Modified seedbox screening test to identify field resistance to brown planthopper (BPH) [Philippines]

In field screening for resistance to BPH [brown planthopper] at IRRI [International Rice Research Institute; Philippines], some varieties are resistant in the field but susceptible at early seedling stage in the greenhouse. The standard seedbox screening tests (SSST) were modified to identify field-resistant varieties in the greenhouse. Varieties in which resistance is expressed in older plants are useful because their resistance maybe stable and not easily broken down by the selection of virulent biotypes. The feeding behavior of the South Asia BPH population differs from that of Southeast Asia BPH. Some varieties that are resistant in Southeast Asia are not resistant in South Asia and vice versa. A collaborative project compared the SSST and the modified standard seedbox screening test (MSST) in tests conducted in the Philippines, Bangladesh, Solomon Islands, and Sri Lanka. Seeds of eight varieties and methods of conducting the tests were sent from IRRI. Varieties were selected on the basis of their reactions in SSST and in IRRI fields. Sinna Sivappu was the resistant (R) check, TN1 was the susceptible (S) check. IR26 was selected as the basis for testing IR46. IR26 is S to biotype 2 in the SSST and in the field; IR46 is S in the SSST but R in the field. ASD7 is R check for biotypes and 1 and 2 and S check for biotype 3. Kencana, Utri Rajapan, and Triveni are S in the SSST, but moderately R to R in the field. Tests insects were reared on 60- to 80-d old TN1 plants except for biotypes 2 and 3, which were reared on Mudgo and ASD7 at IRRI. In the commonly used SSST, 25 seeds of each variety are sown in a 60- x 45- x 7-cm seedbox in 20-cm rows with 5-cm spacing between rows. Varieties are arranged in a randomized complete block design with one row of each variety replicated four times. At 7 d after sowing (DAS), each seedling is infested with 8 to 10 2d- or 3d-instar nymphs. When plants in the S TN1 check are killed, damage is scored by the standard evaluation system for rice (SES)