Capsidiol content in CM-334 pepper roots infected with Nacobbus aberrans and its effect on second stage juveniles

Godinez-Vidal, D., M. Soto-Hernandez, M. Rocha Sosa, E. Lozoya-Gloria, R. I. Rojas-Martinez, L. Guevara Olvera, y E. Zavaleta-Mejia. 2010. Capsidiol content in CM-334 pepper roots infected with Nacobbus aberrans and its effect on second stage juveniles. Nematropica 40: 227-237. The objectives of the present work were to compare the accumulation of the phytoalexin capsidiol in roots of chilli pepper (Capsicum annuum L.) CM-334 non-infected and infected with Nacobbus aberrans, and to determine the effect of capsidiol on second stage juvenile's nematode (J(2)) in vitro. Capsidiol content in roots of plants inoculated with 2000 J(2) and maintained in growth chambers was lower than in the non-inoculated ones. The reduction was significant at 7 (Tukey, alpha = 0.01) and 14 (Tukey, alpha = 0.05) days after nematode inoculation. In plants of an experiment carried out under greenhouse conditions with soil naturally infested with N. aberrans, a lower accumulation of capsidiol was also shown in plants infected by the nematode in comparison to the non-infected ones. Differences were significant at 14 (Tukey, alpha = 0.01) and 21 (Tukey, alpha = 0.05) days after planting into the infested soil. Exposure of N. aberrans juveniles to capsidiol resulted in nematode immobilization. This effect increased with higher capsidiol concentration (from 0.01 to 1.50 mu g of capsidiol/ mL) and longer exposure periods. Juvenile's immobilization was observed at 24 h of exposure being more evident at 72 h, where differences were highly significant at all tested concentrations in comparison to the control (Tukey, alpha = 0.0001). However, the phytoalexin effect was only nematostatic since J(2) recovered their mobility when capsidiol was replaced by water. The reduction of phytoalexin accumulation in nematode infected roots and the capsidiol toxicity to N. aberrans suggest that the plant defense mechanisms of chilli pepper CM-334 may be arrested by the nematode to favor its establishment and development.