Genetic diversity analysis of Xanthosoma sagittifolium (L.) schott using molecular markers

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dc.contributor.advisorAsha Devi, A
dc.contributor.authorKrishnaveni, Vijayakumar
dc.contributor.authorKAU
dc.date.accessioned2021-09-06T06:22:13Z
dc.date.available2021-09-06T06:22:13Z
dc.date.issued2020
dc.descriptionPGen_US
dc.description.abstractThe study entitled “Genetic diversity analysis of Xanthosoma sagittifolium (L.) Schott using molecular markers” was carried out at the Division of Crop Improvement, ICAR-Central Tuber Crops Research Institute, Sreekariyam, Thiruvananthapuram during 2019-2020. The objective of the study was to analyze the genetic variation in tannia based on morphological and molecular characteristics. The knowledge can be exploited for crop improvement programs of Xanthosoma and can be used to develop a core collection. Thirty accessions were selected for the study. For morphological analysis, observations on all the below-ground characteristics of the plant viz., tuber characters were taken (using IPGRI descriptors). The recorded data were analyzed using various statistical methods such as diversity indices (percentage distribution of traits, Shannon's diversity index and Simpson's diversity index), PCA, similarity matrix, cluster analysis and ANOVA. The Shannon Weaver’s diversity index ranged from 0.24 to 0.98 whereas, the Simpson’s diversity index ranged from 0.13 to 0.62. The time of harvest, the position of the cormel apex and the exterior surface of the corm showed no variation and remained constant for the accessions studied. Cluster dendrogram resulted in four major clusters and one outlier. Cluster I had four sub clusters (Ia, Ib, Ic and Id) comprising seven, five, six and five accessions. Cluster II, III and IV consisted of two accessions each, while Xa-JG/2016-1, the only pink-fleshed accession in the set remained an outlier. Cluster II grouped the two accessions, TTn-14-6 and Xa-152 which produced elongated pencil-like cormels that were unmarketable. The rest of the accessions showed variability in tuber shape, size and colour as well as colour of corm apex. PCA revealed that accessions Xa-Ju/10-8, Xa-67, Xa- 152, and Xa-JG/2016-1 showed maximum variability. Based on the coefficient of variation, the degree of variability was found to be high for corm weight, number of cormels produced per plant and cormel weight. For molecular analysis, DNA was isolated by employing a slightly modified version of Dellaporta protocol. Good quality DNA ranging from 1.06 (TTn14-5) - 2.34 (Xa-HOB-T8-2) was obtained. A total of 24 ISSR primers were taken for screening of which, 14 were selected at an annealing temperature of 56.3oC. The selected primers were UBC 807, UBC 808,UBC 809, UBC 810, UBC811, UBC817, UBC818, UBC824, UBC825, UBC827, UBC834, UBC 836, UBC 845 and (GA)9 AC. The PCR products were resolved in 2% agarose and the polymorphic bands obtained were subjected to various analyses. The primers showed 91.64% polymorphism and the total number of bands ranged from 7 to 19. UBC 808, UBC 810, UBC 818 and UBC 824 showing 100% polymorphism. Cluster analysis was done based on Euclidean distance in which the thirty accessions were grouped into four major clusters with the maximum number of accessions in cluster I (22). It had two sub clusters Ia and Ib along with three divergent lines viz., TTn14-1, Xa-JG/2016-1 and Xa-AD/2014-18. One of the sub clusters comprised two duplicates TTn14-9 and Xa-MNS/14-1 as well as TTn14-5 and Xa-MTS-local which showed 100% similarity. Of the three accessions grouped under cluster IV, TTn14-6 and Xa-152 produced elongated pencil like cormels, whereas, Xa-AD/2014-17 produced normal cylindrical cormels. Cluster II had two accessions collected from the Northeast region pooling together. Apart from ISSR markers, cross compatibility of taro SSR markers with tannia accessions was also checked using nine SSR markers (Ce1 B03, Ce1 F04, Ce1 F12, Uq73-164, Uq84-207, Uq97- 256, Uq110-283, Uq132- 147 and Uq201-302) using various temperature regimes and PCR conditions. However, specific bands were not obtained and it was found to be incompatible in accordance with previous studies. The morphological and molecular assessment aided in identification of duplicates and variants present among the germplasm collection whereas the characters which were found contributing to major variability can be used to identify good yielding varieties and eliminate undesirable ones. The data generated from this study is useful for formation of core collection, effective conservation, exploitation of the germplasm as well as breeding and improvement programmes.en_US
dc.identifier.urihttps://krishikosh.egranth.ac.in/handle/1/5810175080
dc.keywordsGenetic diversity, molecular markersen_US
dc.language.isoEnglishen_US
dc.pages112p.en_US
dc.publisherDepartment of Plant Biotechnology, College of Agriculture, Vellayanien_US
dc.subPlant Biotechnologyen_US
dc.themeGenetic diversity analysisen_US
dc.these.typeM.Scen_US
dc.titleGenetic diversity analysis of Xanthosoma sagittifolium (L.) schott using molecular markersen_US
dc.typeThesisen_US
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