Developing drought tolerant rainfed lowland rice (Oryza sativa l.) genotypes using marker assisted back crossing technique
Loading...
Date
2017
Authors
Journal Title
Journal ISSN
Volume Title
Publisher
Sokoine University of Agriculture
Abstract
With an objective of developing high yielding drought tolerant rice genotypes, marker
assisted selection was employed in the selection of suitable donor parents and subsequent
introgression of the drought tolerant alleles in the background of susceptible high yielding
variety (TXD 306). Twenty genotypes were evaluated in well irrigated, moderate and
severe stress conditions to select drought tolerant donors. They showed differences in
agronomic and physiological performances. Yield under drought stress was positive and
significantly correlated with spikelet fertility, number of panicles m'2, grain weight, and
plant height, and negatively correlated with number of days to flowering. Fifty SSR
markers were employed to characterize 21 genotypes for drought tolerance. Polymorphism
information content (PIC) values varied from 0.00 to 0.67. Cluster analysis revealed three
clusters. The drought susceptible rice, TXD 306 formed its own cluster. The results
showed substantial levels of genetic diversity sufficient to suit selection of drought tolerant
donors for the breeding programme to improve TXD 306 for drought tolerance.
Combination of markers assisted selection and agro-morpho-physiological performances
were able to identify two drought tolerance donors viz; Mwinula and Moroberekan.
Crosses were done to develop Fi and then BCiFi generations. Foreground selection was
done on 108 BCiFi plants with SSR markers linked to drought tolerance. The heterozygous
BCiFi were selfed to generate BC1F2 seeds. The results of single marker analysis revealed
that SSRs RM 252, RM 264 and RM 566 had significant association with grain yield and
leaf rolling under reproductive stage drought stress. The proportions of phenotypic
variation explained by the markers ranged from 45.9% to 14.0% for tolerance to leaf
rolling and 10.9% to 5.5% for grain yield. Chi-square results observed significant
segregation distortion for the three markers used across the populations studied. In most
cases marker distortion skewed towards susceptibility (74.4%) followed by heterozygosity
(17.9%) and tolerance (7.7%). All BC1F2 populations performed essentially better than theiii
recurrent parent under reproductive stage drought stress. The BC j F j lines should undergo
further evaluation and selection to develop drought tolerant varieties which can be used to
replace the popular high yielding but susceptible varieties in the drought prone rainfed
ecologies.
Description
Thesis
Keywords
Backcross, Drought tolerance, Marker-assisted selection, Rice, SSR markers, Segregation distortion