Abstract
The aim of the current study was to describe the role and mechanism of Bacillus amyloliquefaciens Y1 against the root-knot nematode, Meloidogyne incognita, under in vitro and in vivo conditions. Initially, the exposure of the bacterial culture supernatant and crude extract of Y1 to M. incognita significantly inhibited the hatching of eggs and caused the mortality of second-stage juveniles (J2), with these inhibitory effects depending on the length of incubation time and concentration of the treatment. The dipeptide cyclo(d-Pro-l-Leu) was identified in B. amyloliquefaciens culture for the first time using chromatographic techniques and nuclear magnetic resonance (NMR 1H, 13C, H-H COSY, HSQC, and HMBC) and recognized to have nematocidal activity. Various concentrations of cyclo(d-Pro-l-Leu) were investigated for their effect on the hatching of eggs and J2 mortality. Moreover, the in vivo nematocidal activity of the Y1 strain was investigated by conducting pot experiments in which tomato plants were inoculated with M. incognita. Each and every pot was amended 50 mL of fertilizer media (F), or Y1 culture, or nematicide (N) (only once), or fertilizer media with N (FN) at 1, 2, 3, 4 and 5 weeks after transplantation. The results of the pot experiments demonstrated the antagonistic effect of B. amyloliquefaciens Y1 against M. incognita as it significantly decreases the count of eggs and galls per root of the tomato plant as well as the population of J2 in the soil. Besides, the investigation into the growth parameters, such as the length of shoot, shoot fresh and dry weights of the tomato plants, showed that they were significantly higher in the Y1 strain Y1-treated plants compared to F-, FN- and N-treated plants. Therefore, the biocontrol repertoire of this bacterium opens a new insight into the applications in crop pest control.
Highlights
A wide variety of economically significant crops is at high risk due to nematodes which are parasitic to plants and have a significant negative impact on various agricultural yields worldwide.Several species of plant-parasitic nematodes are known to cause serious reductions in yields of over 2000 vegetables, field crops, grasses and trees [1]
The decrease in the hatching and increase in J2 mortality was noted to depend on the Bacterial Culture Supernatant (BCS) concentrations and the length of the incubation period (Figure 1a,b)
B. amyloliquefaciens Y1 strain was tested for control of M. incognita both under in vitro and in vivo conditions
Summary
A wide variety of economically significant crops is at high risk due to nematodes which are parasitic to plants and have a significant negative impact on various agricultural yields worldwide.Several species of plant-parasitic nematodes are known to cause serious reductions in yields of over 2000 vegetables, field crops, grasses and trees [1]. A wide variety of economically significant crops is at high risk due to nematodes which are parasitic to plants and have a significant negative impact on various agricultural yields worldwide. The root-knot nematodes, Meloidogyne spp., Molecules 2017, 22, 1839; doi:10.3390/molecules22111839 www.mdpi.com/journal/molecules. Meloidogyne spp., are endoparasites, with a worldwide geographical distribution and broad host range [3]. They are a notorious reason behind substantial yield damage in the vegetable crops [4], including tomatoes, which are the most widely grown commercial crop, accounting for 14% of the world vegetable production [5]. Root-knot nematode infections weaken plants by disrupting their water and nutrient supply, which makes them more susceptible towards other opportunistic pathogens [6]
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