bluuebunny/crossref_metadata_2025 huggingface dataset:
Drought Survival and Recuperative Ability of Bentgrass Species Associated with Changes in Abscisic Acid and Cytokinin Production
Authors: DaCosta Michelle , Huang Bingru
Published: January 2019

Abscisic acid (ABA) and cytokinins are two groups of plant hormones that play important roles in regulating plant responses to decreases in soil water availability. The primary objective for this study was to determine whether species variability in drought survival and recovery for colonial bentgrass (Agrostis capillaris L.), creeping bentgrass (A. stolonifera L.), and velvet bentgrass (A. canina L.) were related to changes in ABA and cytokinin content. Plants of ‘Tiger II’ colonial bentgrass, ‘L-93’ creeping bentgrass, and ‘Greenwich’ velvet bentgrass were subjected to two soil moisture treatments: 1) well-watered controls, irrigated three times per week; and 2) drought, irrigation completely withheld for 16 days. For recovery, previously drought-stressed plants were rewatered and irrigated three times per week to evaluate the recovery potential for each species. Drought stress resulted in significant declines in turf quality (TQ), shoot extension rates, canopy net photosynthetic rate (Pn), daily evapotranspiration rate (ET), and cytokinin content, and significant increases in ABA content for all three bentgrass species. Velvet bentgrass exhibited less severe drought injury, as exhibited by higher TQ, Pn, and daily ET rate compared with colonial bentgrass and creeping bentgrass. Velvet bentgrass also had significantly less ABA accumulation, which could allow for continued gas exchange and sustained plant survival during drought stress compared with colonial bentgrass and creeping bentgrass. Upon rewatering after drought stress, colonial bentgrass exhibited more rapid recovery in turfgrass growth and water use compared with creeping bentgrass and velvet bentgrass. The higher recuperative ability of colonial bentgrass could be associated with its more rapid decline in ABA content and increases in cytokinin content compared with creeping bentgrass and velvet bentgrass.
Self-incompatibility and Self-fruitfulness in Pear cv. Agua de Aranjuez
Authors: Sanzol Javier , Herrero Maria
Published: January 2019

Most pear (Pyrus communis L.) cultivars are impaired to set fruit under self-pollination, because self-fertilization is prevented by a gametophytic self-incompatibility system. However, accumulated information in this species shows that often for a same cultivar, after self-pollination, a variable response in fruit set can be obtained in different years or growing conditions. In this work, we characterize self-incompatibility and self-fruitfulness in ‘Agua de Aranjuez’, the main Spanish pear cultivar, which also shows a variable response to self-pollination. Two years with a different fruit setting response after self-pollination, one with no fruit set and the other with a moderate fruit set, were compared for parthenocarpic fruit development and for pollen tube performance. Results show that in both years, this cultivar behaves as self-incompatible with absence of parthenocarpy. In selfed flowers, most pollen tubes are arrested in the upper half of the style, although in a small proportion of the styles, a pollen tube can reach the base of the style and eventually effect fertilization. Self-fertilization, although occurring at a low level, can explain the fruit set levels obtained under self-pollination given that flowers with just one fertilized ovule are able to set fruit. This behavior could explain confusing results about self-fruitfulness in ‘Agua de Aranjuez’ and other pear cultivars.
The Effects of Elevated Root Zone Temperature on the Development and Carbon Partitioning of Spring Wheat
Authors: Monje Oscar , Anderson Sylvia , Stutte Gary W.
Published: January 2019

The effect of elevated root zone temperature (+0, +4, +6, +8, and +11 °C) on growth rates and carbon partitioning of ‘USU-Apogee’ spring wheat (Triticum aestivum L.) plants growing at constant air temperature (24 °C) in Turface was investigated. This experiment was performed to determine if wheat growth responded to elevated root zone temperature (RZT) and if so, to determine the temperatures for those responses. The RZT treatments were initiated 5 d after planting (DAP) to prevent RZT effects on germination from affecting results. The effects of increased RZT on development and carbon partitioning were determined from data collected during destructive harvests at 7, 15, 22, and 28 DAP. At a constant air temperature of 24 °C, reduced plant height was observed by 15 DAP at 30 °C RZT (+6 °C), and reduced leaf area was observed by 22 DAP at 28 °C RZT (+4 °C). Changes in leaf photosynthesis and stomatal conductance (g
S) were not observed until 35 °C RZT (+11 °C), which was lethal by 22 DAP. Changes in carbon partitioning resulted in decreased leaf mass and increased stem and head mass fractions as well as accelerated development of reproductive structures. Although elevated RZT temperatures above air temperature affected physiological and morphologic parameters, they did not change plant phenology.
Genetic Diversity in Cynara cardunculus Determined by Sequence-related Amplified Polymorphism Markers
Authors: Cravero Vanina , Martín Eugenia , Cointry Enrique
Published: January 2019

Twenty-six wild and cultivated accessions of cardoon [Cynara cardunculus L. var. sylvestris (Lam.) Fiori and C. cardunculus var. cardunculus L., respectively] and globe artichoke [C. cardunculus var. scolymus (L.) Fiori] were analyzed to evaluate genetic diversity using sequence-related amplified polymorphism (SRAP) markers. Eleven qualitative and quantitative traits were evaluated and euclidean distances among genotypes were calculated. A total of 15 primer pairs were initially assayed and seven of them were finally selected as a result of their consistent amplification together with the clear banding patterns obtained. Genetic distances were calculated according to standardized Jaccard's distance index. Both matrices were subjected to cluster analysis. Dendrograms showed that cardoons were clearly separated from artichoke. These results showed that SRAP markers will be useful tools for studying genetic diversity in C. cardunculus.
Developmental Changes in Endogenous Abscisic Acid Concentrations and Asymbiotic Seed Germination of a Terrestrial Orchid, Calanthe tricarinata Lindl.
Authors: Lee Yung-I. , Lu Chia-Fu , Chung Mei-Chu , Yeung Edward C. , Lee Nean
Published: January 2019

