Screening of excellent alfalfa varieties with high-yield and disease resistance in Cangzhou, Hebei Province

To determine which varieties of alfalfa with high yield and resistance to diseases are suitable to promote and plant in Cangzhou, the disease incidence of 32 alfalfa varieties was investigated in September 2018, 2019, and 2020. Additionally, the grass yield was measured, the disease resistance of different varieties was evaluated, and the correlation between alfalfa yield and disease incidence was analyzed. The results showed that five main alfalfa diseases occurred in Cangzhou: Alfalfa phoma leaf spot and black stem (Phoma medicaginis), alfalfa anthracnose (Colletotrichum truncatum), alfalfa cercospora leaf spot (Cercospora medicaginis), alfalfa rust (Uromyces striatus), and alfalfa brown spot (Pseudopeziza medicaginis). The incidence of the first three diseases was higher, up to 73.22%, 86.67%, and 91.67%, respectively. The results of variety resistance evaluation showed that all varieties had resistance to the diseases investigated in the field; among them, ‘Aohan alfalfa’, ‘Zhongmu No.3’ and ‘Longdong alfalfa’ showed high resistance to the five diseases mentioned above. The yield of 32 alfalfa varieties ranged from 1.28～4.53 t·ha⁻¹ in different years, and the varieties with the highest and lowest yields were ‘Xinmu No.4’ and ‘Longdong alfalfa’, respectively. The correlation analysis between alfalfa yield and disease incidence showed that the incidence of alfalfa phoma leaf spot and black stem was significantly negatively correlated with the grass yield of ‘Phabulous’ and ‘DSA01-T’ in 2018, 2019, and 2020 (P < 0.05). The incidence of alfalfa brown spot was significantly negatively correlated with the grass yield of ‘Gannong No.4’ and ‘Xinmu No.4’ in 2018 and 2019. The incidence of alfalfa anthracnose was significantly negatively correlated with the grass yield of ‘Shockwave’ in 2018 and 2019, and extremely significantly negatively correlated in 2020. Additionally, the incidence of alfalfa cercospora leaf spot was extremely significantly negatively correlated with the grass yield of ‘Zhongmu No.1’ and ‘Gannong No.4’ in 2020. The comprehensive analysis results showed that ‘Aohan alfalfa’, ‘Zhongmu No.3’, ‘Phabulous’, ‘Xinmu No.4’, and ‘Gannong No.4’ performed well and should be recommended to plant locally.