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

Abstract

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 “Santiagueña 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 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 Santiagueña clones, points to the need to select and maintain individual plant selections within morphologically indistinguishable varieties.

Introduction

The specialized photosynthetic system in cacti known as Crassulacean Acid Metabolism (CAM) provides greater water to dry matter conversion than C3 and C4 photosynthetic pathways (Nobel, 1988; Han and Felker, 1997). The combination of this conversion efficiency and the great biodiversity in fruit colors (red, orange, purple, pink, yellow, and lime-green) (Griffiths and Hare, 1907; Pimienta, 1990; Barbera et al., 1995; Inglese et al., 1995; Parish and Felker, 1997), results in great potential for the flat stemmed Opuntias in arid lands.

While there are many excellent general descriptions of the variability in Opuntia fruit types (Griffiths and Hare, 1907; Monjauze and LeHouerou, 1965; Russell and Felker, 1987; Nobel, 1988; Wessels, 1988; Pimienta, 1990; Barbera et al., 1995), there are few journal articles that report yields and fruit quality measurements on genetically broadly based selections from replicated field trials. Gutierrez-Acosta et al. (2002) reported used cluster analyses to distinguish 3 main fruit groups from 24 accessions in Mexico but did not list individual fruit measurements for the accessions. Nieddu et al. (2002) listed general descriptions of 6 Italian cultivars but did not provide quantitative data on yields or fruit quality. Barbera et al. (1992) reported on the changes in fruit quality during ripening of the 3 major Sicilian Opuntia cultivars in commercial orchards but did not report yield data. From Israel, there is considerable data on fruit maturity and use of N fertilization to stimulate off season Opuntia fruit production (Nerd et al., 1991, Nerd et al., 1993), and discovery of a low seedy parthenocarpic fruit (Weiss et al., 1993), but as far as we are aware no comparisons of fruit quality/yield from replicated field trials. There are reports of fruit yield/quality from a broad based germplasm collection in Texas (Gregory et al., 1993; Parish and Felker, 1997; Cowan and Felker, 1999; Wang et al., 1998) and the resultant comparison of 12 of these clones in Argentina (Felker et al., 2002a). Due to 3 days of continuous below freezing weather in Texas in December 1989 (minimums of −12 °C on 2 days), that killed all Opuntia ficus indica accessions (Wang et al., 1998), the germplasm collections by the Texas group after 1989 emphasized freeze hardiness. Felker and Nerd made a major germplasm collection at high elevation sites in northern Mexico whose initial fruit quality was reported by Cowan and Felker (1999). Of special interest was the germplasm selected by Martinez (1968) in which 32 seedlings out of 200,000 seedlings planted survived a 1963 freeze of −16 °C in Saltillo, Mexico. Other interesting materials were those reported by Borrego-Escalente et al. (1990) that were reported to survive −16 °C.

In 1999, eighteen accessions representative of the Texas collection, with emphasis on recently collected high elevation sites in northern Mexico were established in a randomized complete block trial in Argentina. It would be presumptuous to assume that the imported germplasm was superior to the naturalized local Santiagueña cactus variety, as our measurements of fruit quality and yield in local farmers fields indicated great variability in yield (Felker et al., 2002b). Thus individual plant selections of the local variety were made from farmer's fields and university research plots and established one year later in the replicated trial with the 18 accessions from Texas. For the first time in Argentina this trial was able to compare fruit quality/yield of the local variety in a replicated field trial.

Our Texas work (Parish and Felker, 1997) reported on fruits from spiny and spineless species such as O. ficus indica, O. hyptiacantha, O. amyclea etc and that spine characters were in part, used to distinguish the species. However DNA molecular marker data has raised significant doubts on the validity of the traditional taxonomic approaches to the classification of the commercial O. ficus indica fruit types. Wang et al. (1999) examined RAPD patterns in what were presumed to be 8 very contrasting Opuntia clones. The two most similar clones were the spiny O. hyptiacantha 1287 and the spineless O. ficus indica clone 1281. Moreover, O. ficus indica clone 1281 had a greater genetic affinity to O. hyptiacantha clone 1287 than the other spineless O. ficus indica clones 1279, 1321 and 1294. The major distinguishing feature between O. ficus indica clone 1281 and O. hyptiacantha clone 1287 was the presence of spines. This data has cast doubt on the traditional taxonomy, such as described by Scheinvar (1995) that used spine characters to distinguish species. A recent traditional taxonomic work (Kiesling, 1999) based on segregation of morphological characters within Opuntia progeny (among other characters) has also come to the conclusion that spine characters should not be used to differentiate species among the commercial Opuntia fruit types and lists all flat stemmed fruit types as simply O. ficus indica. We concur with this opinion and thus in this paper simply use O. ficus indica for these commercial fruit types.