Changes in endogenous abscisic acid (ABA) concentrations were investigated in developing seeds and the pretreated seeds of Calanthe tricarinata, a hard-to-germinate terrestrial orchid. ABA concentration was as low as 2.16 to 2.26 ng·mg−1 fresh weight at the proembryo stage [60 to 90 days after pollination (DAP)] and then continuously increased to 11.6 ng·mg−1 fresh weight at 210 DAP. Seed maturation was accompanied by a dramatic decrease in water content and a prominent accumulation of protein and lipid bodies within the embryo proper. The optimum time for asymbiotic seed germination was obtained from immature seeds at 150 DAP. At this stage, the embryo proper reached its maximum size, and the seedcoat became dehydrated and gradually shrunk into a thin layer. By 180 DAP, seed germination declined sharply as seed approached maturity. Mature seeds pretreated with ultrasound (45 min), 1% NaOCl (45 to 60 min), or 1N NaOH (45 min) were effective in improving the germination percentage and lowering seed ABA concentrations. Our results suggest that high concentrations of endogenous ABA in orchid seeds may play a critical role in arresting embryo growth and in preventing seed germination.
Salinity and Water Effects on ‘Hass’ Avocado Yields
Authors: Oster James D. , Stottlmyer D.E. , Arpaia M.L.
Published: January 2019

A field experiment was conducted between 1992 and 1997 in a commercial orchard of mature ‘Hass’ avocados on Mexican seedling rootstock (Persea americana Mill.) to determine how yield was influenced by the amount of irrigation water applied and the frequency of application. Three amounts of water (targeted at 90%, 110%, and 130% of estimated crop evapotranspiration) were applied at three frequencies (one, twice, and seven times per week) with microsprinklers located beneath the tree canopy. The site was set up as a randomized complete block design with six blocks, each including one replicate of all irrigation treatments. One or two trees located at the center of the replicates were used to measure yields and tree size, and as the locations where samples of soil and soil water were obtained for analysis from beneath the tree canopy. The average electrical conductivity and chloride concentration of the irrigation water, corrected for rain, were 0.7 dS·m−1 and 1.8 mmol·L−1, respectively. From May 1994 to Nov. 1996, salinity of the saturated-paste extracts of soil samples obtained in the 0- to 120-cm depth interval averaged ≈2 dS·m−1 for all irrigation treatments. Irrigation treatments also had little influence on the maximum soil-water salinity, ≈4 dS·m−1, in and below the lower portion of the root zone. Consequently, irrigation treatments had little influence on the fraction of applied water that was not used by the crop, the leaching fraction. Chloride concentrations in leaves were affected by applied water but did not attain levels that are associated with leaf injury. Trees irrigated seven times per week had lower yields than trees that received less frequent irrigation. During the last 2 years of the experiment, when yields no longer increased with time, the yields for treatments irrigated once and twice per week increased with increasing amounts of applied water. We were able to explain the influence of both amount of applied water and soil salinity on avocado yields and leaching fraction using production function concepts. Yields increased with increasing amounts of applied water because of increased water availability for crop use before a soil-water salinity of ≈4 dS·m−1 restricted water uptake. The threshold salinity above which yield decline occurred was determined to be 0.57 dS·m−1 and yield declined by 65% per unit of salinity above the threshold. Our results suggest that maximum yields of ‘Hass’ avocado on Mexican seedling rootstock are not achievable when the average annual salinity of irrigation water, including rainfall, is greater than ≈0.6 dS·m−1.
Orange Tree Fibrous Root Length Distribution in Space and Time
Authors: Morgan Kelly T. , Obreza T.A. , Scholberg J.M.S.
Published: January 2019

Understanding the growth pattern of fibrous, orange tree [Citrus sinensis (L.) Osbeck] roots enables proper fertilizer placement to improve nutrient uptake efficiency and to reduce nutrient leaching below the root zone. The objective of this study was to develop relationships defining citrus fibrous root length density (FRLD) as a function of soil depth, distance from the tree trunk, and tree size. Root systems of 18 trees with tree canopy volumes (TCV) ranging from 2.4 to 34.3 m3 on two different rootstocks and growing in well-drained sandy soils were sampled in a systematic pattern extending 2 m away from the trunk and 0.9 m deep. Trees grown on Swingle citrumelo [Citrus paradisi Macf. × Poncirus trjfoliata (L.) Raf.] rootstock had significantly greater FRLD in the top 0.15 m than trees on Carrizo citrange (C. sinensis × P. trifoliata). Conversely, Carrizo citrange had greater FRLD from 0.15 to 0.75 m below the soil surface. FRLD was significantly greater for ‘Hamlin’ orange trees grown on Swingle citrumelo rootstock at distances less than 0.75 m from the tree trunk compared with those on Carrizo citrange. Fibrous roots of young citrus trees developed a dense root mat above soil depths of 0.3 m that expanded both radially and with depth with time as trees grow and TCV increased. Functional relationships developed in this study accounted for changes in FRLD with increase in tree size.
Nickel Deficiency Affects Nitrogenous Forms and Urease Activity in Spring Xylem Sap of Pecan
Authors: Bai Cheng , Reilly Charles C. , Wood Bruce W.
Published: January 2019

