Molecular identification of isolated bacterial strain
The universal primers of 16 s rDNA gene amplified ~ 1550 bp (Fig. 1) for the bacterial isolate. 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. This isolate was recorded at GenBank data base as B. wiedmannii NRC211 under accession number LC626774
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.
Effect of application frequency of different bio agents on nematode Meloidogyne javanica reproductive parameters
Recorded data revealed that all tested treatments, whether single or in combination resulted in variable significant reduction in the nematode reproductive parameters (Table 1). It was observed that NPK single treatment reduced M. javanica juveniles in soil by 57.5, 66.8 and 73.8% at planting time, after one and 2 months, respectively than the untreated control. The percent reductions in number of galls were found to be 62.6, 64.7 and 72.0% at the same time intervals, respectively. For egg masses, the number was found to be 61.6, 66.1 and 70.1% respectively, than the untreated control.
Concerning A. chroococcum Az single treatment, the percent reduction of M. javanica juveniles in soil compared to the untreated control plants ranged 64.9, 70.5 and 77.7%, respectively. The respective number of galls was reduced by 65.6, 68.6 and 69.6%. Similarly, the number of egg masses decreased by 61.6, 66.2 and 70.1%.
For B. wiedmannii NRC211 Bw single treatment, the percent reduction of M. javanica juveniles in soil compared with the untreated control, ranged from 71.8, 75.0 and 78.0%, respectively. While, the respective number of galls was reduced by 68.9, 70.2 and 72.6%. The egg masses were similarly reduced by 67.2, 70.6 and 74.6%. Similar patterns in percent reduction of nematode reproductive parameters were observed by frequent application of combined treatments with the bio agents i.e. increased percent reduction was correlated with the frequency of application, as shown in (Table 1).
It is noted that Az plus Bw treatment overwhelmed all other treatments in controlling 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, followed by the application of NPK + Az + Bw treatment, which induced significant (P ≤ 0.05) reduction 73.2 and 74.6% in M. javanica galls and egg masses, respectively, compared to the untreated control. However, single application of either NPK, or Az, or Bw produced significant reduction by 72.0, 69.6, 72.6%, in galls number, respectively than the untreated control (Table 1).
Effects on peanut crop production
Concerning the effect of frequent applications of single or combined bio agents on peanut production, the recorded data indicated that the peanut production increased with increasing frequency of application in all treatments (Table 2). Thus, NPK single treatment increased peanut yield by 117.4, 363.0 and 634.8%, respectively than the control. Application of Az single treatment increased peanut yield production to 39.1, 165.2 and 330.4%, respectively than the untreated control. Moreover, by B. wiedmannii NRC211 single treatment, the yield increased by 39.1, 108.7 and 273.9%, respectively than the untreated control.
In addition, obtained data revealed that cumulative effects of bioagents resulting from repeated application produced significant increase in peanut yield than the untreated control. Microbial fertilizer NPK single treatment produced the highest peanut yield of 634.8% as well as 608.7% for the combined application of NPK + Az compared to the untreated control. However, non- significant difference was found in the peanut yield between the application of either NPK alone or NPK + Az. While 497.8% increase was recorded due to the combined application of NPK + Az + Bw (Table 2).
Effects on peanut growth parameters
Data in Table 2 revealed that all peanut growth parameters were increased in both single and combined treatments. In NPK single or combined treatments, significant percentage of increase in the number of pods was estimated than the untreated control. Moreover, the data indicated that frequent application of NPK single treatment increased weight of 200 seeds by 0.0, 31.8 and 65.9%, respectively, than the control. As for Az single treatment, the percentage increase in the number of pods ranged from 126.0, 191.3 and 256.5%, respectively, than the control. Also, Az single treatment produced variations in weight of 200 seeds by 17.2, 10.4 and 35.0%, respectively, than the control. Concerning Bw single treatment, pod number was increased by 160.9, 186.9 and 234.7%, respectively and of 2.7, 19.5 and 40.9% in 200 seeds weight, compared to the control (Table 2).
Application of NPK + Az + Bw combined treatment produced the greatest percentage of increase 244.1 and 455.1% in fresh and dry weight of peanut plant, respectively, than to the untreated control, followed by 434.4% increase in dry weight for Az single treatment. Whereas, the application of NPK combined with Bw resulted in 181.3% increase in fresh weight than the control. Moreover, single application of NPK produced the highest level in pods weight 1082.0%. In addition, the highest increase in the weight of 200 seeds was observed in the combined application of both NPK + Az (72.7%) than the control. Furthermore, the applications of Az either single or combined with NPK recorded the highest percentage increase by 256.5% for each in the number of pods than the control (Table 2).
Effects of bio agents on oil content of peanut seeds
Concerning the effects of frequent application of bio agents either single or combined on oil percentages, the data in (Table 2) clearly showed that the oil content of seeds only increased with increasing the frequency of the application of NPK combined with either Az and/or Bw.
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