The resistance and tolerance of different cocoa varieties to cocoa swollen‐shoot virus in Ghana

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SUMMARY The resistance and tolerance to infection with cocoa swollen‐shoot virus (virulent strain A) of forty‐five and thirty‐eight cocoa progenies respectively was estimated using a manual inoculation method. Resistance was estimated from the proportion of inoculated seedlings which developed symptoms, and tolerance from the severity of these symptoms during a 4‐month period. Resistance was found among Nanay, Iquitos and Scavina, all Upper Amazon types; and an inter‐Nanay cross was outstandingly resistant and offers scope for improvement by breeding. Some Amazon‐Amazon and Trinitario‐Amazon progenies snowed tolerance, especially those with Trinitario T9/21 as a parent. Some progenies seem sufficiently promising for field testing to select varieties suitable for planting in those areas in Ghana where swollen‐shoot disease is epidemic.