Transfer of Reniform Nematode Resistance from Diploid Cotton Species to Tetraploid Cultivated Cotton

The reniform nematode (Rotylenchulus reniformis) is a semi-endoparasitic organism in which the female penetrates the root cortex establishing a permanent feeding site (Robinson et al., 1997). It has become a serious threat to cotton (Gossypium hirsutum L.) production in Arkansas and the mid-South (Zhao et al., 2000) because yield losses in infested fields may exceed 50% under stress conditions (Smith and Cothren, 1999). The most cost-effective method of pest management is host-plant resistance (Stewart, 1994); however, no commercial cultivars tested to date have shown resistance. Robbins and Stewart (1996) identified a number of sources of resistance within G. arboreum (A2), G. herbaceum (A1), and G. longicalyx (F1). These sources are diploid species; therefore, the material must be genetically enhanced for use in tetraploid cultivated cotton. The objectives of this project are: (1) to develop hybrid materials between resistant reniform nematode diploid cottons and tetraploid cultivated cotton, and (2), to identify molecular markers genetically linked to reniform nematode-resistance gene.