*2.3. Disease Evaluation*

Seven days post inoculation, the plants were assessed for disease symptoms using the 0–5 scale of the Chinese standard NY/T 2060.1-2011 (Ministry of Agriculture of the People's Republic of China 2011), which consisted of the following: 0 = no disease symptoms; 1 = emergence of brown lesions in the roots and stems with no to slight wilting of leaves; 2 = extension of root and stem lesions by 1–2 cm, the leaves wilted and had fallen off; 3 = root and stem lesions exceed 2 cm and leaves clearly show wilting or defoliation; 4 = large brown lesions on stems are extended and dehydrated, with the exception of the uppermost leaves which have been lost; and 5 = plant death. According to the disease grade of each plant, the disease index (DI) of each identification material was calculated. The DI was calculated using the equation below:

$$\mathrm{DI} = \frac{\Sigma(\mathbf{s} \times \mathbf{n})}{\mathbf{N} \times \mathbf{S}} \times 100\,,$$

where s is the disease level ranging between 0 and 5; n is the number of plants with corresponding disease level; N is the number of plants investigated in each F2; and S is the representative value of the highest grade.
