Linghe Zeng

Comparative Transcriptional Profiling of Two Contrasting Rice Genotypes under Salinity Stress during the Vegetative Growth Stage

Rice (Oryza sativa), a salt-sensitive species, has considerable genetic variation for salt tolerance within the cultivated gene pool. Two indica rice genotypes, FL478, a recombinant inbred line derived from a population developed for salinity tolerance studies, and IR29, the sensitive parent of the population, were selected for this study. We used the Affymetrix rice genome array containing 55,515 probe sets to explore the transcriptome of the salt-tolerant and salt-sensitive genotypes under control and salinity-stressed conditions during vegetative growth. Response of the sensitive genotype IR29 is characterized by induction of a relatively large number of probe sets compared to tolerant FL478. Salinity stress induced a number of genes involved in the flavonoid biosynthesis pathway in IR29 but not in FL478. Cell wall-related genes were responsive in both genotypes, suggesting cell wall restructuring is a general adaptive mechanism during salinity stress, although the two genotypes also had some differences. Additionally, the expression of genes mapping to the Saltol region of chromosome 1 were examined in both genotypes. Single-feature polymorphism analysis of expression data revealed that IR29 was the source of the Saltol region in FL478, contrary to expectation. This study provides a genome-wide transcriptional analysis of two well-characterized, genetically related rice genotypes differing in salinity tolerance during a gradually imposed salinity stress under greenhouse conditions.

Evaluation of salt tolerance in rice genotypes by physiological characters

AbstractThe use of physiological characters as selection criteria in salt tolerance breeding requires the identification of the contribution each individual character makes to salt tolerance. Rice genotypes were evaluated for salt tolerance in terms of grain yield and physiological characters. Plants of twelve genotypes were grown in sand tanks in a greenhouse and irrigated with Yoshida nutrient solution. Sodium chloride and calcium chloride (5:1 molar ratio) were added at two concentrations to give moderate (4.5 dS m-1) and high (8.3 dS m-1) salinity treatments. One set of plants was harvested at 635 °Cċd (accumulative thermal time) after planting to determine LAI and mineral ion concentrations. Another set of plants was allowed to grow to maturity. High genotypic diversity for LAI and shoot ion contents was observed. LAI contributed the most to the variation of the grain yield under salt stress. Significantncorrelations between LAI and yield components in both salt-tolerant and-sensitive genotypes further confirmed the significant contribution of LAI to grain yield. K-Na selectivity increased with increasing salinity. Conversely, Na-Ca selectivity decreased with increasing salinity. Significant correlations were identified between grain yield and both Na-Ca and K-Na selectivity. Highly significant (p<0.001) correlations were identified between Na-Ca selectivity and the rankings among genotypes for grain yield. Thus, Na-Ca selectivity could be one salt tolerance component and an useful selection criterion in screening for salt tolerance.

Identification of associations between SSR markers and fiber traits in an exotic germplasm derived from multiple crosses among Gossypium tetraploid species.

Genetic improvement in yield and fiber quality is needed for worldwide cotton production. Identification of molecular markers associated with fiber-related traits can facilitate selection for these traits in breeding. This study was designed to identify associations between SSR markers and fiber traits using an exotic germplasm population, species polycross (SP), derived from multiple crosses among Gossypium tetraploid species. The SP population underwent 11 generations of mixed random mating and selfing followed by 12 generations of selfing. A total of 260 lines were evaluated for fiber-related traits under three environments in 2005 and 2006. Large genotypic variance components in traits were identified relative to components of genotypexa0×xa0environment. Eighty-six primer pairs amplified a total of 314 polymorphic fragments among 260 lines. A total of 202 fragments with above 6% allele frequency were analyzed for associations. Fifty-nine markers were found to have a significant (Pxa0<xa00.05, 0.01, or 0.001) association with six fiber traits. There were six groups identified within the population using structure analysis. Allele frequency divergence among six groups ranged from 0.11 to 0.27. Of the 59 marker–trait associations, 39 remained significant after correction for population structure and kinship using a mixed linear model. The effect of population sub-structure on associations was most significant in boll weight among the traits analyzed. The sub-structure among the SP lines may be caused by natural selection, the breeding method applied during development of inbred lines, and unknown factors. The identified marker–trait associations can be useful in breeding and help determine genetic mechanisms underlying interrelationships among fiber traits.

