Low-Temperature Response to Major Agronomic Traits by Using Recombinant Inbred Line(RIL) Populations Derived from Towada × Kunmingxiaobaigu

Development of the recombinant inbred line populations （RILs） is important basis to detect QTLs for cold tolerance at booting stage in rice. A set of 230 RILs derived from the cross of Towada and Kunmingxiaobaigu were used for evaluation of low-temperature response on major agronomic traits of plant height （PH）, panicle length （PL）, panicle exsertion （PE）, spikelet fertility （SF）, specific spikelet fertility （SSF）, and spikelets per panicle （SPP） under natural low-temperature growing environments in Yunnan Province, China. The results showed PH, PE, and SPP were mainly attributed by genotypes. PL was mainly influenced interactively by the genotypes × environments. SF and SSF were mainly controlled by the environments. Under the five different growth environments, F values of the six agronomic traits mentioned above ranged from 4.019 to 97.284. Significant difference was revealed between the lines. Under every environment, it indicated significantly positive correlation between SF and SSF, with correlation coefficients ranged from 0.826 to 0.885. It indicated significantly positive correlation between PH, PL, and PE. Under five different growing environments, variation coefficients of the six characters ordered in SSF （66.3%） 〉 PE （57.4%） 〉 SP （37.2%） 〉 SPP （16.2%） 〉 PH （9.6%） 〉 PL （6.4%）. SSF, PE and SF were most sensitive to low temperature stress at booting stage, while SPP, PH and PL being least. The RILs of Towada/ Kunmingxiaobaigu can be used as a genetic population to investigate cold tolerance at booting stage. SSF, PE and SF are most sensitive to cold tolerance at booting stage in rice. So far the the variation of PH, PL, and SPP related to cold tolerance are not clear under natural low-temperature environment. More tested environments and years are required to identify and evaluate cold tolerance at booting stage in rice.

Development of Permanent Mapping Populations RILs in Diploid A Genome

Recombinant inbred lines(RILs) serve as powerful tools for genetic mapping.RILs are obtained by crossing two inbred lines followed by repeated selfing or sib-mating to create a set of new

QTL Mapping for Dough Mixing Characteristics in a Recombinant Inbred Population Derived from a Waxy×Strong Gluten Wheat (Triticum aestivum L.)

Protein and starch are the most important traits in determining processing quality in wheat. In order to understand the genetic basis of the influence of Waxy protein （Wx） and high molecular weight gluten subunit （HMW-GS） on processing quality, 256 recombinant inbred lines （RILs） derived from the cross of waxy wheat Nuomai 1 and Gaocheng 8901 were used as mapping population. DArT （diversity arrays technology）, SSR （simple sequence repeat）, HMW-GS, and Wx markers were used to construct the molecular genetic linkage map. QTLs for mixing peak time （MPT）, mixing peak value （MPV）, mixing peak width （MPW）, and mixing peak integral （MPI） of Mixograph parameters were evaluated in three different environments. The genetic map comprised 498 markers, including 479 DArT, 14 SSR, 2 HMW-GS, and 3 Wx protein markers, covering 4 229.7 cM with an average distance of 9.77 cM. These markers were identified on 21 chromosomes. Eighteen additive QTLs were detected in three different environments, which were distributed on chromosomes 1A, 1B, 1D, 4A, 6A, and 7D. QMPT-1D.1 and QMPT-1D.2 were close to the Glu-D1 marker accounting for 35.2, 22.22 and 36.57% of the phenotypic variance in three environments, respectively. QMPV-1D and QMPV-4A were detected in all environments, and QMPV-4A was the nearest to Wx-B1. One minor QTL, QMPI-1A, was detected under three environments with the genetic distances of 0.9 cM from the nearest marker Glu-A1, explaining from 5.31 to 6.67% of the phenotypic variance. Three pairs of epistatic QTLs were identified on chromosomes 2D and 4A. Therefore, this genetic map is very important and useful for quality trait related QTL mapping in wheat. In addition, the finding of several major QTLs, based on the genetic analyses, further suggested the importance of Glu-1 loci on dough mixing characteristics.

Quantitative trait loci analysis for rice seed vigor during the germination stage

Seed vigor is an important characteristic of seed quality,and rice cultivars with strong seed vigor are desirable in direct-sowing rice production for optimum stand establishment.In the present study,the quantitative trait loci (QTLs) of three traits for rice seed vigor during the germination stage,including germination rate,final germination percentage,and germination index,were investigated using one recombinant inbred line (RIL) population derived from a cross between japonica Daguandao and indica IR28,and using the multiple interval mapping (MIM) approach.The results show that indica rice presented stronger seed vigor during the germination stage than japonica rice.A total of ten QTLs,and at least five novel alleles,were detected to control rice seed vigor,and the amount of variation (R2) explained by an individual QTL ranged from 7.5% to 68.5%,with three major QTLs with R2>20%.Most of the QTLs detected here are likely to coincide with QTLs for seed weight,seed size,or seed dormancy,suggesting that the rice seed vigor might be correlated with seed weight,seed size,and seed dormancy.At least five QTLs are novel alleles with no previous reports of seed vigor genes in rice,and those major or minor QTLs could be used to significantly improve the seed vigor by marker-assisted selection (MAS) in rice.