Distribution and molecular diversity of arborescent<i>Gossypium</i>species

Mexico is a center of diversity of Gossypium . As currently circumscribed, arborescent Gossypium species (subsection Erioxylum ) are widely distributed in dry deciduous forests located from Sinaloa in the north of its range to Oaxaca in the south of its range. However, extensive morphological variation exists among accessions from these different geographic regions. The objective of this work was to determine whether the observed morphological variation is reflected at the molecular level. Molecular diversity and phylogenetic relationships were estimated with 210 randomly amplified polymorphic DNA fragments and 766 amplified fragment length polymorphism fragments among 33 accessions of arborescent Gossypium, including 23 of Gossypium aridum , the most widely distributed of the arborescent Mexican diploid Gossypium species. Over 90% of the fragments were polymorphic; however, each accession contained only between 32% and 46% of the total loci. Two thirds of the loci among the G. aridum accessions had allelic frequencies lower than 80%. The genetic distance between Gossypium gossypioides (subsection Selera ) and species of subsection Erioxylum ranged between 0.64 and 0.84. The genetic distance between two recognized species, Gossypium lobatum and Gossypium schwendimanii , within subsection Erioxylum was 0.32. Most molecular data support the traditional classification of Gossypium species and the geographical ecotypes of the G. aridum accessions. A newly collected accession, US-72, of subsection Erioxylum was genetically distant (range, 0.42–0.54) from the other species of the subsection. Molecular data support the recognition of this taxon as a new species. The molecular diversity among accessions of G. aridum was greater than that among the species of subsection Erioxylum. The results indicate this subsection deserves additional study to establish a defensible taxonomic treatment of the various taxa and to resolve genetically distant geographical ecotypes.

Hali tarjima qilinmagan