The influence of the inoculation with plant growth-promoting fungi (PGPF) isolates on growth enhancement of onion plants and progress of white rot disease in onions, caused by Sclerotium cepivorum, was evaluated. The tested PGPF isolates were Phoma sp. GS8-1, Phoma sp. GS 8-3, Trichoderma asperellum SKT-1, Fusarium equiseti GF18-3 and Penicillium simplicissmum GP17-2. Abnormal shape and lysis in the mycelia of the pathogen were reported in dual cultures of PGPF and S. cepivorum using scanning electron microscopy. The germination of sclerotia was reduced after soaking in culture filtrates of PGPF. The highest reduction was recorded in P. simplicissmum GP17-2 treatment (70.85%). The results demonstrated that the treatments with PGPF isolates significantly enhanced the plant height, root length, bulb perimeter and plant dry weight. Additionally, PGPF clearly reduced disease severity of white rot disease of onions. Among PGPF isolates, T. asperellum SKT-1 and P. simplicissmum GP17-2 showed the best effects in reducing the incidence and severity of white rot and enhancing onion growth. On the other hand, the levels of peroxidase and polyphenol oxidase were improved in the treated onion plants than in the untreated plants at 7 days after induction treatments. Similarly, early and strong expressions of defence genes, PR1 and PR2, were reported in plants treated with PGPF. Overall, this research suggested that PGPF treatments generated favourable effects on the suppression of white rot disease of onions.

Pea (Pisum sativum L.) is subjected to attack by certain soil-borne phylogenetic of fungus-like eukaryotic microorganisms such as Pythium debaryanum and soil-borne fungi Rhizoctonia solani and Fusarium solani which cause damping-off diseases. Isolation of associated fungi and P. debaryanum and three species of Trichoderma was carried out from soil rhizosphere of pea plants. Antagonistic effect of Rhizobium leguminosarum combined with Trichoderma lignorum, T. longibrachiatum and T. koningii against pathogenic fungi was investigated in vitro and in vivo under greenhouse conditions. The effect of combinations between the tested Rhizobium sp. and the other tested Trichoderma spp. on the disease incidence caused by the pathogenic microorganisms was evaluated when used as seed and soil treatments. Disease assessments, nitrogen fixation and yield parameters after 50 and 90 days from sowing in comparison with un-treated and fungicide treatments were recorded. Mycoparasitic activity of the tested Trichoderma spp. against each of the pathogenic fungi and Pythium debaryanum was studied using scanning electron microscope. Results showed that the soil treatments were more effective in controlling damping-off disease than seed treatments in overall experiments. Combination of R. leguminosarum with T. longibrachiatum gave the best results in reducing percentage of post-emergence damping-off (13.33 and 6.67%) and root rot (14.72 and 9.58%) caused by P. debaryanum and R. solani, respectively. Survived plants, nitrogen fixation and yield parameters were also increased. Treatment of R. leguminosarum combined with T. koningii against infection by F. solani gave the best results in reducing percentages of post-emergence damping-off (6.67%) and root rot (13.06%) with increment of survived plants, nitrogen fixation and yield parameters. In conclusion, combinations of R. leguminosarum with the Trichoderma species were effective than application of each one alone against pea damping-off disease.

Applicability of salt-tolerant bacterial isolates (F1 and E1) of Rhizobium leguminosarum biovar viciae was compared with the mineral Nitrogen fertilization on faba bean plants, under saline field conditions. Higher magnitudes of shoot length, dry weight of shoots and roots than control and N-fertilized plants were achieved. Results were more pronounced due to use dual combinations of F1 or E1 with 25 % N-supply. Parameters of N2-fixation, seed yield and its crude proteins of both faba bean cultivars (Nubaria 1 and Sakha 1) were also, enhanced due to superiority of the dual treatments. So, utilization of salt-tolerant rhizobial isolates could be attributed to overcome the harmfull effect of soil salinity on growth, nodulation and seed productivity of faba bean plants. On the other hand, the largest diameter of inhibition zone reached 4.20 cm which representing 46.67 % growth inhibition of Rhizobium which was achieved via 1 g L-1 of Vitavax under laboratory conditions. Slope fitting data of the experimental values showed constant inhibitory effect of Ground-up, Malathion and Vydate with increasing their concentrations against Rhizobia. For Vitavax, sharp ascending slope was resulted; indicating induction of further inhibition with additional dose would be expected.

Rhizobium leguminosarum biovar viciae isolated from salt-affected faba bean fields were in vitro tested. Different isolates were found to be varied in their tolerance to salinity. F1 and E1 were found to be the most salt-tolerant isolates even at EC-level of 12 ds m-1. Seeds of Nubaria 1 cv. were inoculated with either F1 or E1, in comparison with a less salt-tolerant one (F9) in pots their salinity were adjusted at 0, 3, 6, 9 and 12 ds m-1 under aseptic conditions. Number and dry weight of nodules were decreased strongly by increasing salinity levels in comparison with control. Significant enhancement of N % accumulated in the shoots was also noticed due to the biological inoculation with both Rhizobium isolates in presence or absence of salinity. Under non-aseptic conditions, efficacy of F1 and E1 with the effect of mineral N-supply (25 and 100 %) was compared. In addition to Nubaria 1 cv., Sakha 1 cv. was also used in the evaluation process for N-fixation at 0, 6, 9 ds m-1 levels. Number of nodules formed on Nubaria 1 at 9 ds m-1 was highly increased from 7.86 and 5.44 for 25 and 100 % N-supply to 82.33 and 93.33 for F1 and E1, respectively. Accordingly, nodular dry weights were also increased to 0.40 and 0.41 g plant-1 for F1 and E1 instead of 0.13 and 0.08 g plant-1 for 25 and 100 % N, respectively. The beneficial effects of F1 and E1 inoculation were also extended to enhance N % of shoots and seed yield parameters. Therefore, the symbiotic N2-fixation process has a great potential to improve growth and productivity of faba bean plants in comparison with the mineral N-supply to overcome the harmful effects of salinity.

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