Tracing the geographic origins of two forms of Opuntia ficus-indica cultivated in Argentina using haplotype diversity patterns, and cytogenetic and morphological analyses

MONTENEGRO G.; ACOSTA C.; CAEIRO L; VARONE L. ; LAS PEÑAS M. L.

GENETIC RESOURCES AND CROP EVOLUTION

SPRINGER

Lugar: Berlin; Año: 2024

0925-9864

Opuntia ficus-indica L., widely known as prickly-pear, tuna, or nopal, is one of the several long-domesticated cactus species and the most widespread and economically important cactus crop. It is cultivated for its fruits and cladodes, which are used as fodder and human food. This species would have been domesticated in Mexico in pre-Hispanic times. In Argentina, two forms of O. ficus-indica are present: the horticultural (spineless, f. ficus-indica) and the wild (spiny, f. amyclaea) forms. It has been proposed that the presence/absence of spines is a genetically controlled trait, suggesting that the species would have been introduced more than once in our country. We conducted a molecular and cytogenetics study to 1) characterize the genetic variability of O. ficus-indica in Argentina, (2) infer the geographic origin of the two forms cultivated in our country, and (3) analyze if the morphotypes of Opuntia ficus-indica are related to genetic differentiation. Five haplotypes were identified through chloroplast genome sequencing conducted in 38 individuals. Most spineless individuals in Argentina exhibited haplotype Q16-H1, except for samples from Salta and Mexico, which showed different haplotypes. Notably, all spineless individuals in Argentina had yellow flowers, except for the sample from Salta, which had orange flowers. The Q16-H1 haplotype was common among spiny samples except for samples from Santiago del Estero and Catamarca which had Q16-H4 and showing characteristics resembling O. sulphurea. Regarding the geographic distribution, haplotype Q16-H1 was widespread in Argentina, whereas Q16-H4 and Q16-H5 were found only in northwestern Argentina. Molecular dating estimated haplotype divergences ranging from 1.10 to 1.20 million years ago. The cytological analysis revealed that most populations were octoploid (2n=2x=88), except for one diploid population from Mexico (2n=2x=22). Overall, this study provides insights into the genetic variability, geographic distribution, and cytological characteristics of O. ficus-indica in Argentina. Although the number of individuals from Mexico was low, the results of chloroplast sequences and cytogenetic data indicate the occurrence of a single haplotype of the species associated with both spineless and spiny forms in Argentina reflecting a single introduction event and its subsequent dispersion mainly through asexual reproduction. The haplotype diversity found is due to hybrids between O. ficus-indica and Opuntia species native to Argentina.