Abstract

GONZALEZ-CRUCES, Agustín et al. Epidemiology of Bean common mosaic virus and Alternaria alternata in 12 Phaseolus vulgaris genotypes. Rev. mex. fitopatol [online]. 2022, vol.40, n.2, pp.188-220.  Epub Oct 03, 2022. ISSN 2007-8080.  https://doi.org/10.18781/r.mex.fit.2202-8.

Research objective was to assess phytosanitary response and epidemiological behavior in 12 Phaseolus vulgaris genotypes and develop etiological-epidemiological methodologies applicable to plant breeding studies. In 2020 spring-summer season, assessments were conducted at flowering (June) and fructification stages (August). Severity was evaluated with a 6-class logarithmic-diagrammatic scale setup in App-Monitor® v1.1. Genotype health was determined using an Integrated Damage Index (IDI), weighted and adjusted for disease severity and coverage-plant vigor (IV), which was estimated with images (RGB, 14mpx) captured with dron-Phantom-3 at 5 m height from genotype centroid. In SAS v9.4, t-test and ANOVAs, followed by Tukey (p = 0.05), were performed for different experimental settings. Disease spatial patterns were analyzed with kriging and omnidirectional variograms in SURFER v10. Forty-three total samples were used for isolation, pathogenicity testing, and molecular identification with universal primers ITS1/ITS4, NIb2F/NIb3R, PBL1v2040/PCR1c for eukaryotes, Potyvirus and Begomovirus, respectively. Final data matrix included 22 variables, 859 observations and 18,898 metadata. Alternaria alternata and Bean common mosaic virus (BCMV) were identified in 100% of samples analyzed with 99% homology. Vaquita Negro, Garrapato and Canario were statistically the most susceptible genotypes (37.3 - 58% severity) for BCMV, while Canario and Tipo Flor de Mayo (41.4-42.7%) were for A. alternata (p = 0.05). Oti and Negro Perla had higher climatic adaptability and tolerance to both pathogens with IV > 0.7 and IDI < 0.43. Spatially, BCMV presented random dispersion of foci and a block-edge effect with continuous contagion of up to 5.6 meters. Vaquita Negro and Bayo Mecentral showed uniform virus spread, presumptively due to high viral transmissibility by seed. In contrast, except for Tipo Flor de Mayo and Canario, which exhibited significant coalescence of foci, A. alternata had spatial dependence of less than 8 plants. Wind and hail damage significantly favored A. alternata infection (p = 0.05) suggesting its opportunistic condition.

Keywords : Virus; Fungi; Bean; Geostatistics; Scales; Android application; Severity.