| Molecular markers linked to Rht3 and Gai3 genes that affect the expression of a-amylase The wheat dwarf gene Rht3 derived from Torn Thumb, a Tibetan wheat of China, is a dominant gene with the insensitivity to gibberellic acid. The alleles of Rht3 show overdominance for grain yield of hybrid F1 and depress of the ~-amylase activity in ripened grains. So it抯 possible utilization in hybrid wheat breeding is of great concern It抯 found that Rht3 is also closely related with the x-amylase activity, GA transduction, resistance to preharvest sprouting and processing quality of wheat. The irnpoitance of studies on molecular mapping and isolation of Rht3 is obvious The hereditary mode of Rht3 has been clarified, but whether Rht3 and Gai3 are two independent genes still remains as a problem to be answered In this dissertation systematic studies on the genetic relationship between Rht3 and Gai3 and how they affect the ci-amylase activity were made using large BC22F2 populations derived from two set of dwarf isogenic lines including Yangmai3 and Suirnai3 as well as their prototypes The dissertatior~ also present RAPD and RFLP markers linked to Rht3 and Gai3 which could be of use for the applications and map-based cloning of Rht3 The results of this paper revealed that Rht3 and Gai3 are tightly linked to each other with the recombination rate of 0 045眥) 010 and 0 140? 011 in the two segregating populations, respectively Rht3 and Gai3 could depress the gene expression of i-arnylase, reduce its activity and hence enhance the resistance to pre-harvest sprouting Higher effects of Rht3 compare to Gai3 on ni-amylase activity and resistance to pre-harvest sprouting were discovered from data of the recombinants. The results of isoelectric focusing isoenzyme (IEF) of a-amylase verified that Rht3 and Gai3 mainly inhibit the expression of a-Amy 1 gene located on the long arms of hornoeologous group 6 of wheat. The results also expressed that a-Amy 1 isoenzyme electrophesis patterns within the populations are very complicated which probably show the cornplex expression mechanism of a-Amy 1 regulated by Rht3 and Gai3. In the RAPD analysis, out of 310 random primers (lObp) screened, only 3 primers e.g. UBC3 89, OPV-0 6 and 51060 revealed polymorphisms in NIL, and fragments SIO6OI9a6 and S10602000 amplified by primer S1060 were shown as to be linked to Rht3 and Gai3 with a genetic distance 16.7cM and 29.5cM. respectively. In RFLP analysis, 53 probes specific for short arms of homoeologous group 4 were screened, and Xpsr584, XksuF8 and Xcdo3S showed polymorphism between the bilLs. The linkage analysis showed that Xpsr5S4 co-segregated with Rht3 and Gai3 genes. Homoeologous grouping of R. kanwji chromosomes introduced in wheat via RFLP analysis Twenty six DNA probes located on 7 homoeolgous groups of wheat were screened to reveal the RFLP between 45 wheat-R.kamoji derivatives, R.kamoji, Chinese Spring and Yairnai5. The results showed that most probes could produce more than 3 hybridized bands showing distinct polymorphisms between Chinese Spring, Yangmai 5 and 1? .kamoji. The introduced R.kamoji chromosomes in the 16 wheat-R.kamo,i chromosome lines including addtions, substitutions or possible translocations were grouped into homoeologous group 1, 3, 5, 6 and 7. Alien chromosome pairs could be readily transmitted into the descendants. Of the 16 alien chromosome lines, the added chromosomes in K139, K141, K214, K218, K219 and K224 disomic ad...
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