Determination of BTH-induced wheat resistance to Puccinia striiformis

Stripe rust, caused by Puccinia striiformis f. sp. tritici (Pst), is one of the most damaging wheat plant diseases across the globe. Exploration of resistant cultivars is one of the most economic and preferred control methods of stripe rust diseases. Wheat resistance to stripe rust fungi could easily be lost due to rapid virulent variations in Pst races. Benzothiadiazole (BTH), a novel and powerful elicitor, could induce systemic acquired resistance (SAR) in plants. So far no report has focused on BTH-induced wheat resistance to stripe rust fungi at maturity growth stage. Hence in this study, wheat cultivars of "Huixianhong" seedlings and "97148" mature plants were pre-treated with BTH and inoculated with Pst race CYR23. Disease index and control efficiencies evaluations indicated improvements in wheat resistance to Pst and induction of SAR by BTH. In "Huixianhong" wheat seedlings, resistance to Pst significantly increased and stripe rust disease index reduced by 29.69~49.77. Meanwhile stripe rust disease control efficiency in "Huixianhong" wheat seedlings after BTH treatment reached 90%. Optimum concentration and time interval of BTH pre-treatment tests also showed that 0.3 mmol·L^-1 of BTH concentration and 6~7 days intervals between BTH treatment and Pst inoculation were the best. Furthermore, BTH-induced wheat resistance to Pst was noted to last at least 15 days after Pst inoculation. Mature "97148" wheat cultivar sprayed with different concentrations (0.1~1.0 mmol·L^-1) of BTH showed nominal fluctuations in disease index, but with much stronger wheat resistance to Pst. Meanwhile grain yield of 0.3 mmol·L^-1 BTH-treated plants reached 675.32 kg·667m^-2, which was 19.3% higher than the control. The results also indicated that BTH sprayed at different wheat growth stages (e.g., tillering, pre-jointing and tillering/pre-jointing) had no influence on the efficiency of BTH-induced wheat resistance to Pst. Compared to the control, however, BTH treatment impacted disease index of Pst and grain yield of wheat at each different growth stage. Due to stronger seedling assays, BTH-induced wheat resistance to Pst in mature plants lasted at least 60 days. In conclusion therefore, the study demonstrated that BTH induced wheat resistance to stripe rust fungi at both seedling and maturity stages. This finding was significant in controlling stripe rust disease of wheat and other field crops.