bluuebunny/crossref_metadata_2025 huggingface dataset:
Carbohydrate Balance and Accumulation during Development of Near-isogenic Tomato Lines Differing in the AGPase-L1 Allele
Authors: Petreikov Marina , Yeselson Lena , Shen Shmuel , Levin Ilan , Schaffer Arthur A. , Efrati Ari , Bar Moshe
Published: January 2019

Soluble sugar accumulation is a major determinant of tomato (Solanum lycopersicum) fruit quality. One strategy of increasing sugar levels in the mature fruit is via the increase of the transient starch pool in the immature fruit, which is subsequently degraded to contribute to its soluble sugar levels. ADP-glucose pyrophosphorylase [AGPase (E.C. 2.7.7.27)] is a limiting enzyme in starch synthesis and we therefore developed introgression lines of cultivated tomato harboring the wild species (Solanum habrochaites) allele for the regulatory large subunit (L1H
) of this heterotetrameric enzyme. Comparison of numerous near-isogenic lines of tomato segregating for the L1 allele, during multiple seasons, showed that the wild species allele led to an increase in fruit total soluble solids concentration (TSS) without a concomitant decrease in fruit size. Rather, in practically all lines studied, fruit size increased together with TSS, leading to an even larger increase in TSS × yield. A comparative developmental study of fruit carbohydrates, starch, and sugars between genotypes showed that the wild species allele led to increases in fruit size, carbohydrate concentration, and carbohydrate content of the whole fruit unit. This was related to a large increase in the transient starch reservoir that, upon degradation, accounted for the subsequent increase in soluble sugars. These results are evidence that modifying fruit sink carbohydrate metabolism via a single rate-limiting enzymatic step can increase the net import of photoassimilate into the fruit.
Short-term Aluminum Stress Differentially Affects the Photochemical Efficiency of Photosystem II in Highbush Blueberry Genotypes
Authors: Reyes-Diaz Marjorie , Alberdi Miren , Mora Maria de la Luz
Published: January 2019

Aluminum (Al) toxicity is a major agronomic problem in acid soils. Most studies regarding Al stress focus on phenomena occurring in the roots; however, less is known about the effects of Al stress on photosynthetic apparatus functionality. Our aim was to rank three highbush blueberry (Vaccinium corymbosum) cultivars according to their tolerance to acid and Al stresses. Additionally, the levels of Al toxicity for highbush blueberry were established. ‘Brigitta’, ‘Legacy’, and ‘Bluegold’ were grown in a greenhouse in hydroponic solutions containing different Al concentrations (0, 25, 50, 75, and 100 μm) for 0 to 48 h and were allowed to recover (without Al) over 24 h. In all Al-treated cultivars, root growth inhibition was found at the highest Al treatment. However, ‘Brigitta’ also showed root growth up to 75 μm Al. Photochemical parameters decreased substantially due to Al treatments in ‘Bluegold’ (up to 98% inhibition) and ‘Legacy’ (up to 80% inhibition) without total recovery. In contrast, ‘Brigitta’ showed a better photosystem II performance and root growth than the other cultivars. These results suggest that ‘Brigitta’ is the best cultivar for use in acid soils with Al toxicity, followed by ‘Legacy’. ‘Bluegold’ was highly sensitive to Al stress. In addition, Al toxicity levels for blueberries depend on the genotype studied.
Accumulation of Macro- and Micronutrients and Nitrogen Demand-supply Relationship of ‘Gala’/‘Malling 26’ Apple Trees Grown in Sand Culture
Authors: Cheng Lailiang , Raba Richard
Published: January 2019

Six-year-old ‘Gala’/‘Malling26’ (‘M.26’) apple (Malus ×domestica Borkh.) trees grown in sand culture were provided with a total of 30 g of N per tree as enriched 15N-NH4NO3 in Hoagland's solution via fertigation to determine the magnitude and seasonal patterns of accumulation of macro- and micronutrients and the demand-supply relationship of N. Crop load was adjusted to 8.2 fruit/cm2 trunk cross-sectional area, at king fruit diameter of 10 mm by hand-thinning. At each of seven key developmental stages throughout one annual growth cycle, four trees were excavated and destructively sampled for complete nutrient analysis. Nutrient concentrations in leaves and fruit fell within the recommended optimal range, and the fruit yield was 18.8 kg/tree (equivalent to 52.45 t·ha−1) with an average fruit weight of 181 g. The net accumulation of N, P, K, Ca, Mg, and S from budbreak to fruit harvest was 19.8, 3.3, 36.0, 14.2, 4.4, and 1.6 g/tree, respectively, and that for B, Zn, Cu, Mn, and Fe was 93.6, 60.9, 46.5, 184.8, and 148.7 mg/tree, respectively. Nutrient accumulation by new growth (fruit plus shoots and leaves) accounted for over 90% of the net gain for N, P, K, Mg, S, and B in the whole tree and a large proportion of the net gain for Ca, Zn, Mn, and Fe (from 58.1% for Zn to 87.2% of Fe) from budbreak to fruit harvest. Differential nutrient accumulation patterns were found in shoots and leaves and fruit. The most rapid accumulation of all nutrients in shoots and leaves took place during active shoot growth from bloom to the end of shoot growth. The accumulation pattern of most nutrients corresponded well with the accumulation of dry matter, with continued accumulation observed only in total Ca and Mn in shoots and leaves after the end of shoot growth. Nutrient accumulation in fruit largely followed its dry matter accumulation, and a large proportion of the nutrient accumulation (from 58.1% for Zn to 77.4% of K) occurred from the end of shoot growth to fruit harvest. At harvest, fruit contained more P, K, B, and Fe, whereas shoots and leaves had more N, Ca, Mg, S, Zn, and Mn. Most of the N demand by new growth at bloom was provided by tree reserve N. Remobilization of N from perennial parts of the tree was found to support rapid fruit expansion from the end of shoot growth to fruit harvest. The most rapid uptake from current season's N supply occurred from bloom to the end of shoot growth, corresponding to the highest tree N demand. At harvest, 62.4% of the total N in new growth was in shoots and leaves, with the balance in fruit. Reserve N and current season's N uptake each contributed about 50% to the total N in the whole tree at harvest.
Genotypic Variation in the Response to Suboptimal Temperature at Different Plant Densities in Cut Chrysanthemum
Authors: van der Ploeg Anke , Carvalho Susana M.P. , Heuvelink Ep
Published: January 2019

