Identification of the locus controlling leaf rolling and its application in maize breeding.

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Increasing planting density is one of the most important strategies for generating higher maize yields. Moderate leaf rolling decreases mutual shading of leaves and increases the photosynthesis of the population and hence increases the tolerance for high-density planting. Few genes that control leaf rolling in maize have been identified, however, and their applicability for breeding programs remains unclear. Here we identified a maize () mutant with extreme abaxially rolled leaves and found that the size of the bulliform cells within the adaxial leaf blade surface increased in the mutant. Bulk segregation analysis mapping in an F population derived from a single cross between and inbred line Gui18421 with normal leaves identified the locus on chromosome 2. Sequential fine-mapping delimited the locus to a 233.56-kb genomic interval containing three candidate genes. Sequence alignment between and Gui18421 identified an 8-bp insertion in the coding region of , which led to a frame shift causing premature transcription termination in mutant. Meanwhile, both deep sequencing and Sanger sequencing showed that was present in Gui18421 but was absent in . A pair of near isogenic lines (NILs) carrying the Gui18421 allele (NIL) and the allele (NIL ) were developed, and the leaves of NIL plants had greater light transmission and photosynthetic rate in the middle and lower canopy than did those of NIL plants under high-density planting. Furthermore, NIL had a higher seed setting rate, more kernels per ear, and an increased kernel weight per ear than NIL, and the grain yield of NIL was not affected as the planting density increased, suggesting that the locus can be used for genetic improvement of high-density planting tolerance. Taken together, the identification of and evaluation of yield-related traits for NIL and NIL provide an excellent target for future maize improvement.

SUPPLEMENTARY INFORMATION

The online version contains supplementary material available at 10.1007/s11032-024-01534-0.