RESUMO
A white rust infected leaf of Brassica juncea var. Varuna bearing non-erumpent zoosporangial blisters was used as explant to grow a dual culture of Albugo candida and Brassica juncea on MS medium supplemented with NAA (1.0 mg/L), BAP (1.0 mg/L), biotin (1.0 mg/L), ascorbic acid (25.0 mg/L), thiamin hydrochloride (1.0 mg/L), glycine (0.5 mg/L) and casein hydrolysate (1.0 mg/L). The host callus and the pathogen established a complete balance in culture. The morphology of the mycelium, haustoria, zoosporangia, antheridia, oogonia and oospores in dual culture was identical to that of infected intact plant. Oospore formation was favoured over that of sporangia. Oospore germination by germ-tube was evident. Pathogenicity test of the fungus in dual culture further confirmed the viability of the fungus. Rate of growth of dual culture was faster than normal callus. Although the fungus grew on the substratum for a short distance away from infected callus on the surface of the medium; it did not grow independently when connections with host callus was severed. Growth of dual culture was influenced by light quality, temperature, vitamins, carbohydrates and amino acids in the medium. These differential responses can be used for future studies on host pathogen interactions and for breeding of disease resistant plants.
Assuntos
Brassica/microbiologia , Oomicetos/crescimento & desenvolvimento , Doenças das Plantas/microbiologia , Brassica/crescimento & desenvolvimento , Técnicas de Cocultura/métodos , Microscopia de Contraste de Fase , Oomicetos/citologia , Oomicetos/patogenicidadeRESUMO
A hydrocarbon degrader isolated from a chronically oil-polluted marine site was identified as Rhodococcus sp. on the basis of morphology, fatty acid methyl ester pattern, cell wall analysis, biochemical tests and G + C content of DNA. It degraded up to 50% of the aliphatic fraction of Assam crude oil, in seawater supplemented with 35 mM nitrogen as urea and 0.1 mM phosphorus as dipotassium hydrogen orthophosphate, after 72 h at 30 degrees C and 150 revolutions per minute. The relative percentage of intracellular fatty acid was higher in hydrocarbon-grown cells compared to fructose-grown cells. The fatty acids C16, C16:1, C18 and C18:1 were constitutively present regardless of the growth substrate. In addition to these constitutive acids, other intracellular fatty acids varied in correlation to the hydrocarbon chain length supplied as a substrate. When grown on odd carbon number alkanes, the isolate released only monocarboxylic acids into the growth medium. On even carbon number alkanes only dicarboxylic acids were produced.