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A dwarf mutant, designated LB4D, was obtained among the progeny of backcrosses to a wild rice introgression line. Genetic analysis of LB4D indicated that the dwarf phenotype was controlled by a single semidominant dwarfing gene, which was named LB4D. The mutants were categorized as dn‐type dwarf mutants according to the pattern of internode reduction. In addition, gibberellin (GA) response tests showed that LB4D plants were neither deficient nor insensitive to GA. This study found that tiller formation by LB4D plants was decreased by 40% compared with the wild type, in contrast to other dominant dwarf mutants that have been identified, indicating that a different dwarfing mechanism might be involved in the LB4D dominant mutant. The reduction of plant height in F1 plants ranged from 27.9% to 38.1% in different genetic backgrounds, showing that LB4D exerted a stronger dominant dwarfing effect. Using large F2 and F3 populations derived from a cross between heterozygous LB4D and the japonica cultivar Nipponbare, the LB4D gene was localized to a 46 kb region between the markers Indel 4 and Indel G on the short arm of chromosome 11, and four predicted genes were identified as candidates in the target region. [ABSTRACT FROM AUTHOR]

Abstract: Many rice breeding programs have currently reached yield plateaus as a result of limited genetic variability in parental strains. Dongxiang common wild rice (Oryza rufipogon Griff.) is the progenitor of cultivated rice (Oryza sativa L.) and serves as an important gene pool for the genetic improvement of rice cultivars. In this study, heterotic loci (HLs) associated with six yield-related traits were identified in wild and cultivated rice and investigated using a set of 265 introgression lines (ILs) of O. rufipogon Griff. in the background of the Indica high-yielding cultivar Guichao 2 (O. sativa L.). Forty-two HLs were detected by a single point analysis of mid-parent heterosis values from test cross F1 offspring, and 30 (71.5%) of these HLs showed significantly positive effects, consistent with the superiority shown by the F1 test cross population in the six yield-related traits under study. Genetic mapping of hsp11, a locus responsible for the number of spikelets per panicle, confirmed the utility of these HLs. The results indicate that favorable HLs capable of improving agronomic traits are available. The identification of HLs between wild rice and cultivated rice could lead to a new strategy for the application of heterosis in rice breeding. [Copyright &y& Elsevier]