Identification of new sources of resistance to fungal leaf and head blight diseases of wheat

Tan spot (TS), Stagonospora nodorum blotch (SNB), spot blotch (SB), and Septoria tritici blotch (STB) caused by Pyrenophora tritici-repentis, Parastagonospora nodorum, Cochliobolus sativus and Zymoseptoria tritici, respectively, are the four important fungal leaf spotting diseases of wheat with global importance. These diseases reduce the photosynthetic area of leaves resulting in poor grain filling and lower yields; particularly when the penultimate and flag leaves are severely infected. Fusarium head blight (FHB) is another important fungal disease that infects wheat heads causing significant yield and quality deterioration including mycotoxins contamination. Host plant resistance is one of the main strategies in the management of these diseases. To identify new resistant sources to TS, SNB, STB, SB and FHB, 110 wheat cultivars and advanced breeding lines from different geographic origins were evaluated in growth chambers and field nurseries at the International Maize and Wheat Improvement Center (CIMMYT), Mexico. These materials have been previously evaluated for their field FHB resistance (combination of type I and II resistance) and performed well, but in the current study they were tested in greenhouse with point inoculation to confirm exclusively their type II resistance. The frequency of resistant lines was similar for TS, SNB and STB with 45, 40 and 33 genotypes, respectively. However, only 11 lines showed resistance to SB while 51 genotypes showed FHB type II resistance. Two genotypes of Chinese origin, NANJING 8611 and NANJING 4840, exhibited broad-spectrum resistance to all of the studied diseases and were not significantly different (P ≤ 0.01) from the resistant check of the respective diseases. The multiple disease resistant accessions identified in this study could be utilized in breeding programs aimed at improving wheat resistance to either individual or multiple leaf and head blight diseases.