Identification of Quantitative Trait Loci for Grain Appearance and Milling Quality Using a Doubled-Haploid Rice Population

Improving grain quality, which is composed primarily of the appearance of the grain and its cooking and milling attributes, is a major objective of many rice-producing areas in China. In the present study, we conducted a marker-based genetic analysis of the appearance and milling quality of rice （Oryza sativa L.） grains using a doubled-haploid population derived from a cross between the indica inbred Zhenshan 97 strain and the japonica inbred Wuyujing 2 strain. Quantitative trait locus （QTL） analysis using a mixed linear model approach revealed that the traits investigated were affected by one to seven QTLs that individually explained 4.0%-30.7% of the phenotypic variation. Cumulatively, the QTL for each trait explained from 12.9% to 61.4% of the phenotypic variation. Some QTLs tended to have a pleiotropic or location-linked association as a cause of the observed phenotypic correlations between different traits. Improvement of the characteristics of grain appearance and grain weight, as well as an improvement in the milling quality of rice grains, would be expected by a recombination of different QTLs using marker-assisted selection.

Identification of QTL and underlying genes for root system architecture associated with nitrate nutrition in hexaploid wheat

The root system architecture(RSA) of a crop has a profound effect on the uptake of nutrients and consequently the potential yield. However, little is known about the genetic basis of RSA and resource adaptive responses in wheat(Triticum aestivum L.). Here, a high-throughput germination paper-based plant phenotyping system was used to identify seedling traits in a wheat doubled haploid mapping population, Savannah×Rialto. Significant genotypic and nitrate-N treatment variation was found across the population for seedling traits with distinct trait grouping for root size-related traits and root distribution-related traits. Quantitative trait locus(QTL) analysis identified a total of 59 seedling trait QTLs. Across two nitrate treatments, 27 root QTLs were specific to the nitrate treatment. Transcriptomic analyses for one of the QTLs on chromosome 2 D, which was found under low nitrate conditions, revealed gene enrichment in N-related biological processes and 28 differentially expressed genes with possible involvement in a root angle response. Together, these findings provide genetic insight into root system architecture and plant adaptive responses to nitrate, as well as targets that could help improve N capture in wheat.

Doubled Haploid Production Using an Improved Anther Culture Protocol for Sorghum[Sorghum bicolor(L.)Moench]

Sorghum[Sorghum bicolor(L.)Moench]can benefit from accelerated breeding and release of improved varieties through doubled haploid technology.The technology has been used in speeding up the breeding of other major cereals such as wheat,maize and rice,for which generally widely applied optimised protocols exist.A reproducible protocol for the crop,that can overcome genotype dependency and other species-specific challenges such as phenolic exudation is however lacking.This study aimed at sorghum doubled haploids production thereby contributing to the development of an improved protocol.From the 28 hybrid genotypes,both F1 registered-and experimental hybrids involved,this study successfully produced haploids from five genotypes and subsequently,four confirmed doubled-haploid lines on W14mf medium or its modification with 1.0 gl^(-1)L-proline,1.0 gl^(-1)L-asparagine and 1.0 gl^(-1)KH_(2)PO_(4).Medium 190-2Cu was used for regeneration and rooting,which occurred successfully,if the calli were transferred on to it less than 7 days after induction,and temperature was maintained at 25°C under light condition.Genotype dependency was not wholly overcome;however,sorghum’s high tillering ability and abiotic stress tolerance were observed to contribute to attainment of haploid plantlets.Spontaneous diploids producing seeds at rates of upto 80.5%were obtained,therefore eliminating the need for colchicine duplication.