Articles
SSR AND EST-SSR MARKERS FOR OPUNTIA SPP. FINGERPRINTING AND GENETIC DIVERSITY EVALUATION
Article number
940_2
Pages
29 – 35
Language
English
Abstract
Opuntia spp. belong to the Cactaceae family and are native to Central America.
The most economically important species is O. ficus indica, cultivated both for fruits and cladodes.
The genus includes other important edible species (from diploid to octoploid) which are widespread as wild or domesticated in many arid or semi-arid regions worldwide (including the Mediterranean area). Several accessions are cultivated in the different growing areas but little is known about their ancestry and the level of genetic diversity.
The cultivated genotypes were selected by farmers mainly for the absence of thorns and for fleshy fruits.
Although these common features, a polyphyletic origin of the most diffused cultivated genotypes has been hypothesized.
In fact, cross-hybridization is well documented in Opuntia spp., so that the widespread cultivars likely arose from different parental species.
With the main aim of investigating the level of intraspecific genetic diversity and fingerprinting the most widely grown cultivars, a molecular analysis based on SSR markers was carried out at Catania University.
In particular, 6 SSRs previously isolated from O. echios and 2 new EST-SSRs isolated from O. streptacantha were used to analyze 62 wild and cultivated genotypes belonging to 16 Opuntia species, coming from plantings throughout the world and now maintained at the experimental station of Catania University.
SSR amplifications produced from one to eight alleles per locus, confirming the high ploidy level of most of the genotypes.
The analysis revealed a high level of genetic diversity, especially in the Mexican germplasm.
However, the analysed loci were monomorphic in most of the Italian genotypes (Bianca, Rossa, Gialla and the Trunzare accessions) indicating that these cultivars were probably the results of somatic mutations.
The SSRs segregation analysis allowed to discriminate zygotic seedlings from apomictic demonstrating the usefulness of these markers in cactus pear breeding.
The analysis added new information to better understand the ancestry of the cultivated cultivars and the variation between Opuntia species and cultivated cultivars.
The most economically important species is O. ficus indica, cultivated both for fruits and cladodes.
The genus includes other important edible species (from diploid to octoploid) which are widespread as wild or domesticated in many arid or semi-arid regions worldwide (including the Mediterranean area). Several accessions are cultivated in the different growing areas but little is known about their ancestry and the level of genetic diversity.
The cultivated genotypes were selected by farmers mainly for the absence of thorns and for fleshy fruits.
Although these common features, a polyphyletic origin of the most diffused cultivated genotypes has been hypothesized.
In fact, cross-hybridization is well documented in Opuntia spp., so that the widespread cultivars likely arose from different parental species.
With the main aim of investigating the level of intraspecific genetic diversity and fingerprinting the most widely grown cultivars, a molecular analysis based on SSR markers was carried out at Catania University.
In particular, 6 SSRs previously isolated from O. echios and 2 new EST-SSRs isolated from O. streptacantha were used to analyze 62 wild and cultivated genotypes belonging to 16 Opuntia species, coming from plantings throughout the world and now maintained at the experimental station of Catania University.
SSR amplifications produced from one to eight alleles per locus, confirming the high ploidy level of most of the genotypes.
The analysis revealed a high level of genetic diversity, especially in the Mexican germplasm.
However, the analysed loci were monomorphic in most of the Italian genotypes (Bianca, Rossa, Gialla and the Trunzare accessions) indicating that these cultivars were probably the results of somatic mutations.
The SSRs segregation analysis allowed to discriminate zygotic seedlings from apomictic demonstrating the usefulness of these markers in cactus pear breeding.
The analysis added new information to better understand the ancestry of the cultivated cultivars and the variation between Opuntia species and cultivated cultivars.
Authors
S. Currò, M. Caruso, G. Las Casas, S. La Malfa, A. Gentile
Keywords
simple sequence repeats, cactus pear, polyploidy
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