| Fupingqiuzi(Malus prunifolia Borkh.)is a particular Malus germplasm from Shaanxi province,and one of the main apple rootstocks in the northwest of China,because of the strong resistance to stress and adaptability to environment.So it is an important resource for germplasm creation and resistance research.However,when Fupingqiuzi was used to artificial cross as either male parent or female parent,the fruit setting rate was very low.Therefore,7 kinds of Malus resources,such as Fupingqiuzi(M.prunifolia Borkh.),Huochengbaiguozi(M.sieversii Roemer.),Dongbaiguo(M.prunifolia Mill.),Pajam 2,G.41,'Gala'(M.domestica Mill.)and 'Honey Crisp'(M.domestica Mill.),were selected as materials in this study.Pollen morphology and activity,stigma receptivity,growth of pollen tube and S-genotype were detected by observing,artificial crossing investigating and genotyping.The aim was to preliminary analyze the main reasons of the low fruit setting rate of Fupingqiuzi when hybridize as hybrid parent.It would provide some reference for increase the fruit setting rate,and the basis imformation for full use of this special and important resource.The main results were as follows:(1)7 kinds of Malus resources belong to N3P4C5 pollen grains,the shape was basically similar,for the prolate or perprolate.The equatorial plane was elliptic,there are three germination ditches on the polar surface.Among them,Fupingquzi,Huocheng baiguozi,Dongbaiguo pollen grains the largest.(2)Pollen output and deformity rate between the existence of a certain relationship,the higher the deformity rate,the lower the amount of output.The pollen deformity rate of Fupingqiuzi was as high as 40%,and the amount of pollen output were only 21709.44 grains per flower.In addition to Fupingqiuzi pollen breeding type was facultative cross,the other materials were specific outcrossing.Pollen deformity rate and pollen output did not affect pollen activity,but different milling methods had an effect on pollen activity.Fulingqiuzi pollen has a high deformity rate and a small amount of output,but the pollen activity was the stronger,and the natural milling pollen activity is higher than the dried milling pollen.(3)The stigma receptivity of Fulingqiuzi field hybridization pollination in the flowering 2-3 days was optimum.(4)There were differences in the growth characteristics of pollen tubes after stigma pollination of different apple resources.When Fupingqiuzi as the female parent cross-pollination,the pollen tubes were able to reach the basal part of the pollen tube,and Fupingqiuzi self pollination the pollen tube grew slowly in the early,but later reached the basal part of the pollen tube.However,when Fupingqiuzi as the male parent cross-pollination,there was little or no pollen tube to reach the basal part of the style.The yield of positive and negative hybrid combinations was different in different hybrid combinations,and the same hybrid combinations positive and negative hybrid has different.Fupingqiuzi as the female parent the average fruit yield was 11%,and the self-pollination rate was 73%.However,the average hybridization rate was only 4% when Fupingqiuzi was used as male parent.(5)A total of 17 clear and complete bands were obtained by S-gene specific PCR.There were 8 different nucleotide sequences,which size respectively were 541 bp(S1),350 bp(S2),370 bp(S6),883 bp(S10),536 bp(S24),712 bp(S44),685 bp(S46)and 708 bp(S51).According to the results of S-allele sequenced,the 'honey-brittle','Gala',Fupingqiuzi,Pajam 2,G.41,Huochengbaiguozi and Dongbaiguo S-genotypes identified as: S2S24,S2S46,S6S51,S1S10,S1S2,S1S46 and S44S44.In summary,the preliminary view that the main factors of Fupingqiuzi as the male parent hybrid fruit setting rate were the high deformity rate and the low pollen output,which affected the pollination effect and led to the low fruit setting.When Fupingqiuzi as the female parent hybrid,the main facters of the low hybrid fruit setting rate were the pollen tube can not grow normally in the stilus. |
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