Abstract
The effects of treating seeds of the common bean with rhizobacteria before sowing associated with different nitrogen (N) doses on the control of the nematode Meloidogyne javanica was evaluated. The assay was carried out in a greenhouse in random blocks, with a factorial arrangement of 5 × 5 + 1: five N doses (0, 25, 50, 100, and 200 kg/ha); five isolates: Bacillus pumilus (1, 60 and 76), Bacillus subtilis.-34, Bacillus sp.-36, and one control treatment. The plants were inoculated with 3,000 nematode eggs/pot. After 60 days the assay was evaluated. In the absence of N, B. pumilus-60 promoted a reduction of more than 50% in the number of galls and egg masses compared to the control. B. pumilus (1 and 76) and Bacillus sp.-36 reduced the number of galls in combination with increased N doses. Treatment of seeds with Bacillus in combination with N fertilization contributed to a reduction in the number of galls and nematode egg masses. B. pumilus (60 and 76) reduced the number of galls and egg masses in the absence of N, indicating a nematicidal effect. The treatments had no effect on the number of second-stage juveniles, eggs, or the plant parameters.
Highlights
The common bean (Phaseolus vulgaris L.) has great socio-economic importance in Brazil, it is one of the main components of the diet due to its high protein content (Soares et al, 2006)
A significant reduction in the number of egg masses and galls per root was identified between plants subjected to the combined treatments compared with the control (Dunnett’s test, p < 0.05)
The largest reductions in number of egg masses in comparison to controls were observed in the B. pumilus-60/0 N (54.68%), B. subtilis-34/25 kg/ha urea (62.50%), B. pumilus-1/50 kg/ha urea (66.8%), B. subtilis-34/100 kg/ha urea (84.6%), and B. pumilus-1/200 kg/ha urea (83.17%)
Summary
The common bean (Phaseolus vulgaris L.) has great socio-economic importance in Brazil, it is one of the main components of the diet due to its high protein content (Soares et al, 2006). The nematode specie Meloidogyne javanica (Treub) Chitwood is one of the main causes of reductions in bean crop yields, especially in regions routinely subject to high temperatures that increase environmental stress and affect plant tolerance to the nematode (Pedrosa, 2000). The losses in common bean crops caused by parasitism by M. incognita (Kofoid; White) Chitwood and M. javanica may reach up to 90% (Agudelo, 1980). The standard measures to control Meloidogyne spp. in common bean crops are crop rotation, fallow periods, and use of resistant varieties. The farmers prefer to cultivate crops during the three annual seasons in irrigated areas, which causes an increased nematode population density in these regions
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