The Global Fund to Fight AIDS, Tuberculosis, and Malaria, and the US-based Centers for Disease Control and Prevention (CDC).

Dry witches' brooms from cocoa were imported from various areas within Bolivia, Brazil, Colombia, Ecuador, Trinidad and Venezuela. Basidiocarps of Crinipellis perniciosa were induced to form on these brooms and seedlings of different types of cocoa were inoculated with basidiospores either on the hypocotyl or cotyledon bud. Host reactions were assessed mainly by recording stem base swelling and broom development at the cotyledon node (hypocotyl inoculations) or the extent of swelling and branching of shoots (cotyledon bud inoculations). Results from 30 experiments indicated considerable diversity amongst isolates in inducing disease symptoms, but suggested that two groups or populations of C. perniciosa exist on cultivated cocoa. One group (A), comprising isolates from Bolivia and Pichilingue (Ecuador) and most isolates tested from Colombia, induced severe symptoms on cocoa with Scavina 6 as one parent; the other group (B), comprising isolates from Brazil, Trinidad and Venezuela, did not. Within these groupings variants could be further distinguished by particular host reactions. Isolates from Ecuador, especially from the Oriente, a centre of diversity for Theobroma cacao, showed a range of pathogenicity comparable to that found amongst isolates from cultivated cocoa over a much wider area.

An isolate of Sclerotinia sclerotiorum from oilseed rape was grown on sterilized wheat grain for 3 weeks at 20 C, followed by 4 weeks at 4oC. Harvested sclerotia were buried 1 cm deep in compost in plastic containers and kept at 10oC until apothecial stipes appeared (c. 6 weeks). When these dishes were placed under near‐UV light (14 h/day) at 22oC, apothecia matured in 5 days. The method also induced apothecia from sclerotia of 35 other isolates of S. sclerotiorum obtained from 17 different hosts.

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.

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