Abstract
ABSTRACT The tall coconut (Cocos nucifera L.) has great socioeconomic importance in Brazil and was first introduced on the coast of the north-eastern region, where it has been exploited in a semi-extractivist manner. The goal of this study was to quantify the genetic divergence between accessions introduced and preserved at the International Coconut Genebank for Latin America and the Caribbean, estimate the efficiency of descriptors used in the discrimination of the accessions, and indicate the essential descriptors for the activities of characterisation and evaluation. The accessions used were: Polynesia Tall; Tonga Tall; West African Tall; Rennel Tall; Rotuma Tall; Vanuatu Tall; Malayan Tall and Brazilian Tall Praia-do-Forte. Thirty-five quantitative descriptors recommended for the species were used. Genetic divergence was estimated by the Mahalanobis’s generalised distance and the cluster analysis was performed using the unweighted pair group method with arithmetic mean (UPGMA). The relative importance of the descriptors was measured according to Singh and Jolliffe’s methods, and the variables were selected taking into consideration the matching information in the two methods, eliminating those that were discarded in the two procedures. The agronomic characteristics indicated that the first canonical variable explained 90.25% of total variance. The most efficient descriptors for detecting the genetic divergence were: fruit equatorial circumference; nut polar and equatorial circumference; quantity of liquid endosperm; total fruit weight; nut weight; stem height; girth of stem at 1,5m height; number of leaflets; and number of bunches. The most dissimilar accessions according to the agronomic characteristics were Rotuma Tall and West African Tall, which can be primarily indicated as genitors for the formation of segregating populations in breeding programmes.
Highlights
The coconut tree (Cocos nucifera L.) is an exotic species which, being useful for the Portuguese colonizers in their expeditions to America, was introduced in the State of Bahia, north-eastern region of Brazil in 1553 (HARRIES, 1977)
The objectives of the present study were to quantify the genetic divergence among accessions of tall coconut preserved in the ICG-LAC, and estimate the efficiency of descriptors used in the discrimination of the accessions to indicate the essential descriptors for the activities of characterisation and evaluation of coconut germplasm
The analysis of the agronomic characteristics by means of canonical variables explained about 90.25% of total variance in the first variable
Summary
The coconut tree (Cocos nucifera L.) is an exotic species which, being useful for the Portuguese colonizers in their expeditions to America, was introduced in the State of Bahia, north-eastern region of Brazil in 1553 (HARRIES, 1977). The natural populations are integrated into the landscapes of coastal areas and the common coconut variety found in Bahia is very similar to other varieties seen in Jamaica, South America, and West and East Africa (ROMNEY; DIAS, 1979), as well as to other varieties belonging to the Indo-Atlantic group (MARTINEZ et al, 2009). Brazil has 271,000 hectares cultivated with coconut tree, spread across almost the entire national territory (FAOSTAT, 2016). About 70% of coconut production is located in the north-eastern coastal strip and part of the northern region. The areas of production are still mostly exploited in a semi-extractivist manner. The cultivation has low average productivity due to the cultivation of non-improved genotypes that feature low productive potential and production instability, as well as susceptibility to biotic and abiotic stresses
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