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STUDIES ON GENETIC DIVERSITY AND POPULATION DIFFERENTIATION OF TRADITIONAL RICE LANDRACES FROM DIFFERENT AGRO-ECOLOGICAL NICHE ENVIRONMENTS

KrishiKosh

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Title STUDIES ON GENETIC DIVERSITY AND POPULATION DIFFERENTIATION OF TRADITIONAL RICE LANDRACES FROM DIFFERENT AGRO-ECOLOGICAL NICHE ENVIRONMENTS
Ph.D.
 
Creator GAYACHARAN
 
Subject ---
STUDIES ON GENETIC DIVERSITY AND POPULATION DIFFERENTIATION OF TRADITIONAL RICE LANDRACES FROM DIFFERENT AGRO-ECOLOGICAL NICHE ENVIRONMENTS
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Description There is limited information available on population structure of farmer landraces and loss
of diversity over time and space. Further, to devise a rational conservation plan (ex situ vs
on-farm), limited case studies are available on population differentiation at DNA level and at
the level of the adaptive variations. Many of the farmer landraces from traditional
production areas have been replaced fast by improved varieties and at times it is difficult to
find the same named landrace from the same household again under continuous cultivation.
Further, nothing much is known about the sampling strategy adopted and the sample size for
the ex situ conserved materials available in genebank. The ex situ conserved germplasm in
genebanks worldwide, therefore, suffers from several deficiencies and is often not a fit
material for population genetic studies. In the present study, an attempt was made to
investigate the population structure of some important ethnic landraces from diverse agroecologies
for molecular (STMS) and morphological diversity analyses. The landraces
comprised populations of coloured rices (red or black), aromatic rices and other local upland
landraces primarily from North-western and North-eastern highlands. The observed pattern
of molecular variations and the morphological adaptive variations of native landraces was
investigated. Often the morphological adaptive variations and even the variation pattern
based on major gene controlled qualitative traits did not match the molecular variations. The
probable explanations could be that the microsatellites are considered to be neutral and thus
provide no assessment of fitness. The forces causing high molecular differentiation could be
due to genetic drift and no selection. Conversely, morphological adaptive traits are generally
believed to be subject to natural selection and their expression is partly under the influence
of environmental factors. The findings suggest that from breeders’/users perspective
adaptive variations are rather more important. At farmers’ level stabilizing selection is
normally operative and majority of the named landraces under both ex situ and on-farm
situations grouped together for adaptive quantitative variations (both Ward’s Minimum
Variance Dendrogram and PCA). Further, the nutritional importance of native landraces
under diverse agro-ecologies suggest that the high nutritional quality of rice landraces can
form a strong basis for changing priorities in rice breeding, putting more emphasis on the
grain nutritional value.
 
Date 2016-03-08T15:54:25Z
2016-03-08T15:54:25Z
2013
 
Type Thesis
 
Identifier http://krishikosh.egranth.ac.in/handle/1/64945
 
Language en_US
 
Format application/pdf
 
Publisher IARI, NATIONAL BUREAU OF PLANT GENETIC RESOURCES, NEW DELHI