Abstract
Cacao is a tree crop of high economic importance and the subject of several studies aiming the genetic improvement of the species with the incorporation of characteristics that are agronomically important to create superior genotypes. In this context, this study aimed to characterize 22 genotypes of cacao for sexual compatibility, which is a trait that is strongly associated with yield. Additionally, we identify genotypes incompatible with clone TSH-1188 through controlled intercrosses, due to the great importance of this clone in cocoa breeding. Fifteen genotypes were characterized as self-incompatible and other seven as self-compatible, considering the retention index (20%) of self-pollinated flowers. Nine genotypes were characterized for the first time: CCN-16, COCA-3310, COCA-3370/5, EB-1017, IMC-119, IMC-97, LCTEEN-37A, NA-45, and UF-612. Cacao genotypes showed flower retention index ranging from 0.0% to 55.1% after 15 days of self-pollinations. The number of retained flowers varied after self-pollination of cacao genotypes at 1, 5 and 15 days after pollination. CCN-51, Catongo, CCN-10 and P-4B, were the genotypes with minor losses of flowers after 15 days of pollination, while IMC-119 and TSH-516 had 100% of loss of flowers between 1 and 5 days after pollination. Moreover, the flower retention index 15 days after cross-pollination with TSH-1188 ranged from 0.0% to 87.5% among the tested genotypes. The results of cross-pollinations identified two genotypes that are incompatibles, EB-1017 and IMC-119. This result is important for future allelic studies of incompatibility in cacao, because it might indicate that these genotypes share the same self-incompatibility allele(s). We conclude, therefore, that this study enable the characterization of this working collection of cocoa germplasm for sexual compatibility and this information is important for subsequent crosses between cacao genotypes.
Highlights
Theobroma cacao L. is a tree of the Malvaceae family that has great economic importance because of its use in the manufacturing of cosmetics, juices, pulps, and especially chocolate [1]
The flower retention index 15 days after cross-pollination with TSH-1188 ranged from 0.0% to 87.5% among the tested genotypes
That this study enable the characterization of this working collection of cocoa germplasm for sexual compatibility and this information is important for subsequent crosses between cacao genotypes
Summary
Theobroma cacao L. (cacao) is a tree of the Malvaceae family that has great economic importance because of its use in the manufacturing of cosmetics, juices, pulps, and especially chocolate [1]. (cacao) is a tree of the Malvaceae family that has great economic importance because of its use in the manufacturing of cosmetics, juices, pulps, and especially chocolate [1]. The cacao flowers, grouped in flower cushions, appear on the trunk and on the branches. They are hermaphrodite and composed of five petals, five sepals, five staminodes, five stamens and a pistil, and the natural pollination occurs mainly by insects of the genus Forcipomyia Meigen, 1818 [2] [3] [4]. Sexual compatibility is a feature of utmost importance for the genetic improvement of cacao, because it is directly associated with yield [8]. Self-compatible plants produce more fruits than self-incompatibles, and, it should be considered as relevant to plan crosses aiming at increased production, as well as for selection of possible clones classified as agronomically satisfactory [9] [10]
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