Abstract
BackgroundPlant parasitic nematodes create serious threat to crop production. In Egypt root knot nematode, Meloidogyne spp. has been considered to be a limiting factor in the production of most crops of which the Peanut (Arachis hypogaea L.) is an important legume and oil crop. Therefore, management of root knot nematodes Meloidogyne spp. is an obligatory challenge. Microbial organisms are extensively used as eco-friendly tools for controlling plant parasitic nematodes as alternative to chemical nematicides. The effectiveness of the commercial bacterial bio-fertilizers NPK containing Bacillus polymyxa, B. circulance, B. megaterium, Pseudomans spp.; the nitrogen fixative bacteria Azotobacter chroocoocum and the bacterial isolate NRC211 were evaluated against the root knot nematode, Meloidogyne javanica infecting peanut plants under field conditions. Identification of the bacterial isolate was made through PCR amplification and sequencing of 16S rDNA gene.ResultsSequencing of 16S rDNA gene revealed that the bacterial isolate NRC211 had 100% similarity with Bacillus wiedmannii strain FSL W8-0169 16S ribosomal RNA. This Bacillus was recorded for the first time under accession number LC626774 on GenBank data base as B. wiedmannii NRC211. Recorded data revealed that all the tested treatments whether single or combined in soil naturally infested with M. javanica, resulted in variable significant reduction in the nematode reproductive parameters with a considerable increase in crop production and oil content of peanut plant. These results were improved by increasing the frequency of application of the bio-agents. In this respect the repeated combined treatment of A. chroococcum and B. wiedmannii NRC211 treatment overwhelmed all other treatments in decreasing nematode reproductive parameters with percentage reductions of 94.8, 79.0 and 80.1% in M. javanica juveniles in soil, galls and egg masses, respectively. This was associated with slight increase in peanut oil content than the untreated control. The repeated combined treatment of NPK plus A. chroococcum produced the highest increase 608.7%, and 72.7% in crop production and plant growth parameters, respectively than the control. While, the oil content in this treatment was increased up to 47.4 g/kg.ConclusionIt was concluded that B. wiedmanni NRC211 is an eco-friendly bio agent that can be applied with other commercial microbial bio-fertilizers in bio-integrating programs for controlling M. javanica infecting peanut plants.
Highlights
Plant parasitic nematodes create serious threat to crop production
Partial DNA sequence was subjected to BLAST search on https://blast.ncbi.nlm.nih.gov/Blast against the available sequences deposited in NCBI database, 16S rDNA gene sequence of bacterial isolate scored 100% with B. wiedmannii strain FSL W8-0169 16S ribosomal RNA
Protease activity of the bacterial strain The results showed that B. wiedmannii NRC211 protease activity was 1.17 μg tyrosine released/min/ml. under the assay conditions
Summary
In Egypt root knot nematode, Meloidogyne spp. has been considered to be a limiting factor in the production of most crops of which the Peanut (Arachis hypogaea L.) is an important legume and oil crop. The effectiveness of the commercial bacterial bio-fertilizers NPK containing Bacillus polymyxa, B. circulance, B. megaterium, Pseudomans spp.; the nitrogen fixative bacteria Azotobacter chroocoocum and the bacterial isolate NRC211 were evaluated against the root knot nematode, Meloidogyne javanica infecting peanut plants under field conditions. In Egypt, the root knot nematode Meloidogyne spp. have been considered to be a limiting factor in the production of most crops (Abdelgawad 2014). Bacillus spp. are another group of bacterial agents that have been recognized as one of the most promising groups of nematode antagonists e.g. B_cereus, B. megaterium that have been found to be important for effective management of root knot nematodes and enhancing crop production (El-Wakeel et al 2020). They revealed that A. chroococcum inhibited nematode development and multiplication in the plant
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