Field experiments on the resistance of cocoa to cocoa swollen‐shoot virus

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Abstract
SUMMARY: Progenies from crosses between different Upper Amazon cocoa types and between Upper Amazon and Amelonado were compared for their field resistance to infection with cocoa swollen‐shoot virus (CSSV) virulent strain A. Among the intra‐Amazon progenies, those from crosses of Scavina, Iquitos and Nanay groups showed most resistance. Progenies from crosses within these groups may have sufficient resistance to be of immediate practical value in reducing crop losses in areas where CSSV is widespread. Some Nanay progenies were more resistant than others and this provides scope for improvement by breeding. Progeny of crosses between Upper Amazon and Amelonado parents were less resistant than those from intra‐Amazon crosses.The present results confirm those previously obtained in gauze‐house tests on young plants.