Rice blast disease, caused by Magnaporthe grisea, is the most serious biotic threat to rice (Oryza sativa L.) production worldwide.It causes severe yield losses in Egypt especially in epidemic years. The fungus is highly variable so disease control is a challenge. In this study, the effect of silver nanoparticles (20-30 nm) against rice leaf blast fungus was evaluated under different cultivation conditions both in vitro and in vivo. Under lab conditions, the application of four concentrations of silver nanoparticles to the culture of M. grisea showed significant inhibition of both hyphal growth and number of colonies formed in a dose-dependent manner. Number of spores/ ml decreased with in all treatment. Under greenhouse conditions, Silver nanoparticles were sprayed in concentrations 0, 25, 50, 100 and 200 ppm on rice seedling leaves at three times (3 hours before inoculation, 1 and 5 days after artificial inoculation with spore suspension). Damaged Leaf Area Percentage (DLA %) indicated that the application of 100 ppm silver nanoparticles was highly efficient before and after inoculation (26.7, 15.3 and 20%), respectively compared to the untreated plants of 80%. The chemical fungicides isoprothiolane (Fuji one) and azoxystrobin (Amistar) at a concentration of 100 ppm each showed the lowest DLA (19.6 % and 14.7 %, respectively). Scanning electron microscope results revealed that the silver nanoparticles caused a detrimental effect on mycelial growth.
Rice is a vital food crop for about one-half of the global population. Unfortunately, it suffers from some biotic and abiotic stresses, which negatively affect the yield potential. Rice plants, in Egypt, are subject to infestation with several insect pests, but the most destructive one is the rice stem borer, Chilo agamemnon Bles. In addition, rice blast remains the most serious disease to manage. Blast resistance has consistently been one of the most important objectives of rice breeders in Egypt. The current investigation was conducted at the experimental farm of Rice Research and Training Center, Sakha Agricultural Research Station during 2014 and 2015 rice seasons. The objectives were to find out the efficiency of Trichogramma release in controlling the rice stem borer compared with insecticide, and to identify some novel resistant and high yielding varieties with high broad spectrum of blast resistance and high level of tolerance to stem borer infestation. Seventeen genotypes were evaluated under both natural and artificial inoculation for blast. Also, yield and yield attributes of these genotypes were estimated. The results revealed that all japonica genotypes were resistant or moderately resistant to the stem borer while indica and indica japonica genotypes were almost susceptible to the stem borer. The release of Trichogramma twice, each at a rate of 30,000 individuals /feddan, the first release was ten days before maximum tillering, and the second one was at 20% flowering. The release of this egg-parasitoid reduced the borer infestation, overall the 17 genotypes, by 78-80% white heads, and was relatively more efficient than the application of the recommended insecticide (Furadan at a rate of 6 kg /feddan). Consequently, Trichogramma, as eco-friendly application, could be used as an alternative management for stem borer than insecticide. Blast nursery evaluation revealed that all japonica GZ lines were highly resistant, as well as high yielding, such as GZ10364-22-3-1-2 and GZ10365-2-4-1-2. Under artificial inoculation with specific and virulent blast races, all genotypes were resistant to all aggressive races except Sakha 101 that was susceptible Till now, the genotypes,
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