Variable resistance of bread wheat (Triticum aestivum) lines carrying 2NS/2AS translocation to wheat blast

Wheat blast disease, caused by Magnaporthe oryzae (anamorph Pyricularia oryzae), produces severe damage to wheat production in South America. It was observed that many resistant cultivars contain the 2NS/2AS translocation from Triticum ventricosum. In this study, we evaluate the presence of the 2NS/2AS translocation in 57 advanced breeding lines and one variety 'Caninde 1' from Paraguayan wheat germplasm, using VENTRIUP-LN2 primers. The germplasm 'Caninde 1 and 22' of the breeding lines, found positive for the presence of 2NS/2AS translocation, were inoculated with a single aggressive Magnaporthe pathotype P14-039, to assess their response to wheat blast infection under controlled conditions. Based on the disease infection score, ten of the breeding lines, 'Caninde 1' and 'Milan' (positive control), were classified as resistant. Three of the remaining breeding lines were classified as moderately resistant, five as moderately susceptible and other four as susceptible. Our results show that the expression of 2NS/2AS-based blast resistance is more dependent on genetic background of the inserted germplasm than previously envisioned.