Study On The Effect Of Genetic Distance Between Parents On Fertility Of Interspecific Hybridization Of Pines And Heterosis Of Progeny

The dissertation studied 6 fertility indexes(fruit volume index,average number of seed production,average weight of seed production,100-seed weight,germination rate and seedling rate)of 92 interspecific hybrid combinations of different pines and 20 half-sib controls in Nanning forestry science research institute of Guangxi Zhuang Autonomous Region.The growth of height and DBH in 8a of 20 interspecific hybrid combinations of Pinus elliottii×P.caribaea in Nanning forestry science research institute were synthesized.The main results are as follows:(1)The results showed that the 3 hybrid types of Pinus caribaea ×P.elliottii(C × E),Pinus elliottii ×P.caribaea(E × C)and Pinus elliottii ×P.taeda(E ×T)were better than or close to half-sib control,and Pinus massoniana ×P.elliottii(M × E),Pinus massoniana ×P.taeda(M × T),Pinus massoniana ×P.caribaea(M × C),Pinus taeda ×P.caribaea(T × C),Pinus taeda × P.massoniana(T × M)and Pinus taeda ×P.elliottii(T × E)were much lower than those of the half-sib controls.According to the 6 fertility indexes,the overall performance of hybridization in the subgroup was better than that of intersubgroup hybridization,and that of the 3 hybrids of Pinus elliottii and Pinus caribaea as female parent was better than that of the other 6 hybrids of Pinus massoniana and Pinus taeda as female parent.In addition to Pinus taeda ×P.elliottii(T × E),the living hybrid offspring were obtained in all the 9 hybrids.Especially the living hybrid offspring of Pinus massoniana and 3 kinds of foreign pines were obtained for the first time in relevant studies.It is of great significance to the study of interspecific hybridization breeding of pine trees.(2)The genetic distance between parents of 92 interspecific crosses of different pines was analyzed by linear correlation with 6 fertility indexes.In the range of genetic distance between parents 0.1530-0.8205,6 indexes were negatively correlated with the genetic distance between parents,only cone volume index was negatively correlated with the genetic distance(P = 0.0001),and the other 5 fertility indexes did not reach the significant level.(3)T × M,T × E,E × C,C × E and T × C have positive correlation with their genetic distance,M × T,E × T,M × E and M × C have negative correlation with their genetic distance.The genetic distance between parents(0.1530-0.8205)was negatively correlated with the membership function value of cross fertility evaluation.(4)The growth of height and DBH in 8a of 20 interspecific hybrid combinations of Pinus elliottii×P.caribaea in Nanning forestry science research institute were analyzed statistically.The results of variance analysis showed that there were significant differences between different combinations in the two characters of tree height and DBH(P<0.0001,P<0.0001).(5)Based on the statistical analysis of the Over-HP heterosis and OverMP heterosis of 8a tree height and DBH of 20 interspecific hybrid combinations of Pinus elliottii×P.caribaea in Nanning forestry science research institute,the Heterosis of different combinations showed great difference in the characters of tree height and DBH,and the variation degree of DBH was higher than that of tree height.The two combinations with the highest growth heterosis were S6 × H21 and S6 × H20,and the combination with the lowest growth heterosis was S2 × H20.Among them,2 hybrids showed negative heterosis in different degree in tree height and 8 hybrids showed negative heterosis in different degree in DBH.(6)There was a negative correlation between the genetic distance(0.2309?0.4722)between the parents of Pinus elliottii×P.caribaea and the Over-HP heterosis and Over-MP heterosis of height and DBH of the progeny,but none of them reached a significant level.In the positive advantage,four measures were negatively correlated with genetic distance,and the correlation was not significant;in the negative advantage,four measures were positively correlated with genetic distance,and the correlation was not significant.Further study on the variation trend of growth heterosis and genetic distance between parents showed that the heterosis increased with the increase of genetic distance between parents.When the genetic distance between parents reached 0.3387,the heterosis reached the highest level.With the further increase of genetic distance,the heterosis decreased sharply,although there is a small increase in heterosis at the genetic distance of 0.3648 and 0.3842,the effect is not obvious.It is further speculated that when the genetic distance between parents reaches about 0.3387,the heterosis of the growth of Pinus elliottii×P.caribaea may reach the highest level.