While nickel (Ni) deficiency occurs in certain agricultural crops, little is known regarding the influence of deficiency on metabolic or physiological processes. We studied the influence of Ni deficiency on the reduced-nitrogen (N) composition of early spring xylem sap of pecan [Carya illinoinensis (Wangenh.) C. Koch]. High-performance liquid chromatography (HPLC) analysis of sap composition found the presence of ureido-, amide-, and amino-N substances and that they are quantitatively influenced by tree Ni nutritional status. Ureido-N forms quantitatively dominated amide-N forms with respect to both molar concentration and the forms in which reduced N atoms are present; thus, pecan appears to be predominately a ureide-transporting species. The primary ureido-N substances in sap of Ni-sufficient trees are citrulline ≈ asparagine ≈ xanthine > ureidoglycolate > allantoic acid > allantoin ≈ uric acid ≈ urea. Asparagine is the primary amide-N form, while only traces of amino-N forms (e.g., tryptamine and β-phenylethylamine) are found in xylem sap. Nickel deficiency substantially increased citrulline and allantoic acid in xylem sap while decreasing the asparagine, xanthine, and β-phenylethylamine concentrations. These Ni-linked quantitative shifts in reduced-N forms indicate that Ni nutrition potentially affects intermediates of both the ureide catabolic pathway and the urea cycle as well as the nitrogen/carbon (N/C) economy of the tree. Xylem sap-associated urease-specific activity was also reduced as a consequence of Ni deficiency. These results indicate that Ni deficiency potentially disrupts normal N-cycling via disruption of ureide metabolism.
Use of Marker-assisted Selection to Breed for Resistance to Common Bacterial Blight in Common Bean
Authors: O'Boyle Patrick D. , Kelly James D. , Kirk William W.
Published: January 2019

Common bacterial blight (CBB), incited by the bacterial pathogen Xanthomonas axonopodis pv. phaseoli (Smith) Vauterin et al., is one of the most serious seed-borne diseases of common bean (Phaseolus vulgaris L.) worldwide. Although previous attempts to breed CBB-resistant bean cultivars have had limited success due to the quantitative nature of resistance, progress in marker-assisted selection has created new opportunities for breeders to improve the selection process. The potential of independent linked markers for indirect selection of CBB resistance was evaluated in field experiments in East Lansing and Saginaw, Mich. The presence of the SU91 marker was correlated with lower CBB leaf scores in East Lansing (r = −0.50***) and Saginaw (r = −0.59***) and correlated with pod resistance in Saginaw (r = −0.48***). SU91 exhibited a slight negative correlation with yield (r = −0.20*) in East Lansing but showed no association with yield in Saginaw. Plant selections carrying SU91 were crossed with a different source of CBB resistance linked to the sequence-characterized amplified region marker BC420 on bean linkage group B6. The effects of SU91 and BC420 markers were examined in two greenhouse studies. The presence of SU91 was correlated with lower CBB disease ratings for leaves (r = −0.20*) and pods (r = −0.27***). Presence of BC420 was only correlated with low pod ratings (r = −0.19*) in one experiment and CBB leaf resistance (r = −0.18*) in the second experiment. Presence of both markers resulted in lower levels of CBB resistance than provided by either marker alone, possibly indicating epistatic interactions between the independent loci conditioning CBB resistance in common bean.
Biologically Active Gibberellins and Abscisic Acid in Fruit of Two Late-maturing Japanese Pear Cultivars with Contrasting Fruit Size
Authors: Zhang Caixi , Tanabe Kenji , Tani Hiroko , Nakajima Hiromitsu , Mori Minori , Sakuno Emi
Published: January 2019

Both ‘Atago’ and ‘Shinkou’ are late-season japanese pear (Pyrus pyrifolia Nakai) cultivars with russet-brown fruit, and the progenies of crosses made between ‘Nijisseiki’ and unknown cultivars, but they display different growth habit, fruit size, and fruit quality. To clarify the difference in fruit development between the two cultivars, the levels of endogenous gibberellins (GA1, GA3, and GA4) and abscisic acid (ABA) in fruit were identified and quantified by gas chromatography/mass spectrometry, and a histological study of fruit was carried out. The results showed that cell number rather than cell size of mesocarp is responsible for the difference in fruit size between the two cultivars. Furthermore, analysis of endogenous bioactive gibberellins revealed that ‘Atago’ fruit has much higher levels of GA1, GA3, and GA4 than ‘Shinkou’ fruit during fruit development, particularly during the early period of fruit growth. However, ‘Shinkou’ has a much higher ABA level than ‘Atago’ during the early period of fruit development. Abscisic acid concentration remained at an extremely low level after the first production peak after anthesis in ‘Atago’ compared with ‘Shinkou’.
A Polymerase Chain Reaction-based Linkage Map of Broccoli and Identification of Quantitative Trait Loci Associated with Harvest Date and Head Weight
Authors: Brown Allan F. , Jeffery Elizabeth H. , Juvik John A.
Published: January 2019

