Cocoa: Planting Materials

The importance of selecting the planting materials most suited one’s environment cannot be over emphasized.

Ideally, planting materials selected should be precocious, capable of sustained high yields, easy to manage, resistant to major pests and diseases and also highly adaptable. For obvious reasons, the crops should also be able to satisfy buyer quality specifications such as bean size, chocolate flavour etc.

Presently, there is insufficient information on environment-material interaction to allow for “environmat recommendation” as for rubber. However, a fair amount of data is available on the susceptibility/resistance of the hybrids to two major diseases in Malaysia i.e. Vascular Steak Dieback and Phytophthora palmivora . The latter is responsible for both black pod disease and canker in the field as well as seedling blight in the nursery.

Various authors reported that Sca6, Sca12, Pa35, Na32, Na33 and Amelonado are resistant to P. palmivora (Holliday, 1954: Spence & Bartley, 1966; Leather, 1966; and Gunawardena 1966).

Ang (1978) reported that progenies derived from Pa7 are more susceptible to VSD while those derived from Sca6 and Sca12 are most tolerant.

Ooi & Chew (1985) reported that Amelonado and crosses with Amelonado parentage are generally more susceptible to VSD.

Through the Malaysian Cocoa Growers Council (MCGC), the major cocoa growers imported 9 Keravat clones from Papua New Guinea in 1982. Most of the clones are resistant to VSD in PNG. Unfortunately, some of them are very susceptible to black pod disease under PNG growing conditions. The clones have been distributed to the interested parties and are now being evaluated in both the Pen. Malaysia and Sabah.

Therefore, in areas where VSD is a major problem, one should avoid planting Amelonado and its related crosses and also progenies derived from Pa7 clone. Materials selected for VSD resistance should be the preferred choice.

In areas where black pod/canker is a serious diseases, crosses with Sca6, Sca12, Pa35, Na32, Na33 and Amelonado should be the preferred choices. However, Sca6 and Sca12 crosses have been discarded by some planters on account of their lighter beans.

Another factor that must be taken into account is that the performance of a particular hybrid could vary considerably between locations. (Ooi & Chew 1985). It is therefore advisable to plant as many proven crosses of diverse parentage as possible (say 5 to 10) in any planting.

Another reason for planting in large number of diverse crosses is that a high percentage of them are self-incompatible. To ensure efficient pollination and high yields, it is necessary to plant them as mixed hybrids or in series of narrow blocks of 3-4 rows per hybrid. Planting of large blocks of a single hybrid should be avoided unless these are self-compatible. As a rule of thumb, the width of a block of a single hybrid should preferably be not more than 15 m.

A self incompatible hybrid/clone if planted in a large continuous block would result in poor pollination and hence poor yield. This is amply illustrated in Table 1 below:-

Table 1 : Effect of planting large blocks of self incompatible hybrids on the yield of cocoa

Source : Tan (1982)
Key : * UIT1 x Na32 in 72 continuous rows
UIT1 x Na33 in 51 continuous rows cocoa planted in
** Mixed hybrids
Cocoa planted in 1977

The yield of Fld. K where the pollination was poor was only about 24% of the mixed hybrids on average.

To save guard oneself and also to ensure quality of planting materials, all seeds should be purchased from reputable sources with a research backing.

Reference 
Ooi L.H. and Chew P.S. 1985. Some important agronomic and agricultural practices in cocoa estates. TDMB Plantation Management Seminar, Kuala Trengganu

Note: The full list of references quoted in this article is available from the above paper.