Distribution and Selective Effects of Vrn-A1,Vrn-B1,and Vrn-D1 Genes in Derivative Varieties from Four Cornerstone Breeding Parents of Wheat in China

Vernalization, the process of a long exposure to low temperature to induce flowering in plants, is essential for plants to adapt to cold winters. The presence of vernalization genes Vrn-A1, -B1, and -D1 in four cornerstone breeding parents of wheat in China （Funo, Mentana, Yanda 1817, and Bima 4） and 322 derivative varieties （mostly winter wheat） from these parents were determined using PCR based molecular method. The frequencies of the VRN-1 genes in these derivative varieties were in order of Vrn-Dl（67.1%）〉 Vrn-Bl（19.6%）〉 Vrn-Al（5.3%）, which are similar as the former conclusion that Vrn-D1 is associated with the latest heading time, Vrn-A1 the earliest, and Vrn-B1 intermediate values. The frequencies of Vrn-Al and Vrn-B1 loci in the derivative varieties from winter wheat zones were higher than that from spring winter zones. Based on the wheat breeding history in China and the fact of non-random distribution of Vrn-A1 and Vrn-B1 in the derivative varieties from the four parents, there could be a strong selective effect on VRN-1 genes in different regions where the derivative varieties were cultivated.

Introgression of QTLs Controlling Spikelet Fertility Maintains Membrane Integrity and Grain Yield in Improved White Ponni Derived Progenies Exposed to Heat Stress

To increase the thermotolerance of improved White Ponni（IWP）, two quantitative trait loci（QTLs）, q HTSF1.1 and q HTSF4.1, controlling spikelet fertility under high-temperature stress, were introgressed from Nagina 22 into IWP through marker-assisted breeding. The progenies were subjected to foreground selection of target QTLs using simple sequence repent markers RM431 and RM5757 linked to q HTSF1.1 and q HTSF4.1, respectively. At each generation, foreground selection with single target QTL or both QTLs was done together. The QTL-positive plants were forwarded to next generation by selfing. The F2：3 progenies were subjected to phenotypic analyses under high-temperature stress at the flowering stage. Chlorophyll stability index, malondialdehyde content, grain yield, and yield-related components of the F2：3 progenies were measured. The progenies IWP-295, IWP-277 and IWP-246 harboring both q HTSF1.1 and q HTSF4.1 showed higher fertility percentages under high-temperature stress at the flowering stage. These QTLs were responsible for maintaining membrane integrity and yield under elevated temperature conditions.