This study was conducted at Plant Pathol. Res. Inst., Agric. Res. Center, Giza, Egypt and El-Orman potency, Min. of Agric. at Giza, Egypt during the two successive seasons of 2008 and 2009. The experiments were carried out under greenhouse conditions to investigate the effect of soil types and some seed treatments on Khaya senegalensis root rot disease, their interactions on the growth and chemical constitute of K. senegalensis seedlings. Seedlings of K. senegaleinsis showing root rot symptoms were collected from nurseries at Giza, Qalubyia and Ismailia governorates.
Fusarium solani and Rhizoctonia solani were the most frequently isolated fungi under natural infection at Giza, Qalubyia and Ismailia governorates .
Peat moss or peat moss + sand as planting medium for K.senegalensis in the presence of F. solani or R. solani were generally effective soil for increasing the survived seedlings under all the tested treatments.
Soaking seeds of K. senegalensis in Vitavax-Thirum was the most effective measure in decreasing pre- and post- emergence damping-off and increasing the survived seedlings, grown in soil infested with any of both fungi. Azedarachta indica and Thymus vulgaris extract decreased significantly pre- and post- emergence damping-off as well as improving seedling survivals. Salicylic acid as chemical inducer was generally the best in reducing the post-emergence damping-off compared to oxalic acid with the two fungi. Regarding to plant hormones, Gibberellic acid was the most effective in reducing the post-emergence damping-off disease compared to 1H-Indole-3-butanoic acid (IBA). On the other hand, Khaya seeds treated with A. indica and T.vulgaris, salicylic acid and Gibberellic acid were more effective and showed the highest amount of phenols content, chitinase, polyphenoloxidase enzymes in soil infested with any of the tested fungi.
Root anatomy of K. senegalensis seedling infected with root- rot caused by R. solani showed more damage symptoms than roots infected with F. solani. However, the necrotic tissues and plasmolysis cells were recorded at for both fungi. Treating seeds of K. senegalensis with any of Vitavax-Thiram, A. indica and T. vulgaris extracts, oxalic acid, salicylic acid and Gibberellic acid before planting in soil infested with any of R. solani and F. solani improved some histological characteristics of the root anatomy of the tested plant. In this respect, epidermal cells, cortical regions, phloem and xylem tissues, which were unaffected as result of treating K. senegalensis seeds with Vitavax-Thiram. On the other hand, epidermal cells and cortical regions shown moderate affect by treating seeds with any of these treatments before planting in soil infested with any of the two tested fungi comparing with untreated seeds. |
