Researches On Genetic Diversity And Core Collection Construction Of Amorphophallus Germplasm

Konjac is a plant of the genus Amorphophallus Blume in the Araceae family.It is the only economic crop that can extract a large amount of glucomannan so far,which has high economic value.Amorphophallus has a wide variety of species and a large scale of resources,and it is extremely susceptible to bacterial soft rot during cultivation,which is not conducive to preservation and utilization.Therefore,in this study,the genetic diversity of 204 Amorphophallus germplasm collected in 2020 and 2021 and the original 204 konjac materials collected in Southwest University were analyzed and the core collection was constructed.Only using phenotypic or molecular marker data to construct the core collection may cause the omission of important characters and affect the construction results and utilization of the core collection.Therefore,the genetic diversity analysis and core collection construction of konjac resources are based on phenotypic traits,ISSR molecular markers and SRAP molecular markers.Phenotypic character statistics are based on 195 konjac materials and 16 phenotypic traits.Phenotypic genetic diversity analysis includes average,extreme value,variation range,variance,coefficient of variation,genetic diversity index,correlation analysis,principal component analysis and cluster analysis of 16 phenotypic traits.ISSR and SRAP molecular markers were based on 204 Amorphophallus materials.Genetic diversity analysis included calculation and cluster analysis of percentage of polymorphic loci(PPL),observed number of alleles(Na),average effective number of alleles(Ne),average Nei’s genetic diversity index(H)and average Shannon information index(I).The best strategy for the construction of phenotypic pre-selected core collection of konjac resources was explored from four aspects: genetic distance,sampling method,sampling ratio and cluster analysis.The best strategies of ISSR pre-selection core collection and SRAP pre-selection core collection were compared and analyzed between step-by-step clustering priority sampling method and minimum distance method.The representative evaluation and verification of the pre-selected core collection were carried out,and finally the three pre-selected core collections were integrated to get the final core collection.The main conclusions are as follows:(1)Most of the 16 phenotypic traits had positive correlation.The results of principal component analysis showed that the value of KMO was 0.6760 and the significance was 0.0000.There is a large variation in phenotypic traits,with a genetic diversity index between 0.1147 and 2.4703,between 10% and 81.61%.Cluster analysis was carried out on 195 materials based on phenotypic traits.Can be divided into four categories,including Thailand konjac for a large category,pearl bud konjac materials for a large category,two Yunnan wild konjac and columnar bulbs for one category,and the rest of the materials for one category.(2)The genetic diversity of konjac resources was analyzed based on ISSR data,and the results showed that the genetic diversity of the tested konjac materials was rich.Based on the analysis of ISSR molecular marker data,the average values of observed number of alleles(Na),average effective number of alleles(Ne),average Nei’s genetic diversity index(H)and average Shannon information index(I)were 2.0000,1.5235,0.3141 and 0.4773,respectively.The genetic distance was calculated by SM and cluster analysis was carried out by UPGMA method.204 konjac resources could be divided into 12 categories when the genetic similarity coefficient was 0.64.(3)A total of 150 bands were amplified by 13 pairs of SRAP primers screened by SRAP molecular markers,and the polymorphism rate was 100%.The observed number of alleles was(Na)2.0000,the effective number of alleles(Ne)was 1.4906-1.7709,the average was 1.6536.Shannonsons information index(I)was 0.5601-0.6038,the average was 0.5545,which indicated that SRAP molecular marker was an effective method for genetic diversity analysis of konjac resources.The genetic distance was calculated by SM and cluster analysis was carried out by UPGMA method.When the genetic similarity coefficient was 0.66,204 Amorphophallus materials could be divided into 8groups,which was similar to that of ISSR molecular marker data.(4)The core collection containing 30 collections was constructed based on the phenotypic character data,using Euclidean distance,multiple clustering priority sampling method and the shortest distance method under the sampling ratio of 15% is the best strategy for phenotypic pre-selection of core collection of konjac resources.(5)A core collection containing 40 konjac materials was constructed based on ISSR molecular marker data.Comparing the step-by-step clustering priority sampling method and the minimum distance method to construct the konjac ISSR data pre-selected core collection,it is found that using the minimum distance method,the sampling ratio of 20% is the best strategy.(6)51 core collections were constructed based on SRAP molecular marker data.Using minimum distance method and sampling ratio of 25% was the best strategy to construct core collection of konjac resources based on SRAP data.The retention rate and principal coordinate analysis of the number of alleles(Na),the average effective number of alleles(Ne),the average Nei’s genetic diversity index(H)and the average Shannon information index(I)were used to verify the representativeness of the two pre-selected core collections.The results showed that the two pre-selected core collections could represent the genetic information of the original collection.(7)Based on 51 SRAP pre-selected core collections,the phenotypic pre-selected core collection and ISSR pre-selected core collection were integrated to obtain the final core collection containing 93 materials.Finally,the core collection contains the mean,extreme and variation characteristics of the phenotypic characters of the original collection,removes the redundant genetic information of the original collection,and retains the genetic diversity of the original collection,which can provide a reference for the preservation and utilization of Amorphophallus germplasm.