Electronic Journal of Plant Breeding, 1(4): 899-902 (July 2010) 899 Research Article Correlation studies for shootfly resistance traits in sorghum (Sorghum bicolor (L.) Moench) Sunil Gomashe, M.B.Misal, K.N.Ganapathy and Sujay Rakshit Abstract : A field experiment was conducted to study the relation of different plant characters and shoot fly resistance in sorghum. Leaf glossiness showed high positive correlation with shootfly oviposition and dead hearts. The oviposition percentage on 14 th and 21 st days after seedling emergence exhibited significant positive correlation with dead hearts. Leaf trichome density on adaxial and abaxial leaf surfaces showed significant negative correlation with shootfly dead hearts. The leaf trichome density revealed higher magnitude for resistance due to non-preference for oviposition. Seedling vigour recorded weaker association with dead heart percentage. Genotypic correlation confirmed that the number of trichomes on both surfaces of lamina and leaf glossiness contributed resistance to shoot fly. Thus these characters can be used as selection criteria for breeding shootfly resistance genotypes. Key words: Sorghum shoot fly, correlation, trichome density, oviposition, leaf glossness, resistance Introduction Sorghum shoot fly (Atherigona soccata Rondani) is an important seedling pest (Sherwill et al. 1999) attacks sorghum crop upto 30days from sowing leading to losses estimated as 5% in India (Jotwani 1983), but the infestations at times may be over 90% (Rao and Gowda 1967). The shoot fly females lay eggs singly on the undersurface of the leaves, parallel to the midrib. After egg hatching, the larvae crawl to the plant whorl and move downward between the folds of the young leaves until they reach the growing point. When they feed, they cut the growing tip resulting in drying of the central leaf called dead heart. It is estimated that an increase in 1% of dead hearts would result in loss of 143 kg grain yield per hectare (Chundurwar and Karanjkar 1979). Adoption of chemical methods for insect control in staple food crops is not economically feasible for resource poor farmers of the semi-arid tropics (SAT) as the low crop value per acre precludes the use of insecticides for control of insects (Dhams, 1943). Therefore host plant resistance combined with timely sowing is the most realistic approach to minimize grain and stover yield losses due to insect pests such as sorghum shoot fly. The resistance to shoot fly appears to be a complex trait. Recent reviews on 1 Department of Agricultural Botany, Marathwada Agricultural University, Parbhani 431 402, India. shoot fly resistance reveals that four components governing resistance to this pest viz., non preference for oviposition, antibiosis, seedling resistance and recovery resistance. The traits leaf glossiness, seedling vigour, trichome density on leaf surface, silica contents, lignifications and thickness of cell wall of the cells enclosing the vascular bundles of leaves and some biochemical factors are reported to be associated with shoot fly resistance. To find out the contribution of each character for governing the resistance, it would be necessary to study their correlations. Such investigations would depict a reliable scenario regarding characters associations and criteria for selecting characters for genetic improvement of sorghum for shoot fly resistance. Materials and methods A set of 78 F 1 hybrids were planted along with parents and three checks, viz., susceptible variety (PVK 801), resistant source (IS 18551) and commercial hybrid (CSH 16). The materials were raised in randomized block design with two replications. Maintainer lines (B lines) were also raised to evaluate their susceptibility or resistant reaction to shoot fly. Each parental line and F 1 hybrids were planted in a single row plot (4m) with row to row and plant to plant spacing of 45 and 15cm, respectively. The sowing was carried out on 22 nd September, 2006 for screening in early Rabi (post rainy) season. Each replication consisted of 106 entries, which were divided into two tiers to reduce