Influence of plant growth stage on resistance to anthracnose in Andean lupin (Lupinus mutabilis)

Abstract

Anthracnose, caused by Colletotrichum acutatum, is the most destructive fungal disease of Andean lupin (Lupinus mutabilis Sweet) in Ecuador and of other lupin species around the world. Symptoms of necrotic spots occur throughout the main stem, and infection progresses to cause bending of the main stem and lateral branches, resulting in yield loss. Although there is no known anthracnose resistance, this study aims to assess tolerance of Andean lupin and investigate lupin–C. acutatum interactions. Two Andean lupin genotypes, I-450 Andino and I-451 Guaranguito, were inoculated on the meristematic section of the main stem, either by spraying or by pipetting C. acutatum spores on to an artificial wound. Although the two methods gave similar results, spraying is the preferred method because it mimics natural pathogen infection. Plant-pathogen interactions were assessed at five different phenological stages (leaf stages 2–3, 4–5, 6–7, 8–9, and 10–11) with three C. acutatum isolates by using a 0–5 scale to assess disease symptoms. In both genotypes, anthracnose symptoms were greater at early seedling stage (2–3-leaf stage), decreasing significantly in early vegetative phase (6–7-leaf stage) and increasing again when the flower stage began (10–11-leaf stage). However, the tolerance of these two Andean lupin genotypes to anthracnose was not equally expressed at all developmental stages. We recommend, in a breeding program, that screening for anthracnose first occurs at the 6–7-leaf stage (6 weeks old) and again when flowering starts at the 10–11-leaf stage (10 weeks old) so that the overall tolerance can be determined. This method could be used in lupin breeding programs for improving resistance to anthracnose.

Efficacy of UV‐C radiation to reduce seedborne anthracnose (Colletotrichum acutatum) from Andean lupin (Lupinus mutabilis)

“…For inoculations, 2 mL of C. acutatum suspensions of 10 6 spores mL −1 were sprayed on the apical parts of plants in pod fill, by using a small hand‐held Venturi atomizer (aerograph) with an air pump, following the methodology described by Falconi et al . (). Naturally infected seeds (cv.…”

“…Artificially infected seeds were harvested from lupin plants (cvs I-451 Guaranguito and I-450 Andino) inoculated with C. acutatum isolate Lup 18 (EMBL ITS accession number JN543063) obtained from lupin stems from Cotopaxi province (Falconi et al, 2013). For inoculations, 2 mL of C. acutatum suspensions of 10 6 spores mL À1 were sprayed on the apical parts of plants in pod fill, by using a small hand-held Venturi atomizer (aerograph) with an air pump, following the methodology described by Falconi et al (2015). Naturally infected seeds (cv.…”

“…The total number of infected and germinated seeds in each plot was recorded 1 week after sowing. Anthracnose-infected plants were recorded in 6-to 7-leaf-stage plants, 7 weeks after sowing, based on the twisted stem or brown lesions on stem with masses of pink conidia, as previously described by Falconi et al (2015). Infection, germination, emergence and disease plant percentages were calculated for each treatment.…”

“…Farmers attempt to select apparently healthy seed for the next sowing but are not always successful. This seed is also exchanged within local networks, which increases risk of pathogen dissemination (Falconi et al ., ). Infected seed commonly results in infected plants and low productivity (e.g.…”

Solar UV‐B radiation limits seedborne anthracnose infection and induces physiological and biochemical responses in Lupinus mutabilis

“…JN543061; Falconi et al , ). For inoculations, C. acutatum spore suspensions were sprayed onto blossom and reinoculated on pod fill as described by Falconi et al (). In January 2018, naturally infected seeds of cultivar Criolla were obtained from farmers from both rainy and dry environments in the provinces of Cotopaxi and Chimborazo, respectively.…”