A set of 216 polymerase chain reaction-based molecular markers was screened for polymorphisms using two morphologically dissimilar broccoli (Brassica oleracea L. ssp. italica Plenck) lines, ‘VI-158’ and ‘‘Brocolette Neri E. Cespuglio’. Fifty-nine of these simple sequence repeat (SSR) and sequence-related amplified polymorphic (SRAP) primer pairs generated 69 polymorphisms that were used to construct a linkage map of broccoli from a population of 162 F2:3 families derived from the cross between these two lines. Ten linkage groups were generated that spanned a distance of 468 cM with an average interval width of 9.4 cM. The map was used to identify quantitative trait loci (QTL) associated with differences in harvest date maturity and head weight in the population grown in the same location over 2 years. Heritability estimates for days to maturity and head weight were 0.84 and 0.64, respectively. Four QTL for harvest maturity were identified that described 55.6% of the phenotypic variation in the first year with two of these QTL also detected in the second year of the experiment that described 29.2% of the phenotypic variation. Five QTL were identified as associated with head weight in 1999 and accounted for 71.8% of the phenotypic variability. Two of these QTL accounted for 24% of the phenotypic variability in head weight in 2000. To our knowledge, this is the first linkage map of broccoli and the first combined SSR and SRAP map of B. oleracea, which should provide a useful tool for the genetic analysis of traits specific to ssp. italica.
Light Activation of Contractile Roots of Easter Lily
Authors: Jaffe Mordecai J. , Leopold A. Carl
Published: January 2019

Contractile roots provide for a type of movement in plants that occurs in many plant species but has been given little attention. In the case of Easter lily (Lilium longiflorum Thunb. cv. Nelly White), root contraction serves to pull a bulb down into the soil where environmental conditions are more constant. The contraction is evidenced by a formation of epidermal wrinkles, starting at the base of the root and advancing toward the root tip. The movement function occurs in shallowly planted materials, is lessened at deeper locations, and ceases at a vermiculite depth of ≈15 cm. Examination of the cell shapes and volumes in the contracting sector indicates that movement of the bulb in the soil is achieved by a hydraulic shift in cortical cells. Root contraction is stimulated by light. Perception of the light stimulus does not occur in the root but occurs in the bulblet or possibly in the subtending leaf. Responsiveness to light fades with aging of the root, and experiments with light of different wavelengths indicate that the contraction response is preferentially triggered by blue light.
Cuticular Cracking on Nectarine Fruit Surface: Spatial Distribution and Development in Relation to Irrigation and Thinning
Authors: Gibert Caroline , Chadœuf Joël , Vercambre Gilles , Génard Michel , Lescourret Françoise
Published: January 2019

Investigations on “natural” cuticular cracks were conducted on nectarine fruit [Prunus persica (L.) Batsch var. nucipersica (Suckow) C.K. Schneid.]. A method for quantifying the cuticular crack surface area on a whole fruit basis was proposed. By using a stratified sampling design, the spatial distribution of the cuticular cracks over three regions (stylar end, peduncle, and cheek), their morphology, and the estimation of the total proportion of cuticular cracks on the fruit were studied. These features were examined during fruit development and in response to several fruit growing conditions corresponding to various crop loads and irrigation regimes. Cuticular cracks on nectarine fruit occurred during the final rapid fruit growth stage. Larger fruit presented higher cuticular crack densities in the apical regions than in the cheek regions. Thin and larger cuticular cracks occurred continuously during fruit development. Cuticular cracks represented 10% to 12.5% of the fruit surface area for well irrigated or low crop load trees, whereas they covered less than 4.5% for the heavy crop load and water deficit treatments. Cheek regions largely contributed to the total cuticular crack surface area (>60%), regardless of the fruit growing conditions. After irrigation was restricted, cuticular crack development was limited. A positive relationship was established between the cuticular crack surface area per fruit surface area and the fruit fresh weight.
Antioxidant Activities and Anticancer Cell Proliferation Properties of Wild Strawberries
Authors: Wang Shiow Y. , Lewers Kim S. , Bowman Linda , Ding Min
Published: January 2019

Fruit extracts from 17 to 18 representatives of three strawberry species [Fragaria virginiana Mill., F. chiloensis (L.) Mill., and F. ×ananassa Duchesne ex Rozier] were tested for the ability to inhibit proliferation of A549 human lung epithelial cancer cells. The fruit extracts also were tested for activities against free radicals, (peroxyl radicals, hydroxyl radicals, singlet oxygen, and superoxide radicals), the activities of antioxidant enzymes [glutathione peroxidase (EC 1.11.1.9), superoxide dismutase (EC 1.15.1.1), guaiacol peroxidase (EC 1.11.1.7), ascorbate peroxidase (EC 1.11.1.11), monodehydroascorbate reductase (EC 1.6.5.4), dehydroascorbate reductase (EC 1.8.5.1), and glutathione reductase (EC 1.6.4.2)], and the activities of nonenzyme antioxidant components, ascorbic acid and glutathione. Correlations between the proliferation of cancer cells and these antioxidant activities were calculated. At the species level, F. virginiana fruit extract inhibited the proliferation of A549 human lung epithelial cancer cells to a significantly greater extent (34% inhibition) than the extracts from fruit of either F. chiloensis (26%) or F. ×ananassa (25%) (P < 0.0001). Extracts from fruit of F. virginiana also had significantly greater antioxidant activities and higher activities of antioxidant enzymes and nonenzyme components than did extracts from the other two species. Among individual genotypes, there was a high positive correlation between antiproliferation of A549 cancer cells, antioxidant activities against free radicals, activities of antioxidant enzymes, and activities of nonenzyme components. Although all fruit extracts from all the strawberry genotypes inhibited proliferation of A594 cancer cells, fruit extracts from seven F. virginiana genotypes showed significantly greater antiproliferative effects than any of the F. ×ananassa or F. chiloensis genotypes. These genotypes, CFRA 0982, JP 95-1-1, NC 95-19–1, RH 30, NC 96-48-1, JP 95-9-6, and LH 50-4, may be especially useful in developing cultivars with greater anticancer potential.
Characterization of an Unusual Cytoplasmic Chimera Detected in Bolting Garlic Clones
Authors: Ipek Meryem , Ipek Ahmet , Senalik Douglas , Simon Philipp W.
Published: January 2019