Energy efficiency of greenhouse cut chrysanthemum (Chrysanthemum morifolium Ramat.) may be increased by breeding. In addition to breeding for cultivars with a shorter reaction time at suboptimal temperatures, an alternative approach would be to develop cultivars that are heavier at suboptimal temperatures so that they could be grown at a higher plant density, enhancing the production per unit area. Therefore, the combined effect of temperature and plant density on growth and development of four cut chrysanthemum cultivars was investigated in three greenhouse experiments, carried out in different seasons. For growth-related traits, no interactions between temperature and cultivar were found, limiting the possibilities for breeding. At suboptimal temperatures, growth rate early in the cultivation period decreased as a consequence of a lower light interception resulting from a lower specific leaf area. Thus a higher dry mass production at lower temperature could only be explained by a longer cultivation time. Temperature also influenced external quality, but these effects were cultivar dependent. For instance, temperature affected the slope of the positive linear relationship between total dry mass and number of flowers, reducing number of flowers at low temperature for the same plant dry mass. It is concluded that there are possibilities for breeding for suboptimal temperature-tolerant cultivars.
Carbohydrate Level, Photosynthesis, and Respiration in Creeping Bentgrass as Influenced by Spring and Summer Coring
Authors: Fu Jinmin , Dernoeden Peter H.
Published: January 2019

Carbohydrates provide energy required to maintain healthy plant growth in summer. Coring is performed periodically on creeping bentgrass (Agrostis stolonifera L.) putting greens for numerous reasons; however, its impact on carbohydrate metabolism in creeping bentgrass is unknown. The objectives of this 2-year field study were to examine the effects of coring on rates of photosynthesis (Pn) and whole plant respiration (Rw), and to quantify water-soluble carbohydrates [WSC (i.e., glucose, fructose, and sucrose)], storage carbohydrates [SC (i.e., fructan and starch], and total nonstructural carbohydrates [TNC (i.e., WSC + SC)] in creeping bentgrass leaves and roots during the summer. The study site was ‘Providence’ creeping bentgrass grown on a sand-based root zone and was maintained as a putting green. Three coring treatments were assessed as follows: spring-only coring, spring plus three summer corings, and a noncored control. Pn and Rw were measured about 21 d following coring with hollow tines. Pn and Rw rates generally were similar among all three coring treatments in both years. Hence, summer coring had no apparent negative impact on Pn or Rw. Leaf and root WSC, SC, and TNC levels were similar among coring treatments throughout the summer of each year. However, root TNC levels were lower in July of each year in spring plus summer-cored bentgrass versus other coring treatments. By September, leaves and roots from spring plus summer-cored creeping bentgrass had higher TNC levels when compared with spring-only or noncored bentgrass. Leaf and root SC levels from spring plus summer-cored bentgrass were also higher in September than were observed in noncored bentgrass. Spring plus summer coring benefited creeping bentgrass by promoting an accumulation of carbohydrates in late summer, which could assist plants in their recovery from summer stresses.
Tomato Fruit Shape Analysis Using Morphometric and Morphology Attributes Implemented in Tomato Analyzer Software Program
Authors: Gonzalo Maria Jose , Brewer Marin Talbot , Anderson Claire , Sullivan David , Gray Simon , van der Knaap Esther
Published: January 2019

Reliable analysis of plant traits depends on the accuracy of scoring the phenotype. We report here on the efficacy of two methods in the detection of quantitative trait loci (QTL) controlling fruit morphology in three segregating tomato (Solanum spp.) F2 populations using the software program, Tomato Analyzer. The first method uses fruit morphology attributes such as fruit shape index, blockiness, pear shape, indentation area, and angles of the fruit along the boundary. The second method uses morphometric points to quantify shape. The morphometric data were subjected to principle components analysis (PCA). QTL that control the fruit morphology attributes and the morphometric PCA were identified that revealed that the methods were comparable in that they resulted in nearly identical loci. Novel attributes were added to Tomato Analyzer that improved versatility of the program in measuring additional morphological features of fruit. We demonstrated that these novel attributes permitted identification of QTL controlling the traits.
Genetic Relationships among Slovenian Pears Assessed by Molecular Markers
Authors: Sisko Metka , Javornik Branka , Siftar Aleksander , Ivancic Anton
Published: January 2019

