Lawrence, J.S. 1978
Screening of cacao cultivars for resistance to Phytophthora palmivora in the collection at CATIE, Costa Rica. Revista Theobroma 8: pp. 125-131.
Costa Rica - CATIE Datafile: DIS_PHDS - Disease reaction to Phytophthora ABSTRACT Screening of the CATIE collection for resistance to Phytophthora palmivora was initiated, using point-inoculation with zoospore suspension of unwounded attached pods to evaluate cultivar response. Of the 51 cultivars tested, 9 showed a promising degree of resistance; EET 59, EET 376, POUND 7, UF 713, UF 715, SCAVINA 6, SCAVINA 12, CATONGO, DIAMANTES 800. METHOD The inoculation method used was point inoculation with standard zoospore suspension of attached pods without wounding as described by Lawrence, 1978b [LAW78B]. Pods of known age, one month before maturity were used and whenever possible only one or two pods were selected from each tree. Ten replicate pods per cultivar were inoculated and when sufficient pods were available each cultivar was tested on at least two different occasions. Both percentage successful infection and average lesion diameters were recorded, the latter when lesion sizes on pods of UF 677, a standard, highly susceptible cultivar included in all tests, attained an average diameter of 6 cm. When cultivars were tested twice or more, percentage infection and average lesion diameters were calculated from the sum of all inoculated pods. The same single-sporangium P. palmivora isolate (morphological form 1, compatibility type A2), selected on the basis of pathogenicity on pods, was used in all tests. To maintain infective potential, the isolate was passed through pod tissue every 1-2 months. Zoospore suspensions at a concentration of 2 x 10 to the power of 5 spores/ml were prepared as described in Lawrence, 1978b [LAW78B]. All tests were carried out between April and December, a period which encompassed peaks in P. palmivora incidence and which coincided with the times of higher pod production and greatest rainfall. Disease - Phytophthora palmivora, P. megakarya Local Names: Black Pod, Podredumbre negra, Pourriture Brune, Podridao parda.