1. KAUTIR (Kerala Agricultural University Theses Information and Retrieval)
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Item Genetic diversity analysis of sweet potato (ipomoea batatas (L.) lam.) germplasm using morphological and ISSR markers(Department of Plant Biotechnology, College of Agriculture, Vellayani, 2018) Sabarinath, V B; Shirly Raichal AnilCharacterization of crop germplasm based on determination of amount and distribution of crop genetic diversity is necessary for proper utilization andconservation. This could be achieved through both morphological and molecular tools. This study entitled “Genetic diversity analysis of sweet potato (Ipomoea batatas (L.) Lam.) germplasm using morphological and ISSR markers” was carried out in the Division of Crop Improvement, ICAR-Central Tuber Crops Research Institute, Sreekariyam, Thiruvananthapuram during 2017-2018 with an objective to identify genetic diversity in the sweet potato germplasm based on morphological and molecular markers. ICAR-CTCRI is the National Active germplasm site (NAGS) of tropical tuber crops which maintains 1400 accessions of sweet potato at Sreekariyam and its regional Centre at Bhubaneswar. 54 accessions of sweet potato including 52 accessions from eastern states of India and two wild species I. triloba and I. aquatica were selected from this collection. The study consisted of two parts -morphological and molecular characterization. Morphological analysis was performed by using eighteen sweet potato descriptors as provided by IPGRI (CIP et al., 1991). The recorded data was analyzed statistically by various tools such as PCA and cluster dendrogram using Multivariate statistical package (MVSP 3.22). The dendrogram separated into the accessions into two principal clusters and one outlier at a Euclidean distance of 1.2. The PCA analysis revealed predominant vine colour, leaf lobes type as the major variables that contributed to the clustering of the sweet potato accessions. Molecular analysis was performed using ISSR markers. The genomic DNA was isolated from young leaves using Dellaporta et al. (1983) method. 11 ISSR primers were used for screening of fifty four accessions. After the final PCR using selected primers, the product was resolved in 2% agarose and polymorphic bands were obtained. Primers showed 89.8% polymorphism and the number of bands ranged from 5 to 16 with a mean value of 7.3 polymorphic bands per primer. A total 63 of 80 polymorphic bands were obtained. The data analysed using NTSYS PC 2.02 program generated a dendrogram, which grouped the accessions based on Jaccard‟s similarity coefficient which separated the fifty four accessions into three principal clusters. The first principal cluster comprised of 37 accessions which were grouped into many subclusters and there was lot of intra-clusteral variation. The second principal cluster consisted of 15 accessions and this principal cluster comprised of two accessions with 89% similarity which were also found similar in morphological characterization. The third principal cluster comprised of the two wild species, Ipomoea troloba and Ipomoea aquatica. The similarity between the different accessions ranged between 37-89%. The accessions S1574 and S1576 were 89% similar. The least similar accessions were S1408 and S1572, S1527 and S1572 (37%). A high diversity of 63% existed within the selected accessions.Mantel‟s test also showed significant correlation (r = 0.0985; p = 0.0003) between the molecular and morphological distance matrices. The hexaploid nature of the crop, self-incompatibility, along with the out crossing nature together might have contributed to the high variation observed among the accessions.Item Identification of duplicates in the germplasm of sweet potato (Ipomoea batatas (L.) Lam.) using morphological and molecular markers(Department of Plant Biotechnology, College of Agriculture, Vellayani, 2017) Babitha Babu; Shirly Raichal AnilThe study entitled “Identification of duplicates in the germplasm of sweet potato (Ipomoea batatas (L.) Lam.) using morphological and molecular markers” was carried out at the Division of Crop Improvement, ICAR-Central Tuber Crops Research Institute, Sreekariyam, Thiruvananthapuram during 2016-2017. The objective of the study was to identify duplicates in the sweet potato germplasm based on morphological and molecular markers. Identification and elimination of these common redundant materials will enhance the germplasm viability. Fifty accessions were selected for the study. The study was divided into two phases - morphological and molecular analysis. Morphological analysis was performed by using twenty descriptors as provided by IPGRI (CIP et. al., 1991). The recorded data were analyzed statistically by various tools such as PCA and cluster dendrogram. Cluster dendrogram identified three sets of morphological duplicates and the accessions were separated into six principal clusters and two outliers at a Euclidean distance of 1. The PCA analysis revealed predominant vine colour and secondary vine colour, abaxial vein pigmentation and petiole pigmentation as the major factors that contributed to the clustering of the sweet potato accessions. After morphological analysis, molecular analysis was performed. The genomic DNA was isolated using CTAB method which gave good quality DNA. 11 ISSR primers were used for screening of fifty accessions. After the final PCR using selected primers, the product was resolved in 2% agarose and polymorphic bands were obtained. All the primers showed 100% polymorphism and the number of bands ranged from 9 to 18 with a mean value of 14.7 bands per primer. Using the molecular scoring data, UPGMA clustering was done and the whole fifty accessions were divided mainly into two principal clusters and one outlier. The first principal cluster comprised of 40 accessions which were grouped into many subclusters and there was lot of intraclusteral variation. The second principal cluster consisted of 9 accessions and this principal cluster comprised of two true duplicates which were also found similar in morphological characterization. The outlier was different from all the other accessions and may be due to the peculiar leaf shape which is not seen in other accessions selected in the study. SD-29 was different from all the remaining accessions by a similarity coefficient of 0.61.The similarity between the different accessions ranged between 52-100%. The duplicates S-236 and S-256 were 100% similar. The least similar accessions were SD-39 and S-298 (52%). Thus it can be inferred that a 48% variability or diversity existed within the selected accessions which can be considered as a moderate diversity. The hexaploid nature of the crop, self incompatibility, along with the out crossing nature together might have contributed to the high variation observed among the accessions. Only two duplicates were identified. In future more specific markers may be used for core collection development and to eliminate duplicates.Item Cloning and expression of coat protein gene of sweet potato leaf curl virus (splcv)(Department of Plant Biotechnology, College of Agriculture, Vellayani, 2018) Sruthy, G S; Makeshkumar, T