Chlorophyll stability index as an aid in screening for heat tolerance in cocoa( Theobroma cacao L.)

Abstract

Chlorophyll stability index (CSI) of 20 Cocoa genotypes were estimated. Results showed that CSI varied from 25 .0 to zero. The highest CSI was recorded for the Criollo variety and the lowest in the NC 34, a genotype obtained from Nigeria. The CSI is inversely related to the heat resistance of chlorophyll and thus may be related to drought tolerance. The 'P' combinations (hybrids derived from the collections of Pound) are considered as more tolerant to heat and moisture stress, and such combinations are found to have low CSI values. This finding is further supported by higher proline accumulation and better germination and seedling growth of these genotypes under induced moisture stress. Thus in cocoa, CSI seems to be a parameter that can be used for screening for heat tolerance.