Studies On Strong Seed Dormancy Of T. Aestivum Ssp. Tibetanum Shao

T.aestivum ssp.tibetanum is a kind of special semi-wild hexaploid wheat resources,only distributing in Tibet of China.It has special characters,such as hulled glume and brittle spikelet.However,seed dormancy,another important character,was little reported.We have had observed and tested more than 10 accessions of them for dormancy,and found that every of them was 0 or near 0 percentages both with threshed seeds' and intact spikes' germinations.T.aestivum ssp.tibetanum cv.Q1028 was identified for seed dormant property by testing its' seed germination percentages of intact spikes,seeds with bract powder,normal seeds,seeds of pierced coat, sectioned embryos,and germination percentages of intact spikes and seeds at various stage after harvest.The result showed that the seed dormancy of Q1028 was very high. Its germination percentage of seed was 0%after harvest.The dormancy of Q1028 came from embryo dormancy itself mainly.The cross of Q1028 with ZhengMai9023,which was non-dormant,was analyzed on P₁,P₂,F₁,F₂,BC₁ and BC₂ plants.The result showed that the seed dormancy of Q1028 was very high.Its germination percentage of seed was 0.75%at wax maturity.At eight weeks after maturity,its germination percentage of seed was only 2.25%.Its seed dormancy was controlled as partial dominant trait by two complementary genes.At least one gene between them was related with red capsule of seed.Besides,it was possible that other genes controlled maintaining time of seed dormancy.Molecular markers analysis in the extremeness population,Using SSR markers, the two loci were located on 3AL and 1B,respectively.The one located on 3AL was named as SD-1,which possibly has been located by other researchers;the other one located on 1B was named as SD-2,which hasn't been reported before.Further molecular mapping showed that SD-1 was linked with SSR marker in the order of Xgwm5-Xwmc651-Xwmc664-Xgwm155-SD-1 with genetic distances of 4.2 cM,6.9 cM,20.9 cM,10.9 cM,respectively.At the same time,another one pair of primer located on chromosome arm 1BL,Xgwm498,were found being linked to strong seed dormancy.The 167 F₂ individuals were then amplified with marker Xgwm498.The statistic genetic distance between Xgwm498 and dormancy locus was calculated to be 30.6 cM using the software Mapmaker3.0.According to F₂ generation germination data,the agronomical characters of 30 dormancy plants has been significantly improved than of Q1028,especially for No.135,No.123,No.135,No.257,No.278 and No.279.They have these characters such as flexible hull,dense spike and not brittle spikelet,beside strong seed dormancy. They are the precious genetic material for breeding.