Factors influencing the production of basidiocarps and the deposition and germination of basidiospores of Crinipellis perniciosa , the causal fungus of witches' broom on cocoa ( Theobroma cacao )

The production of basidiocarps by Crinipellis perniciosa on detached, dead witches'brooms from cocoa was assessed in relation to temperature, light, cocoa clone, age of broom and type of tissue, in cabinets with a daily cycle of 8 h wet and 16 h dry. More basidiocarps formed and matured at 20–25°C than at 25–30°C. In the latter regime the pilei were smaller and white, instead of the usual crimson colour, and the stipes were longer. No basidiocarps formed at 30–35°C. At 20–25°C. more basidiocarps formed and matured with light at 100 μE m ‐2 s ‐1 during the wet period than at 10 μE m ‐2 s ‐1 . Only one basidiocarp and five primordia developed on 20 brooms kept in the dark. Brooms from 10 cocoa clones at Pichilingue. Ecuador, differed in basidiocarp productivity. most basidiocarps forming on brooms from Seavina and least on ICS clones. The numbers of basidiocarps produced on brooms aged 1.2.3 or 4 months when detached from cocoa trees were similar but time to initiation of the first primordium differed considerably. More basidiocarps formed at nodes than internodes. The discharge of basidiospores was optimal at 20–25°C and 80% RH: germination was optimal in water agar films. Neither process was dependent on light.