Physiology, growth, and metabolism of seed-derived cocoa varieties in response to field stress conditions

A total of fifteen best seed-derived cocoa varieties known for their high combining abilities for vigour and yield were evaluated at the vegetative stage between 29 to 39 months after planting. Environmental factors, physiology, growth, carbohydrate, carbon, and nitrogen metabolism resilience of the varieties in response to field stress conditions during wet and dry main growing seasons were evaluated. The plants were then subjected to the environmental stress conditions (high temperature, low rainfall, and soil moisture content) at dry growing season as stress conditions, compared to wet season as unstress conditions (optimum temperature, high rainfall, and soil moisture). Physiology and growth of the varieties during wet season or in dry season conditions did not differ significantly but differed in their response to the seasons. The varieties exhibited a tight stomatal regulation and reduced photochemical efficiency at various magnitudes. Leaves relative chlorophyll content unchanged with high relative water content culminating in the reduction of electrolyte leakage during dry season stress conditions. The varieties accumulated soluble sugars, starch, non-structural carbohydrate, carbon and nitrogen under high temperature, low rainfall, and soil moisture content during dry season. Correlation analysis revealed strong relationships between the physiology, growth, and central carbon metabolism parameters. These findings were prominence in varieties AMAZ 15-15 x EQX 78, CRG 2029 x AMAZ 3-2, CRG 2029 x CRG 0314/102, CRG 9006 x AMAZ 3-2 and PA 150 x CRG 0314/102.