Lesion size as a criterion for screening oat genotypes for resistance to leaf spot

Abstract

In Brazil, increased leaf spot disease (Pyrenophora chaetomioides Speg.) frequency and intensity on cultivated spring oat (Avena sativa) requires that plant pathologists and breeders rapidly identify oat genotypes with greater resistance. Criteria are needed to compare and evaluate oat genotypes to screen large numbers of lines, quantification of resistance components under controlled conditions allowing year-long screening and the rejection of susceptible lines before lengthy field trials. There is a need to determine which resistance components are associated with leaf spot intensity in the field, as estimated from the area under the disease progress curve (AUDPC). We assessed various oat P. chaetomioides resistance components under controlled conditions in seedlings of 26 oat genotypes chosen from recommended varieties and elite breeding lines to determine the association of resistance components with the AUDPC, obtained by evaluating each genotype in the field. The resistance components estimated were: initial lesion size (ILS) and final lesion size (FLS); rate of lesion expansion (r); and area under the normalized and corrected lesion expansion curve (AULECc). All correlations were positive and significant at p00.01 and were distributed into moderate (0.5< r<0.8) and strong (0.8≤r<1) correlation classes. The strongest average correlations occurred with the AULECc (0.827), ILS (0.801) and FLS (0.801) components. These results indicate which components may be useful in resistance screening, with FLS possibly being the most useful criterion because it is less laborious to obtain and speeds up the selection process for leaf spot resistance.

Identification and characterization of Pyrenophora species causing leaf spot on oat (Avena sativa) in western China

“…Presently, Pyrenophora chaetomioides (syn. Pyrenophora avenae , anamorph = Drechslera avenae ) is considered to be the main causal pathogen of DLS, also called striped leaf spot, in oats (Cegiełko et al, 2011; Silva et al, 2012). In initial stages of the disease, it causes light brown to reddish‐brown oval spots on the leaves while the centre of the spot is grey and white, and the edges are brown with a wide yellow halo.…”

Assessing Quantitative Resistance against Leptosphaeria maculans (Phoma Stem Canker) in Brassica napus (Oilseed Rape) in Young Plants

“…If area of leaf lesions could be used to assess quantitative resistance in field conditions, it would be a valuable method for breeders. Leaf lesion area has been used to assess quantitative resistance against other fungal pathogens [5] , [39] – [40] . However, there is a need to test a wide range of cultivars under different conditions to investigate the relationship between the area of phoma leaf lesions in autumn and the severity of phoma stem canker in the following summer.…”

Impact of Fusarium Head Blight in Reducing the Weight of Oat Grains

“…In southern Brazil during the last few decades, oats (Avena sativa L.) have become an excellent option for the winter/spring cultivation season after the major summer crops, such as maize and soybeans (Silva, Martinelli, Federizzi, Chaves, & Pacheco, 2012). However, the favourable environmental conditions, principally high humidity, occurring during winter and spring means that oat crops can be attacked by many pathogens, with Fusarium head blight (FHB or scab) having recently become a much more frequent problem.…”