Six common fungicides, Dithane M45, Kocide 2000, Ridomil Gold Plus, Score, Equation Pro and Kemazed were tested for controlling the draceana leaf spot fungi. All the tested fungicides significantly decreased the in vitro growth of the tested dracaena leaf spot fungi. Percentage of inhibition on colony diameter ranged between 49.64% with Dithane M45 to 82.18% with Score which was followed by Kemazed (69.15%). However, inhibition of spore germination was the highest (72.8%) by Dithane M45, while inhibition of germ tube reached 89.91% with Kemazed. Meanwhile, in the in vivo tests, treatment with Kemazed decreased disease incidence of leaf spots on potted plants to 16.67% compared to 100% for the untreated inoculated control. On the other hand, the bacterial and fungal biocontrol agents tested proved to be effective against the dracaena leaf spot fungi. The in vitro assays conducted showed that the bacterial biocontrol agents namely, Stenotrophomonas maltophilia, Pseudomonas ultimum, P. fluorescens, P. putida, P. aeruginosa, Bacillus subtilis, B. megaterium, significantly decreased colony growth diameter (76.84-45.69%) of dracaena leaf spot fungi as well as spore germination (48.80-23.20%) and length of germ tube (88.77-65.65%) of the germinated spores compared to untreated control. Treatment with S. maltophilia showed the most consistent highest inhibition effect, followed by P. ultimum, B. subtilis, and B. megaterium, respectively. The in vivo tests of the most effective bacterial bioagents supported the in vitro results. Treatment with S. maltophilia showed the highest effect as it decreased disease incidence and disease index to 29.33% and 7.6%, respectively in comparison with 100% and 83.6% for the untreated inoculated control in the potted dracaena plants (cv. Bicolor). Meanwhile, the in vitro tests of the three Trichoderma spp., i.e. T. harzianum, T. hamatum and T. album showed significant inhibition effect on colony growth diameter of the tested dracaena leaf spot fungi in which T. harzianum showed the highest inhibition effect (75.02%), while T. album was most effective to inhibit spore germination (48%) and germ tube (90.21%) of the germinated spores. The in vivo tests of the fungal biocontrol agents supported the in vitro results. T. album (Bio-Zeid) showed the highest effect and decreased disease incidence and disease index on potted plants to 19.99% and 4.39%, respectively compared with 100% and 92.8% for the untreated inoculated control.
Four different highly economic value pepper cultivars Trezaa, Emberu, Mazurka and Taranto usually grown in Egypt were used to evaluate the efficacy of certain resistance inducers to enhance resistance of pepper fruits against gray mould fungus. Pathogenicity tests with Botrytis cinerea (BC-3 isolate) revealed that cv. Mazurka (Red Colour) was most tolerant and exhibited 40.15% rot severity, while cv. Emberu (Yellow Colour) was highly susceptible and showed 79.12% rot severity. The other two pepper cultivars, that is, cv. Trezaa and Taranto showed severity of 50.23 and 52.75%, respectively. Treatment of pepper fruits with resistance inducers salicylic acid (SA); abscisic acid, methyl jasmonate and calcium chloride significantly decreased gray mould development under laboratory conditions. Calcium chloride was the most effective on all pepper cvs. mentioned earlier and inhibited diameter of rotting area with overmean of 40.6%. This was followed by SA as 34.01%. Abscisic acid and methyl jasmonate, however, showed lower mean inhibition of 16.8 and 18.8%, respectively. Meantime, treatment of pepper fruits with such resistance inducers and calcium chloride increased activity of the defense related enzymes, that is, polyphenol oxidase (PPO), peroxidase (POD), phenylalanine ammonia lyase (PAL) as well as the total phenols where SA and calcium chloride were the most effective. This could explain potentiality of such compounds to enhance pepper resistance to control B. cinerea of the gray mould of pepper.
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