Production of a visible flower stalk, or bolting, has been used as a major trait to categorize garlic (Allium sativum L.) clones. Analysis of mitochondrial genome variation with polymerase chain reaction (PCR) revealed differences between bolting and nonbolting clones of garlic. Screening 333 garlic accessions from diverse geographic origins revealed a 1403-bp mitochondrial DNA marker associated with bolting that the authors call “Bolt Marker” (BltM). Bolt Marker did not amplify in any of the 131 nonbolting clones, whereas amplification of this marker was observed in 127 of 130 (97.7%) garlic clones that bolted completely in Wisconsin. Seventy-two garlic clones bolted incompletely (clones in which some but not all of the plants bolted), and this marker was not amplified in 69 (95.8%) of these clones. Because of the significant association of BltM with bolting, this PCR-based marker can be used to discriminate complete-bolting garlic clones reliably from nonbolting and incomplete-bolting ones. Sequence characterization of this marker revealed that BltM is a chimera involving both mitochondrial and chloroplast DNA. The DNA sequences including and flanking both the 5′ and 3′ ends of this marker are consistent with an ≈4.8-kbp chloroplast DNA fragment having been inserted into the mitochondrial genome downstream from the mitochondrial cox3 gene. Sequence alignment of the chloroplast genes in this chimeric region with the homologous sequences in GenBank indicate the presence of deletions, insertions, and single nucleotide polymorphisms in the coding sequences, resulting in putative, incomplete open reading frames or frame shift mutations. Hence, the authors speculate that this insertion may have occurred long ago in the evolution of garlic.
Photochemical Efficiency and Recovery of Photosystem II in Grapes After Exposure to Sudden and Gradual Heat Stress
Authors: Kadir Sorkel , Von Weihe Michael , Al-Khatib Kassim
Published: January 2019

Damage and capacity to recover of photosystem II (PSII) from long exposures to heat stress were investigated in grapes using chlorophyll fluorescence. Two wine grapes, Vitis aestivalis Michx. cv. ‘Cynthiana’ and French-American hybrid ‘Vignoles’ (Vitis L. hybrid), were exposed to a sudden heat shock (SHS) and a gradual heat shock (GHS) at 40/35 °C. After heat stress, plants were moved to a greenhouse to allow PSII to recover from heat treatments. Changes in maximum quantum efficiency of PSII, indicated by the ratio of variable fluorescence and maximum fluorescence (Fv/Fm), were observed after 3, 6, and 12 days of heat stress and after 3, 7, 14, and 21 days recovery periods of damage to PSII. Total leaf area (LA) and leaf, shoot, and root biomass were determined at the end of the experiment. Regardless of the heat treatment, increasing duration of exposure to high temperature caused a decline in Fv/Fm in both cultivars. Heat stress treatments also caused a progressive decline in LA as well as leaf and shoot biomass. Maximum quantum efficiency of PSII was observed after 3 days of exposure in both cultivars, regardless of the heat stress treatment. ‘Vignoles’, however, showed higher PSII photochemical efficiency 12 days after heat exposure. GHS was less detrimental to PSII compared with SHS heat treatment. The damaged PSII of ‘Vignoles’ recovered faster than that of ‘Cynthiana’. A positive relationship was observed between Fv/Fm and LA of plants exposed to heat treatments. Based on Fv/Fm values, this study indicates that PSII of ‘Vignoles’ is more thermostable and can recover faster than that of ‘Cynthiana’ leaves, regardless of the heat treatment. These results suggest that ‘Vignoles’ is generally more heat-tolerant than ‘Cynthiana’ and changes in Fv/Fm ratio under heat stress conditions could be a good indicator for screening heat-resistant grape cultivars.
Abnormal Microspore Development Leads to Pollen Abortion in a Seedless Mutant of ‘Ougan’ Mandarin (Citrus suavissima Hort. ex Tanaka)
Authors: Hu Zhiyong , Zhang Min , Wen Qigen , Wei Jie , Yi Hualin , Deng Xiuxin , Xu Xianghua
Published: January 2019

Seedlessness is of commercial importance in citrus (Citrus L.). Seedless ‘Ougan’ mandarin (C. suavissima) was selected from a bud sport mutation that occurred in ‘Ougan’ mandarin. We analyzed their pollen viability through KI-I2 and FDA staining, and examined the anthers of wild-type (seedy) and seedless mutant ‘Ougan’ mandarin using histological and cytochemical methods to characterize the process of pollen development. No pollen fertility was detected in this mutant. Pollen abortion in anthers of the mutant occurred at the tetrad stage of microspore development, and almost all the tetrads were abnormal. The mutant had heterogeneous microspore populations, including monads, dyads, triads, tetrads, and polyads in the same microsporangium. Pollen grain number per anther of the mutant was 21.9% less than the wild type. Morphology of mature pollen grains using SEM showed that the shape of mature pollen grains from both wild type and mutant is similar, but the microsporangia of the latter contained pollen grains of more variable sizes. At the early mature pollen grain stage, abundant starch grains and lipids appeared in the wild type's pollen, but fewer amounts were observed in the mutant. Moreover, the tapetal cells of the wild type accumulated lipids, but not those of the mutant. Results indicated that the abnormal development of the microspore led to pollen abortion in the mutant, and this could be the reason for its seedlessness. However, the genetic reasons for the aberrant tetrads are not clear and are under investigation.
Genetic Relatedness of Ornamental Ficus Species and Cultivars Analyzed by Amplified Fragment Length Polymorphism Markers
Authors: Fang Jinggui , Chen Jianjun , Henny Richard J. , Chao Chih-Cheng T.
Published: January 2019

