Abstract
The cactus pear is a widely cultivated plant in the Northeast of Brazil, contributing significantly to the feeding of livestock, especially in times of drought. Because of the high variation between phenotypic varieties grown in this region, it is essential to study the genetic diversity. The objectives of this study were to characterize the genetic diversity in seven varieties of cactus pear, genera Opuntia and Nopalea, through 19 morphological and behavioral characteristics, and to determine the phenotypic correlation and importance of these characteristics to the variability among genotypes, using multivariate analysis techniques. The study was conducted at the experimental station of Agronomic Institute of Pernambuco (IPA), located in city of Arcoverde, State of Pernambuco, Brazil using randomized block design with three replications. The materials IPA-100003, IPA-200016, IPA-200008, IPA-100004, IPA-200021, IPA-200205 and IPA-200149 were evaluated for 19 quantitative characteristics of the plants. The collected data were analyzed by analysis of variance by F test, and the means grouped by the Scott-Knott test (p<0.05). The broad-sense heritability and phenotypic correlation characteristics were estimated. The genetic diversity was estimated by multivariate methods (unweighted pair group method with arithmetic mean-UPGMA, Tocher, principal component and canonical variables). Analyses of variance and genetic diversity revealed significant differences among genotypes, with the possible formation of two, three or four genetically distinct groups. The heritability values ranged from 79.6 to 97.0% for all 19 quantitative characteristics. The water content and cladode fresh matter are the characteristics that contributed most to the genetic divergence among the materials. Moreover, these characteristics are significantly and positively correlated with dry matter, width, length and cladode area. Thus, the genetic variability among the studied varieties of cactus pear and their potential use in breeding programs are confirmed. The uni and multivariate methods used for the genetic divergence differ and gather genotypes in two, three or four groups. Key words: Brazilian semiarid, forage, genetic distance, grouping, multivariate analysis.
Highlights
The cactus pear (Opuntia spp. and Nopalea spp.) is a cactaceae originally from Mexico, which is exploited since the pre-Hispanic period, holding the greatest genetic diversity and one of the largest cultivated areas in the world with over 28.3 million hectares
There were no significant differences among cactus pear varieties for thickness (CT), fresh matter (CFM), water content (H2O) of the cladodes, width (PW), height (PH), fresh mass (FM), desirability (DESIR), and incidence of diseases (DIS) in the plants (Table 2)
Ferreira et al (2003) and Neder et al (2013), studying the genetic diversity of cactus pear (Opuntia ficus indica Mill.), reported significant differences among 38 accesses studied in relation to CT, CL, CW, number of cladodes (NC), FM, dry matter (DM), PH and PW
Summary
The cactus pear (Opuntia spp. and Nopalea spp.) is a cactaceae originally from Mexico, which is exploited since the pre-Hispanic period, holding the greatest genetic diversity and one of the largest cultivated areas in the world with over 28.3 million hectares.
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