Evaluation Efficiency of Different Isolate of Actinomycetes for Control of Cucumber Seedling Damping-off Disease Caused by Rhizoctonia solani (Khun)

Fayyadh, M.A. and L.K. Awad. 2021. Evaluation Efficiency of Different Isolate of Actinomycetes for Control of Cucumber Seedling Damping-off Disease Caused by Rhizoctonia solani (Khun). Arab Journal of Plant Protection, 39(4): 281-288. https://doi.org/10.22268/AJPP-39.4.281288 This study was conducted in Plant Protection Department, College of Agriculture, University of Basrah during the period 2017-2018 aimed to isolate and identify Actinomycetes from different environmental sources and evaluate their efficiency to control cucumber damping off disease caused by Rhizoctonia solani. 28 isolates of Actinomycetes were isolated from different sources from the Basrah region. All such isolates were gram positive, amylase and catalase positive and they had branched hyphae. Molecular identification following amplification of 16sRNA confirmed that Actinomycetes isolate No 6 isolated from soil had a similarity of 99% with Streptomyces griseus, whereas the isolate No 66 isolated from date palm roots had a similarity of 99% with Brevibacterium celere. The nucleotide sequence of the two isolates has been deposited at NCBI with Genbank accession number LC501385.1 for S. griseus and LC501386.1 for B. celere. The dual culture technique showed that Actinomycetes isolates S. griseus and B. celere had high antagonistic activity against Rhizoctonia solani, which produced inhibition zones of 7 and 15 mm in dimeter, respectively. On the other hand, volatile compoundsreleased from S. griseus and B. celere inhibited the growth of R. solani by 68 and 81.5%, respectively. Pot experiment showed that all actinomycetes isolates significantly reduced cucumber seedling damping–off incidence caused by R. solani. Keywords: Actinomycetes, Rhizoctonia solani, Cucumber, Biological Control

The Effect of Various pH Medium on the Secondary Metabollites Production from Trichoderma harzianum T10 to Control Damping Off on Cucumber Seedlings

Damping-off is one of the main diseases in cucumber seedlings caused by Pythium sp. Secondary metabolites of Trichoderma harzianum T10 can conduct the control of the disease. The pH of the medium influences the production of secondary metabolites. The research aimed to determine the effective pH medium on production of T. harzianum T10 secondary metabolites, and the effect of the T. harzianum T10 secondary metabolites application in damping-off disease control also to the growth of cucumber seedling. The research was consist of two steps; 1) in vitro assay with various pH levels 5; 3; 3.5; 4; 4.5; 5.5; 6; 6.5; and 7, 2) In planta treatments consisted of control, fungicide (Mancozeb), secondary metabolites in pH 5 and 5.5 with the concentration of 5, 10 and 15% each. The research showed that: 1) the effective pH medium for the production of T. harzianum T10 secondary metabolites was 5 and 5.5. 2) application of the T. harzianum T10 secondary metabolites on pH 5 and 5.5 with a concentration of 5, 10, and 15% could decrease the disease incidence and support cucumber seedling growth.

Hydrogen sulfide negatively regulates cd-induced cell death in cucumber (Cucumis sativus L) root tip cells

Background Hydrogen sulfide (H2S) is a gas signal molecule involved in regulating plants tolerance to heavy metals stress. In this study, we investigated the role of H2S in cadmium-(Cd-) induced cell death of root tips of cucumber seedlings. Results The results showed that the application of 200 μM Cd caused cell death, increased the content of reactive oxygen species (ROS), chromatin condensation, the release of Cytochrome c (Cyt c) from mitochondria and activated caspase-3-like protease. Pretreatment of seedlings with 100 μM sodium hydrogen sulfide (NaHS, a H2S donor) effectively alleviated the growth inhibition and reduced cell death of root tips caused by Cd stress. Additionally, NaHS + Cd treatment could decrease the ROS level and enhanced antioxidant enzyme activity. Pretreatment with NaHS also inhibited the release of Cyt c from the mitochondria, the opening of the mitochondrial permeability transition pore (MPTP), and the activity of caspase-3-like protease in the root tips of cucumber seedling under Cd stress. Conclusion H2S inhibited Cd-induced cell death in cucumber root tips by reducing ROS accumulation, activating the antioxidant system, inhibiting mitochondrial Cyt c release and reducing the opening of the MPTP. The results suggest that H2S is a negative regulator of Cd-induced cell death in the root tips of cucumber seedling.

EFFECTS OF PEAT AND PEAT-ZEOLITE SUBSTRATES ON QUALITY, GROWTH INDICES OF CUCUMBER SEEDLINGS AND CROP PRODUCTIVITY

The objective of this study was to evaluate peat and zeolite mixtures substrates performance on cucumber seedling quality and crop yield. The research was carried out in a greenhouse covered with double polymeric film at the Institute of Horticulture, Lithuanian Research Centre for Agriculture and Forestry. Cucumber seedlings were grown in different substrates: peat, peat + zeolite 1 : 1, peat + zeolite 2 : 1, peat + zeolite 3 : 1 and peat + zeolite 4 : 1. Cucumber seedlings grown in peat and zeolite substrates are shorter; the leaf area is smaller than that of the seedlings grown in peat alone. The dry mass of the aboveground part of these seedlings is lower (difference insignificant), however, the root mass is higher than those grown in peat alone. The addition of zeolite to peat substrate does not have any positive effect on the photosynthesis pigment content in cucumber seedling leaves. The physiological growth indices of the seedlings grown in peat-zeolite substrates were lower compared to those grown in peat. When zeolite is added to peat substrate, net assimilation rate is higher compared to those grown in peat. Higher yields (significant difference) were demonstrated by cucumbers, the seedlings of which had been grown in peat-zeolite substrates.