Ten commercial rice cultivars were evaluated to partial resistance for blast disease under greenhouse conditions at Rice Research and Training Center, Sakha, in 2000 season .Ten isolates of Pyriculuria grisea collected from different locations were tested and identified on the international differential rice varieties (IDV) and commercial rice cultivars. Five from the new cultivars i.e Giza 177, Giza 178, Sakha 101, Sakha 102, and Sakha 104 showed susceptible reactions to one or two of the tested isolates. Giza 159 and Giza 171 were susceptible to all tested isolates. The isolates placed in seven race-groups i.e. two isolates for each of group IA, IC and ID, whereas, one isolate conformed each of IB, IG, IH and II races. Two races I A-69 (Isolate No.5) as highly virulent and IG-1 (isolate No.52) as a less virulent on the IDV were selected to study partial resistace parameters. Total number of lesions / leaf or plants, sporulation density and lesions type that developed differed greatly among cultivars. The number of lesions decreased by increasing leaf age. High numbers of necrotic spots (type 1-2) on new rice cultivars than on old cultivars could be attributed to hypersensitivity phenomenon. The new rice cultivars had lower number of type 4 lesions and less number of spores / lesion (sporulation capacity) than the old cultivars. This is may reflect a level of partial resistance in addition to major gene effects on the new cultivars than the old ones.
Although silicon is not considered an essential element, but a lot of researchers mentioned that plant development, growth and yield have been increased by the application of Silicon to soil and or plant. Also it is known to reduce rice diseases. Experiments were conducted in 1999Experiments were conducted in , 2000Experiments were conducted in and 2001 to study the effect of different sources of silicon on rice diseases ie. blast, brown spot and false smut in Egypt. So, Silicon was applied to soil at the rate of 10 or 20 g./ m 2 and spray 2 or 4 g./ L. of Magnesium silicate (MgSi) were tried, silica gel 0.25 or 0.5 g/m 2 , sodium metasilicate 20 g/m 2 in soil. On the other hand burnt or unburnt rice husk or rice straw at the rate of 100 or 200 g/m 2 , were used as silicon sources applied to soil. The conclusion from these experiments can be summarized as follows: MgSi as spray or soil application; burnt rice straw 200 g/m 2 and burnt rice husk 100 g/m 2 significantly decreased both leaf and panicle blast severity. For the brown spot disease, the severity of infection was significantly decreased with all silica sources in seasons 2000 and 2001. The most effective treatments were burnt rice husk at the rate of (100 g/ m 2 ) in soil, burnt rice straw (200 g/m 2 ) and MgSi (20g/m 2 ) incorporated into soil and two sprays of MgSi at complete vegetative growth and one spray at booting stage. The most effective treatment in case of false smut disease was recognized by the application of MgSi sprayed twice during leaf stage and the third one at booting, in spite of the significant decrease due to the addition of other sources of silica on either percent or severity of false smut infection. In addition, an experiment was conducted to study the effect of MgSi at the rate of 2 g/L as a sprayed with Beam individually or alternatively. The results revealed that Beam and MgSi when sprayed at leaf, followed by MgSi at late booting, was the best treatment for both blast and brown spot. While in case of false smut MgSi as foliar application at late booting gave the lowest infection in spite of the significant effect of the other treatments. * Time of application was 30 days after transplanting (DAT) ** Time of application was 90 days after transplanting (DAT) *** Time of application were 30 &60 days after transplanting (DAT) vegetative growth stage * Beam was followed by MgSi as spray 30.T. D.A ** Time of application was 30 days after transplanting (DAT) *** Time of application was 90 days after transplanting (DAT)
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