RESUMO
The southern root-knot nematode (RKN), Meloidogyne incognita, causes significant damage to vegetable production and is a major problem in greenhouse tomatoes. The effect of a combination of fluopyram and abamectin, at a mass ratio of 1:5, was studied for RKN control. Pot trials showed that fluopyram, abamectin, and their combination at three dosages increased the height, stem diameter, root fresh weight, shoot fresh weight, and the root length of tomato plants. The RKN control efficacy of the 1:5 combination at 450 g a.i./ha was 74.06% at 30 days after transplanting (DAT), and the control efficacy of the combination at 337.5 and 450 g a.i./ha differed significantly from those of other treatments at 60 DAT. The root-galling index (RGI) control efficacy of the combination at 450 g a.i./ha and of fluopyram (41.7% SC) only at 450 g a.i./ha were better than the control efficacies of other treatments, and these two treatments significantly increased root activity. Field trial results showed that the soil nematode control efficacy was similar to that of the pot trials at 30 and 60 DAT. The RGI control efficacy of the combination at 337.5 and 450 g a.i./ha and of fluopyram (41.7% SC) only at 450 g a.i./ha differed significantly from those of the two other treatments. The tomato yields of the 1:5 combination at 450 g a.i./ha were increased by 24.07 and 23.22% compared to the control in field trials during two successive years. The combination of fluopyram and abamectin provides good nematode measure, and it can increase tomato yields. It provides an effective solution for the integrated management of southern RKN.
RESUMO
Chromosome substitution (CS) lines in plants are a powerful genetic resource for analyzing the contribution of chromosome segments to phenotypic variance. In this study, a series of interspecific cotton (Gossypium spp.) CS lines were used to identify a new germplasm resource, and to validate chromosomal regions and favorable alleles associated with nematode or fungal disease resistance traits. The CS lines were developed in the G. hirsutum L. TM-1 background with chromosome or chromosome segment substitutions from G. barbadense L. Pima 3-79 or G. tomentosum. Root-knot nematode (Meloidogyne incognita) and fusarium wilt (Fusarium oxysporum f. sp. vasinfectum) (races 1 and 4) resistance alleles and quantitative trait loci (QTL) previously placed on cotton chromosomes using SSR markers in two interspecific recombinant inbred line populations were chosen for testing. Phenotypic responses of increased resistance or susceptibility in controlled inoculation and infested field assays confirmed the resistance QTLs, based on substitution with the positive or negative allele for resistance. Lines CS-B22Lo, CS-B04, and CS-B18 showed high resistance to nematode root-galling, confirming QTLs on chromosomes 4 and 22 (long arm) with resistance alleles from Pima 3-79. Line CS-B16 had less fusarium race 1-induced vascular root staining and higher percent survival than the TM-1 parent, confirming a major resistance QTL on chromosome 16. Lines CS-B(17-11) and CS-B17 had high fusarium race 4 vascular symptoms and low survival due to susceptible alleles introgressed from Pima 3-79, confirming the localization on chromosome 17 of an identified QTL with resistance alleles from TM1 and other resistant lines. Analyses validated regions on chromosomes 11, 16, and 17 harboring nematode and fusarium wilt resistance genes and demonstrated the value of CS lines as both a germplasm resource for breeding programs and as a powerful genetic analysis tool for determining QTL effects for disease resistance. CS lines carrying small alien chromosome segments with favorable QTL alleles could be used for effective introgression of biotic stress resistance or many other desirable traits by targeting gene interactions and reducing linkage drag effects.