Cytological And Biochemical Basis Of Cross Incompatibility In Poplars Cytological And Biochemical Basis Of Cross Incompatibility In Poplars

Cultivating superior varieties by hybridization method has been an important and effective way of breeding, however, the presence of interspecific hybrid incompatibility brings the problems in distant hybridization. The causes of hybrid incompatibility are very complex, and its mechanism is still not very clear. However,there are less literatures on the researches of hybrid incompatibility mechanism. In this study, the female Populus Canadensis Moench and male Populus Canadensis Moench, P. alba×P. glandulosa were selected as hybrid materials so as to observe and determine the physiological indicators such as cytological changes, microtubule cytoskeleton changes, protective enzyme content changes in stigma, and endogenous hormone changes in different compatible pollination conbinations. The results showed the pollen tube elongation speed in compatible pollination (P. canadensis Moench x P. canadensis Moench) was higher than that of incompatible pollination (P. Canadensis Moench×P. alba×P. glandulosa). At48h after pollination, the stigma appeared wilting, the pollen tube of P. Canadensis Moench had grown into the ovary, while that of P. alba×p glandulosa was still at1/2of the whole style. The microtubule cytoskeleton observed by low melting point wax embedded sections method showed depolymerized and rearranged microtubule during the early recognition processes of pollen and stigma in the incompatible pollination.The contents of the four physiological indexes also changed with the pollen tube elongation. The SOD activity of both kinds of pollination combination began to decrease after pollination, in which, the SOD activity of the compatible pollination increased at2h and decreased at5h after pollination; the SOD activity of the incompatible pollination increased at5h and decreased at10h after pollination. The POD activity of both kinds of pollination combination kept increasing after pollination. And the contents of CAT and MDA presented fluctuations in the process, but the overall contents of CAT and MDA of the compatible pollination were higher than that of the incompatible pollination. Meanwhile, the compatible pollination and incompatible pollination lead to coordinated variation of endogenous hormone content. High levels of IAA, GA3and ZR hormones promoted the pollen germination and pollen tube elongation, and the ABA contents of the incompatible samples were significantly higher than that of the compatible samples, which showed that high concentration of ABA played an inhibition role in pollen identification, pollen germination and pollen tube elongation. The comprehensive analysis of the experimental results and depth exploration of causes of interspecific cross-incompatibility of poplars provided a theoretical basis and condition for the depth development of poplar crossbreeding work and also have a great significance for the biological breeding of poplars.