Assessment of the individual and combined effects of Rht8 and Ppd-D1a on plant height, time to heading and yield traits in common wheat

Grain yield in cereal crops is a complex trait controlled by multiple genes and influenced by developmental processes and environment. Here we report the effects of alleles Rht8 and Ppd-D1 a on plant height, time to heading, and grain yield and its component traits. Association analysis and quantitative trait locus mapping using phenotypic data from 15 environments led to the following conclusions. First, both Rht8 and Ppd-D1 a reduce plant height. However, Ppd-D1 a but not Rht8 causes earlier heading.Second, both Rht8 and Ppd-D1 a promote grain yield and affect component traits. Their combined effects are substantially larger than those conferred by either allele alone.Third, promotion of grain yield by Rht8 and Ppd-D1 a is through increasing fertile spikelet number. We speculate that Rht8 and Ppd-D1 a act independently and additively in control of plant height, grain yield and yield component. Combination of the two alleles is desirable for adjusting plant height and enhancing grain yield and abiotic stress tolerance.

Improvement on Mixograph test through water addition and parameter conversions

To improve Mixograph testing effect, Farinograph measurements were adopted as a quality standard and changes in water absorption and parameter conversion in Mixograph test were explored. Comparative study showed that increasing water absorption to about 73% and converting original parameters to compound parameters in Mixograph tests signiifcantly increased their predictive power for lfour quality. These efforts also enabled the adoption of ifxed water addition level in Mixograph test and simpliifed the test procedure signiifcantly. With the success in parameter conversions, Mixograph test results were successful y described by Farinograph parameters, which al ow breeders to compare and exchange test results easily. Al these changes optimized the ofifcial method of Mixograph test with simpliifed procedure and enhanced reliability and made the Mixograph being the superior tool for quality assessment in wheat-breeding programs.

Genetic Analysis of Chromosomal Loci Affecting the Content of Insoluble Glutenin in Common Wheat

In common wheat, insoluble glutenin （IG） is an important fraction of flour glutenin macropolymers, and insoluble glutenin content （IGC） is positively associated with key end-use quality parameters. Here, we present a genetic analysis of the chromosomal loci affecting IGC with the data collected from 90 common wheat varieties cultivated in four environments. Statistical analysis showed that IGC was controlled mainly genetically and influenced by the environment. Among the major genetic components known to affect end-use quality, 1BL/1RS translocation had a significantly negative effect on IGC across all four environments. As to the different alleles of Glu-A1, -B1 and -D1 loci, Glu-Ala, Glu-Blb and Glu-Dld exhibited relatively strong positive effects on IGC in all environments. To identify new loci affecting IGC, association mapping with 1355 DArT markers was conducted. A total of 133 markers were found associated with IGC in two or more environments （P 〈 0.05）, ten of which consistently affected IGC in all four environments. The phenotypic variance explained by the ten markers varied from 4.66% to 8.03%, and their elite alleles performed significantly better than the inferior counterparts in enhancing IGC. Among the ten markers, wPt-3743 and wPt-733835 reflected the action of Glu-D1, and wPt-664972 probably indicated the effect of GIu-A1. The other seven markers, forming three clusters on 2AL. 3BL or 7BL chromosome arms, represented newly identified genetic determinants of IGC. Our work provided novel insights into the genetic control of IGC, which may facilitate wheat end- use quality improvement through molecular breeding in the future.