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El Niño–Southern Oscillation hindering effects on self-pollination of cocoa Nacional clones in Ecuador

Abstract:

Self-compatibility is a key trait in cocoa Nacional (CN) clones to secure self-pollination (SP). However, SP in CN clones has not been assessed for tolerance to ENSO elicited soil waterlogging. Therefore, the aim of this investigation was to analyse the impact of ENSO on SP and cross-pollination (CP) effectiveness in ten CN L-H encoded clones, the SP clone CN EET-103 and the Trinitario CNN-51. In the 2016 season that followed an ENSO event, the L21-H43 and L29-H04 clones showed 1.2 fold higher index of self-compatibility (ISC >0.92) than CNN-51 and EET-103, and were categorised as waterlogging tolerant. In contrast, the remaining eight L-H clones had the lowest SP, CP and ISC in 2016, and were considered waterlogging sensitive. This is the first report on the hindering effects of ENSO on SC and CP in waterlogging-sensitive CN clones, and on the existence of the waterlogging tolerance trait in two L-H clones. Based on the present results, soil anoxia must be included among the constraints hindering cocoa productivity, and waterlogging tolerance should be a trait considered by cocoa breeders. Self-compatible and waterlogging tolerant CN clones with higher SP, CP and ISC can add value to cocoa plantations that are vulnerable to ENSO conditions.