“Comparison of methods for early evaluation of resistance to witches´ broom (crinipellis perniciosa (stahel) singer) in cocoa (theobroma cacao L.)"

Abstract

Three sets of trial were carried out in order to test early evaluation of resistance to Crinipellis perniciosa. In all experiments clons SCA 6, SCA 12, CCAT 4675, BE 10 and EET 95 cocoa clones were inoculated with a spore suspension of 1 x 10 4 basidiospores/ml. Two trials dealt with Basidiospores germination on leaf disks and plant extract. Clones showed statistically significance and highly significant for spores germination on leaf disks and water extract respectively. With methods dealing with seedling inoculation disease incidence was 100% and quite severe for all methods: Holliday test, a modified Holliday and the belt spray method. In theses trials, no differences between clones were observe for the incubation period or disease incidence; only the belt spray method gave statistically significant differences for cotyledon persistence on seedlings. In the field inoculation method, the clones showed significant differences for the infection incidence in branches and infection incidence per plant. Basidiospores germination percentage in the leaf disk method and watery extracts method showed a positive correlation with branch infection percentage (0.70 y 0.90) and plant infection percentage (0.90 y 0.70). Cotyledon permanence in the automatic inoculation method was positively correlated with the infection percentage in branches (0.70) and plants (0.60).