Exploiting interspecific heterosis between African rice and Asian rice

Abstract The objective of this study was to explore the heterosis of partial interspecific hybrids between African rice ( Oryza glaberrima Steud.) and Asian rice ( Oryza sativa L.) and its correlation with genetic distance. Sixty‐nine rice accessions including 57 introgression lines (ILs) were tested for population structure and genetic distance. Forty‐nine crosses between ILs and a test variety, Shengtai1 (ST1), were evaluated for midparent heterosis of nine agronomic traits. Population structure, genetic distance, and the proportion of O. glaberrima genome (PGG) of ILs and heterosis of the test crosses were estimated and analyzed. The PGG of the ILs ranged from 1.22 to 49.71%, with an average of 15.29%. The genetic distance between parents of the tested crosses was positively correlated to the PGG of ILs ( r  = .95, P  < .01). Positive heterosis was scored on plant height (12.23%), panicles per plant (19.97%), panicle length (10.37%), spikelets per panicle (24.06%), thousand‐grain weight (14.00%), length/width ratio of grain (0.03%), and grain yield per plant (60.77%) of the partial interspecific hybrids. Although the introgression of more African genomic genes could effectively increase the genetic distance between ILs and the test variety that lead to positive heterosis for most agronomic traits, it could also increase the possibility of the occurrence of interspecific sterility that might decrease the seed setting rate and result in negative heterosis (−2.57%). These data indicated that the introgression of African rice genes into the genome of Asian rice could effectively broaden the genetic diversity, and the deployment of ILs as parents could be a potential way for exploiting interspecific heterosis in rice.