Effect of abscisic acid, salicylic acid, potassium silicate, and trichoderma harzianum as biocontrol agent to induce the tomato resistance against early blight disease caused by alternaria solani

Abstract EN

In the present study and under greenhouse conditions, tomato plants cv.

Albium, grown in potted soil inoculated with the early blight fungus A.

solani, were treated with isic acid (ABA), salicylic acid (SA), and potassium silicate (PS) abiotic inducers, singly, and in combination with the biotic inducer Trichoderma harzianum.

The different tested inducers significantly decreased the intensity (severity) of early blight disease on tomato, as well as some growth characteristics, photosynthetic capacity, defense-related enzymes and expression analysis of the PR1, PR3 and PR5 genes using Real Time-q PCR.

PS+ Trichoderma showedthe lowest diseaseintensity, followed by ABA+ Trichoderma, and Trichoderma treatment had the highest disease intensity when compared to untreated inoculated control.

PS + Trichoderma, ABA+ Trichoderma, and SA+ Trichoderma were also the most effective for the best growth characteristics (fresh shoot, dry shoot, fresh root, dry root weight, and total fruits weight/plant).

Photosynthetic pigment content was significantly increased with all treatments by chemical inducer and T.

harzianum compared with A.

solani treatment.

PS + Trichoderma was the most effective and significantly enhanced chlorophyll "A" and chlorophyll "B"content comparing with the A.

solani treatment, while, the highest level of carotene content was observed with alt+ABA+ Trichoderma treatment at 2days post inoculation.

Peroxidase (POD), polyphenol oxidase (PPO) and Phenylalanine Ammonia-Lyase (PAL) enzymes activity and PR1, PR2 and PR5 gene expressions were significantly increased in all treatments with chemical inducer comparing with the treatment by A.

solani, In addition to the treatment by chemical inducer combined with Trichoderma were the most effective compared with chemical inducer alone.

The maximum POD, PAL activities and PR1gene expression were observed with alt+PS + Trichoderma followed by alt+ABA+ Trichoderma while, PR2, PR5 gene expressions and POD activity reached the highest level with alt+PS+ Trichoderma followed by alt+SA+ Trichoderma and alt+ABA+ Trichoderma.

Trichoderma was of the highest rate of the number of cfu in treatment with alt+PS+ Trichoderma with cfu was 5.9 x10, while the number of cfu in treatment with alt+ABA + Trichoderma was 3.77 x10⁷ and the treatment with alt+SA + Trichoderma was 3.68 x10⁷.