Antibacterial effect of Bradyrhizobium spp., Pseudomonas spp., and Bacillus subtilis against pathogenic fungus Rhizoctonia solani on peanut plant

الملخص

Microorganisms such as fungi, bacteria, viruses, and
nematodes are integral parts of agro-ecosystems. Some of them are harmful
to plant pathogens, whereas, others are neutral or beneficial in their effects on
plant growth. The total agricultural losses of economic crops which amount
to about 50–75% are caused by soil-borne pathogenic fungi of Rhizoctonia
spp., Fusarium spp., Verticillium spp., Sclerotinia spp., Pythium spp. And
Phytophthora spp. The losses are due to seed rot, root rot, and wilt diseases
in different crop fields and greenhouses
Aimes: the present study aimed to evaluate the antagonistic effect of the
studied bacteria i.e., Pseudomonas fluorescens, Pseudomonas chlororaphis,
and Bacillus subtilis were tested against three tested isolates of R. solani

Methods: The biocontrol tests were carried out using fungal and bacterial
bioagents. The tested fungal bioagents were three isolates of Trichoderma
viride. culture collection, three isolates for Rhizoctonia spp were Previously
obtained from peanut plants with diseased roots. The bacterial antagonistic
include one isolate of Bacillus subtilis and one isolate of Pseudomonas
fluorescens.
Results: Showed that Bacillus subtilis had the highest suppression effect
(100%) with the three tested isolates of Rhizoctonia solani compared to
Pseudomonas fluorescens and P. chlororaphis.
Pseudomonas fluorescens had the lowest bacterial in its suppression
effect on the tested fungal growth R. solani 5 (16.7%), R. solani 3 (5.6%), and
R. solani 12 (0.0%). Peanut seeds germinated with treated by Bradyrhizobium
isolates i.e., 208, 209, 210and Bradyrhizobium mixed, Bradyrhizobium +
Trichoderma harzianum, Trichoderma alone, Bradyrhizobium +
pseudomonas fluorescence results showed that followings: The isolate
Bradyrhizobium (208) gave the best germination percentage of peanut seeds
(4.1667 cm length). The moderate germination of peanut seeds with the;
Trichoderma harzianum, mixed Bradyrhizobium, and Bradyrhizobium + P.
fluorescences had given (2.73, 2.40, and 2.33 cm of roots length). The lowest
germination of peanut seeds was obtained in the (control) treatment (1.43). A
significant inhibitory effect on radial growth of the three tested R. solani
isolates due to Trichoderma viride isolates. Moreover, Trichoderma viride
isolate 1 showed the highest inhibitory effect with three tested R. solani,
(100%) with R. solani isolates 5 and 12, and R. solani isolates 3 (88.9%).