Rice fungus

Blasticidins pyrimidine antibiotics synthesized by Streptomyces griseochromogenes (see Nucleoside antibiotics). They inhibit the growth of fungi, e.g. the rice fungus, Piricularia oryzae, and a few bacteria. The antibiotic effect is due to suppression of polypeptide chain elongation during protein biosynthesis. 

Allyloxy-l,2-benzisothiazole 1,1-dioxide (232), known as Probenazole or Oryzaemate, is useful in the control of rice blast fungus under field conditions (75SST(3)54l). 

Monascus is cultivated on solid media in Asian countries to produce a red colorant named Anka and used as a food ingredient. A Chinese medical book on herbs published in the first century first mentioned the terms ang-kak and red mold rice. Red mold rice has been used as a food colorant or spice in cooking. In 1884, the French botanist Philippe van Thieghem isolated a purple mold on potato and linseed cakes and named it Monascus ruber. This ascomycete was so named because it has only one polyspored ascus. In 1895, Went isolated a mold from the red mold rice obtained from a market in Java, Indonesia. This fungus was named Monascus purpureus, after which several other species were isolated around the world. 

Microorganism and cultivation conditions Rhizopus sp. 26R criltivated in 20 g solid substrates composed of wheat bran, rice bran and rice husk (6 12 2) in a plastic bags. Initial pH and moisture content were 5.7 and 58%, respectively. The fungus was incubated at 32°C for 6 days. 

Different ratios of the solid substrates, wheat bran, rice bran and rice husk, were done and the activity of the pectinases was compared in Figure 5. The mixture of wheat bran, rice bran and rice husk in the ratios of 9 9 2 or 6 12 2 appeared to be two of the best composition ratios for growth of the fungus and the pectinase production.The ratio of 6 12 2 was selected for the enzyme production since rice bran was cheaper than wheat bran and locally obtained. 

Bansal, V., Ahmad, A., Sastry, M. (2006) Fungus-mediated biotransformation of amorphous silica in rice husk to nanocrystalline silica. Journal of the American Chemical Society, 128, 14059-14066. 

Signs Lesions appear on the leaves of rice plants and vary in size. They are usually diamond shaped and have a gray or white center with a brown or reddish-brown border. Crop loss of 50-90% has been reported. Lesions also appear on the rice head but are brown or black in color. Rice grains do not develop properly. In severe neck infections, the stem will break and the head will drop off. The fungus can infect the roots and also invade the plant s vascular system blocking the transport of nutrients and water from the roots. ... 

A recent search for general and specific elicitors from L. maculans demonstrated that the phytotoxins sirodesmin PL (1) and deacetylsirodesmin PL (2) are general elicitors since both induced the production of phytoalexins in resistant brown mustard and in susceptible canola [31]. Furthermore, two specific elicitors, a mixture of cerebrosides C (13) and D (14), were reported from mycelia of liquid cultures of L. maculans virulent on canola (Fig. 9.5) [19]. Previously, cerebrosides C (13) and D(14) were reported from a number of phytopathogenic fungi and were reported to induce the production of phytoalexins in rice plants and disease resistance to the rice blast fungus [32]. 

Blasticidins are produced by Streptomyces grieseochro -mogens and inhibit several species of bacteria and fungi (31). Pseudomonas is particularly vulnerable to blasticidin S. Piricularia oryzae causing the blast disease of rice is widely controlled with blasticidin S in Japan. It is applied to the rice plants after infection by the fungus has already ocurred(32), since the antibiotic affects the myce -lial phase more than the spore phase. It would be desirable to search for spore killing antibiotics to control soil-inhabiting microbes and to destroy the inoculum before it infects the crop. 

Kato, T., Y. Yamaguchi, T. Namai, and T. Hirukawa. Oxygenated fatty acids with anti-rice blast fungus activity in rice plants. Biosci Biotech Biochem 1993 57(2) 283-287. 

Monosubstituted pyrrolo[2,3- ]pyridine derivatives substituted at positions 2 or 6 of the ring system, 26, exhibit antifungal activity against Pyricularia oryzae, a fungus that causes rice blast <1997JFA2345>. 

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