Inheritance of tolerance to rice tungro bacilliform virus (RTBV) in rice (Oryza sativa L.).

From a large number of rice varieties tested, no variety was identified as resistant to tungro bacilliform virus (RTBV). Only in Utri Merah was the RTBV multiplication restrictive, whereas other varieties such as Kataribhog and Pankhari 203 were identified as tolerant. These varieties were crossed with a susceptible variety. TN1, to study the inheritance of restrictive multiplication and tolerance to RTBV. After 3 weeks of inoculation with RTBV, F1; F2, and F3 progenies were assessed by enzyme-linked immunosorbent assay (ELISA). The RTBV concentration in all F1 populations was intermediate between parents. The frequency distribution of F2 seedlings with various levels of RTBV concentration indicated that the RTBV tolerance is controlled by multiple genes. The RTBV concentrations in F1 and F2 progenies from the Utri Merah x TN1 cross revealed that restrictive multiplication of RTBV in Utri Merah is a polygenic character. The continuous variation observed in F2 populations from crosses between tolerant varieties and Utri merah indicated no allelic relationships between tolerant and restrictive multiplication traits.