Phenotypic Investigation And Genetic Analysis Of Multiple Pistillate Flowers In Cucumber

Yield is an important agronomic trait of cucumber.Besides being affected by environmental factors such as temperature,light,water,CO₂,soil,etc.,it is also related to its branching,parthenocarpy rate,flowering time and female flower rate.Among them,female flower rate plays a crucial role in the yield of cucumber.The phenomenon of producing two or more female flower buds at one node is called multi-female flower trait,which is an important indicator of female flower rate.In this study,four all-female parents,SB-2,1983G,Gy14 and AM297,with significant differences in the number of female flowers,were selected for field statistics and observation of the morphology of female flower bud tissue sections.Then,SB-2,1983G and Gy14 were used as the female parent,and AM297 was used as the male parent to construct the population,respectively.After crossing,F₁plants self-crossed to obtain F₂.Through the investigation and analysis of the number of nodes of F₂female flowers,it was determined that F₂（SB-2×AM297）population was suitable for genetic analysis of female flowers.In this study,four all-female SB-2,1983G,Gy14 and AM297,as well as F₂（SB-2×AM297）,F₂（1983G×AM297）and F₂（Gy14×AM297）were measured for all-female yield and multiple female flowering rate.The specific results are as follows:1.Tissue sections were taken from terminal buds and internode axils of four all-female parents SB-2,1983G,Gy14 and AM297 after 30 days of sowing,and field phenotypes were observed at the fruiting stage.It was found that there were differences in the number of female flowers per node and the number of female flower buds.SB-2 had only one female flower bud at each node,while 1983G,Gy14 and AM297 had two female flower bud nodes at both terminal and lateral buds.In conclusion,SB-2 is a mono-female parent,and it does not have the trait of multiple female flowers,while 1983G,Gy14 and AM297 have the trait of multiple female flowers.2.F₁was obtained by crossing SB-2,1983G and Gy14 as female parent and AM297as male parent,and then F₂was obtained by self-crossing.Through the investigation and analysis of the number of nodes in F₂multiple female flowers,It was found that the number of nodes in F₂（1983G×AM297）,F₂（Gy14×AM297）and F₂（SB-2×AM297）showed a continuous change of 0-16,0-11 and 0-14,which was consistent with the quantitative trait inheritance controlled by multiple genes.The single flower number and multi-flower number of F₂（SB-2×AM297）were in accordance with theχ2 test of Mendelian segregation ratio of 3:1,and significance analysis showed that the multi-flower character might be a recessive inheritance controlled by single gene.Therefore,an appropriate F₂population of SB-2×AM297 was identified and genetic analysis of multi-female flower traits was carried out.Through BSA mixing and genome resequencing analysis of single and multiple female flowers,it was found that genes related to multiple female flowers were linked on chromosome 1,6 and 7 of cucumber.Five polymorphic markers SSR1045,SSR1046,SSR6100,SSR6101 and SSR7027 were found on chromosomes 1,6 and 7 by molecular marker analysis.3.The yield of SB-2,1983G,Gy14,AM297 and F₂（SB-2×AM297）of cucumber were measured.It was found that the number of female flowers,yield per plant and yield per hectare of Gy14 were the highest.The single melon weight of 1983G is the lightest,but its yield per plant and yield per hectare are higher due to the large number of female flowers.In contrast,SB-2 had the highest melon weight per plant,but the yield per plant and the yield per hectare are the lowest due to the low number of female flowers.In conclusion,the multiple female flower character of cucumber can increase the yield by increasing the number of commercial melons.The nodes of F₂（1983G×AM297）,F₂（Gy14×AM297）and F₂（SB-2×AM297）were compared and analyzed.By calculating the nodes of them,it was found that the nodes of F₂（1983G×AM297）had the highest mating rate,up to 29.59%.The mating rates of F₂（SB-2×AM297）and F₂（Gy14×AM297）are low,which are 19.49%and 19.47%respectively.The above research is helpful to deepen the understanding of the compound female flower character of cucumber,and provide the theoretical basis for increasing the yield of cucumber.