Potato tubers (Solanum tuberosum L.) is considered as one of the most essential vegetable crops worldwide, The most communal viruses attacking potato all over the world are potato leaf roll virus (PLRV), potato virus Y (PVY) and potato virus X (PVX). Our current study aimed to eradicate potato viruses PVY, PVX and PLRV through shoot tip meristem via tissue culture combined with thermotherapy and chemotherapy. Sprouts of potato cultivars ex. Spunta, Selana, Diamond and Cara were used as biological material for investigating their performance using shoot tip meristem. During multiplication stage, the resulted plantlets were subjected to ribavirin (50 mg/L), while the untreated plantlets served as control. In general, the control treatment (0.0 mg/L) provided the best results, while ribavirin (50 mg/L) gave reverse effect on the estimated vegetative parameters (shoot length (cm), number of leaves and number of shoots). Detection of the presence and absence of PVY, PVX and PLRV using DAS-ELISA technique indicated that, thermotherapy and chemotherapy treatments for shoot tip meristem culturing minimized the occurrence percentage of PVX, PVY and PLRV in all tested potato cultivars compared to positive control. The results of RT-PCR revealed that, the amplicons of amplified fragments and primed by PVX-, PVY-and PLRV-specific sense and antisense primers were appeared only in the positive control (lane 1 at ~750, 801 and 548 bp), respectively, while, no amplicons appeared in the rested treatments. In conclusion, shoot tip meristem followed by thermotherapy and chemotherapy treatments enhanced the growth of potato plantlets and suppressed potato viruses.

Abstract:The inhibitory effect of the fungicides Acrobat copper, Previcure-N and Unilax, the inducer resistance chemicals (IRCs) bion, chitosan, salicylic acid and zinc sulphate and the bioagents Bacillus polymyxa, B. subtilis and Pseudomonas fluorescens on sporangial germination of fungus like Pseudoperonospora cubensis, the causal of cantaloupe downy mildew was tested in vitro. The role of the tested fungicides, IRCs and bioagents on management of cantaloupe downy mildew was evaluated under greenhouse conditions. In addition, the alternation between the sprayed tested fungicide Unilax, IRC chitosan and bioagent P.fluorescens on management of the disease under field conditions was investigated. The inhibitory effect of the tested fungicides, IRCs and bioagents on sporangial germination of P. cubensis revealed that they caused significant reduction to the germinated sporangia. The tested fungicides were the most efficient ones followed by the bioagents then IRCs. Disease management showed the same trend of in vitro experiment when they sprayed on artificially inoculated cantaloupe plants with the sporangia of the causal fungus like under greenhouse conditions. Under field conditions, spraying cantaloupe plants with the tested fungicide Unilax still the most efficient trial for management the disease during 2012 and 2013 growing seasons compared with spraying any of IRC (chitosan) and the bioagent (P. fluorescens) alone . However, spraying the tested fungicide in alternation with the tested IRC and the bioagent ranked the second efficiency of disease management. Meanwhile, spraying the tested fungicide in alternation with any of the tested IRC and bioagent was of moderate efficiency.