A sample of 94 pear (Pyrus L.) genotypes, traditionally present in the Slovenian landscape, was analyzed by amplified fragment length polymorphism (AFLP) and SSR (SSR), focusing on the assessment of genetic relationships. The analyzed samples involved germplasm of Pyrus communis L., P. nivalis Jacq., and P. pyraster L. The AFLP technique, using five EcoRI and MseI primer combinations, revealed molecular polymorphism at a level of 65.95%, representing 93 polymorphic bands among the total of 141 scored. With SSR analysis, 64 polymorphic alleles were found at seven microsatellite loci, with an average of 9.14 alleles per locus. Genetic distances among the individuals being studied were calculated using the Dice coefficient of similarity, and a dendrogram supported by AFLP and SSR data was constructed using the neighbor-joining method. The clustering method grouped the analyzed genotypes into three main clusters. The first cluster included the P. communis germplasm. The genotypes resembling P. nivalis were grouped in the second largest cluster, which could be divided in to four subclusters. The germplasm of P. pyraster, in this cluster, was found to be much less distinct than we had assumed. The most typical cultivar group in the third cluster was ‘Vinska Mostnica’. The study indicated that P. nivalis germplasm is frequently present in Slovenia, but not as a pure species.
Changes in Abundance of Enzymes Involved in Organic Acid, Amino Acid and Sugar Metabolism, and Photosynthesis during the Ripening of Blackberry Fruit
Authors: Famiani Franco , Walker Robert P.
Published: January 2019

Although information is available regarding the content of various metabolites such as sugars and organic/amino acids in blackberry (Rubus L.), little is known about its enzyme composition. The aim of this study was to investigate changes in the abundance of various enzymes during the ripening of blackberry. Blackberry is an aggregate fruit, composed of a receptacle and several drupelets attached to it, which in turn, are composed of the flesh (mesocarp plus epicarp) and seed enclosed in the endocarp; therefore, these parts were analyzed separately along with the pedicel. The enzymes studied participate in organic/amino acid and sugar metabolism and photosynthesis, processes known to be important in fruit development. These enzymes were phosphoenolpyruvate carboxykinase [PEPCK (EC:4.1.1.49)], phosphoenolpyruvate carboxylase [PEPC (EC:4.1.1.31)], pyruvate, orthophosphate dikinase [PPDK (EC:2.7.9.1)], cytosolic aspartate aminotransferase [cyt AspAT (EC:2.6.1.1)], aldolase (EC:4.1.2.13), glutamine synthetase [GS (EC:6.3.1.2)], and ribulose-1,5-bisphosphate carboxylase/oxygenase [RUBISCO (EC:4.1.1.39)]. To avoid problems in measuring enzyme activity, the approach taken was to use antibodies specific for each enzyme in conjunction with immunoblotting of sodium dodecyl sulfate polyacrylamide gel electrophoresis. During ripening, there were marked changes in abundance of several of these enzymes and these changes were dependent on the tissue investigated. PEPCK appeared when organic acids decreased in the flesh and was only detected in this tissue, whereas PPDK was not detected in any tissue. In the flesh, there was a large decrease in abundance of RUBISCO, plastidic GS, and plastidic aldolase, but little change in cytosolic GS, cytosolic aldolase, and PEPC. In seeds, there was a decrease in the abundance of all enzymes. In the receptacle and pedicel, apart from a large decrease in RUBISCO in the receptacle, there was little change in enzyme abundance.
Age-related Resistance of Diverse Cucurbit Fruit to Infection by Phytophthora capsici
Authors: Ando Kaori , Hammar Sue , Grumet Rebecca
Published: January 2019

Phytophthora capsici causes severe losses in vegetable production, including many cucurbit crops. Our previous work showed that cucumber (Cucumis sativus) fruit are most susceptible to P. capsici when they are very young and rapidly elongating, but develop resistance as they approach full length at 10 to 12 days postpollination (DPP). In this study, fruit from seven additional cucurbit crops representing four species, melon (Cucumis melo), butternut squash (Cucurbita moschata), watermelon (Citrullus lanatus), and zucchini, yellow summer squash, acorn squash, and pumpkin (Cucurbita pepo), were tested for the effect of fruit development on susceptibility to P. capsici. Field-grown fruit of the different crops varied in overall susceptibility. Zucchini and yellow summer squash were the most susceptible, with the majority of fruit exhibiting water-soaking symptoms within 24 hours postinoculation. Fruit from all of the crops exhibited size-related decrease in susceptibility, but to varying degrees. Cucumber had the most pronounced effect. In infested fields, cucumber fruit were found to be most frequently infected at the blossom end. Comparison of the peduncle and blossom end showed a difference in susceptibility along the length of the fruit for cucumber, butternut squash, and zucchini. Greenhouse-grown, hand-pollinated pumpkin, acorn squash, and butternut squash showed an age-related decrease in susceptibility similar to field-grown fruit. For all of these fruit, a pronounced reduction in susceptibility accompanied the transition from the waxy green to green stage at ≈3 to 8 DPP.
Leaf Chlorophyll Fluorescence Parameters and Huanglongbing
Authors: Sagaram Madhulika , Burns Jacqueline K.
Published: January 2019

