Differential response of chili pepper genotypes to single and combined association with the mycorrhizal fungus Rhizophagus irregularis and the root pathogen Phytophthora capsici

Abstract

Chili pepper (Capsicum annuum L.) is an important horticultural crop in Mexico in terms of both diet and culture. However, chili pepper production is associated with excessive use of agrochemicals both pesticides and mineral fertilizers causing adverse environmental and human health problems. Hence, alternative biological disease control measures and crop nutrition strategies are needed. Arbuscular mycorrhizal fungi (AMF) that naturally associate with roots of most crop plants including chili pepper are known to promote plant nutrition and root health, represent a biological alternative to reduce the use of agrochemicals in chili pepper production.In three greenhouse pot experiments, we examined the response of five chili pepper genotypes to single and combined inoculation with the AMF Rhizophagus irregularis and the root pathogen P. capsici in terms of plant growth response and root disease development. Main results showed that inoculation with R. irregularis caused differential plant growth promotion in the five chili pepper genotypes examined, but had no effect on the disease development caused by P. capsici. Single inoculation with P. capsici resulted in differential root disease development in the chili pepper genotypes. Most interesting, a Chilaca landrace genotype not only showed resistance against P. capsici, but on the contrary also resulted in plant growth promotion. In conclusion, our work show that the examined chili pepper genotypes responded differentially to single inoculation with R. irregularis and P. capsici, but dual inoculation had no effect on the level of root disease caused by P. capsici. The observed resistance to P. capsici in the Chilaca landrace could be a source of resistance to the pathogen in plant breeding programs and used directly by chili pepper growers that could also benefit from pre-inoculating chili pepper transplants with AMF before planting in terms of plant growth promotion.