Ornamental Ficus L. is a group of lactiferous trees, shrubs, and woody root-climbing vines that are cultivated either as landscape plants in the tropics and subtropics or as foliage plants used worldwide for interiorscaping. With the recent rapid expansion of the ornamental plant industry, more new Ficus species and cultivars have been introduced. However, no study has thus far addressed the genetic relationships of cultivated ornamental Ficus. Using amplified fragment length polymorphism (AFLP) markers with near-infrared fluorescence-labeled primers, this study analyzed the genetic relatedness of 56 commercial cultivars across 12 species. Forty-eight EcoRI + 2/MseI + 3 primer set combinations were initially screened, from which six primer sets were selected and used in this investigation. Most cultivars were differentiated by their AFLP fingerprints, and their relationships were determined using the unweighted pair-group method of arithmetic average cluster analysis. The 56 cultivars were divided into 12 clusters that correspond to 12 species, indicating that no interspecific hybrids of ornamental Ficus are in commercial production. The 12 species are genetically diverse, with Jaccard's similarity coefficients ranging from 0.21 to 0.43. However, cultivars within three species—Ficus benjamina L., Ficus elastica Roxb. Ex Hornem., and Ficus pumila L.—are genetically close. Twenty-seven of the 29 cultivars of F. benjamina and five cultivars of F. pumila had Jaccard's similarity coefficients of 0.98 or higher respectively. Nine cultivars of F. elastica shared Jaccard's coefficients higher than 0.96. These results indicate potential genetic vulnerability of these cultivars within the three species. Because there are increasing reports of invasive pests in the ornamental plant industry, strategies for conserving genetic resources and broadening genetic diversity of cultivated Ficus are discussed.
Postharvest Highbush Blueberry Fruit Antimicrobial Volatile Profiles in Relation to Anthracnose Fruit Rot Resistance
Authors: Polashock James J. , Saftner Robert A. , Kramer Matthew
Published: January 2019

Fruit of highbush blueberry (Vaccinium corymbosum L.) produce antimicrobial volatiles, including trans-2-hexenal, that may confer resistance to anthracnose fruit rot, an important postharvest disease caused by Colletotrichum acutatum J.H. Simmonds. To investigate whether aromatic volatiles in highbush blueberry fruit are associated with postharvest fruit rot resistance, we compared volatiles emitted from whole fruit and extracts from fruit kept in air at 20 °C for 0 to 6 days postharvest from cultivars having a wide range of resistance to anthracnose. Antimicrobial volatiles detected included the aldehydes, trans-2-hexenal and hexanal; the monoterpenes, limonene, linalool, 8-hydroxylinalool, α-terpineol, and terpinyl acetate; and the sesquiterpenes, cadinene, caryophyllene, and α-farnesene. There were significant correlations between some detected volatiles and these differed in whole fruit and extracts. Hexanal (in fruit extracts), trans-2-hexenal, terpinyl acetate, and cadinene emissions increased in most cultivars when fruit were kept in air at 20 °C for various times postharvest. Volatile emissions from whole fruit and extracts varied widely among the cultivars with early ripening cultivars generally showing higher volatile emissions than later ripening cultivars. Although the cultivars tested differed in quantities, and in some cases, the types of volatiles produced, these differences were not related to pedigree (i.e., species composition) nor to known anthracnose resistance ratings. Except for the confounded emissions of terpinyl acetate and cadinene, more than 80% of the variation observed for each volatile was attributable to the cultivar (genetic), year (environmental), and cultivar–by-year interaction. The results suggest that, although antimicrobial aldehydes and terpenes emitted from fully ripe highbush blueberry fruit and extracts might be important flavor and aroma components, they do not significantly contribute to disease resistance against anthracnose fruit rot.
Genetic Markers Linked to the Dwarfing Trait of Apple Rootstock ‘Malling 9’
Authors: Pilcher R.L. Rusholme , Celton J-M. , Gardiner S.E. , Tustin D.S.
Published: January 2019

Little is known of the precise physiological or genetic basis of the phenomenon of rootstock-induced dwarfing in apple (Malus × domestica Borkh.). Phenotypic assessment and genetic marker analysis of a segregating population of apple rootstocks derived from a cross between the dwarfing rootstock ‘Malling 9’ (‘M.9’) and the vigorous rootstock ‘Robusta 5’ (‘R5’) was undertaken over a 5-year growth period. Clear segregation of the appearance of the ‘Braeburn’ scions permitted expert visual classification of each tree into four growth habit classes: dwarfed, semidwarfed, intermediate, or vigorous. Measurements of the cross-sectional area of the trunk of each tree correlated clearly with the expert-assigned phenotypic class. This clear segregation facilitated bulked segregant analysis (BSA) of the ‘M.9’ × ‘R5’ population, and the Dwarfing 1 (Dw1) gene was located in a 2.5-cM region at the top of the linkage group 5 of ‘M.9’. The gene Dw1 was mapped between the random amplified polymorphic DNA marker NZraAM18_700 and the microsatellite marker CH03a09, identified by BSA and the genome scanning approach, respectively. Dw1 is the first reported mapped locus controlling the dwarfing ability of the apple rootstock and maps to a chromosome region not previously known to contain quantitative trait loci or major genes that contribute to tree architecture and development. The identification of a group of trees in the ‘M.9’ × ‘R5’ population exhibiting a vigorous phenotype although their rootstocks possess alleles from the Dw1 region of ‘M.9’ suggests that more loci may be involved in conditioning the dwarfing phenotype. Dw1 is a major component of dwarfing, as most of the dwarfing and semidwarfing rootstocks carried the dwarfing allele of this locus. Genetically mapping Dw1 is a major step in unraveling the mechanism behind the dwarfing ability of apple rootstocks.
Morphologic and Agronomic Diversity of Brassica napus Crops
Authors: Soengas Pilar , Cartea Maria Elena , Velasco Pablo , Padilla Guillermo , Ordás Amando
Published: January 2019

