Atypical, green leaf blotch lesions on barley leaves infected by Rhynchosporium secalis (OUD) Davis

Atypical, green leaf blotch lesions were observed on senescent leaves in winter barley crops and sometimes developed on barley leaves inoculated with conidia of Rhynchosporium secalis in a glasshouse. Similar atypical lesions were induced on barley leaves inoculated with conidia of R. secalis and then grown in controlled environments at 10 degrees C and 80% rh. Microscopic examination of green lesions from these three sources showed that hyphae of R. secalis had colonized the subsidiary cells of stomata so that guard cells were swollen, resulting in enlarged stomatal pores. Additionally, spore initials had erupted through the leaf cuticle of some leaves. Most spore initials did not develop into mature conidia when leaves were incubated for 24 h at 20 degrees C in a closed chamber at 100% rh, but aerial hyphae grew out from the leaf surface. Thus, atypical green lesions produced a much smaller number of spores than typical leaf blotch lesions.Peer reviewe

Control of foliar diseases in barley:towards an integrated approach

Barley is one of the world's most important crops providing food and related products for millions of people. Diseases continue to pose a serious threat to barley production, despite the use of fungicides and resistant varieties, highlighting the impact of fungicide resistance and the breakdown of host plant resistance on the efficacy of control measures. This paper reviews progress towards an integrated approach for disease management in barley in which new methods may be combined with existing measures to improve the efficacy of control in the long-term. Advances have been made in genetic mapping of resistance (R) genes and in identifying novel sources of genes in wild barley populations and land races. Marker assisted selection techniques are being used to pyramid R genes to increase the durability of resistance. Elicitors to induce host resistance used in combination with fungicides can provide effective disease control in the field and could delay the evolution of fungicide insensitivity. Traits that may contribute to disease tolerance and escape have been identified and the extent of genetic variation within barley germplasm is being determined. Tools are being developed to integrate the above methods via an assessment of the risk of economic injury occurring from disease to guide decisions on the requirement for fungicide treatment. Barriers exist to the adoption of integrated management approaches from growers and end-users further down the supply chain (e. g. acceptance of variety mixtures) and policy incentives from government may be required for it to be taken up in practice. © 2012 KNPV