Infectious Process of Colletotrichum truncatum in Resistant and Susceptible Genotypes of Lima Bean ( Phaseolus lunatus )

Colletotrichum truncatum is the causative agent of anthracnose in lima beans ( Phaseolus lunatus L). This fungus induces symptoms of spots on leaves and pods. Despite its importance, the interaction between C. truncatum and lima beans is unknown. This study aimed to analyse the events of penetration, colonisation and sporulation of C. truncatum on leaves and pods of resistant and susceptible genotypes of P. lunatus . Two genotypes of P. lunatus were selected for the study: a genotype with a source of resistance (BGP‐UFPI 832) and a susceptible genotype (BGP‐UFPI 860). Conidia began to germinate on the abaxial leaf surface 6 h after inoculation, with the formation of appressoria. Penetration occurred directly through the cell wall, with no penetration through stomata observed. During the colonisation process, the fungus produced secondary hyphae in the internal parenchymatic leaf tissues 30 h after inoculation in the susceptible genotype and only 42 h after inoculation in the resistant genotype. Symptoms of leaf spots were observed in susceptible genotypes 66 hai (hours after inoculation), while in resistant accessions, at the same incubation time, the symptoms were yellowing of the leaves. Sixty‐six hours after inoculation (hai), necrotic spots were observed in plants of the susceptible genotype, while in plants of the resistant genotype, only leaf yellowing was observed. One hundred and forty‐four hours after inoculation, acervulus and spores were observed, confirming the biological cycle of the fungus.