ISSN: 0041-3216 (Online), 0041-3216 (Print)
Volume 88 Number 4
Trinidad selected hybrids: An investigation of the phenotypic and agro-economic traits of 20 selected cacao cultivars. (175)
A recurrent breeding programme was very successfully conducted over a period of 60 years by the Ministry of Food Production, Land and Marine Affairs (MFPLMA) Trinidad and Tobago, and has resulted in the production of the Trinidad Selected Hybrid (TSH) varieties. The aims were to obtain Ceratocystis wilt (CR) and Witches’ Broom (WB) resistance, large bean size and low pod index (PI) while maintaining the traditional fine or flavour bean quality. The parental types used were ICS 1 (for large bean size), SCA 6 (for Witches Broom (WB) resistance), POUND 18 (strong vigour, CR) and IMC 67 (CR, high yielding). Other types used, to a lesser extent, were ICS 95 and POUND 7. The objectives of this study were to facilitate the identification of 20 selected TSH varieties in the field and to examine the phenotypic diversity among them. In addition, evaluation of their commercial and breeding value, in terms of yield potential, compared to the parental types was undertaken. Morphological characterization of the TSH varieties was based on 23 fruit and 12 flower traits. Traits observed for the 5 parents included 9 based on fruits and 7 on flowers. The coefficient of variation of the quantitative flower and fruit traits of the TSH varieties ranged from 6.9% to 11.5% and 5.4 % to 16.6%, respectively. The characteristics of economic interest, viz. bean number, cotyledon weight and Pod Index (PI) ranged from 42.2 ± 2.42 to 61.4 ± 2.89; 0.74g ± 0.02 to 1.49g ± 0.06 and 12.0 ± 0.67 to 26.1 ± 0.7, respectively. The varieties with the best yield potential were TSH 730, 1095, 1102, 1104, and 1362. TSH 1102 was outstanding with the largest number of beans and ovules. A large improvement in bean traits and PI has been observed in the TSH progeny. Principal Components Analysis revealed a clear separation of the parental types from the progeny that was also found using Cluster Analysis. Wet bean weight, PI, pod width, number of beans and cotyledon weight contributed significantly to the separation of the varieties in the first plane of the Principal Component plot.
Keywords: Cacao, Theobroma cacao, Trinidad selected hybrids, phenotypic traits, principal component analysis, cluster analysis