Chlorophyll fluorescence and photochemical and nonphotochemical quenching parameters were measured in 20 genotypes of Citrus spp. or relatives grown in the greenhouse and commercial ‘Valencia’ sweet orange (Citrus sinensis) trees at two Florida locations. The purpose was to determine the utility of measurements for early huanglongbing [HLB (Candidatus Liberibacter asiaticus)] detection in asymptomatic trees and to examine the leaf response to HLB infection. Polymerase chain reaction (PCR)-negative healthy and PCR-positive symptomatic, asymptomatic, and distant asymptomatic leaves were used for fluorescence analysis using a portable chlorophyll fluorometer. Greenhouse-grown genotypes were separated into mild, moderate, and severe symptom groups based on leaf mottling, color, and size. In general, mild symptom genotypes were characterized by increased photosystem II (PSII) excitation pressure and unregulated heat dissipation and decreased regulated heat dissipation, whereas moderate and severe symptom genotypes increased loss of photosynthetic efficiency and increased unregulated and regulated heat dissipation. Distant asymptomatic leaves could be distinguished from healthy ones in moderate and severe symptom genotypes by increased total and regulated heat dissipation measurements. In the field, overall photosynthetic efficiency and total regulated heat dissipation measurements could distinguish between healthy and asymptomatic ‘Valencia’ sweet orange leaves at the location with slow or more recent infection, but not at the location where infection appeared to progress faster or was of longer duration. Starch content followed a similar pattern. The results indicate that no single measurement uniquely described the relationship between HLB and the host in asymptomatic and healthy leaves, but accuracy of field-based detection could be strengthened by a combination of total nonphotochemical quenching, overall photosynthetic efficiency, starch content, and PCR analyses. Chlorophyll fluorescence and quenching measurements suggest a PSII-based explanation for, and temperature dependency of, leaf symptom development.
Cold Acclimation Responses of Three Cool-season Turfgrasses and the Role of Proline-associated Pentose Phosphate Pathway
Authors: Sarkar Dipayan , Bhowmik Prasanta C. , Young-In-Kwon  , Shetty Kalidas
Published: January 2019

The role of the antioxidant response system in association with the proline-associated pentose phosphate pathway for cold adaptation was investigated in three cool-season turfgrasses during a cold acclimation period. As phenolic biosynthesis and antioxidant stimulation is proposed to be linked to the proline-associated pentose phosphate pathway, this study was aimed to determine the active role of proline in metabolic regulation and its relationship with the cold stress tolerance mechanism of cool-season turfgrasses. In this study, significant accumulation of total soluble phenolics and higher total antioxidant activity was observed in creeping bentgrass (Agrostis stolonifera L.), kentucky bluegrass (Poa pratensis L.), and perennial ryegrass (Lolium perenne L.) during cold acclimation, confirming the direct and indirect role of phenolics to counter low temperature-induced oxidative stress. A positive correlation between high phenolic content and the proline-associated pentose phosphate pathway was also found in investigated turfgrass species during a cold acclimation period. Low succinate dehydrogenase activity along with the high glucose-6-phosphate dehydrogenase activity in cold-acclimated turfgrass species suggested a probable shift of carbon flux from the energy-consuming tricarboxylic cycle to the alternative energy-efficient proline-associated pentose phosphate pathway to induce a better cold stress tolerance mechanism in these cool-season turfgrasses. Higher proline accumulation in cold-acclimated turfgrass species also supported the above findings and a probable proline oxidation to support mitochondrial oxidative phosphorylation was observed in acclimated kentucky bluegrass based on the activity of proline dehydrogenase, which likely supports the active metabolic role of proline in stress-induced situations. Through this study, a significant variation in cold stress tolerance mechanisms was observed among three investigated cool-season turfgrass species during cold acclimation. Furthermore, a high cold stress tolerance characteristic was observed in kentucky bluegrass by adapting a more efficient pathway for an antioxidant response linked to proline accumulation.
The Expression of Self-compatibility in Almond May Not Only Be Due to the Presence of the Sf Allele
Authors: Kodad Ossama , Socias i Company Rafel , Sánchez Ana , Oliveira M. Margarida
Published: January 2019

The pistil (S-RNase) and the pollen [S-haplotype-specific F-box protein (SFB)] components of the Sf
allele, presumably conferring self-compatibility in almond {Prunus amygdalus Batsch [syn. P. dulcis (Mill.) D.A. Webb]}, were identified and sequenced in ‘Ponç’, a local Spanish almond cultivar, confirming their identity with the published sequences of these components. Despite the presence of the Sf
allele, the ‘Ponç’ phenotype was self-incompatible as confirmed by different pollination tests, including self pollen tube growth, fruit set after self-pollination, and fruit set in bagged branches. However, the pistil and the pollen of ‘Ponç’ were fully viable when pollinated by a cross-compatible pollen or used on a cross-compatible pistil. The fact that ‘Ponç’ presents two different S-proteins with RNase activity may indicate an active function of its Sf
-RNase, whereas in the self-compatible almond cultivars thus far studied, the Sf
-RNase has been inactive. This activation indicates that the presence of the Sf
allele may not be the exclusive source of self-compatibility in almond, and other factors may also be involved in the expression of almond self-compatibility.
Selection of Stratified Core Sets Representing Wild Apple (Malus sieversii)
Authors: Richards Christopher M. , Volk Gayle M. , Reeves Patrick A. , Reilley Ann A. , Henk Adam D. , Forsline Philip L. , Aldwinckle Herb S.
Published: January 2019

