BPH resistance evaluation
To conduct the BPH resistance test at the seedling stage, eight
seedlings of each line were placed in a plastic cup, 10 cm in diameter,
and infested with six second to third instar BPHs per plant at the
third-leaf stage (approximately 15 days). The plant survival rate of
each cup was recorded 5–7 days after BPH infestation. Four 15-day-old
seedlings of OE, knockout, and NIP were transplanted into a plastic
bucket (30 cm in diameter), and normal management practices were
performed. Each bucket was infested with second to third instar BPHs, at
a density of 30 insects per shoot, when the plants began heading
(approximately 75 days). Thereafter, the green shoots of each plant were
counted when the knockout lines died after BPH infestation
(approximately 21 days). Here, the green shoot rate, taken as the plant
survival rate, was used to indicate the BPH resistance level of adult
plants. A higher rate indicates a stronger resistance against BPH. Three
cups or buckets were designed for each test, and each test was repeated
three times.