African rice (Oryza glaberrima) genomic introgressions impacting upon panicle architecture in Asian rice (O. sativa) lead to the identification of key QTLs

Abstract

AbstractBackgroundDeveloping high yielding varieties is a major challenge for breeders tackling the challenges of climate change in agriculture. The panicle (inflorescence) architecture of rice is one of the key components of yield potential and displays high inter- and intra-specific variability. The genus Oryza features two different crop species: Asian rice (Oryza sativaL.) and the African rice (O. glaberrimaSteud). One of the main morphological differences between the two independently domesticated species is the structure (or complexity) of the panicle, withO. sativadisplaying a highly branched panicle, which in turn produces a larger number of grains than that ofO. glaberrima. The genetic interactions that govern the diversity of panicle complexity within and between the two species are still poorly understood.ResultsTo identify genetic factors linked to panicle architecture diversity in the two species, we used a set of 60 Chromosome Segment Substitution Lines (CSSLs) issued from third generation backcross (BC3DH) and carrying genomic segments fromO. glaberrimacv. MG12 in the genetic background ofO. sativaTropical Japonica cv. Caiapó. Phenotypic data were collected for rachis and primary branch length, primary, secondary and tertiary branch number and spikelet number. A total of 15 QTLs were localized on chromosomes 1, 2, 3, 7, 11 and 12 and QTLs associated with enhanced secondary and tertiary branch numbers were detected in two CSSLs. Furthermore, BC4F3:5lines carrying different combinations of substituted segments were produced to decipher the effects of the identified QTL regions on variations in panicle architecture. A detailed analysis of phenotypes versus genotypes was carried out between the two parental genomes within these regions in order to understand howO. glaberrimaintrogression events may lead to alterations in panicle traits.ConclusionOur analysis led to the detection of genomic variations betweenO. sativacv. Caiapó andO. glaberrimacv. MG12 in regions associated with enhanced panicle traits in specific CSSLs. These regions contain a number of key genes that regulate panicle development inO. sativaand their interspecific genomic variations may explain the phenotypic effects observed.