Characterization of cactus pear germplasm in South Africa

[摘要] English: South Africa hosts one of the largest cactus pear germplasm collections in the world. However, not all the varieties have been fully characterised, and evaluated for fruit quality, nutritional quality for use as fodder, and disease resistance. In this study, 38 South African cactus pear (Opuntia ssp.) varieties were characterised using AFLP markers to circumvent G X E effect on phenotypic characterisation. With the use of nine primer combinations, the varieties were grouped into four main clusters based on 346 fragments (per sample) of which 48% were polymorphic between samples. The dendrograms generated indicated that commercially cultivated varieties were dispersed amongst the different clusters indicating that they represent the genetic diversity within the germplasm. Genotype specific fragments were generated using six primer combinations, allowing the unique identification of nine varieties, three of which are commercially cultivated (Meyers, Roedtan, and Santa Rosa). Varieties that are recommended for commercial cultivation in the Mokopane district of the Limpopo Province, based on fruit quality and yield are Gymno Carpo, Malta, Algerian, Morado, Meyers, and Roedtan. These varieties meet the minimum requirements for cactus pear fruit production in South Africa. Nutritional quality evaluation of pruned cladodes from a commercial orchard in the Free State Province indicated that the varieties, Malta, Gymno Carpo, and American Giant ranked the highest in terms of CP content. Varieties that yielded the highest DM content were Messina, Nepgen, and Cross X. Varieties that ranked the highest for OM content were Cross X, Nepgen, and Sicilian Indian Fig. Gymno Carpo and Malta are amongst the varieties recommended for cultivation for fruit, as such they can be used as dual purpose crops for the production of both fodder and fruit. Evaluation for disease resistance indicated a quantitative mode of resistance across all varieties for all three fungal pathogens tested. The most resistant varieties surveyed in this study across all three fungal pathogens were Amersfoort, Meyers, and Algerian. Roly Poly, Direkteur, and Zastron were the more susceptible varieties. Of the three fungal pathogens tested, P. virens was the least affected by the antagonistic activity of the yeast isolates. Isolate 25 (Rhodotorula mucilaginosa) performed well against all three pathogens, whilst the remainder of the isolates displayed inhibition at varying degrees.

[发布机构] University of the Free State