Genetic Mapping Of Male Sterility Gene LMS In Lettuce And Identification Of Heterosis In Stem Lettuce

Lettuce(Lactuca sativa),an annual or biennial herb of the genus Lactuca in the Composite family,is one of the most important vegetables in the world.Male sterility is an important way to utilize heterosis in plants and has been widely used in production practice.The mechanism of male sterility has been thoroughly in many plants,but the studies on dominant nuclear sterility are relatively few.There are also few related on dominant nuclear sterility in lettuce.Lettuce is a self-pollinating plant and artificial hybridization is difficult.In this study,we used map based cloning method to obtain the candidate gene Ls KT2 which controlled male sterility.At the same time,we constructed different hybrid combinations by using lettuce materials available in the laboratory.We identified their heterosis and selected 4 excellent combinations.The main results are as follows:1.Four fertility isolation populations were constructed by crossing dominant male sterile material MS collected in the laboratory with Salinas,PI251246,S24 and S34 respectively,and we mapped LMS gene between maker LG2-204.40 and maker LG2-204.68 about 280 Kb region.2.We selects Ls KT2 as the candidate gene which encodes a potassium transporter after functional annotation and sequence analysis of 11 genes in the candidate interval.3.A missense mutation occurred on the eighth exon of Ls KT2 gene located in the conserved domain of the potassium ion transporter family.This missense mutation only occurred in male sterile materials among all lettuce materials.4.We investigated the 10 botanical characters of 42 lettuce materials and then we constructed 54 hybrid combinations according to their botanical characters.5.We statistically analyzed the stem diameter traits of the parents and hybrids.Most of the cross combinations showed positive heterosis in the middle parent advantages and high parent advantages.6.We selected four best combinations with strong heterosis among 54 hybrid combinations,and then we introduced the male sterile traits into their parents.This study provided theoretical guidance and material basis for the utilization of heterosis in the future.