Evaluation of cotton polyphenols as factors of resistance to root-knot nematode and Fusarium wilt

The terpenoid aldehyde content of cotton (Gossypium hirsutum L.) roots of a root-knot nematode (Meloidogyne incognita ) resistant strain (A623) was higher initially and increased faster after inoculation than that of a susceptible strain (M-8). The presence of gossypol and five other terpenoid aldehydes in root exudates was confirmed. These terpenoid aldehydes were also found in the soil surrounding roots where cotton plants had grown; highest concentrations occurred in soils around the resistant inoculated strain. There was not a significant negative correlation of terpenoid aldehyde concentrations in healthy roots with root-knot nematode egg masses in infected roots of 10 other strains of cotton. However, the terpenoid aldehyde concentrations of roots of 17 cotton strains were significantly negatively correlated with fusarium (Fusarium oxysporum f.vasinfectum wilt incidence.