Improvement of Genetic Purity of Breeder Seed by Introducing Line Cultivation Method for Myanmar’s Major Rice Cultivars

Aims: Since the genetic purity of rice seed significantly affects paddy yield and quality, many rice production countries have been attempting to improve seed quality. This study aimed to demonstrate the effectiveness of breeder seed production using line cultivation to ensure traceability of ancestral information by line and individual selection, to improve the genetic purity of breeder seed in Myanmar that has been degraded due to pedigree mixtures. Study Design: Observational and analytic study design was used to evaluate the effect of the introduction of line cultivation method in practical activities of breeder seed production in Myanmar under the project for improvement of seed purity of breeder seed. Place and Duration of Study: Department of Agricultural Research at Yezin, Ministry of Agriculture, Livestock and Irrigation, Myanmar, from June 2012 to December 2016. Methodology: Using nine major rice cultivars in Myanmar, the line cultivation method was evaluated through measurement of the standard deviation and the variance component ratio in heading date, culm length, panicle length, and panicle number from 2012 to 2016. DNA polymorphism analysis by simple sequence repeat (SSR) markers was also conducted using breeder seed of the Sinthukha variety multiplied in 2013, 2014, 2015, and 2016 for the evaluation. Results: Standard deviations of heading date, culm length, panicle length and panicle number in 2016 were significantly decreased compared to the first year of the introduction of the line cultivation method. Average heading duration among sister lines of all varieties was reduced from 8.25 days in 2013 to 5.25 days in 2016, and the uniformity of heading time among sister lines was improved. The variance component ratio of each trait in 2016 was the highest since 2013. The analysis of breeder seed by SSR markers revealed that the DNA polymorphism ratio of Sinthukha seed in 2016 was lower than that of 2013. This demonstrated that Sinthukha seed in 2016 had improved genetic purity. Consequently, it is considered that other cultivars multiplied by the line cultivation method have improved their genetic purity as well. Conclusion: Line cultivation is an effective method to improve genetic purity and maintain genetic stability of the breeder seed in Myanmar’s rice cultivars. Genetically pure breeder seed would improve quality of downstream seed such as certified seed. Consequently, it is expected that productivity and quality of rice will be improved thus income of farmers will increase.