Study on Improvement of Rice Productivity and Quality in Myanmar
-Improvement of Genetic Purity in Breeder Seed Multiplication of Rice Cultivars and Variation of Agricultural Traits of Rice Cultivars by Cropping Season-
Tomoyuki FUJII
Rice cultivation is the most important in Myanmar agriculture, and paddy field occupy 47.4% of the total cultivated area. However, the yield has stagnated at 3.9 tons/ha for the past few years, which is low compared to around 5.0 t/ha in other Asian countries. To solve such a situation, Japan International Cooperation Agency (JICA) implemented technical cooperation project for improvement of seed quality of rice from 2011 to 2017.This study was conducted for the purpose of verifying the effects of JICA's efforts scientifically, and to examine the possibility in an enhancement of rice productivity and its quality.
The study is consisted from the clarification of the issues in rice production in Myanmar, the demonstration of genetic stability in major rice cultivars and the evaluation of variation in agronomic traits of cultivars under the different environment conditions. Nine major cultivars in Myanmar, Theedatyin, Manauthukha, Sinthukha, Sinthwelatt, Kyawzeya, Shwewartun, Ayeyarmin, Pawsanyin and Hnangar were used in the study. These cultivars were photoperiod-insensitivity except for Hnangar.
The investigation of rice production in Myanmar clarified that many farmers use self-saved seeds, and breeder seed quality has degraded because of the mixture of sister lines by the conventional multiplication method which have no pedigree record. It was also found that the right cultivars were not planted in the right places.
Instead of conventional method, the line cultivation method to ensure traceability of ancestral information by line and individual selection was
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introduced to breeder seed multiplication for improvement of genetic purity.
The study revealed that standard deviations of heading date, culm length, panicle length and panicle number of all cultivars in 2016 were significantly decreased compared to the first year of the introduction of the line cultivation method. Average heading duration among the sister lines of all cultivars were reduced from 8.25 days in 2013 to 5.25 days in 2016. The variance component ratio of each trait in 2016 was the highest since 2013. The analysis of breeder seed by SSR markers indicated 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. These results suggested that the line cultivation method is effective to improve genetic purity and maintain genetic stability of the breeder seed. Genetically pure breeder seed would improve quality of downstream seed such as foundation seed, registered seed, and certified seed.
Agronomic traits of eight photoperiod-insensitive cultivars were evaluated during wet season (WS) and dry seasons (DS) in Yezin, Hmawbi and Myungmya.
Heading date, culm length, panicle length, panicle number and paddy yield were evaluated by Tukey-Kramer method and ANOVA to identify main components explaining phenotypic variations by genotypes, locations, cropping seasons and year. This will enable to select suitable cultivar to the land and to establish efficient cropping system.
It was found that heading date of all cultivars in WS of Yezin and Myaungmya were about 11 to 16 days earlier than those in DS except for Theedatyin, though Yezin is in dry zone about 320 km north of Myaungmya of delta zone. On the other hand, in Hmawbi located in the same delta zone as Myaungmya at about 100 km west, heading dates in WS and DS were almost the same time in all cultivars. The delayed heading date in DS of Yezin and Myaungmya should be due to low temperatures at night during the panicle-formation stage. In Hmawbi, the early heading in DS could be due to the high day temperature, and the late heading in the WS could be due to the high night
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temperature, compared to Myaungmya. These variations of heading date should be attributed to day and night temperature which effect panicle-formation in WS and DS at each location. Culm length in WS was longer than that in DS for all cultivars at every location except for 2015 DS at Myaungmya. The air-dry effect is likely to be a cause of this variation.
Analysis of variance revealed that phenotypic variance of heading date and culm length was highly associated to genotype, season, and location as well as their interactions. In analysis of variance separately conducted in WS and DS showed that genotype, location and interaction between genotypes and location were found to be associated to heading date and yield. Genotypes, and interaction of genotypes by season were significant component of phenotypic variance of yield.
Yield would varies depending on the amount of solar radiation and temperat.
High solar radiation would affect during grain ripening stage and increase the yield of early/middle matured cultivars in DS. High temperature in late DS would affect during booting and flowering stage, and decrease yield of late matured cultivars by sterility. And low night temperature in mid DS would affect during panicle-formation stage and sterile flower resulted in low yield.
The results suggest that the cultivar trials at different locations need to be conducted both in WS and DS to improve the efficiency of selection for widely adopted cultivars as well as to make efficient cropping system in Myanmar.
However, the yield data was obtained only a single year, therefore further study is required to clarify variation of the yield under the different environment conditions.
According to the farmers survey conducted in the project sites of the JICA technical cooperation in the Ayeyarwady Region in December 2017, farmers who used CS for paddy production in WS and DS of 2016 and 2017, the yield increased by 14.6% in WS and 13.3% in DS compared to those without using CS.
Based on these results, the expected yield was calculated. Assuming that all farmers will replace self-saved seeds of 18 cultivars to CS of the same18