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Hybridization
Hybrid vigour between parents showing good combining ability can be readily exploited in cocoa. Large number of crosses has been made in CPCRI and potentialities of the parents have been assessed. Significant yield improvement in first generation hybrids and heavy demand for improved planting material led to explorative crossings in many cocoa producing countries. Experimental evidence now suggests that direct approach to breeding for yield is successful. Heritability estimates ranging from moderate to high and large additive components of variation indicate easy progress towards high yields.
Method of hand pollination
In artificial pollination, a flower bud which will open the following day, recognised by its whitish colour and swollen appearance, is selected. The bud is covered with hood of plastic tube/hose pipe piece 5 cm x 1.5-2 cm, which is sealed to the bark using materials like plasticine/ glaze putty. The tube is covered with muslin cloth at the top, kept in place with a rubber band. This ensures circulation of air and exclusion of insects. Opened flowers are collected from the desired male parent and stamens are carefully taken out by pushing the corresponding petal. One entire anther with a part of the filament is deposited on the stigma. One or two staminodes may be pinched off to give access to the stigma. Emasculation is not necessary due to the presence of self-incompatibility. For selfing also, hand pollination is done using stamens from the same flower. The pollinated flowers are labeled using tin foil pieces fixed in the cushion using ball pins. The hoods are removed 24 hours after pollination and in three to five days, fertilisation is confirmed by the visual swelling of the ovary. In order to prevent undue shedding and wilting of fruits from hand pollinations, it is usual to remove all the developing fruits on the tree produced by open pollination. Developing pods are covered with wire mesh after six to eight weeks to protect them from mammalian pests. The pods are collected at maturity, beans are extracted and sown in the nursery.
Copyright©Bioinformatics Centre and Library, CPCRI Kasaragod