We estimate the minimum core size necessary to maximally represent a portion of the U.S. Department of Agriculture's National Plant Germplasm System apple (Malus) collection. We have identified a subset of Malus sieversii individuals that complements the previously published core subsets for two collection sites within Kazakhstan. We compared the size and composition of this complementary subset with a core set composed without restrictions. Because the genetic structure of this species has been previously determined, we were able to identify the origin of individuals within this core set with respect to their geographic location and genetic lineage. In addition, this core set is structured in a way that samples all of the major genetic lineages identified in this collection. The resulting panel of genotypes captures a broad range of phenotypic and molecular variation throughout Kazakhstan. These samples will provide a manageable entry point into the larger collection and will be critical in developing a long-term strategy for ex situ wild Malus conservation.
Transcription Factor Families Regulate the Anthocyanin Biosynthetic Pathway in Capsicum annuum
Authors: Stommel John R. , Lightbourn Gordon J. , Winkel Brenda S. , Griesbach Robert J.
Published: January 2019

Anthocyanin structural gene transcription requires the expression of at least one member of each of three transcription factor families: MYC, MYB, and WD40. These transcription factors form a complex that binds to structural gene promoters, thereby modulating gene expression. Capsicum annuum L. (pepper) displays a wide spectrum of tissue-specific anthocyanin pigmentation, making it a useful model for the study of anthocyanin accumulation. To determine the genetic basis for tissue-specific pigmentation, we used real-time polymerase chain reaction to evaluate the expression of anthocyanin biosynthetic (Chs, Dfr, and Ans) and regulatory (Myc, MybA
, and Wd) genes in flower, fruit, and foliar tissue from pigmented and nonpigmented C. annuum genotypes. No differences were observed in expression of the Wd gene among these tissues. However, in all cases, biosynthetic gene transcript levels were significantly higher in anthocyanin-pigmented tissue than in nonpigmented tissues. MybA
and Myc transcript levels were also substantially higher in anthocyanin-pigmented floral and fruit tissues. Our results demonstrate that differential expression of C. annuum MybA
as well as Myc occurs coincident with anthocyanin accumulation in C. annuum flower and fruit tissues. In contrast to the situation in flowers and fruit, differential expression of MybA
and Myc was not observed in foliar tissue, suggesting that different mechanisms contribute to the regulation of anthocyanin biosynthesis in different parts of the C. annuum plant. Cloning and sequencing of MybA
genomic and cDNA clones revealed two introns of 249 and 441 bp between the R2R3 domains. Whereas the Myb R2R3 domains were conserved between C. annuum and Petunia ×hybrida Vilm., the sequence of the non-R2R3 domains was not conserved, with very little homology in these related Solanaceous species.
A Common Genetic Basis for Cross-sensitivity to Mesotrione and Nicosulfuron in Sweet Corn Hybrid Cultivars and Inbreds Grown throughout North America
Authors: Pataky Jerald K. , Williams Martin M. , Riechers Dean E. , Meyer Michael D.
Published: January 2019

Mutation of a cytochrome P450 (CYP) gene on the short arm of chromosome five, referred to as nsf1 or ben1, conditions sensitivity to certain P450-metabolized herbicides in corn (Zea mays L.). Previous research has shown that the sweet corn inbred Cr1 is sensitive to nicosulfuron, mesotrione, and at least seven other P450-metabolized herbicides with five different modes of action. Although the nsf1/ben1 CYP gene has not been sequenced from Cr1, a QTL that conditions cross-sensitivity to P450-metabolized herbicides was detected in a segregating population of Cr1 × Cr2 (herbicide tolerant) on the short arm chromosome five in tight linkage disequilibrium with the nsf1/ben1 CYP locus. Sweet corn hybrid cultivars and inbreds that had been identified in previous research as being susceptible to injury from P450-metabolized herbicides were tested in this study to determine if they were allelic with Cr1 for cross-sensitivity to nicosulfuron and mesotrione. These cultivars and inbreds were developed by 12 independent commercial breeding programs. These cultivars include sugary, sugary enhancer, and shrunken-2 endosperm types that are grown for processing and fresh consumption in markets throughout North America and in other temperate climates throughout the world. Each hybrid cultivar, their F2 progeny, and progeny from testcrosses of cultivars with Cr1 and Cr2 were evaluated for responses to mesotrione and nicosulfuron. Each inbred line, progeny from crosses of inbreds with Cr1 and Cr2, and F2 progeny from crosses of inbreds with Cr1 were also tested. Based on segregation of progeny from testcrosses with Cr1 and Cr2 and the F2 generation, 45 sweet corn hybrid cultivars and 29 sweet corn inbreds, including lines from each of the 12 breeding programs, appeared to be sensitive to nicosulfuron and mesotrione as the result of a gene that is the same as or very closely linked to the gene in Cr1. None of the cultivars or inbreds appeared to be sensitive to these herbicides as a result of other independent genes; however, additional genes that modify responses to these herbicides may be present in a few cases. The presence of a gene conditioning sensitivity to nicosulfuron and mesotrione, and probably to several other P450-metablolized herbicides, provides an explanation for varied levels of injury and inconsistent responses of sweet corn hybrid cultivars under differing environmental conditions. This information provides a basis from which an industry-wide concern with herbicide sensitivity in sweet corn can be addressed by various methods, including the elimination of an allele rendering germplasm sensitive.
Interspecific Crosses and Backcrosses between Diploid Vaccinium darrowii and Tetraploid Southern Highbush Blueberry
Authors: Chavez Dario J. , Lyrene Paul M.
Published: January 2019

