Field resistance of potato cultivars to foliar early blight and its relationship with foliage maturity and tuber skin types

Abstract

Three field experiments were carried out to assess the level of resistance of several cultivars to early blight (EB) and to examine the association between host resistance and either foliage maturity or tuber skin types. A total of 26 cultivars were used in Exps. 1 and 2, and 24 in Exp. 3. Plants were inoculated with isolates of Alternaria grandis at 31 days after planting. EB severity was quantified in each plot every seven days. The approach to determine the resistance levels of potato cultivars was based on multivariate analysis techniques. The tested cultivars responded as either resistant, moderately resistant, moderately susceptible or susceptible to EB. Most of the cultivars were classified as susceptible or moderately susceptible to EB. Resistant cultivars were mid-season, mid-late or late maturity. None of the susceptible cultivars were later maturity (mid-late or late maturity). In most cases, susceptible cultivars were earlier maturity (early or mid-early maturity). Most resistant cultivars had rough, mid-rough or smooth skin. None of the susceptible cultivars had rough skin. In most cases, susceptible or moderately susceptible cultivars had smooth skin. Obtaining potato cultivars that are resistant to this destructive disease will help reduce production costs and the need for costly fungicides.

Resistance status of cultivated potatoes to early blight (Alternaria solani) in Denmark

“…In the interpretation of the resistance classes, the use of the word ‘resistant’ was avoided so as to avoid any confusion with absolute or complete resistance, in contrast to previous studies (Lynch et al ., ; Duarte et al ., ) in which some cultivars have been classified as resistant, while the cultivars in question only showed slow development of early blight. Pinto et al .…”

“…Recently, Duarte et al . () used four epidemiological parameters in a multivariate analysis to make a comprehensive classification of the resistance level of potato cultivars in Brazil.…”

“…Unfortunately, no potato cultivar has been reported to be completely resistant to early blight. However, cultivar resistance to early blight has been reported to be horizontal or partial in nature; thus the intensity of the disease varies on different cultivars (Holley et al, 1983;Christ, 1990;Boiteux & Reifschneider, 1993;Duarte et al, 2014;Odilbekov et al, 2014), compared to vertical or complete resistance where infection is totally stopped. Besides, resistance to early blight has been shown to be related to foliage maturity of the cultivar (Christ, 1990;Duarte et al, 2014); early maturing cultivars are the most susceptible, whereas late maturing cultivars show less susceptibility (Johanson & Thurston, 1990).…”

“…epidemiological parameters or 'curve elements', that describe the disease development and allow susceptibility to be compared and that are key to comparing disease epidemics (Campbell et al, 1980). Usually, curve elements such as the rate of the disease progress, area under the disease progress curve (AUDPC), and time to reach 50% severity can be used singly (Holley et al, 1983;Odilbekov et al, 2014) or simultaneously in a multivariate analysis to compare disease epidemics on different cultivars to identify partial resistance (Anderson et al, 1990;Duarte et al, 2014).…”

Characterization of Alternaria isolates and reaction of potato genotypes to early blight

“…In general, evaluation for resistance to early blight is carried out in the field and in greenhouse, where plants are subjected to both natural infection and artificial inoculation by conidia (NACHMIAS et al, 1988;DUARTE et al, 2013 and2014). However, the latter is limited by the difficulty in producing sufficient spores of Alternaria spp.…”