Pyramiding nn16 and rin1 alleles to balance plant height and node number at high latitudes

Breeding dwarf or semi-dwarf soybean varieties is an effective strategy to enhance lodging resistance and thereby increase yield potential. However, soybean plant height is co-determined by the number of nodes and internode length. Reducing plant height often leads to a decrease in node number, which subsequently reduces pod number and ultimately results in lower yield. Thus, balancing node number and internode length is of great significance for increasing soybean yield. Here, we identified a node number-regulating locus, NUMBER of NODES 16 (NN16), encoded by FLOWERING LOCUS T (FT5a). Variations in the promoter and 3' untranslated region (3' UTR) of nn16 downregulate its expression and increase node number. In addition, the reduced internode 1 (rin1) gene that we previously reported shortens internode length but slightly reduces node number. To increase node number while shortening internode length, we constructed near-isogenic lines (NILs) carrying the genotypes RIN1 ^HH43 /NN16, rin1/nn16, RIN1 ^HH43 /nn16, and rin1/NN16. Among these NILs, the rin1/nn16 genotype showed optimal plant height and the highest seed weight per plant. Collectively, our findings provide theoretical support and breeding resources for cultivating soybean cultivars with shortened internodes and increased node number, thereby further improving seed weight per plant.

The online version contains supplementary material available at 10.1007/s11032-026-01682-5.