Local landraces of rice from Sri Lanka : variation in the genome and traits related to drought resistance

• Main Author: Munasinghe, Mayuri Swarnamalee
• Published: University of Aberdeen 2013
• Subjects: 580; Rice
• Online Access: http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.600103

A set of 135 rice landraces from different geo-climatic regions of Sri Lanka were tested for their rooting characteristics with high throughput physiological screening methods. In the preliminary screening, nearly half of the variation in toxicity symptoms observed in all 135 landraces due to herbicide layer (TRIK, 100 mg / plant) buried at 30cm depth was explained by landrace. Deep rooted and shallow rooted landraces were distinguished by herbicide score. Selected 36 landraces with diverse herbicide scores were tested in hydroponics for 5 weeks for root traits. Root length and root thickness had significant genotypic differences explaining 60% and 30% of the variation. From 36, 12 landraces were then grown in rhizotrons for 6 weeks and their root characteristics were confirmed. Genotypic differences accounted for 62, 74 and 54% of variation in root length, root angle and root thickness. Root screening concluded that Podi wee-1, Sinnavellai, Niyan Wee-1 and 2 are the most deep rooting, drought resistant landraces among the set of 135 Sri Lankan landraces. These landraces showed better relative growth than shallow rooted landraces under drought environment. Cluster analysis of SNP data from 378 markers indicated that there are 6 different subpopulations among landraces. The most deep rooted, upland landrace Podi Wee-1was identified as a tropical japonica variety .Other deep rooted landraces, Sinnavellai, Niyan Wee-1 and Niyan Wee-2, were grouped as indica 2, a significantly different group from all other indicas due to their high mean herbicide score and high drought resistant properties. None of the OryzaSNP indica landraces grouped with the indica 2, suggesting that the indica 2 group identified here represents a local subpopulation of indica adapted to drought prone environments. It was proven that differences in rooting depth were associated with genetic variation both at the whole genome level.