Abstract
ABSTRACT Dwarf coconut tree is the main variety for commercial use in Brazil, which ranks fourth in world coconut production. However, the genotypes used still have limitations and genetic variability is required. The aim of this study was to estimate the genetic variability in dwarf coconut accessions preserved at the Germplasm Bank of Brazil at different harvesting times and using agronomic descriptors of plant and fruits. The accessions Brazilian Green Dwarf-Jiqui, Cameroon Red Dwarf, Malayan Red Dwarf, Brazilian Red Dwarf-Gramame, Brazilian Yellow Dwarf-Gramame, and Malayan Yellow Dwarf were assessed by means of 30 descriptors Variance analysis was performed and the genetic diversity was quantified by using the Mahalanobis’ generalized distance and expressed by means of UPGMA clusters, Tocher optimization, and canonical variables. The maximum likelihood analysis was used to estimate the components of variance with the data of each plant in a sample of 11 descriptors of great importance for the genetic improvement of the coconut tree. A phenotypic divergence was found among the accessions using the UPGMA clusters, Tocher optimization and graphic dispersion obtained with canonical variables. The use of the maximum likelihood analysis confirms the existence of genetic variability in the accessions for the descriptors fruit polar and equatorial diameter, nut polar diameter, total fruit weight, and epicarp thickness, which presented a heritability varying from 0.17 to 0.39. There is a possibility of genetic gains with the selection of these traits for use of accessions in breeding programs.
Highlights
The coconut tree is a monospecific palm composed of three botanical varieties: Cocos nucifera L. var. typica, C. nucifera L. var. nana, and C. nucifera L. var. aurantiaca (LIYANAGE, 1958)
The accessions Brazilian Green Dwarf-Jiqui (BGDJ), Cameroon Red Dwarf (CRD), Malayan Red Dwarf (MRD), Brazilian Red Dwarf-Gramame (BRDG), Brazilian Yellow Dwarf-Gramame (BYDG), and Malayan Yellow Dwarf (MYD) were assessed during three cultivation cycles from 2014 to 2016, resulting in three assessments indicated as Year 1 (2014), Year 2 (2015), and Year 3 (2016)
In the joint analysis of year 3, this accession was placed in a subgroup next to other accessions and the first group was formed by the BGDJ and BRDG accessions (Figure 1C)
Summary
The coconut tree is a monospecific palm composed of three botanical varieties: Cocos nucifera L. var. typica (tall coconut), C. nucifera L. var. nana (dwarf coconut), and C. nucifera L. var. aurantiaca (intermediate coconut) (LIYANAGE, 1958). The dwarf variety is small in size, reaching up to 12 m when fully grown, an early cycle when compared to the tall coconut, and depending on the environment, it can start flowering around two years and six months after planting, producing a high number of small fruits (150 to 200 fruits/plant/year) (MENON; PADALAI, 1958; ARAGÃO et al, 2002). This variety is composed of yellow, green, and red cultivars (OHLER, 1984). Brazil occupies the fourth position, with a production of over 2,649,246 tons in a planted area of 234,012 ha (FAOSTAT, 2016), and the green dwarf is the cultivar mainly used for commercial production
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