DIAMONDBACK MOTH (LEPIDOPTERA, PLUTELLIDAE) RESISTANCE OF BRASSICA-NAPUS AND BRASSICA-OLERACEA LINES WITH DIFFERING LEAF CHARACTERISTICS

Canola quality oil produced from oilseed rape, Brassica napus L. (Bras sicaceae), is a relatively new crop in the United States and is damage d by a number of insect pests, including the crucifer specialist diamo ndback moth, Plutella xylostella (L.). Greenhouse tests were performed to evaluate resistance in normal-leafed ('Bingo','Cobra', 'Oscar') an d glossy-leafed B, napus plants ('glossy Bingo' and plant introduction s (PI) 469895, 470055, 470055-2, and 470064) to identify potential res istant sources to diamondback moth. Normal-leafed PI 171538, originall y described as B. napus and recently reclassified as B. oleracea, also was evaluated for resistance with B. napus plants and B. oleracea cul tivars of broccoli, 'Green Comet', 'Green Valiant', and collard 'Vates '. Plants of Cornell line 92-8611, a broccoli with glossy-leaf type (g lossy broccoli), were used as the resistant control in all trials. B. napus entries failed to show feeding nonpreference or antibiosis compa rable to that of glossy broccoli. Furthermore, no significant differen ces were detected between normal and glossy-leafed B. napus lines for most of the parameters tested. Within the tested B. napus entries, PI 470055 exhibited low levels of feeding damage in the restricted-feedin g test and some level of antibiosis against diamondback moth. However, B. oleracea entry PI 171538 showed a greater or comparable level of r esistance to that of glossy broccoli. Nonpreference for larval feeding and adult oviposition were exhibited by PI 171538. In feeding tests, PI 171538 was less defoliated compared with other B. oleracea entries. Diamondback moth larvae reared on PI 171538 leaves for 5 d had a lowe r head capsule width compared with larvae reared on other entries. In an oviposition preference test, PI 171538 received 0.9% of eggs as com pared with normal-leafed B. napus plants (2.1- 4.4%) and glossy brocco li, which received 7.0% of eggs. The experiments indicate that the nor mal-leafed B. oleracea entry PI171538 has considerable resistance agai nst diamondback moth. PI171538 is a newly discovered source of resista nce and has leaf characteristics that differ from the previously repor ted diamondback moth-resistant B, oleracea lines.