Mass screening of different rice genotypes to rice striped stem borer, Chilo suppressalis Walker (Lep.: Pyralidae), under the field condition

In this study, a total of 98 Iranian and exotic rice genotypes were tested for their resistance to the Striped Stem Borer, Chilo suppressalis, under field conditions in Rice Research Institute of Iran, Mazandaran branch, Amol. The experiment was carried out in a randomized complete blocks design and three replications. At the reproductive stage, five whole plants per plot were randomly selected and cut off at the base, and percent of white head, number of larvae per hill, plant height, stem diameter, and tiller number per hill were measured. The rice genotypes Novator, G2-Gan74, Estrella, Rashtline-1, and IR72860, had the lowest amount of percent of white head, with means of 1.6%, 2.7%, 2.3%, 2.8%, and 3.2%, respectively, and the genotypes IR72-B, Iranian-New-Hybrid, Fars promising line, IR64-MutantW, IR50 had the highest amount of percent of white head with means of 43.5%, 43.4%, 37.6%, 35.8 %, and 34.8%, respectively. Moreover, genotypes Novator, Estrella and G2-Gan74 had the lowest mean larvae per a whole plant (0.1, 0.1 and 0.2, respectively), while genotypes Chinese-Hybrid1, IR72-B, and Binam had the highest mean larvae per a whole plant, with means of 10.3, 9.7, and 8.9, respectively. Rasht-Line-1 had the lowest mean plant height (74.4 cm), Fars promising line had the lowest mean number of tillers per hill (9.13), and Iranian New-Hybrid had the lowest mean stem diameter (4.44 mm). On the other hand, the Tarom-ARG2 genotypes had the highest mean plant height (138.26 cm), Sahel had the highest mean number of tillers per hill (17.6), and Dorfak had the highest mean stem diameter (12.72 mm).There were significant correlations between percent white head and the number of larvae per a whole plant, and between percent white head and number of tillers per hill, but there no significant correlations was found with plant height and stem diameter. The rice genotypes were grouped on Ward’s clustering procedure into two main clusters, totally four sub-cluster. The rice genotypes such as Novator, Estrella, Rashtline-1 were found to be less sensitive to Chilo suppressalis. Also, in this study, 19 rice genotypes including Novator, Estrella, G2-Gan74, Rashtline-1, Shirodi, Nemat, IR64-Mutant-F3076, MashhadDomsiah/Neda, {(A78.1/LocalAbiji)/(khazar/Tarom)} were recognized as resistant genotypes at field condition. Some of them can be tested in further experiments.