Faske, T. R. and J. L. Starr. 2009. Mechanism of resistance to Meloidogyne incognita in resistant cotton genotypes. Nematropica 39:281-288. Meloidogyne incognita is an economically important plant-parasitic nematode on cotton (Gossypium hirsutum) across the U.S. Cotton Belt. Few studies have characterized the mechanism of resistance in cotton based on the biology of M. incognita. Penetration, post-penetration development, and reproduction of M. incognita were determined on eight cotton genotypes. Resistant genotypes included Clevewilt, Wild Mexican Jack Jones (WMJJ), five primitive accessions; TX-1174, TX-1440, TX-2076, TX-2079, and TX-2107 and one susceptible control, cv. Deltapine (DP) 90. Root penetration by M. incognita on developing radicles was similar among resistant genotypes and susceptible control. The mechanism of resistance for all resistant genotypes was based on delayed (P ≤ 0.05) maturity of M. incognita. This delayed maturity contributed to lower eggs per gram of root, egg masses per root system, and Pf/Pi values; however, eggs per egg mass were similar among all genotypes. Thus, resistance to M. incognita had a greater influence on nematode development than penetration or fecundity. The rate of delayed nematode development varied among resistant genotypes, thus suggesting diversity in resistant genes among these cotton genotypes. Further, these data confirm resistance in the primitive accessions from Mexico and suggest that they may be useful new sources of resistance to M. incognita.
