Comparison of Opuntia ficus indica varieties of Mexican and Argentine origin for fruit yield and quality in Argentina

A randomized complete block field design for Opuntia ficus indica fruit production and quality in Argentina compared 19 of the most promising fruit accessions identified from previous Texas field trials to 8 individual selections of the naturalized Argentine "Santiaguena variety" and one South African clone. The genetic material originating from Texas consisted of recently collected fruit varieties from high elevation sites in northern Mexico which should possess increased cold hardiness and the best accessions from among 100 accessions evaluated over a 15 year period in Kingsville, Texas. The Argentine accessions were selected for high yield from on-farm field trials and university field plots. The Argentine varieties were established about half a growing season after the Texas varieties. The yields ranged from 3000 to 22,000 kg ha(-1) for the 4th growing season for the accessions from North America and from 2100 to 6400 kg ha(-1) in the 3rd growing season for the Argentine naturalized genetic materials. The Argentine varieties had the greatest e fruit pulp firmness (about 2 kg) and sugar contents (13.4-15.2) but had a lower percentage pulp (40-47%) than the North American materials. For the first time this work demonstrated significant differences in yield and sugar content among the naturalized Argentine varieties leading the way to the first selected varieties. In some of the accessions, even at maturity, the inner pulp lacked structural integrity and easily broke apart on peeling. These accessions had both a low pulp firmness (less than 1 kg) and a low percentage of pulp to peel firmness. The ratio of pulp to peel fruit firmness at maturity varied greatly among the accessions obviating the possibility of evaluating pulp firmness from peel firmness measurements. The highly significantly negative correlation between fruit firmness (p=0.005) and pH among the accessions is reminiscent of auxin-induced pH decreases that lead to increased cell wall plasticity. Two of the spineless Texas accessions (1279 and 1300) with dark purple fruit could not be distinguished on the basis of cladode or fruit color or overall plant morphology. In agreement with prior Texas evaluations, clone 1300 had significantly greater yield but significantly lower sugar than the other indistinguishable clone 1279. These significant quantitative intravarietal differences in clones 1279 and 1300, combined with intravarietal differences in the externally indistinguishable Santiagueria clones, points to the need to select and maintain individual plant selections within morphologically indistinguishable varieties. (C) 2004 Elsevier Ltd. All rights reserved.