Study On Effects Of Ph Gene And Kr Gene On Fertilization And Embryo Development In Bread Wheat Wide Cross

Qinling rye is one of the cultivated species in China. It has many advantages, such aspowder mildew resistance, stripe rust resistance, cold resistance, drought resistance, a lotof spikelets, a lot of tillers and so on. It is a very useful way to advance wheat's characterof anti-disease and anti-unfavorable environment by transfering the available genes ofQinling rye to bread wheat by wide cross. However, a lot of bread wheat have a lowcrossability with Qinling rye and cannot obtain hybrids from hybridizing with Qinling rye.Even if the hybrids are obtained, the hybrids are sterility because of the low pairing of theparental homoeologous chromosome. It needs great effort to resolve these problems byyoung embryo culture and chromosome doubling. The crossability and the pairing ofparental homoeologous chromosome of wheat×rye are respectively controlled by Kr geneand Ph gene. The available genes of Qinling rye can be transferred to bread wheat byutilizing the bread wheat carrying Kr gene and Ph gene as parental bridge. Nevertheless,most of the hybrids obtained from wheat×rye are abnormal, small and crimple, havinglittle endosperm.In this research, the bread wheat carrying Ph gene and Kr gene including ChangingWhite wheat (CW), Yinong White wheat ("J-11 "), Kaixianluohanmai (KL), ChineseSpring (CS) and its mutants of ph2a, ph2b and ph1b were respectively hybridized withQinling rye. The fertilization and embryo development is observed by means of paraffinwax, and the frequency of fertilization, frequency of embryo formation and the percentageseed set of each cross combination were calculated. The results are as follows:The cross of the seven bread wheat with Qinling rye have very high frequency offertilization and embryo formation, and both reach to 80%. It is showed that the seven bread wheat have high crossability with Qinling rye in the degree of embryology. Most ofthe primary endosperm nucleus began to divide before zygocyte's first dividing, It is sameto the selfing wheat. Whereas, the embryo development lagged behind that of the selfingwheat.The high percentage seed set in the cross of the seven bread wheat with Qinling ryereach to 80%, because the recessive gene kr can promote the embryo and the endosperm todevelop in harmony.There are four bread wheat including KL, CSph2a, CSph2b and CSph1b carryingrecessive gene ph. Four days after pollination, it was observed in their embryo sacs that theprimary endosperm nucleus was transforming into cells. There are other three bread wheatincluding "J-11", CW and CS carrying dominant gene Ph. Seven days after pollination,it was observed in their embryo sacs that the primary endosperm nucleus was transforminginto cells. It reveals that recessive gene ph has the effect to promote the early developmentof primary endosperm nucleus.Eleven days after pollination, in the embryo sacs of CSph1b and "J-11", it wasobserved that first embryo differentiation. Besides, it was observed a lot of endospermdisaggregation in the embryo sacs of CSph1b, ranging from four days to eleven clays afterpollination. And it was only observed a lot of endosperm disaggregation in the embryo sacsof "J-11" eleven days after pollination. It is obvious that, ph1b gene and kr4 gene caninduce embryo differentiation and endosperm disaggregation. Furthermore, the phlb geneis much more remarkably induce endosperm disaggregation.The effect on the embryo development of wheat-rye hybrids from large to small is:ph1b＞phKL＞ph2a and ph2b. Moreover, it is difficult to differentiate the effect of ph2aand ph2b.