Genetic Resistance and its Residual Effects for Control of the Root‐Knot Nematode‐Fusarium Wilt Complex in Cotton1

Abstract

Two cotton (Gossypium hirsutum L.) cultivars and a breeding stock (‘Deltapine 16’, ‘Auburn 56’, and Auburn 623 RNR, respectively), having in order low, intermediate, and high resistance to the root‐knot nematode‐fusarium wilt disease complex [caused by Meloidogyne incognita acrita (Kofoid & White) Chitwood and Fusarium oxysporum Schlecht. f. vasinfectum (Atk.) Snyd. & Hans.], were grown in nematicide, DBCP (1,2‐dibromo‐3‐chloropropane), treated vs. untreated plots for 3 years.Fumigation did not significantly increase lint yield of Auburn 623 RNR compared with 36 and 77% increases for Auburn 56 and Deltapine 16, respectively. Auburn 623 RNR without fumigation was more effective for controlling root‐knot nematodes than Auburn 56 and Deltapine 16 with fumigation and was equally effective as those cottons with fumigation for controlling fusarium wilt disease. In unfumigated plots, Auburn 623 RNR vs. Auburn 56 and Deltapine 16 also had lower root‐knot nematode numbers (83/500‐cm3 of soil vs. 717 and 1,581, respectively) and lower fusarium wilt percentages (5% vs. 47%, respectively). In the fourth year of the study, susceptible ‘Stoneville 213’ cotton was grown without fumigation in all plots where the above cottons had been grown. Stoneville 213 following unfumigated Auburn 623 RNR had 147 kg/ha (21%) and 270 kg/ha (47%) higher lint yields than following unfumigated Auburn 56 and Deltapine 16, respectively. Stoneville 213 had smaller root‐knot nematode populations following unfumigated Auburn 623 RNR than following fumigated Deltapine 16 and no greater incidence of fusarium wilt disease than when it followed fumigated Auburn 56 and Deltapine 16. If the high level of resistance exhibited by Auburn 623 RNR can be bred into cotton cultivars, it should reduce much of the present root‐knot nematode and fusarium wilt damage to cotton and to susceptible crops following resistant cotton in rotations.