Construction Of Core Collections Of Max Gourd

Wax Gourd and Chieh-qua(Benincasa hispida Cogn.var.chieh-qua How.)belong to a Cucurbitaceae Benincasa Savi plant.They have a long history of cultivation and have rich genetic diversity.The narrow genetic diversity and the rising similarity coefficient between varieties seriously restricted the development of breeding work.Strengthening the protection and evaluation of existing germplasm resources,clarifying genetic relationships among resources,and building core collection have important research significance for promoting the conservation of biodiversity of wax gourd and promoting the sustainable use of resources.Therefore,there is an urgent need to develop the construction of core collections and genetic diversity analysis of wax gourd.SSR(Simple Sequence Repeat)markers were employed to analyze the genetic diversity of 340 wax gourd germplasm resources at the molecular level 111 germplasms were screened out to form the core collection of wax gourd.The main conclusions are as follows:1.B214 and B227 are two kinds of experimental materials with different phenotypes.To optimized the SSR-PCR reaction system of wax gourd by using primer SSR304 and experimental materials B214 and B227.To establish an orthogonal experiment design of L16(45)with four levels and five factors.The five factors were the concentration of Mg2+,the concentration of dNTPs,Taq polymerase,the concentration of DNA temple and the concentration of prime.The results showed that the optimum reaction system of SSR-PCR includes of 2 μl 10×Taq Buffer(20 mM Mg2+),dNTPs(10 mM)0.4 μl,SSR prime 1 μl(10 μM),Taq Polymerase 0.5 μl(2U),DNA temple(50 ng/μl)1 μl,ddH2O make up to 20 μl.2.By using gennme DNA of 6 wax gourd collections with different geograophic sources and different phenotypes,to choose polymorphic and reproducible primers from the SSR primers that synthesized by the specific SSR markers developed based on the sequencing information of wax gourd.19 polymorphic and reproducible primers were selected from 419 SSR primers for PCR amplification in 340 samples.Totally 182 bands were amplified including 169 polymorphic bands.The polymorphic percentage is 92.86%.3.A clear and reproducible band on 8%polyacrylamide gel electrophoresis pattern was counted as "1",and a band that did not appear at the same location was counted as "0".Generates the original matrix consisted of the numbers "1" and "0".Cluster and analysis with the original matrix showed that when the compression ratio is 30%the genetic diversity of the original germplasm population can be retained to the greatest extent.Plus with the extreme materials,a core collection which contains of 111 wax gourd germplasms based on SSR molecular data was constructed.4.Cluster analysis with UPGMA method by DPS V 16.05 software showed that the genetic relationship between 111 core collections of wax gourd cultivars was not related to geographical origin,but there was a certain correlation between the size of the wax gourd cultivars,the seed type and the color of the pericarp.