Genetic diversity analysis in imported wild melon(Cucumis melo L.) germplasm resources based on morphological characters

WANG Jiming; SHANG Jianli; LI Na; XU Yongyang; MA Shuangwu

doi:10.13925/j.cnki.gsxb.20160190

Abstract：[Objective] Melon (Cucumis melo L.) is one of the most important crops with a high variability in fruit traits among different gemplasm,ranging from non-sweet fruits that are inedible or harvested before maturity and consumed as vegetables,to sweet fruits with high sugar concentrations that are eaten in salads or as dessert,melon could be divided in two group based on ovary pubescence or edible value with melon group and wild melon group,wild melon genotypes possess slender vines,monoecious flowers and small,inedible fruits,mainly distributed in Asia,Africa,and Oceania etc.India is rich in wild melon and semi-wild melon germplasm resource,and was considered as origin center of melon according to the recent research results,studying on wild melon originated form India is help for exploring melon originating and spreading,the aims of this study were to provide the scientific basis for the evaluation,classification,and effective utilization of the imported wild melon germplasm which mainly oriented from India.[Methods] 100 accessions wild melon germplasm introduced form the North Central Regional PI Station (the U.S.A.),which originated form India (92 accessions),Costa Rica (1 accession),Maldives (2 accessions),America (1 accession) and China (1 accession),all germplasm planted at Zhongmou County,Zhengzhou,Henan Province,China,fruit characters data were collected during planting period,including 7 quality characters with fruit shape,ground color of fruit skin,vein color of fruit skin,vein shape of fruit skin,flesh color,flesh texture,flesh taste,and 9 quantitative characters with fruit length,fruit width,index fruit shape,weight of single fruit,flesh thickness,total soluble solid content,1 000-seed weight,seed length,seed width to analyze the genetic diversity.To carry out germplasm clustering and genetic relationship analysis,thin skin melon ‘Guang xi li gua’,thick skin melon ‘Kalakekouqi’ ‘Sairekekouqi’,wild melon ‘Mapao’ ‘Wild melon’,dudaim melon ‘Kangua’ which originated from China were also used as standard germplasm in this study.[Results] The diversity index (Shannon's index,H') range of quality characters for the imported melon germplasm was 0.17-1.88 with the average of 0.98,ground color of fruit skin,vein color of fruit skin,vein shape of fruit skin had greater diversity index with excess of 1.0,ground color of fruit skin the manly showed light yellow (42％ of total germplasm) and yellow (29％ of total germplasm),vein color of fruit skin were mainly deep green (19％ of total germplasm),red brown (17％ of total germplasm),vein shape of fruit skin were mainly dot (18.0％ of total germplasm),speckle (22.0％ of total germplasm),streak (23.0％ of total germplasm),and 30％ of total germplasm had no vein shape of fruit skin.Flesh texture and flesh color were mainly crisp and white with 91.0％ and 80.0％ of total germplasm respectively,most germplasm flesh taste were sour (96.0％ of total germplasm) and a few germplasm flesh taste were bitter (4.0％ of total germplasm).Quantitative characters for the imported melon germplasm were 0.98 and 1.79,respectively,which showed quantitative characters had more rich genetic diversity,the variation coefficient of 5 fruit quantitative characters were more than 30％,the maximum variation coefficient was that of fresh fruit weight with 100％,and flesh thickness followed it with 63.27％,fruit diameter,fruit shape index,seed width had smaller variation coefficient with 4.22％,18.01％,16.92 and 15.15％,respectively.Germplasm cluster analysis showed that all melon germplasm could be divided into two groups at Euclidean distance 3.0 based on UPGMA method with Group Ⅰ and Group Ⅱ,Group Ⅰ included standard germplasm of cultivated melon ‘Guangxi Ligua’ ‘Kalakekouqi’ ‘Sairekekouqi’ and dudaim melon ‘ Kangua’,were total 92 accessions germplasm with complex fruits traits,could be considered as semi-wild germplasm group,Group Ⅱ included standard germplasm of wild melon and were total 14 accessions germplasm with light fruits (most fruits were less 0.1 kg) and acid or bitter of flesh taste,could be considered as wild germplasm group,furthermore,Group Ⅰ could be divided into Subgroup i that included standard germplasm of thin skin melon and Subgroup ii that included standard germplasm of thick skin melon,which mean thin skin melon and thick melon maybe evoluted from wild germplasm independently.[Conclusion] Fresh fruit quantitative characters of the imported melon germplasm had more rich genetic diversity than quality character,and fresh fruit weight had the maximum variation,was consistent with the results of previous studies on cultivated melon and wild melon.The results of germplasm cluster analysis showed that wild melon germplasm mainly oriented from India were closely correlated to China cultivated melon and wild melon germplasm,e.g.most imported wild melon germplasm could be clustered one group with thick skin melon ‘Kalakekouqi’ ‘Sairekekouqi’ from China,showed that thick skin melon had more closed relationship with wild melon germplasm,inferred the imported wild melon germplasm may play important role for the origin and evolution of China cultivated melon,and India may be a origin center of cultivated melon.