Exploitation of ortet–ramet relationship for the development of superior cocoa (Theobroma cacao L.) clones

Abstract

Identification of clones with promising growth and yield characteristics remains imperative for cocoa improvement in Ghana. This study assessed the relationship between selected trees from seed origin and their derived clones as a strategy to identify superior cocoa clones. Two experiments consisting of 40 progeny families, and 160 derived clones (plus 20 parents) respectively, were conducted at the Cocoa Research Institute of Ghana, New Tafo-Akim, from 2008 to 2022 to assess the genetic association between the two populations. Agronomic traits measured included stem diameter (vigour) at the juvenile and reproductive phases of growth, as well as bean yield and its components. Significant genetic variation was estimated among the ortets and their ramets for all measured traits. Relatively wide variation and superior performance were observed among the ramets compared with the ortets for all measured traits suggesting the achievement of substantial genetic improvement in the ramets to warrant selection progress. Additionally, the results revealed significant regression co-efficients and correlation patterns, along with high realized heritability values between the ortets and their ramets for bean yield and pod value indicating that high yielding clones with desirable pod values could be identified by relying on the genetic relationship between the progeny families and their derived clones. The high yielding ramets, CRG 0148/418, CRG 0121/106, CRG 0149/210, and CRG 0150/114 identified are therefore, invaluable for utilization in cocoa enhancement programmes across the globe.