Physiological Characteristic Analysis,Genetic Analysis And Gene Mapping Of Leaf Color Mutant In Melon

Melon?Cucumis melo L.?is cucumis belongs to cucurbitaceae it has a number of variation types,the leaf color of the melon mainly is yellowish green,light green,green and deep green.In order to reveal the genetic mechanism of melon leaf color traits,leaf color mutant?MT?,the wild type?WT?were used as research materials to construct segregation population of leaf color,agronomic traits,physiological characteristics and chloroplast ultrastructure of MT were investigated,the preliminary study regularity and characteristics of MT from the physiological level and chloroplast structure.Using the method of the second-generation sequencing,the candidate region associated with MT was obtained,laying the foundation for the preliminary mapping.The main results were as follows:1.The results of MT agronomic traits showed that yellowing traits of the leaf color was expressed in the seedling stage.With the growth and development of the plant,the color of the leaf gradually turns to green,the plant growth becomes weak,the growth period lags behind,and in the late growth stage,there is premature aging,but it can normally bloom,so it is a non-lethalized yellowing mutant.In the fructescence,compared with WT,the plant height,stem diameter,leaf area and SPAD value of MT reduce 9.45%,3.03%,7.75%and 6.44%,respectively.2.The results of MT fruit characteristics showed that the longitudinal diameter and transverse diameter of WT and MT were trended to increase from pollination to maturity,compared with the day of pollination,the fruit shape indexs of maturity were reduced by33.70%and 35.42%respectively.3.The results of MT determination of photosynthetic pigment contents in different stages showed that the photosynthetic pigment contents were increase from cotyledon stage to fruiting stage in WT and MT,but the photosynthetic pigment content of MT significantly lower than WT.In the fruiting stage,compared with WT,chlorophyll and carotene of MT were reduced by 25.69%and 21.26%respectively.4.The results of MT chloroplast ultrastructure showed that MT significant differences with WT.The chloroplast grana lamella of MT was irregular stack,spacing,loosely arranged,and was not clear in double membrane structure.While chloroplast grana lamella closely arranged regularly,structure developed normally,starch grains,membrane structure could be clearly seen in WT.5.The results of MT photosynthetic rate measurement in adulthood showed that the net photosynthetic rate had no significant difference between WT and MT,but the stomatal conductance,transpiration rate andintercellular CO₂ concentration reached significant difference,increased by 47.95%,31.87%and 12.80%respectively than the WT.6.The results of MT oxidase activity and determination showed that the activity of superoxide dismutase?SOD?was trended to increase first and then decrease from seedling stage to fruit stage,Peroxidase?POD?activity and malondialdehyde?MDA?content was trended to increase,catalase?CAT?activity was always trended to decrease.In fruiting stage,MT SOD,POD enzyme activity and MDA were dramatically higher than WT,but there was no significant difference in CATase activity between MT and WT.7.The results of MT genetic analysis showed that MT self-crossed progeny phenotype could stable heredity and the color of leaf was manifested as yellow,F₁generation of crosses and reciprocal crosses are green,the proportion of offspring in F₂ and backcross population of separation ratio was 3:1 or 1:1,showed that the mutant was nuclear inheritance and temporarily named named ypl.8.BC₁F₂ population were used to gene mapping,DHL92 as melon reference genome,using bioinformatics analysis and sequencing BSA to gained the candidate area on chr9?11.27 Mb-14.83 Mb?.There are 206 functional genes with annotations,20non-synonymous mutation genes and 30 genes in SNP loci in the candidate regions.By 31pairs of polymorphic primers were selected by InDel and SSR primers,and by F₂generation plant validation,the upstream marker of gene linkage was obtained.