Leandro Mozzoni

Genetic Analysis of High Sucrose, Low Raffinose, and Low Stachyose Content in V99-5089 Soybean Seeds

Seed sugar content is an important trait for food-grade soybeans [ Glycine max (L.) Merr.]. Few reports exist on the genetics of soybean seed sucrose and oligosaccharides contents. The objective of this research was to determine the inheritance of high sucrose and low raffinose and stachyose contents in V99-5089 soybean seeds. The sucrose, raffinose, and stachyose contents were investigated in 125 F3-derived progenies developed from a cross between ‘Ozark’ and V99-5089. The bimodal distribution with good fit to single gene segregation ratio was observed for sucrose content with high sucrose as recessive, for raffinose content with low raffinose as recessive, and for stachyose content with low stachyose as recessive in the V99-5089-derived population. Strong correlations were recorded between sucrose and raffinose (r = −0.88) and between sucrose and stachyose (r = −0.96), indicating that the desirable food-grade soybean progenies with high sucrose and low oligosaccharides content (low raffinose and low stachyose) can be selected from V99-5089-derived populations. This research provides breeders an excellent germplasm, i.e., V99-5089, with high sucrose, low raffinose, and low stachyose content to use as parent in soybean food-grade breeding programs.

Differentiation of Bean pod mottle virus isolates based upon host symptoms

Accessions from Glycine, Phaseolus, and Vigna genera were screened for their reactions to different subgroups of isolates of Bean pod mottle virus (BPMV) in order to establish a differential host system. Screening results indicated that the BPMV isolates differed in pathogenic aggressiveness but not in virulence. No major resistance genes were found in soybean (Glycine max) or G. soja since all screened accessions showed mosaic or necrotic symptoms to BPMV inoculation. However, these accessions expressed differences in severity of symptoms when challenged by various BPMV isolates. The inoculation of G. tomentella accessions did not result in mosaic symptoms, and some accessions did not support systemic infection of some of the isolates. Resistance, presented as a hypersensitive reaction, was observed in some of Phaseolus and Vigna genotypes, and resistant response or susceptibility was stable to all the isolates used in the screening. In conclusion, the selected G. soja genotypes PI 407019, PI 464889A, and PI 464928, and ‘Amsoy 71’ soybean may help to separate severe (reassortant) from mild isolates of BPMV based upon their phenotypic reactions.

Genetic Analysis of Resistance to Sudden Death Syndrome Caused by Fusarium virguliforme in Hartwig Soybean

Host resistance is the most effective strategy for soybean (Glycine max) sudden death syndrome (SDS) management. The objective of this study was to determine the inheritance of resistance to SDS in soybean cv. Hartwig under greenhouse conditions. One-hundred and fifty F2:3 lines derived from the cross of the SDS-resistant cultivar ‘Hartwig’ with the SDS-susceptible cultivar ‘Camp’ were inoculated with sorghum seeds colonized with a F. virguliforme reference isolate from Arkansas (AR-171). The experiment was arranged in a randomized complete-block design with two replications. Each block included a pot of each F2:3 line and two pots of each parent with eight plants per pot. The experiment was repeated to give a total of four replications. Disease incidence (DI) and disease severity (DS) were rated on a pot basis at 21 and 28 days post-inoculation. A disease index (DX) was calculated as ((DI x DS)/11). The 95% confidence intervals (CI) for DX of the parents were calculated and used to classify the F2:3 lines as susceptible, resistant or segregating. Segregating lines were scored on an individual plant basis. Chi-square tests determined the goodness-of-fit of observed F2:3 segregation data to the expected genetic ratios. Hartwig (SDS-R) and Camp (SDS-S) consistently had low and high DX ratings, respectively. The DX of SDS foliar ratings of the F2:3 lines segregated in a 7:8:1 (resistant:segregating:susceptible) ratio (χ2 = 4.514, P = 0.1046), indicating that Hartwig carries two dominant genes conferring resistance to SDS and can serve as a good source of resistance for crossing in a breeding program.

Quantitative trait loci for salt tolerance in soybean

ABSTRACT Soybean [Glycine Max (L.) Merr.] growth and yield are adversely affected by soil salinity. Identification of salinity tolerance genes that improve soybean performance in saline soils is a highly effective way to use and develop soybean genotypes with high salt tolerance. The objective of this study is to identify and confirm quantitative trait loci (QTL) associated with salt tolerance using an F2:3 mapping population derived from the cross Ozark (salt-sensitive) × Jake (salt-tolerant). This population was screened in the greenhouse for salt stress using 120 mM NaCl and evaluated for leaf scorch score (LSS), percentage of dead plants (PDP), leaf chlorophyll, and leaf chloride content, and genotyped using a SoySNP 6K chip. A major QTL on chromosome 3 was confirmed, and a minor QTL on chromosome 19 and additional single nucleotide polymorphism (SNP) markers associated with salt tolerance were found in this study. These markers, once validated, will be valuable for marker-assisted selection in a soybean breeding program.