Abstract
Incorporation of submergence tolerance, controlled by Sub-1 locus, into local rice varieties was attempted by using DNA marker assisted breeding. Submergence tolerance among tested rice varieties was accurately phenotyped by evaluating acclimative shoot response. Submergence intolerant varieties displayed greater shoot elongation while submergence tolerant plants showed restricted elongation during submergence. During de-submergence all susceptible varieties withered and perished while tolerant plants showed nearly 100% survival and they were assigned the survival score of 1. Microsatellite DNA markers RM 464A and RM 219 that are linked to Sub-1 were used to genetically screen for Sub-1 locus. Two alleles (226 and 231 bp) of RM 464A marker were detected among the tested varieties. All the tested varieties displayed 226 bp allele of RM 464A with the exception of variety Bw 363 (231 bp). Higher allelic variability (190, 214, 220 and 230 bp) for RM 219 marker was observed. The polymorphism detected for RM 464A and RM 219 between varieties IRRI 119 (Sub-1 donor) and Bw 363 has allowed us to identify specific alleles of the two markers. The haplotype of 226 bp allele of RM 464A and 220 bp allele of RM 219 were used as diagnostic alleles or gel bands to monitor Sub-1 in IRRI 119 × Bw 363 cross. Easily-scorable bands for these two markers accurately and reliably distinguished submergence tolerant plants in a F2 population. These results demonstrated that the two studied DNA markers can be used to introgress Sub-1 locus into local rice varieties to achieve submergence tolerance. Ceylon Journal of Science (Bio. Sci.) 41 (2): 125-136, 2012 DOI: http://dx.doi.org/10.4038/cjsbs.v41i2.5382
Highlights
Rice (Oryza sativa L.) is the staple food for more than half of the world’s population (Jena and Mackill, 2008)
-scorable bands for these two markers accurately and reliably distinguished submergence tolerant plants in a F2 population. These results demonstrated that the two studied DNA markers can be used to introgress Sub-1 locus into local rice varieties to achieve submergence tolerance
Correct phenotyping is essential to establish and validate the DNA markers linked to Sub-1 locus which is responsible for submergence tolerance
Summary
Rice (Oryza sativa L.) is the staple food for more than half of the world’s population (Jena and Mackill, 2008). Flash flooding which takes place during the monsoon season is a serious problem for rice production in the rainfed lowlands of South and Southeast Asia. 50% of the rice growing land in the region is affected by flash flooding at various stages of growth (Toojinda et al, 2003). In this context, having submergence tolerant rice varieties is very important in minimizing flood damages in rice production. Both iron toxicity and submergence are two major environmental problems prevalent in the Western Province of Sri Lanka that hamper rice productivity in this region. It has been reported that the floods in Ampara, Polonnaruwa, Anuradhapura and Batticaloa districts during December 2010 to January 2011 were very destructive and nearly 90% of ‘Maha’ season rice crop (approximately 450,000 tons) in these districts has been destroyed (FAO country report, 2011)
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