The Genetic Analysis And Localization Of Fruit Length Gene And Sex Type Gene In Melon (Cucumis Melo L.)

Fruit length and sex type（monoecy,andromonoecy）are two valuable traits in melon.Fruit length determines fruit shape in melon and affects the consuming behaviors.It is a key factor to prevent from the mechanical damage,reduce transportation cost,prolong the shelf life.Nowadays,andromonoecy is presented in most melon cultivars and it will cost a great deal of manpower and capital during the artificial emasculation.Therefore,it is essential to inbreed monoecious melon cultivar with excellent fruit shape.In this paper,167 BC₁individual plants obtained from the cross between the monoecious melon cultivar‘Snake melon’with long fruit and the andromonoecious melon cultivar‘Xizhoumi 25’with round fruit were regarded as the mapping population and SSR markers were used to investigate the genetic mechanism,perform the primary gene localization for fruit length gene and sex type gene（monoecy,andromonoecy）in melon.The followings are several main results:（1）The segregation of fruit length and sex type（monoecy,andromonoecy）in BC₁population were investigated and the result shows that fruit length conforms to the polygenic inheritance,and sex type（monoecy,andromonoecy）is probably controlled by two genes.（2）SSR markers in melon Chromosome 2 were employed to perform the primary localization for fruit length and sex type.The result suggests that the two QTLs are tightly linked;SSR247159 is the tightly linked marker for fruit length QTL;SSR232201 and CMGA36/SSR235092 are the tightly linked markers for sex type.（3）SSR247159 tightly linked to fruit length QTL in Chromosome 2 was validated in 48melon cultivars with different fruit lengths.The result shows that SSR247159 can be applied to inbreed the melon cultivar with different fruit shapes by marker-assited select.（4）The fruit length data and the sex type data in 6 families from the selfing of six individuals in BC₁ population were investigated and analyzed to show that two recombinants between fruit length QTL and sex type gene a were probably identified in F26 family and F40family.This provides a visual evidence for the conclusion that the fruit length gene in Chromosome 2 and sex type gene a are probably subject to two different genes.（5）The sex type（monoecy,andromonoecy）segregation of individual plants in 4generations（P₁ and P₂,F₁,BC₁,P₁BC₁F₂,）shows that there exists another sex type（monoecy,andromonoecy）gene denoted as“pa”and its action mode were also characterized.（6）SSR markers in the left 11 chromosomes except Chromosome 2 were employed to perform the primary localization for another sex type gene pa in BC₁ population.The result shows that no QTL for another sex type gene pa was found,but 4 markers among all 5 polymorphic markers identified are from Chromosome 5.