Diversity and Virulence ofAlternariaspp. Causing Potato Early Blight and Brown Spot in Wisconsin

Abstract

Early blight, caused by Alternaria solani, along with brown spot, caused by A. alternata, have the potential to reduce quality and yield in potato production globally. Prior to this study, the incidence, disease impact, and fungicide resistance attributes of A. alternata in Wisconsin were poorly understood. Potato pathogens were isolated from foliar lesions at three commercial locations in Wisconsin in 2012 and 2017 and were initially morphologically identified as A. solani (n = 33) and A. alternata (n = 40). Identifications were further corroborated with the phylogenetic analysis of the internal transcribed spacer (ITS), translation elongation factor 1 (TEF1), gapdh, Alt a 1, and OPA10-2. A multigene phylogeny of ITS, TEF1, gapdh, and Alt a 1 showed five genotypes of A. alternata and one single genotype of A. solani. We demonstrated that the A. alternata isolates were virulent on potato cultivars Russet Burbank (P < 0.013) and Atlantic (P < 0.0073), though they caused less disease than A. solani (P < 0.0001 and P < 0.0001, respectively). A. alternata caused little disease on the breeding line 24-24-12 (P = 0.9929), and A. solani caused fewer disease symptoms on 24-24-12 than on Russet Burbank (P < 0.0001) or Atlantic (P < 0.0001). Breeding line 24-24-12 may be a promising source of potential resistance for the two diseases. There was no significant difference in virulence of different A. alternata genotypes, and no significant difference in virulence or genotype clustering among isolates from the three locations. Isolates of A. alternata that induced chlorosis caused larger lesion areas than isolates that did not in Russet Burbank (P < 0.0001), Atlantic (P < 0.0001), and 24-24-12 (P = 0.0365). There was no significant difference in virulence between quinone outside inhibitor (QoI)-sensitive and QoI-resistant isolates of A. alternata. This study enhanced our understanding of potato early blight and brown spot in Wisconsin, and suggested that A. alternata in addition to A. solani should be carefully monitored and possibly uniquely managed in order to achieve overall disease control.

The Influence of Trichoderma harzianum Rifai T-22 and Other Biostimulants on Rhizosphere Beneficial Microorganisms of Carrot

“…Biostimulants significantly reduced the colonization of the studied organs by these microorganisms. According to many authors [104][105][106], Alternaria spp. are common pathogenic species that cause diseases of various plants.…”

Review: Holistic pest management against early blight disease towards sustainable agriculture

“…The reduction in the spore density of A. solani starts at a distance of 400 m and from 600 m further away the initial population of EB at crop emergence is negligible 25 . A. alternata achieves longer dispersal distances than A. solani , showing seven times higher aerial conidial concentration than A. solani , probably due to the smaller spores 26 . New infections of A. alternata in a field probably come from locations surrounding the field, whereas the localized canopy of host plants within a field is the primary source of A. solani conidia.…”

Induced expression of CYP51 associated with difenoconazole resistance in the pathogenic Alternaria sect. on potato in China

“…Potato production is challenged by many pests and diseases. Among them, the foliar disease of early blight, which causes premature defoliation and significant yield loss, is one of the major factors constraining potato production. This disease is caused by several species in Alternaria genus, including A. solani , A. grandis , A. alternata , A. longipes , A. tenuissima , A. dumosa , and A. arborescens etc., but dominant species recovered from diseased potato may vary substantially in space and time.…”