Abstract
Cotton producers worldwide suffer with the losses caused by the presence of phytonematodes. The aim of the present study was to investigate the inheritance of resistance to Meloidogyne incognita race 3 in Gossypium hirsutum variety punctatum accession TX 25. Accessions of Gossypium sp. were obtained from the germplasm bank of Embrapa Cotton. Two experiments were performed in two consecutive years. In the first experiment, a susceptible parental line, FiberMax 966, a resistant parental line, TX 25, and their F 1 , F 2 and backcross generations were tested. In the second experiment, parental lines FiberMax 966 and TX 25, their F 2 generation, and genotypes M315 (resistant), LA887 and DeltaOpal (moderately resistant) were tested. In both experiments, plants were inoculated with 2000 eggs and J2 of M. incognita race 3. The gall index, egg mass index and reproduction factor were evaluated 120 days following inoculation. In the first experiment, plants from the F 1 and backcross generations were susceptible. Plants from the F 2 generation presented a 3:1 resistant-to-susceptible ratio in the two experiments, indicating oligogenic resistance.
Highlights
In spite of their high productivity, cotton producers suffer crop losses due to the presence of phytonematodes
The aim of this study was to investigate the resistance of wild cotton accession TX 25 to M. incognita race 3
Genotype TX 25 was highly resistant when compared to the standard susceptible control, FiberMax 966, according to the Starr and Mercer (2010) classification (Table 2)
Summary
In spite of their high productivity, cotton producers suffer crop losses due to the presence of phytonematodes. Main are of cotton plant-parasitic nematode species Meloidogyne incognita (Kofoid & White, 1919, Chitwood, 1949), Rotylenchulus reniformis (Linford & Oliveira, 1940) Pratylenchus brachyurus (Godfrey, 1929) Filipjev & Sch. Sttekhoven, 1941 (Galbieri et al (2009) evaluated the resistance of 22 cotton genotypes against M. incognita and observed that 21 genotypes allowed nematode reproduction. Agronomy most affected genotypes generated a 65% loss of production when compared to the resistant genotypes. The use of resistant cultivars is the most affordable method for the control of nematodes, because it do not increase production costs, do not interfere with the environment, and do not lead to environmental imbalances (Davis & Stetina, 2016). Genetic resistance is the safest method for decreasing damages caused by M. incognita to cotton crops (Barbosa et al, 2009). In Brazil, there are currently no cotton varieties that combine
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