Genotypic and environmental effects on cottonseed oil, nitrogen, and gossypol contents in 18 years of regional high quality tests

Determination of environmental influence on seed traits is critical for genetic improvement of seed quality in upland cotton (Gossypium hirsutum L.). The objective of this study was to analyze the relative contribution of environment and genotype (G) for seed oil, nitrogen (N), and gossypol contents using historical data from the regional high quality (RHQ) tests conducted from 1996 through 2013. The 18-year tests of RHQ were divided into six 3-year cycles with an average of about 20 genotypes and 7–10 testing locations (loc) in each cycle. Variance components of oil, N, and gossypol contents were estimated in each cycle and expressed as percentages of the total variance. Highly significant Gxa0×xa0loc effects were identified for all seed quality traits in each cycle. For oil content, variance estimates of G to the total variance ranged from 20 to 57xa0% in different cycles. For N content, loc was the main source of variance with variance estimates of loc to the total variance ranging from 44 to 73xa0% in different cycles. In most cycles, loc and G were the main source of variance for free-gossypol content. For most seed quality traits, there was not a clear trend of changes among testing cycles for the variance estimates of G to the total variance. Broad-sense heritability for oil content, N content, and free-gossypol ranged from 0.79 to 0.96, 0.65 to 0.86, and 0.28 to 0.93, respectively. Highly significant Gxa0×xa0loc interactions indicate that multiple location trials for testing seed quality traits are necessary. However, heritability estimates for these seed traits indicate stability across environments as well as the potential for genetic improvement. Significant reduction in seed index was observed in half of the testing cycles with a range of 10.4–9.52 within cycles. Correlation between seed index and oil content was positive with r values ranging from 0.23 to 0.77 in different cycles.

Commonality analysis and selection of parents for within-boll yield components in upland cotton

AbstractRelationshipsn between lint yield and within-boll yield components are important for genetic improvement of lint yield in cotton (Gossypium hirsutum L.) cultivars. F2 plants derived from crosses between germplasm lines and high yielding cultivars were analyzed to determine the contributions of within-boll yield components to lint yield and to select parents with desirable combining ability for multiple within-boll yield components. Forty-five F2 hybrids were planted at two field sites in 2010 and 2011 with 4 and 3 replicates, respectively. There were a total of six yield components analyzed including lint percentage (LP), seed number per boll, lint weight per seed (LW_S), seed surface area per seed, lint weight per unit seed surface area (LW_SA), and lint number per unit seed surface area (LN_SA). The contributions of these yield components to lint yield were analyzed by commonality analysis that separated the contributions to lint yield into the unique contributions of single yield components and the common contributions of the single yield components with one or more other yield components. The unique contributions of the six yield components to lint yield ranged from 1.6 to 21xa0% of total variation for lint yield in the 2-year experiments. The greatest common contributions to lint yield among all combinations of the six yield components were identified for a combination of four components, LP, LW_S, LW_SA, and LN_SA with 67 and 44xa0% of the total variation of lint yield in 2010 and 2011, respectively. Results suggest that all four of these yield components should be considered simultaneously in breeding for genetic improvement of lint yield. The germplasm line SP225 was detected as a good combiner with positive general combining ability (GCA) for LP (1.4xa0%), LW_SA (0.03xa0mgxa0mm−2), and LN_SA (14.3 no mm−2), and favorable GCA for fineness (−3.1xa0mgxa0km−1).

Correlated selection responses of fiber properties measured by high volume instrument and advanced fiber information system in Upland cotton

Fiber properties measured by high volume instrument (HVI) and advanced fiber information system (AFIS) are currently being used in Upland cotton (Gossypium hirsutum L.) breeding. It would be interesting to know if it is equally efficient in selection for parameters measured by the two instrumental systems and how are the correlated selection responses of the parameters between the two systems. A study was designed to determine the correlated selection responses between fiber properties measured by the two systems in F3, F4, and F5 generations of two crosses, FM 832xa0×xa0SP 205 and MD 52nexa0×xa0JJ 1145ne. Selections for HVI-fiber length, HVI-short fiber content, and HVI-maturity were made in the F3 generation and the correlated responses of AFIS-fiber properties to the selections were estimated in the subsequent F4 and F5 generations. Selections for AFIS-fiber length, AFIS-short fiber content, and AFIS-maturity were made in the F4 generation and the correlated responses of HVI-fiber properties to the selections were estimated in the F5 generation. Moderate to high realized heritability was identified for both HVI- and AFIS-fiber properties. Significant correlated selection responses of fiber length and maturity between the HVI and AFIS methods were consistently observed in both crosses, suggesting similar genetic basis for fiber length and maturity measured by HVI and AFIS. Therefore, equal effectiveness is expected of the selection for both traits by the two instrumental systems. Correlated selection responses of short fiber content parameters between the HVI and AFIS methods were not consistent, suggesting a possible different genetic basis or differential variations of measurement quality between the two systems.