Discoloration of wheat kernels by Pyrenophora tritici-repentis

Infection of wheat kernels by Pyrenophora tritici-repentis (Ptr) causes primarily a pink/red discoloration. Dark smudge and black point are also commonly observed. These types of kernel discoloration cause downgrading of wheat. A series of studies on Ptr-kernel infection are summarized here. Infected durum wheat kernels germinated faster than uninfected ones, but seedlings derived from the former had reduced vigour. Emergence of plants derived from infected seed was also reduced. However, no transmission of Ptr-infection from seed to emerging durum wheat seedlings was observed. Studies on durum wheat also showed that there was no association between discoloration of glumes and discoloration of kernels, or between tan spot development on leaves and discoloration of kernels. Wheat cultivars of different quality classes and species showed differences in the prevalent type of symptom developed upon inoculation with Ptr. In addition, the incidence and severity of the discoloration were genotype-dependent, and the discoloration was more apparent in white than in red-seeded cultivars. A study examining the effect of incubation conditions on the development of kernel discoloration caused by Ptr in durum wheat indicated that the length of incubation period mainly affected the severity of infection, whereas temperature of incubation affected percent kernel infection, including development of black point.