A Brassica napus L. crop called nabicol traditionally has been grown by farmers in northwestern Spain for many years and is an important horticultural product during the winter season. The relationship of nabicol to other B. napus crops has been studied based on simple sequence repeat (SSR) data. However, molecular and morphologic classifications often disagree. The objectives of this research were to study the morphologic and agronomic relationships of nabicol landraces to other B. napus crops and to compare those relationships with the ones already known, based on SSR data. Thirty-five B. napus populations from different geographic origins and uses were evaluated. Data were recorded on 17 morphologic and agronomic traits. Principal component analysis and cluster analysis were performed to classify the populations. Eight principal components (94% of the total variability) were standardized to produce the Mahalanobis' generalized distances, and a cluster analysis was conducted using the unweighted pair group method with arithmetic averages. There are no major differences between B. napus var. pabularia (DC.) Rchb. (nabicol, couve-nabiça, forage rape) and B. napus var. oleifera DC. (oilseed rape), and they probably share a common origin. Rape kale (B. napus var. pabularia) and rutabaga [B. napus var. napobrassica (L.) Rchb.] cultivars are separated from the rest and probably they have an independent origin or domestication. Molecular and morphologic classifications are complementary, and both are necessary to classify germplasm correctly and to clarify genetic relationships among B. napus crops.
Inheritance of Leaf Spots and Their Genetic Relationships with Leaf Shape and Vein Color in Caladium
Authors: Deng Zhanao , Goktepe Fahrettin , Harbaugh Brent K.
Published: January 2019

The ornamental value of caladium (Caladium ×hortulanum Birdsey) depends to a large extent on its foliar characteristics. Efficient genetic improvement of caladium foliar characteristics requires a good understanding of the inheritance of these traits, including leaf shape, color, and spots. This study was conducted to determine the inheritance of leaf spots in caladium and to understand their relationships with leaf shape and main vein color. Eighteen controlled crosses were made among eight commercial cultivars expressing red or no leaf spots, and progeny of these crosses were observed for segregation of leaf spots as well as leaf shape and vein color. A single locus with two alleles is shown to be responsible for the presence or absence of leaf spots in caladium, with the presence allele (S) dominant over the absence allele (s). The major spotted commercial cultivar Gingerland is heterozygous for this trait. Leaf spots are inherited independently from leaf shape, but they are closely linked with the color of the main leaf veins. The recombination frequencies between the leaf spot locus and the main vein color locus ranged from 0.0% to 8.9% with the crosses or the parental cultivars used, with an average of 4.4%. Leaf spots and vein colors represent the first linkage group of ornamental traits in caladium and possibly in other ornamental aroids. The knowledge gained in this study will be valuable when it comes to determine what crosses to make for development of new cultivars. It may be also useful to those interested in determining the inheritance of similar traits in other ornamental plants, including other ornamental aroids such as dieffenbachia (Dieffenbachia Schott).
Lignin Deposition Converts Juice Sacs to “Brown Thorns” in a Citrus Triploid Hybrid
Authors: Hu Zhiyong , Liu Qing , Tan Meilian , Yi Hualin , Deng Xiuxin
Published: January 2019

In this article, we describe a novel biological phenomenon that the tips of the juice sac of citrus hybrid HRB turned brown and became tough like many “brown thorns”; HRB is a triploid hybrid regenerated from the cross of diploid tangerine BDZ (Citrus reticulata Blanco cv. Huanongbendizao) with an allotetraploid somatic hybrid HR [Hamlin sweet orange (Citrus sinensis Osbeck) + rough lemon (Citrus jambhiri Lush)]. Histochemical analysis indicated that the “brown thorn” of HRB resulted from lignin deposition. The juice sac of HRB had 4.6- and 3.8-fold content of lignin of its parents tangerine and HR, respectively. Microscopy observation of the cross-sections of the juice sac verified that the cell wall of the “brown thorn” was lignified. Moreover, the cell walls near the “brown thorns” were obviously thickened. Analysis of enzyme activity indicated that the peroxidase (POD) activity of HRB was significantly higher than its parents. Quantitative real-time polymerase chain reaction analysis showed that the transcript abundance of the cinnamate 4-hydroxylase (C4H) gene in HRB was 6.5- and 3.4-fold of its parent BDZ and HR, respectively, but the POD gene transcript abundance was lower than its parent with 1/2-fold of BDZ and 1/7-fold of HR. These facts led to the conclusion that POD and C4H were the key regulating factors for lignin biosynthesis in juice sacs of the hybrid HRB. The POD gene, one member of the POD family, with transcript abundance lower than its parent indicated that this POD isoenzyme was not the regulating factor of lignin biosynthesis, and further study should be carried out to determine which POD isoenzyme is the key factor for lignin biosynthesis.
Using AFLP Markers for the Analysis of the Genetic Diversity of Apricot Cultivars in Tunisia
Authors: Krichen Lamia , Martins Joao M.S. , Lambert Patrick , Daaloul Abderrazzak , Trifi-Farah Neila , Marrakchi Mohamed , Audergon Jean-Marc
Published: January 2019

