic effect was suspected to lead their variations. The effect of both interactions was important to cassava traits [13].


## 3.3. Physiological Characteristics: Chlorophyll Index and Photosynthetic Rate

Chlorophyll index (CI), photosynthesis rate, and transpiration rate (TR) among genotypes were varied (Figure3, Table 7). Adira 1 had the highest CI (46.5), whereas Mangu L had the lowest (10.0). Among the groups, the highest CI was recorded in G5 and the lowest in G3, whereas CI in groups G1, G2, and G4 was 36.2, 27.7, and 27.0, respectively. Gas exchange activity was identified by photosynthetic and transpiration rates. G5 also showed the highest photosynthetic rate (33.4), while G2 was the lowest (27.8), whereas photosynthetic rate of groups G1, G3, and G4 was 31.7, 28.1, and 28.1, respectively. Mangu L had the lowest photosynthetic rate (22.6), while Genjah Bayam (32.6) had the highest. TR did not differ much among groups, i.e., G1 (6.4), G2 (6.2), G3 (5.7), G4 (5.8), and G5 (5.7). Daplang Gureh and Vati 2 showed the highest transpiration rate and Ubi Ketan the lowest.Figure 3
Photosynthesis rate and chlorophyll index of 29 cassava genotypes in Indonesia. PR, photosynthetic rate; CI, chlorophyll index; TR, transpiration rate.Table 7
Photosynthetic rate and chlorophyll index pattern of cassava groups.
GroupNChlorophyll indexPhotosynthesis rate (μmol m−2 s−1)Transpiration rate (mmol H2Om−2 s−1)G12Min30.929.24.9Max4633.57.1Average36.2 ± 5.1231.7 ± 1.66.4 ± 0.7G210Min6.517.53.7Max67.734.87.4Average27.7 ± 13.227.8 ± 4.56.2 ± 0.8G32Min8.7233.7Max33.6307.2Average24.6 ± 8.228.1 ± 2.05.7 ± 1.2G49Min9.717.33.6Max67.733.57.4Average27.0 ± 11.028.1 ± 3.95.8 ± 1.0G56Min420.63.3Max48.133.47.4Average48.1 ± 11.233.4 ± 3.85.7 ± 0.9Physiological changes follow morphological changes in plants responding to environmental stress [14]. As reported by [15], CI can serve as adaptation indicator to environmental stress. CI is involved in gas exchange functions such as photosynthesis and transpiration, and [16] considered it as a possible indirect indicator of photosynthetic capacity. Environmental stress could significantly decrease CI, indicating impaired photosynthesis [17]. It is difficult for plant to escape the environment in which they are currently growing, so they must passively adapt to changing or even adverse conditions; therefore, evolution can occur in the process of their long-term adaptation [18].


## 3.4. Yield Characteristics

Yield characteristics consider both storage units and storage root weight. Figure4 shows both characteristics for all genotypes. The highest weight corresponded to UK 1 (5 kg) and the lowest to Manalagi (1.1 kg), while Darul Hidayah (14) had the highest number of storage roots and Daplang G (6) the lowest. Eight genotypes had a storage root weight >3.5 kg plant−1, namely, Ketan, IR, Kunir, Mangu B, UK 1, UJ 3, Malang 1, and Genjah Bayam. More than half of all genotypes (19) had >10 storage roots (Table 8). G2 showed the highest weight and biggest number of storage roots, i.e., 3.1 kg plant−1 and 11.5 storage root plant−1, respectively. G4 showed the lowest weight of storage root (1.1 kg plant−1) and G3 the lowest number of storage roots (8.5 plant−1). NSR/P did not significantly differ among groups.Figure 4
Yield characteristics of genotypes cassava in Indonesia. NSR/P, number of storage root/plant; WSR/P, weight of storage root/plant.Table 8
Yield characteristics of genotype groups.
GroupNWSR/PNSR/PRangeAverageRangeAverageG123.5  –  3.62.1 ± 0.111.7 – 14.011.0 ± 1.6G2101.4 – 5.03.1 ± 1.15.7 – 13.011.5 ± 2.5G321.2 – 1.82.2 ± 0.411.3 – 11.78.5 ± 0.2G491.1 – 3.92.5 ± 0.97.3 – 14.310.2 ± 2.5G561.5 – 3.62.8 ± 0.98.7 – 13.711.0 ± 1.9NSR/P, number of storage root/plant; WSR/P, weight of storage root/plant.The number and weight of storage root yield attributes regulate the sink capacity. Nineteen genotypes had >10 storage roots. This indicates that some genotypes can be potential candidates for dry land conditions. Under water deficit conditions, almost all cassava genotypes resulted in <10 storage roots and about 5–8 root storage plant−1 [19]. In addition, 20 genotypes had >2 kg plant−1 storage root, with 3 having >4 kg plant−1. Since, the weight of storage root of cassava in dry land is usually 1–1.8 kg plant−1 [19]. This result shows the characteristic candidates of high production in dry land.


## 3.5. Correlation among Characteristics

The correlation among characteristics was analyzed to determine relationships between characteristics. Two signs are positively correlated if one increases quantitatively and other decreases quantitatively or if both decrease [12]. The correlation among characteristics was low to moderate (Figure 5). Moderate correlations were found for HP∗PL, HP∗PR, CI∗PR, CI∗WSR/P, and NSR/P∗WSR/P, while low correlations were identified for HP∗TR, PL∗TR, PL∗CI, PL∗NSR/P, PL∗WSR/P, CI∗TR, and CI∗WSR/P. Vegetative growth as indicated by both HP and PL affects photosynthesis and transpiration, whereas higher plant will increase photosynthesis, and a longer petiole would increase transpiration. Since CI affects photosynthetic, TRs further support to increase the weight of storage root. Negative correlations between transpiration rate and yield and photosynthesis rate and NSR/P were found as well.Figure 5
Correlation among characteristics of cassava genotypes in Indonesia. Positive correlations are displayed in blue, and negative correlations are displayed in red. Color intensity and circle size are proportional to the correlation coefficients. PR, photosynthetic rate; CI, chlorophyll index; TR, transpiration rates; HP, height of plant; PL, petiole length; NSR/P, number of storage root/plant; WSR/P, weight of storage root/plant.Positive and moderate correlations among CI, photosynthesis rate, transpiration rate, and storage root weight could be considered storage root accumulations. The correlation of plant growth to physiological activities [20], plant growth to yield characteristics [21], and physiological activities to yield [22], among yield characteristics [23], had been reported. Morphological and physiological description is an important first step for successful high-yield cassava breeding for dry areas. The morphological characteristics of well-adapted plants were plant height, lobe characteristics, and petiole orientation, and the physiological traits were CI, TR, and photosynthesis rate.


## 4. Conclusions

The initial 29 genotypes were clustered in 5 groups. A specific group for genotype from same site was not found. The differences and relations among genotypes were very clear. It indicates the presence the genetic diversity of cassava germplasm in Indonesia. The key characteristics of groups were upward petiole orientation (G1), nine lobes (G2), prominent foliar scars (G3), winding lobe (G4), and elliptic-lanceolate (G5). Nineteen genotypes had >10 storage roots, and 20 genotypes had >2 kg/plant of storage root, of which 3 had >4 kg/plant. The morphological and physiological traits finding was very important to early data to contribute to the successful high-yield cassava breeding for dry areas. The morphological characteristics were plant height, lobe characteristics, and petiole orientation, while the physiological traits include CI and photosynthesis rate.



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