ISSR Analysis Of Genetic Diversity In Sweetpotato (Ipomoea Batatas) Germplasm Resource

Sweet potato is one of the major crops in our national products,recently,with the acting of exploiting to the value of the sweet potato in foods,medicine,industry and feedstuff,more and more attention has been paid to the breeding.Cultivating fine sweet potato cultivars yield,high quality,strong adversity measure to realize the sustainable and easy to store is the first development of sweet potato production.And it is also the long-term objectives sweet potato breeding workers.While to make clear of the relations in sweet potato varieties,and to research their genetic diversity is very important to the breeding.In this paper,the technique of ISSR molecular markers was used to study genetic diversity of 70 good sweet potato cultivars,and to analyse their genetic relationship.The purpose is to provide a basis for sweet potato hybridization.This paper optimized the reaction system of ISSR fitting for analyzing the genetic diversity of sweet potato by two orthogonal test design.20μL reaction system contains 40ng DNA,1.25 mmol/L MgCl₂,0.25 mmol/L dNTP mix,1.00μmol/L primer,2 U Taq DNA polymerase,2μL 10×PCR buffer,0.4μL 2.0%formamide.An optimized PCR reaction system for ISSR analysis was established:PCR was performed in a 20μL reaction.The temperature profile used for PCR was 94℃for 5min,followed by 10 cycles of 94℃for 50s,55-50℃for 45s,72℃for 1 min30s,then 35 cycles of 94℃for 45s,52℃for 45s,72℃for 1 min30s,and was terminated with a 7min DNA extension step at 72℃. In this reseach,8 ISSR primers were respectively chosen for they showed strong,reproducible amplification and distinct polymorphisms from 16 primers.The results were indicates:8 ISSR primers generated 65 bands,of which polymorp6ic bands number was 61,8.125 bands per primer in average.The polymorphic percentage is 93.8%.Any amplified band was regarded as a character,and the binary data matrix was set out according to the bands existed or not.The Jaccard coefficient was worked out by using NTSYS-pc software.The result of genetic similarity analysis for 70 sweet potato cultivar genotypes showed that Jaccard coefficient ranged from 0.54 to 0.95,suggesting that there was a close genetic relationship among them and a rich genetic polymorphism among the sweet potato cuitivars due to the Jaccard coefficient.According to the clustering analysis of ISSR's results,70 sweet potato cultivars were divided into 2 groups.The first group contains 48 sweet potato cultivars,most of which are Domestic cultivars.There is certain comparability genetic basis of the sweet potato which Stem from China;This indicated that inherit variances of sweet potato are very enrich in Chinese local populations,and supports the hypothesis that China was the secondary center of sweet potato diversity.The cluster analysis results showed that Domestic seeds not only has obvious genetic diversity,but also appears obvious association;The variety from America has long genetic distance,so has favorable polymorphism and breeding value;The most varieties from Japan gather independently,so their relationship is near.During ISSR-PCR amplification,some sweet potato cultivars produced distinctive bands,and some didn't produce distinctive bands,according to which,they could be identified.It is difficult for some cultivars to be differentiated by amplifying with a primer,and several primers be used.The research proved that ISSR molecular markers could reflect the genetic differences and the genetic diversity among all sweet potato cultivars.Also it discussed the analyses of technologies as well as systems of ISSR,providing some suggestions for the sweet potato breeding.