Black Point and Smudge in Wheat

There are various types of discolouration that can affect common (Triticum aestivum L.) and durum [T. turgidum L. ssp. durum (Desf.) Husn.] wheat kernels grown on the Canadian Prairies. Black point and dark smudge, mostly associated with Alternaria alternata (Fr.) Keissl., and Cochliobolus sativus (Ito & Kurib.) Drechs. ex Dast. [anamorph Bipolaris sorokiniana (Sacc.) Shoemaker] are common discolourations of cereal seed, which occur in most regions where these crop species are grown. Red smudge, caused by Pyrenophora tritici-repentis (Died.) Drechs. [anamorph Drechslera tritici-repentis (Died.) Shoemaker], is also ubiquitous, especially in durum wheat. These types of kernel discolouration vary significantly in incidence and severity depending on environmental conditions during kernel maturation. Kernel discolourations are downgrading factors in wheat and thus can cause significant economic losses in years conducive to the development of these diseases. In most cases, kernel discolouration has been associated with the presence of fungal pathogens. Some studies have shown that black point in wheat might not be initiated by fungal infection. However, a recent study showed that although abiotic factors, such as high humidity levels, can promote the occasional development of black point or dark smudge on durum wheat kernels under controlled-environment conditions, fungal infection by C. sativus or A. alternata was the main factor associated with their development. Further research to determine the main causes of black point under field conditions and different soil types is needed to identify resistance to the various types of discolouration, and determine the most effective screening techniques. Unpredictability of weather will continue to be a risk factor in grain downgrading and the resulting economic losses to cereal producers. Thus, it is necessary to continue research on these important wheat diseases.