Diploid Vaccinium darrowii Camp has been used in breeding tetraploid southern highbush blueberry (Vaccinium corymbosum L.) as a source of reduced chilling requirement, adaptation to hot, wet summers, and resistance to leaf diseases. V. darrowii in Florida is quite variable, but most crosses have involved only one V. darrowii clone, Fla. 4B. The use in breeding of a wider range of V. darrowii accessions would provide beneficial diversity in the blueberry cultivated gene pool. The purpose of this research was to determine the functional 2n gamete frequency of numerous V. darrowii genotypes when crossed with tetraploid V. corymbosum, and to study the pollen fertility and backcross ability of the interspecific (V. darrowii × V. corymbosum) hybrids to V. corymbosum. Crosses between diploid V. darrowii and tetraploid highbush blueberry cultivars had low fruit set compared with the V. darrowii × V. darrowii and highbush × highbush crosses. The unusually high number of hybrids per pollinated flower (HPF) in certain 4x-2x or 2x-4x crosses was attributed to high functional 2n gamete production in certain V. darrowii genotypes. Diploid Vaccinium fuscatum Aiton and diploid V. darrowii × V. fuscatum hybrids, when crossed with southern highbush blueberry cultivars, were equally productive of hybrids whether used as male or female parents. Variation in frequency of functional 2n gametes in V. darrowii, expressed as high HPF, was present within plants (megaspores vs. microspores) and among V. darrowii plants. Of the 114 interspecific (V. darrowii × V. corymbosum) hybrids studied, 106 had pollen stainability >50%. This indicated that most of these hybrids were tetraploid, because triploid blueberries, like most triploid plants, are highly sterile. Twenty-two V. darrowii × V. corymbosum hybrids were backcrossed to tetraploid highbush blueberry cultivars. Fruit set was variable, but large populations of vigorous hybrids were obtained. Lower fruit set was associated with hybrids that had lower pollen fertility. It should be possible to obtain plants of cultivar quality in a few generations of backcrosses.
Molecular Mapping of Ty-4, a New Tomato Yellow Leaf Curl Virus Resistance Locus on Chromosome 3 of Tomato
Authors: Ji Yuanfu , Scott Jay W. , Schuster David J. , Maxwell Douglas P.
Published: January 2019

Resistance to begomoviruses, including bipartite tomato mottle virus (ToMoV) and monopartite tomato yellow leaf curl virus (TYLCV), has been introgressed to cultivated tomato (Solanum lycopersicum) from Solanum chilense accessions LA1932 and LA2779. A major gene, Ty-3, responsible for resistance to ToMoV and TYLCV was previously mapped on the long arm of chromosome 6. In the present study, we identified a 14-cM S. chilense introgression on the long arm of chromosome 3 in some resistant breeding lines derived from LA1932. A new begomovirus resistance locus, Ty-4, was mapped to the 2.3-cM marker interval between C2_At4g17300 and C2_At5g60160 in the introgression. Analysis of a population segregating for Ty-3 and Ty-4 demonstrated that Ty-3 accounted for 59.6% of the variance, while Ty-4 only accounted for 15.7%, suggesting that Ty-4 confers a lesser effect on TYLCV resistance. Recombinant inbred lines (RILs) with Ty-3 and Ty-4 had the highest level of TYLCV resistance. The PCR-based markers tightly linked to the Ty-4 locus as well as the Ty-3 locus have been recently used in our breeding program for efficient selection of high-levels of begomovirus resistance and now allow for efficient breeding by marker-assisted selection.
Salt-induced and Salt-suppressed Proteins in Tomato Leaves
Authors: Zhou Suping , Sauve Roger , Fish Tara , Thannhauser Theodore W.
Published: January 2019

Tomato (Solanum lycopersicum cv. Money Maker) seedlings at the two-leaf stage were grown in one-half strength Hoagland solution supplemented with 50 mm NaCl for 4 days, with 100 mm NaCl for 4 days, with 150 mm NaCl for 4 days, and with a final concentration 200 mm NaCl for 2 days. Solutions were refreshed every 2 days for treated and untreated seedlings. Non-treated plants were grown in nonamended one-half strength Hoagland solution. Three biological replicates (BR) were included for treated and control experiments. At the end of treatments, the uppermost three newly expanded leaves from all 12 plants in each BR were collected and bulked to extract total protein. Proteomic analysis resulted in the identification of several salt-induced and salt-suppressed proteins. Salt-induced proteins were: vacuolar H+-ATPase A1 subunit isoform (1.6-fold), germin-like protein (1.5-fold), ferredoxin-NADP (+) reductase (1.2-fold), quinone oxidoreductase-like protein (4.4-fold), heat-shock protein (4.9-fold), and pyrophosphorylase (1.7-fold). Salt-suppressed proteins were: ATPase alpha subunit (−1.5-fold) and rubisco activase (−1.4-fold). Proteins identified in this study affect cellular activities for antioxidant, stress protection, carbon fixation, and carbohydrate partitioning in young tomato leaves under salt stress.
Exogenous Cytokinin Induces “Out of Season” Flowering in Protea cv. Carnival
Authors: Hoffman Eleanor W. , Bellstedt Dirk U. , Jacobs Gerard
Published: January 2019

