Study on the Botrytis cinerea fungus, causing gray mold disease in tomatoes grown in greenhouses, and the effect of some fungicides and bio-agents on the inhibition of fungal growth In Vitro

Abstract

Abstract Botrytis cinerea infects more than 1400 plant species globally, resulting in severe damage pre- and post-harvest. This study aimed to isolate and identify B. cinerea from tomato plants grown in local greenhouses and assess the inhibitory capacities of local Bacillus strains against B. cinerea. Various B. cinerea isolates were isolated from infected tomato plants that exhibited distinct symptoms. The ITS sequences and phylogenetic analysis of all B. cinerea isolates exhibited 99% homology with B. cinerea Pathogenicity tests on healthy tomato vegetative growth or detached leaves using QB13, QBuk1, and QUna B. cinerea isolates fulfilled Koch’s postulates. Symptomatic characteristics resulting from the artificial inoculations of tomato gray mold closely resembled those of the original diseased leaves and stems collected from the field after 7 Days post inoculation (DPI). Seven strains of Bacillus subtilis (64C1, 88D, 65D, 64C2, 41D1, 23A2, and 102) tested in-vitro against B. cinerea demonstrated that all Bacillus subtilis isolates displayed notably strong antagonistic effects against B. cinerea. Mycelial growth inhibition ranged from 37% (isolate 65D) to 60% (isolate 102) compared to the untreated control. The most substantial inhibitory effects against B. cinerea were statistically observed with isolates 88D and 102, which exhibited inhibition rates of 58% and 60%, respectively. Morphological and molecular identification and pathogenicity analysis revealed that all 20 B. cinerea isolates obtained from infected tomato plants from greenhouses exhibited a highly pathogenic effect on tomato plants. This study establishes the basis for developing natural biocontrol agents to fight gray mold caused by B. cinerea on tomato plants. In this study, isolates of B. cinerea gathered from tomato greenhouses in Al Qassim region were tested against some fungicides namely; Switch 62.5 WG (Fludioxonil 250g/kg & Cyprodinil 375 g/kg), Teldor 50 SC (Fenhexamid 50% w/v), Bellis 38 WG (Boscalid 25.2 w/w & Pyraclostrobin 12.8% w/w), Topcinal 45 W/V (Thiophanate methyl 45% w/v) and Talent 25 EC (Tebuconozole 25% w/v), using mycelium growth and conidial germination and were undergone in vitro assessment. Fungicide concentration trials for mycelial growth were performed. The results showed that all tested fungicides significantly reduced the linear growth of B. cinerea compared to the control. Specifically, Bellis, Switch, and Talent fungicides were the most effective, with reductions in colony growth to 75%, 95%, and 99% respectively, followed by Teldor (26.3%) and Topcinal (28.6 %) at 50 ppm. The control showed the highest colony growth.