Genetic variation of rice (Oryza sativa L.) germplasm in Cambodia

Abstract

Genetic variations of 179 rice (Oryza sativa L.) accessions from Cambodia were clarified based on the analyses for heading date, chromosome components, and blast resistance. The dominant accessions were found in three regions; early heading in North East (NE), medium in Central (CT), and late in South East (SE) along the Mekong River in the investigation at Ishigaki, Japan. In contrast, wide variations were observed in two regions, South West (SW) and North West (NW) located around Tonle Sap Lake. Polymorphism data of SSR markers showed that accessions were classified into Japonica Group (cluster Ib), and Indica Groups (IIa and IIb). In the NW and SW, the accessions of all three clusters were found, but these accessions in NE, CT, and SE, were limited to one or two clusters. Accessions were classified again into two clusters, A1 as having high resistance and A2 as having moderate resistance. Remarkable differences of these frequencies of clusters, A1 and A2, were found in the SE, SW, and NW, and similar with these of the whole accessions were in NE and CT. Rice accessions varied among the five regions, and there was a dramatic difference between the regions along Mekong River and the regions around Tonle Sap Lake.

Keywords: Cambodia; blast resistance; genetic variation; heading date; rice (Oryza sativa L.).

Fig. 1.

Relationships between maturity type in Cambodia and genetic variation of day to heading at Japan. Three categories for heading date, Early, Middle, and Late, is the classification under the environmental condition at CARDI, Phnom Penh, Cambodia. Investigation was carried out at Ishigaki, Okinawa, Japan, in the second rice cultivation season from July to November of 2017. A total of 176 accessions were investigated for heading date among whole materials. Triangle: Mean.

Fig. 2.

Genetic variation of days to heading in each region of Cambodia. Investigation was carried out at Ishigaki, Okinawa, Japan in the second season from July to November 2017. A total of 176 accessions were investigated for heading date among whole materials. Black: Local accessions in Cambodia. Gray: Improved accessions introduced by IRRI and other foreign countries. Triangle: Mean.

Fig. 3.

Geographic distributions of rice accessions from Cambodia in each clusters group classified by polymorphism data of SSR markers. Grau region: Sits for collection of rice accessions.

Fig. 4.

Genetic variation for resistant of rice accessions in each cluster group classified based on reaction pattern of 16 standard differential blast isolates. A total of 179 rice accessions from Cambodia, 25 DVs for blast resistance genes, two susceptible controls, LTH and US-2, were included. The mean value of scores to 16 SDBLs was used as the representative data for resistant in each accession. Triangle: Mean.