Resistance Of Barley Cultivars Research Articles

Resistance of barley cultivars and accessions to pathotypes of the spot blotch causative agent

Background. The spot blotch disease caused by the hemibiotrophic fungus Bipolaris sorokiniana has become a serious problem for barley. Utilization of resistant or tolerant barley cultivars ensures sustainable diversity conservation and environmentfriendly crop production. Thus, supplying barley breeders with sources of resistance to harmful diseases is an urgent task. Materials and methods. A set of 100 barley accessions, earlier selected for different levels of resistance to B. sorokiniana, served as the material for this study. Eleven isolates of B. sorokiniana of various geographic origin, belonging to 4 pathotypes, were used for testing. The resistance of barley seedlings was assessed under controlled laboratory conditions, and that of adult plants under artificial infection pressure in the field. Responses to B. sorokiniana were scored using the 0–9 rating scale.Results and conclusions. Barley genotypes with race-specific resistance to the spot blotch causative agent were identified. The percentage of barley genotypes resistant to five isolates of B. sorokiniana pathotype 1 averaged 24.2%; two isolates of pathotype 3, 29.5%; three isolates of pathotype 7, 18.3%; and one isolate of pathotype 0, 37%. Barley accessions manifesting resistance in their seedlings, but susceptible in the phase of milk-wax ripeness, and vice versa, with seedling susceptibility and adult resistance, were identified. Six (6) barley genotypes showed seedling and adult resistance to pathotype 1, nine (9) to pathotype 3, and two (2) to pathotype 7. No barley accessions resistant to all isolates of the pathogen were found.

Determining quantitative resistance of barley cultivars at the seedling stage to net blotch caused by Pyrenophora teres

Four barley (Hordeum vulgare L.) cultivars, Heartland, Harrington, Johnston, and Kasota, were compared a: the seedling stage for reactions to the net and spot forms of net blotch caused by Pyrenophora teres f. teres and P. teres f. maculata, respectively. Effects of leaf wetness period, leaf position, and inoculum concentration on lesion development were investigated. The linear relationship between inoculum concentration and diseased leaf area was used to estimate inoculum concentrations causing 50% diseased leaf area (ED50) on leaf 2 (the second seedling leaf) and causing 15% diseased leaf area (ED15) on leaf 3 (third seedling leaf). Resistance of cultivars was compared on the basis of ED50 and ED15. The linear relationship of diseased leaf area with time was used to estimate the rate of lesion spread and to compare resistance. Lack of a significant linear relationship over time on leaf 3 for cvs. Heartland and Kasota inoculated with P. teres f. teres reflected resistance in these two cultivars. Both pathogens caused less than half the diseased area on leaf 3 as on leaf 2 in all cultivars. A mist period of 48 h tended to obscure the differences on leaf 2 between resistance and susceptibility. In general, there were positive correlations between the two pathogens based on ED50 or ED15. Pyrenophora teres f. maculata resulted in substantially higher ED50 and ED15 values on cvs. Johnston and Heartland, indicating that P. teres f. maculata was less virulent than P. teres f. teres on these cultivars. ED50 and ED15 values could be used to quantitatively differentiate moderately resistant cultivars from susceptible cultivars at the seedling stage.

Variation in the resistance of barley cultivars and in the pathogenicity of Drechslera teres f. sp. maculata and D. teres f. sp. teres isolates from France

Isolates of Drechslera teres that cause net or spot‐type symptoms on barley (Hordeum vulgare) were collected in 1986 and 1987 from fields in different regions of France. Variations in pathogenicity were evaluated using 12 barley cultivars. The Middle‐Eastern cultivars Arrivate and 79‐S10‐10 were resistant to all isolates except R5 and S5. The Ethiopian cultivar C1 5791, previously reported to be resistant, was susceptible to the R5 and S5 biotypes. There was a high correlation coefficient between the classification of cultivars for resistance to D. teres f. sp. teres and D. teres f. sp. maculata. A method for conserving the virulence of the isolates on straw is evaluated. The virulence level of the isolates was the same after 4 years of storage using this method.