Apricot (Prunus armeniaca L.) culture is present in a wide range of areas and microclimates in Tunisia. Each of them contains several specific cultivars and shows a high level of morphological diversity. To characterize the related diversity, surveys were performed in the four main apricot cultivation areas, where 31 cultivars representing apricot landraces were sampled. DNA was extracted and amplified with five different EcoRI–MseI AFLP primer combinations. Autoradiographs revealed 203 polymorphic markers in a total of 295 detected fragments. A set of redundant marker patterns was identified and deleted from the binary data matrix, data analysis being performed on a total of 167 polymorphic markers. In a dendrogram calculated by the Ward clustering technique, two major groups were identified, separating nine cultivars from the other 22. Three subgroups have been revealed in each of the main groups. The groups and subgroups identified on the genetic basis are closely related to the geographic origin of the cultivars. Analysis of the actual repartition suggested at least the introduction of two independent gene funds in the northern and central prospected areas, followed by a local diversification and then a dissemination phase. Their interaction occurred at least in the two sites of Testour and Sbikha.
The Genetic Variability of Sicilian Lemon Germplasm Revealed by Molecular Marker Fingerprints
Authors: Siragusa Mirko , De Pasquale Fabio , Abbate Loredana , Martorana Letizia , Tusa Nicasio
Published: January 2019

There is a high level of diversity among lemons [Citrus limon (L.) Burm. f. (2n = 2x = 18)] in Sicily, where each growing area has a wide range of landraces mostly derived from bud mutation. Because this variability represents an important resource for future breeding programs and genetic improvement, the relationships among the principal 36 accessions of Sicilian lemon, belonging to three different cultivars (Femminello, Monachello, and Lunario), were examined by intersimple sequence repeat and random amplified polymorphic DNA markers. Three ‘Femminello’ accessions from nearby Italian regions were also examined to study the genetic flow from the continent. The disputed case of the accession ‘Eureka Messina lemon’ was also examined, using ‘Frost Eureka’ as a control. Our results confirmed the extreme polymorphic nature of the three principal Sicilian cultivars and the presence of a wide range of different genotypes. Twenty-two Sicilian genotypes were recognized as unique accessions, reflecting the richness of the lemon germplasm present in Sicily. Each growing area showed the presence of several genetically different landraces, probably preserved by genetic isolation, whereas the continental accessions appeared extremely similar to the island genotypes, showing an exchange of germplasm from the island to the continent.
Rib Discoloration in F2 Populations of Crisphead Lettuce in Relation to Head Maturity
Authors: Jenni Sylvie , de Koeyer David , Emery George
Published: January 2019

Rib discoloration is a physiological disorder associated with heat stress in crisphead lettuce (Lactuca sativa L.). Rib discoloration resistance was studied in a 2-year field experiment using parental and F2 plant populations from a cross of ‘Emperor’, a resistant cultivar, and ‘Eldorado’, a susceptible cultivar. Rib discoloration was evaluated in terms of incidence (percentage of plants with symptoms) and severity (on a 1–5 scale) and was correlated with maturity traits. The rib discoloration severity ratings for the two reciprocal F2 populations were intermediate between the two parents and were not significantly different, indicating the lack of cytoplasmic inheritance for rib discoloration in ‘Emperor’ and ‘Eldorado’. In both parents and F2 progenies, rib discoloration severity was strongly correlated with stem length, head height, head diameter, and head weight, but not with head density. In the resistant parent, more severe rib discoloration was associated with denser heads, whereas in the susceptible parent, the expression of the disorder was independent of head density. The chi-square tests rejected the hypothesis for monogenic segregation in some plantings but not in others. Resistance to rib discoloration is likely to be controlled by more than one gene with a high heritability (h2 = 0.57, P < 0.0001).
Outcrossing in Florida Avocados as Measured Using Microsatellite Markers
Authors: Borrone James W. , Olano Cecile T. , Kuhn David N. , Brown J. Steven , Schnell Raymond J. , Violi Helen A.
Published: January 2019

Avocado (Persea americana Mill.) possesses a unique flowering mechanism, thought to promote out-crossing, in which the male and female parts of the perfect flower function at different time periods. Cultivars are classified as Flowering Type A, where flowers are functionally female the morning of one day and functionally male the afternoon of the next day, or Flowering Type B, where flowers are functionally female in the afternoon and functionally male the next morning. Avocado growers typically interplant cultivars of opposite flowering types to maximize yield. Recently, it has been hypothesized that 90% to 95% of avocado flowers are self-pollinated in southern Florida. However, this hypothesis does not address whether mature, marketable avocado fruit in Florida are the result of outcrossing. To determine whether avocado fruit in southern Florida result from self-pollination or outcrossing, fruit were harvested from a commercial orchard in Miami-Dade County, Florida, from a block consisting of two cultivars, Simmonds (Flowering Type A) and Tonnage (Flowering Type B), interplanted in approximately equal numbers. Seeds were germinated and the resulting progeny were genotyped using eight fully informative, microsatellite markers. Seventy-four percent of the ‘Simmonds’ progeny and 96% of the ‘Tonnage’ progeny were judged to be the result of cross-pollination, with an estimated overall outcrossing rate of 63% to 85% within this particular block of the orchard. Seedlings judged to be the result of cross-pollinations between ‘Simmonds’ and ‘Tonnage’ are being maintained at the U.S. Department of Agriculture-Agricultural Research Service, Subtropical Horticulture Research Station and are being evaluated for segregation of important agronomic and horticultural traits.