The cytokinin concentration in the xylem sap of Protea L. cv. Carnival (Protea compacta R. Br. × Protea neriifolia R. Br.) shoots was determined at regular intervals from 11 weeks before until 10 weeks after spring budbreak. Cytokinin levels were high during the early phases of spring shoot growth. Benzyladenine (BA) at 50, 250, or 500 mg·L−1 was applied to entire shoots on 22 Feb., 12 Apr., and 22 May 2001 (fall in the southern hemisphere) or only to terminal buds on 22 May 2001 at 500 mg·L−1. Most of the terminal buds sprouted and initiated an inflorescence when BA application at 500 mg·L−1 in May was directed only to terminal buds, whereas lower flowering percentages (0%–35%) were achieved when the entire shoot was treated. After whole shoots were treated with BA in Apr. 2001, between 5% and 45% floral reversion was observed. High flowering percentages of 87% to 93% were recorded when BA was applied at 500 mg·L−1 to the terminal bud in the dormant state or up to the stage when sprouting buds reached the green point development stage. Later applications were less effective, inducing 42% to 43% inflorescence initiation. The flowering time of BA-induced inflorescences was advanced by more than 2 months compared with flowers that initiated naturally on the spring flush.
Particle Film Mechanisms of Action That Reduce the Effect of Environmental Stress in ‘Empire’ Apple
Authors: Glenn David M.
Published: January 2019

Heat stress is a limiting factor of plant productivity throughout the world and kaolin-based particle films (PF) have demonstrated that the reflective nature of the resulting plant surface can increase plant productivity primarily by reducing temperature in fruit, leaf, and canopy. The purpose of this study was to evaluate the environmental mechanisms and related physiological responses of ‘Empire’ apple (Malus ×domestica) gas exchange at the canopy level to PF treatments to identify those parameters key to plant response and increased plant productivity. Trees received either no treatment or season-long applications of a PF treatment and each treatment either received no supplemental irrigation or full replacement of evapotranspiration. Studies were begun in 1998 and continued to 2007. Fruit number and fruit weight were measured in all years. Whole canopy carbon dioxide assimilation rates (A) were measured in apple for a 4-year period to determine the relationship with incoming light and vapor pressure deficit (VPD) levels. The photosynthetic response to the irrigation and PF treatments varied between years as a result of environmental variation in VPD and photosynthetically active radiation (PAR) levels. There was a unique treatment response for PAR levels greater than 1600 μmol·m−2·s−1 in which the combination of PF and irrigation maintained midday A at maximum levels compared with other treatments although A was reduced by increasing VPD. This response indicated that although VPD limited A, the combination of PF and adequate water could maintain maximum A rates at full sun levels during the midday period and minimize the midday depression of A that is commonly observed and reduces the daily carbon accumulation. The increased carbon accumulation during the midday period was likely partitioned to the fruit. Increased fruit weight resulting from the PF treatment, compared with the control, was positively correlated with the growing season air temperature and VPD indicating that as the environment becomes hotter and/or drier, the magnitude of the PF response increased as a result of the reduced leaf and fruit temperature and the subsequent physiological effect. The PF treatments reduced radiation and heat load on exposed leaves enabling them to better regulate leaf temperature and improved the light distribution inside the canopy resulting in increased carbon gain at the whole plant scale. Fruit hue angle was reduced and red color improved by PF treatments in 5 of 10 years. The use of PF may be an effective substitute for evaporative cooling to reduce solar injury and to improve apple quality through increased fruit weight. The results indicate that benefits of PF treatments would occur in agroecosystems with large VPDs and high temperatures and that use of irrigation would further enhance the benefits at high PAR levels.
Membrane Polar Lipid Changes in Zoysiagrass Rhizomes and Their Potential Role in Freezing Tolerance
Authors: Zhang Qi , Fry Jack , Rajashekar Channa , Bremer Dale , Engelke Milton
Published: January 2019

Cell membranes play an integral role in freezing tolerance. The objectives of this study were to quantify polar lipids in cold-tolerant ‘Meyer’ zoysiagrass (Zoysia japonica) and cold-sensitive ‘Cavalier’ zoysiagrass (Zoysia matrella) and to evaluate their potential role in freezing tolerance. Grasses were acclimated outside and sampled once monthly between October and January to determine freezing tolerance and lipid composition in rhizomes. Lowest LT50s (temperature resulting in 50% survival) were observed in November for ‘Cavalier’ (−8.5 and −9.6 °C in 2005 and 2006, respectively) and December for ‘Meyer’ (−16.2 and −15.4 °C in 2005 and 2006, respectively). The most abundant lipids in zoysiagrass rhizomes were monogalactosyl diacylglycerol, digalactosyl diacylglycerol, phosphatidylcholine, phosphatidylethanolamine, and phosphatidic acid, which comprised 90% of the polar lipids. Differences in lipid contents and double bond indices (DBI) were detected between ‘Meyer’ and ‘Cavalier’ during cold acclimation, but there were no consistent relationships between lipid classes or DBI and freezing tolerance in zoysiagrass.
Generation of a Mutant Population for TILLING Common Bean Genotype BAT 93
Authors: Porch Timothy G. , Blair Matthew W. , Lariguet Patricia , Galeano Carlos , Pankhurst Clive E. , Broughton William J.
Published: January 2019

Common bean (Phaseolus vulgaris) is the major food legume worldwide, making it an important target for novel approaches of genetic analysis. This study evaluated the use of ethyl methane sulfonate (EMS) for the generation of a mutant population for targeted induced local lesions in genomes (TILLING) in common bean. TILLING is a powerful reverse genetics approach that uses a large mutant population for identification of mutants in loci of interest. Based on overall survival, development, and yield of treated seed, 40 mm EMS was found to be an appropriate concentration for the generation of a mutant population in common bean genotype BAT 93. Higher concentrations of EMS resulted in survival rates of less than 10% and lower concentrations resulted in the generation of fewer mutants. Based on TILLING results from other species, a population of 5000 lines is estimated to be sufficient for saturation of the common bean genome. Phenotypic mutation frequencies and the isolation of targeted mutations in the BAT 93 mutant population indicate that mutagenesis was effective.
Production and Identification of Colchicine-derived Tetraploid Vaccinium darrowii and Its Use in Breeding
Authors: Chavez Dario J. , Lyrene Paul M.
Published: January 2019

