Abstract: The C, N and P stoichiometry are helpful to understand the capacity of carbon assimilation and nutrient utilization efficiency during plant growth, as well as to diagnose nutrient limitation status. There is still a knowledge gap about the effects of disease on plant stoichiometry. In this study, forage oats (Avena sativa) suffering from anthracnose were the object of research conducted in north Shanxi Province. The C, N and P stoichiometry in the shoot of oat were examined at different degrees of disease occurrence. We analyzed the relationship of plant stoichiometry with disease duration, cultivar, and cultivation methods. The results showed that C, N and P contents decreased with the increasing degree of disease occurrence. The C, N and P contents in the plants with serious disease were significantly lower than that of healthy plants with a decreasing rate of 5.4%, 20.0% and 24.2%, respectively. C:N and C:P showed an increasing trend with the increases of the degree of disease occurrence. C:N and C:P of the plants with serious disease were significantly increased by 18.5% and 22.2%, respectively, than that of healthy plants. There was no significant difference for C content among different sampling sites, which indicated that the three varieties of forage oats might have disease tolerance capacity to ensure crop production. However, the stoichiometric values of N and P varied from place to place. The longer the disease duration was, the more reduction of N and P contents. Compared with monoculture oats, the P utilization efficiency of mixture oats was decreased by anthracnose. In summary, anthracnose had negative impacts on carbon assimilation capacity of forage oats in northern Shanxi. Anthracnose increased the restriction of N and P nutrition on the aboveground parts. However, anthracnose significantly improved N and P utilization efficiency. For the production practice, it was recommended to take necessary control measures to reduce the adverse effects of diseases on the economic benefits and ecological functions of forage oats.

Key words: disease, oat, aboveground part, stoichiometry