Factors Contributing to Resistance in Rice to the Rice Water Weevil, Lissorhoptrus Oryzophilus Kuschel.

Studies were conducted in the field and greenhouse to identify sources of rice water weevil (Lissorhoptrus oryzophilus Kuschel) resistance in rice, Oryza sativa L., and determine the mechanisms of resistance. Rice lines of various sources, including breeding lines, somaclone lines and world collection lines, were evaluated. Tolerance was investigated using replicated insecticide treated and untreated plots in a split-plot design, and antibiosis and/or antixenosis were assessed using caged insect-infested plants in randomized block designs. Resistance predictors included rice water weevil larval populations, larval root pruning damage, plant height and grain yield. Anther culture lines 95-2836 and 95-3527, Louisiana breeding lines 8720906 and 8721937, tissue culture lines 112 and 4754, and five lines of various sources (AL6029, LA2218, TX22041, URN199, URN200) exhibited moderate tolerance to the rice water weevil. These lines did not have significant $(P\u3c0.05)$ yield differences between treated and untreated plots, while supporting high larval populations in the untreated plots. Root damage rating data indicated that these lines are capable of recovering from root pruning damage. In addition, the lines exhibiting tolerance produced higher grain yields than the susceptible check Mars. Antixenosis and/or antibiosis tests revealed that two tissue culture lines (244, 2232), three Louisiana breeding lines (8723417, 8723518, 8825454) and two Texas lines (TX12685 and TX13079) sustained significantly $(P\u3c0.05)$ lower rice water weevil larval populations than the susceptible check Mars. Assessment of the percentage of larval populations in different size categories (small (0-3 mm), medium (3-6 mm) and large (6-10 mm)) suggested that nonpreference for oviposition by the adult weevil may be the mechanism of resistance in these lines