Asha, Devi AVinutha, K BKAU2019-12-112019-12-112014http://krishikosh.egranth.ac.in/handle/1/5810137313PGThe study entitled “Genetic diversity analysis in taro [Colocasia esculenta (L.) Schott] of North East India” was carried out at the Division of Crop Improvement, Central Tuber Crops Research Institute, Sreekariyam, Thiruvananthapuram during 2013-2014. The objective of the study was to assess the genetic diversity among taro accessions from North East India, which is considered to be one of the centers of origin of taro, using morphological descriptors and SSR markers. The knowledge can be exploited in the heterotic breeding of taro to develop improved varieties suiting various needs. National and international germplasm repositories conserving root and tuber crops can also use the data to maintain taro germplasm efficiently. Twenty five accessions of taro collected from the various North Eastern states of India and maintained at CTCRI were selected for the study. Morphological characterization was performed at the maximum vegetative stage and tuber characters at harvest using ten quantitative and 28 qualitative traits. A combination of NBPGR and IPGRI descriptors were used to explain the wide range of morphological variability. The data was statistically interpreted in terms of diversity indices, PCA, ANOVA and cluster analysis using R statistical package and SAS program. The diversity indices (H’=0.87; D=1.00) revealed a high level of morphological diversity among the taro accessions. The first four components explained 76.59 per cent of the total variation with leaf margin colour, petiole colour (top 1/3rd, middle and base), leaf colour lower, sheath colour and sinus colour contributing maximum to the variability. ANOVA showed significant (P<0.01) variation for 7 out of the 10 quantitative traits studied. Duncan’s multiple range test gave a grouping based on the mean values of quantitative traits. Five major groups were revealed after hierarchical cluster analysis based on Euclidean distance, which did not bear any relation to the geographical origins of the accessions. A protocol was developed for the isolation of good quality DNA overcoming the high levels of secondary metabolites in taro. PCR conditions for SSR detection in taro were also optimized successfully. Ten out of 18 SSR primers were selected for the study after screening. Denaturing PAGE followed by silver staining was performed to analyze the variability among accessions at the molecular level. The average number of alleles and Shannon’s diversity index ranged from 6.0-12.57 and 1.59-2.37, respectively. The polymorphic marker ratio was found to be high for all the primers (0.76-1.0); however, Ce1 A06, Ce1 B03, Ce1 C06, Ce1 F04 and uq201-302 gave the maximum ratio of one. Cluster analysis based on Jaccard’s distance revealed five broad clusters which could not be correlated to the geographical similarities among the accessions. The parameters estimated from molecular and morphological characterization data established a high level of genetic diversity prevalent in the center of origin. The study revealed the absence of congruence between the clustering pattern and geographical origin suggesting that geographically diverse regions share ecologically similar characteristics and vice versa. Differences in morphological and molecular clustering patterns indicate the wide range of adaptations of the crop to the diverse environments inhabited. Though the Mantel’s test established no correlation (r = 0.1432; p = 0.0648) between the molecular and morphological distance measures, the study could identify two groups of accessions that clustered together in both the methods.ennullThesis