Major Leaf Shape Genes, Laciniate in Diploid Cotton and Okra in Polyploid Upland Cotton, Map to an Orthologous Genomic Region

Gossypium arboreum L, which produces spinnable cotton fibers, is an A-genome diploid progenitor species of tetraploid cotton. With its diploid genome, publicly available genome sequence, adapted growth, and developmental and agronomic attributes, G. arboreum could make an ideal cotton species to study the genetic basis of biological traits that are controlled by orthologous loci in diploid and polyploid species. Leaf shape is an important agronomic trait in cotton. Normal, subokra, okra, and laciniate are the predominant leaf shapes in cotton cultivars. Laciniate in diploids is phenotypically similar to okra leaf shape in tetraploid. In the present study, a population of 135 F-2 plants derived from accessions NC 501 and NC 505 was used for genetic and molecular mapping of laciniate leaf shape in diploid cotton (G. arboreum). An inheritance study showed that laciniate leaf shape was controlled by a single incompletely dominant gene (LL-A(2)). Molecular genetic mapping using simple-sequence repeat (SSR) markers placed the leaf shape locus L-A(2) on chromosome 2. Targeted mapping using putative genes from the delineated region established that laciniate leaf shape in G. arboreum and okra leaf shape in Gossypium hirsutum L. were controlled by genes at orthologous loci. Collinearity was well conserved between the diploid A-(G. arboreum) and D-(G. raimondii Ulbr.) genomes in the targeted genomic region narrowing the candidate region for the leaf shape locus (L-A(2)) to nine putative genes. Establishing the orthologous genomic region for the L loci could help use the diploid cotton resources toward map-based cloning of leaf shape genes in Gossypium.