In Vaccinium L., most tetraploid hybrids between tetraploid cultivated highbush blueberry (V. corymbosum L.) and diploid darrow's evergreen blueberry (V. darrowii Camp) have been produced by exploiting V. darrowii's tendency to produce 2n gametes and a strong triploid block, which greatly reduces the number of triploid hybrids produced. Colchicine-derived tetraploids offer an alternative method of producing V. darrowii plants that will easily cross with tetraploid Vaccinium species. V. darrowii (2n = 2x = 24) seeds were imbibed in 0.2% aqueous colchicine solution for 24 h. The seeds were germinated and seedlings whose morphology suggested colchicine effects were selected at various stages of development. No macromorphological changes were consistently associated with chromosome doubling. However, stomatal guard cells and pollen size increased substantially as a result of chromosome doubling. Several types of plants were identified after colchicine treatment: 1) plants with a doubled LI (epidermal tissues) and LII (internal tissues) plant layers; 2) periclinal chimeras with a doubled LI layer and a normal LII; and 3) periclinal chimeras with a doubled LII layer and a normal LI. Of ≈4000 seedlings that emerged from colchicine-treated seeds, 200 were selected for further examination based on leaf and stem morphology. Of the 200, five appeared to be tetraploid in LI, LII, or both layers based on stomatal guard cell size and pollen size. Crosses between colchicine-derived V. darrowii (4x) plants and southern highbush blueberry (V. corymbosum) cultivars (4x) were successful compared with 4x–2x and 2x–4x crosses using diploid V. darrowii and tetraploid southern highbush blueberry. Stomatal guard cells and pollen screening of the colchicine-treated plants were used as indicators of doubled V. darrowii plants and periclinal chimeras. The results from the crosses between colchicine-treated V. darrowii plants and tetraploid highbush blueberry cultivars confirmed the information obtained by stomata and pollen screening.
Synergistic Effects of Elevated CO2 and Fertilization on Net CO2 Uptake and Growth of the CAM Plant Hylocereus undatus
Authors: Weiss Israel , Mizrahi Yosef , Raveh Eran
Published: January 2019

This study examined the response of the crassulacean acid metabolism (CAM) vine-cactus fruit crop species Hylocereus undatus to two CO2 regimes [enrichment (1000 μmol·mol−1) vs. ambient control (380 μmol·mol−1)] and to two fertilization regimes [0.5- vs. 0.1-strength Hoagland's solution (designated high and low, respectively)]. CO2 enrichment increased total daily net CO2 uptake, nocturnal acid accumulation, shoot elongation, and total dry mass by 39%, 24%, 14%, and 6% (averaging the two fertilization regimes) versus ambient CO2 treatment, respectively. Plants exposed to high fertilization demonstrated 36%, 21%, 198%, and 79% (averaging the two CO2 regimes) increases versus those receiving the low fertilization regime in total daily net CO2 uptake, nocturnal acid accumulation, stem elongation, and total dry mass, respectively. Plants exposed to high fertilization and elevated CO2 demonstrated 108%, 77%, 264%, and 111% increases versus those receiving the low fertilization regime at the ambient CO2 concentration in total daily net CO2 uptake, nocturnal acid accumulation, stem elongation, and total dry mass, respectively. This response was 25% to 71% higher than the summed effects of the separate responses to each factor, indicating a synergistic effect of elevated CO2 and high fertilization. Thus, it is apparent that H. undatus crops grown under a high-fertilization agromanagement regime may benefit from elevated CO2 to a greater extent than those grown with low fertilization.
Partitioning Phosphorus and Potassium in Pecan Trees during High- and Low-crop Seasons
Authors: Smith Michael W.
Published: January 2019

Potassium (K) and phosphorus (P) partitioning were characterized in bearing pecan [Carya illinoinensis (Wangenh.) K. Koch] trees at selected times of the year during three successive years. The first-year trees had little to no crop, followed by a small crop the second year, and a near optimal to excess crop during the third year. Trees bearing a large crop accumulated more K and P in July than trees with little or no crop. K and P content in trees increased from budbreak until July, and then decreased until budbreak the following year. Allocation patterns of K and P among tree components changed during the growing season, with the greatest changes occurring in the annual plant parts. Results indicate that leaves were the principal source of labile K and P for developing fruit. A rapid accumulation of K in the fruit with a concurrent loss from leaves started in July when fruit began a rapid volume increase that continued during carbohydrate deposition in the cotyledon. At first, detectable shuck split K transported to the fruit ceased, but leaf K was partially replenished, presumably from K in perennial tissue because total tree K was static or decreased slightly. In contrast, rapid P transport to fruit began after fruit expansion while cotyledons were developing, presumably associated with oil synthesis and after initial shuck split for storage. Leaf P content continued to decline until leaves were killed by freezing temperatures in the fall. Data indicate that potentially large crops signal additional early season K and P absorption and accumulation in leaves and other tissue long before the fruit are strong K and P sinks. This suggests a complex signaling mechanism, essentially telegraphing a copious demand during the latter part of the growing season.