Abstract
Selecting genetically diverse and complementary parental lines and superior crosses are pre-requisites in developing improved cultivars. The objectives of this study were to determine the combining ability effects and gene action conditioning rice yellow mottle virus disease (RYMVD) resistance and agronomic traits in rice (Oryza sativa L.). Ten parental lines and their 45 F2 progenies were field evaluated in three locations using a 5 × 11 alpha lattice design with two replications. The genotype × site interaction effects were significant (p < 0.05) for the number of tillers (NT), number of panicles per plant (NPP), number of grains per panicle (NGP), percentage of filled grains (PFG), thousand grain weight (TGW), RYMVD resistance and grain yield (GY). The analysis of general and specific combining ability (GCA and SCA) indicated involvement of both additive and non-additive gene action governing inheritance of traits. High GCA/SCA ratio estimate revealed additive genetic effect was predominant. Parental lines Mwangaza, Lunyuki, Salama M-57, Salama M-19, IRAT 256 and Salama M-55, which had negative GCA effects for RYMVD, and families such as SARO 5 × Salama M-55, IRAT 245 × Rangimbili, Rangimbili × Gigante and Rangimbili × Mwangaza, which had negative SCA effects for RYMVD, were selected for RYMV resistance breeding. The crosses Rangimbili × Gigante, Gigante × Salama M-19 and Rangimbili × Salama M-55 were selected due to their desirable SCA effects for GY. The predominance of additive gene effects for agronomic traits and RYMVD resistance in the present breeding populations suggested that rice improvement could be achieved through gene introgression using recurrent selection.
Highlights
Rice (Oryza sativa L., 2n = 2x = 24) is the second most important global crop after wheat in terms of total production [1]
The mean squares and significant tests among genotypes revealed that number of tillers (NT), number of panicles per plant (NPP), number of grains per panicle (NGP), percentage of filled grains (PFG), thousand grain weight (TGW) and grain yield (GY) were significantly (p ≤ 0.05) affected by genotype × site interaction effects (Table 4)
The present study found marked differences in the performance of the test parents and their families
Summary
Rice (Oryza sativa L., 2n = 2x = 24) is the second most important global crop after wheat in terms of total production [1]. More than 90% of rice is grown and consumed in Asia [3,4], while sub-Saharan Africa (SSA) region accounts for about 10% of the global rice production [5]. In East and Southern Africa region, Tanzania is the second largest producer of rice after Madagascar. Rice is ranked as the second most important staple crop after maize (Zea mays) in Tanzania [6,7]. Despite the contribution of rice to food and nutrition security, and enhanced livelihoods of millions of people in Tanzania, the average yield in the country is 1.5 t ha−1 , which is significantly lower than the yield potential of 4.6 t ha−1 reported in Asia [5]
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
