Studies On The Genetic Diversity And Breeding Strategy Of Chinese Cultivated Cowpea

Cotrpea, opa ungUicuIata (L.) Walp., belongs to genus nga in Fabaceae.There are about l50 species in genus nga. As one of the most pulse crops allover the world, it is currently cultivated in all tropical, subtropical areas and sometemPefate areas, such as Africa, Asia, South America, the Mediterranean Basinand the southem states of the USA. WOrid coWPea acreage under cuItivation isestimated to exceed l2l5 million hectares, with an annual production of over 3million tons world-wide. As one of normal imPortant vegetable in China, thepercentage of acreage under cultivation is over l0% of vegetable acreage everyyea p exceeding tO 33 thOusand hectares.In this study, the phylogeny of genus Vigna was investigated based on ITSsequence data of 42 species Which were obtained from GenBank and our practice.And then, the genetic diversity of 76 cultivated coWPea germplasm collecting fromall over the China was evaluated based on RAPD and ITS sequence data.Moreover, coWPea trypsin inhibitor(CpTI) gene was cloned from Chinesecultivated coWPea. The main results were shown as following.l. Low resolution was obtained in genetic variation investigation of differentcoWPea cultivated germplasm of nga unguicuIata based on ITS sequence data,While good results could be obtained in genetic diversity and phylogeny ofdifferem species of genus nga.The ITS sequences contain many variable sites and phylogenetical informativesites among related species of genus nga and phylogenetic relationships amongecies could be established succesfully. The topology of the strict consensus treeand Neighbordoining tree inferred from ITS sequence data shows that:42 species were clustered to three groups. The species from Asia clustered toone grouP and lied in the uppermost of the systematic tree Which suggested these; lvspecies may be speceis of origining later. The bootstraP value is l00%. The geneticdistance betWeen them was below l5% in most cases, which indicated the geneticdiversity among them was low Among them, the distance between U radtata andY mungo, between V angularItr and V umbellata, between V umbellata and Vradtata V mungo, bctween Y anguleris and V radha, Y mungo was abollt l1%,3.5%, 1 l%, l2% respectively Fndermore, the distance between the 4 species andY unguiCulata was faf, reaching to above 33%.The species from America clustered to one group and located in the base of thesystematic tree which suggested these species may be speceis of originating earlier-The bootstraP value is less than 50%. The genetic distance between tl1em wasabout 15% in most cases, Which indicated the genetic diversity level among themwas high.The other species, which origin were unknown, clustered to another group andlocated in the middIe of the systematic tree. The bootstraP value is 63%. Thegenetic distance between them was about 30% in most cases, which indicated thegenetic diversity level among them was higl1 too.All the 76 cultivated coWPea germplasm cbllected from China belong tongaunguiculata ssp. unguiculata. Because the variation level of ITS sequence withinthe 76 cultivars was very low ITS was not suitable for phylogenetic analysis at thelevel of cultivars in nga unguiculata ssp. unguiculata. But, it indicated that thegenetic diversity 1evel was very low among Chinese cultivated coWPea.In our collected germplasm, cultivar Qushichixiaodou must not be member ofmpna unguiculata, maybe it was more reasonable that cultivar Qushichixiaodoubelong to nga umbeIlata based on ITS sequence data. Furtheomore, cultivarChengiiang Nol was 11ot clustered to grouP nga unguiculala, whiIe clustered toY umbellata. But, it must be member of Y unguiculata based on morPhology. So,the taxonomic category of Chengiiang No. l need to be researched further.2. RAPD can be used 'in the study on genetic diversity at the level of specie.Among 76 coWPea cultivars, 73 of which were clustered to two large grouPs basedon RAPD data.