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Title: Genetic diversity study in landraces of rice (Oryza sativa L.) by agro-morphological characters and microsatellite DNA markers
Author: Bajracharya, Jwala
ISNI:       0000 0001 3437 894X
Awarding Body: University of Wales, Bangor
Current Institution: Bangor University
Date of Award: 2003
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The genetic diversity of 632 rice landraces was studied from three ecosites representing three agro-ecozones of Nepal. There were 147 landraces from Jumla (2240-3000 m altitude), 291 from Kaski (668-1206 m) and 194 from Bara (80-90 m). Rice diversity was assessed by agro-morphological traits and microsatellite (SSR) markers. This research was pa1i of the Nepal Country Component of the IPGRI Global Project on "Strengthening the scientific basis of in-situ conservation of agricultural biodiversity on farm". A broad range of landrace diversity was under cultivation under traditional management systems in these three ecosites. The landraces were grown for home consumption, sale, and for religious and cultural purposes and were adapted to a range of agroecological niches. The rice accessions from the three ecosites were evaluated in field experiments in 2000 and 200 l. Each set of landraces was grown in a single trial in Agriculture Research stations of the ecosites. Forty three agro-morphological traits ( qualitative and quantitative) were measured including those that the farmers used in distinguishing these landraces. Using this morphological variability data, diversity measures such as the Shannon Weaver diversity index (H') for qualitative traits, coefficients of variation (CV) for quantitative traits, and three multivariate procedures were used to estimate diversity and relationships within and between the groups of rice landraces that shared the san1e name. There was a moderate to high variability for the studied traits and many of them were useful for assessing the level of genetic diversity. For most morphological traits the landraces from Kaski and Bara were more variable (H' 0.7-0.8 and CV for quantitative traits of 18-20%), compared with landraces from Jumla (H' 0.2 and CV 8%). Cluster analysis and discriminant function analysis based on significant qualitative and quantitative traits discriminated between groups of landraces of the same name in Kaski and Bara. However, Jumla rice landraces having different names were closely related and had a narrow genetic base. Seventy rice accessions (21, 24 and 25) comprising of accessions with 10 different names from each ecosite and a few Nepalese and Indian PPB varieties were assayed for genetic diversity at 39 SSR marker loci using agarose gel electrophoresis. The number and frequency of alleles, the polymorphic information content (Nei's gene diversity, PIC) and multivariate analyses on allelic data were used to measure the diversity within and among the landraces and varieties of rice produced by participatory plant breeding (PPB). The patterns of genetic diversity among landraces revealed by the SSR polymorphisms varied between the study sites and the varieties. Landraces from Kaski and Bara showed a high genetic variation with about 0.34 average molecular genetic diversity (PIC) and about 88% of the markers were polymorphic. Landraces from Jumla hardly varied for the SSR markers tested - only one marker was polymorphic. Multivariate analysis ( cluster analysis) corresponded to the pattern of variation found with the morphological traits. Both showed there was high genetic dissimilarity among groups of Kaski and Bara landraces and low dissimilarity among Jumla landraces. The study showed that the most abundantly grown landrace: Kathegurdi and Laltenger had little within-cultivar variation. Landraces grown in a small area by only a few households and genotypes with culinary importance: Basmati, Jetho Budho, Rato Anadi, Jhinuwa, Nakhisaro and Sathi, had a comparatively large within-and between-cultivar variation. PPB varieties were as diverse as the landraces, when assessed by SSR markers, and PPB is a useful approach for increasing diversity in environments with low landrace diversity. Overall, the study showed that the mid-hill ecosite with diverse agro-ecological environments and the lowland ecosite with most favourable rice growing environments conserved a high level of rice landrace diversity. This diversity in morphological and SSR variation is discussed in relation to management of rice genetic resource of Nepal.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available
Keywords: Nepal