Influence of cytoplasmic male-sterility on expression of physico-chemical traits associated with resistance to sorghum shoot fly, Atherigona soccata (Rondani)

Sorghum is damaged by several insect species, of which the shoot fly, Atherigona soccata, is important in Asia and Africa. Host plant resistance is an effective component for the management of this pest under subsistence farming conditions. With the discovery of the cytoplasmic male-sterility (CMS) system (Milo cytoplasm), there is an increasing emphasis to develop sorghum hybrids to increase the productivity of this crop. In order to develop sorghum hybrids with broad based resistance to shoot fly, it is important to identify CMS, maintainer, and restorer lines with different mechanisms of resistance to this pest. Therefore, the expression of resistance and the components associated with resistance to sorghum shoot fly in a diverse array of shoot fly-resistant and -susceptible CMS and maintainer lines were studied for three years (2002-2004). The shoot fly-resistant CMS lines were preferred for oviposition by the shoot fly females than the corresponding maintainer lines (78.5 to 82.8% versus 71.5 to 79.9% plants with eggs), and had more deadhearts (47.6 to 79.3% versus 41.6 to 74.0%). The shoot fly-susceptible CMS and maintainers were equally susceptible to shoot fly damage. Shoot fly-resistant maintainer lines showed better recovery than the CMS lines. The expression of trichomes on abaxial and adaxial leaf surfaces was more in the maintainer lines than the CMS lines. Leaf glossiness, trichome density, and plumule and leaf sheath pigmentation showed negative associations with oviposition and deadhearts, while leaf surface wetness, chlorophyll content, and waxy bloom were associated with susceptibility. Plants with eggs, deadhearts, leaf surface wetness, leaf sheath pigmentation, leaf glossiness, trichomes on the adaxial surface of the leaf, and waxy bloom can be used as marker traits to select for resistance to A. soccata. The results suggested that the resistance to A. soccata is influenced by factors associated with cytoplasmic male-sterility and the interaction between cytoplasmic and nuclear genes