Showing papers in "Indian phytopathology in 1992"

Toxicity of Polyalthia longifolia against fungal pathogens of rice.

Abstract: Ethanolic extract and essential oil of leaf of Polyalthia longifolia were tested against five rice pathogens, viz., Pyricularia oryzae, Rhizoctonia solani, Fusarium moniliforme, Aspergillus niger and Curvularla lunata. Ethanolic extract besides being more effective, possessed broad spectrum fungi toxicity than essential oil.

Comparison of two methods for assessment of yield loss due to Turcicum leaf blight of maize

Abstract: Grain yield losses due to Turcicum leaf blight were assessed in two hybrids, Deccan and Ganga-S by two methods i.e., on the basis of whole TOWS and on the basis of varying disease levels. The results indicated that the method based on the average grain yield at different levels of infection is more reliable and authentic than the other based on whole TOW basis. The maximum grain loss was observed to be 4S.7 per cent on the rating of 5.0 on a scale of 1-5.

An alternative approach for the chemical control of Fusarium wilt of tomato

Abstract: Effectiveness of 19 non-conventional, mostly non-toxic chemicals in wet seed treatment, used at dilute concentrations (10.4 to 10-2M) in controlling Fusarium wilt of tomato has been tested in potted tomato plants (cv. Patharkuchi) inoculated with Fusarium oxysporum f. sp. lycopersici at the age of 3 weeks. While most of these compounds could reduce wilt symptoms appreciably, cupric chloride, ferric chloride, zinc chloride, manganese sulphate, mercuric sulphate, L-cysteine, IAA and DL-methionine showed very strong protective effect. These reduced leaf symptoms by 52 to 71 %, prevented mortality completely and also limited vascular colonization by the pathogen. Most of the test compounds showed little or no in-vitro fungitoxicity at their effective concentrations and stronger protection was often achieved at lower than higher concentration. It has been concluded, therefore, that these non-conventional chemicals act in plant disease control not so much by any direct toxic action but by inducing resistance in susceptible tomato plants, mediated through host tissue conditioning.

Estimation of crop losses due to grey mildew disease of cotton caused by Ramularia areola

Abstract: A field trial was laid out on H-4 cotton (G. hirsutum L.) for assessment of losses caused due to grey mildew disease during 1986-87 and 1987-88 under natural conditions. The losses in boll bearing, boll size and yield of seed cotton were directly proportional to the disease intensity. Heavy defoliation (92.24 to 99.27%), less boll bearing (12.97 to 15.95 bolls/plant), lowest boll weight (2.33 to 2.78 g/boll) and lowest yield (535.88 kg/ha) were noted from untreated plots having severe disease intensity (43.09 to 46.60%). The per cent loss in yield of seed cotton in untreated plots ranged from 62.67 to 68.69 over treated plots. The qualitative characters of seed cotton were also significantly affected by the disease.

Races of Fusarium oxysporum causing wilt in chickpea: serological and electrophoretic variability

Abstract: The four physiologic races of Fusarium oxysporum f. sp. ciceri causing wilt of chickpea had close antigenic relationships. All the four races showed one prominent cross reaction band. Race 4 was different from races 1,2 and 3 with regard to electrophoretic protein banding pattern. It lacked most of the high molecular weight (approx. 63 kD) protein bands. Two bands with Rf values 0.31 and 0.3'3 were consistently observed in race 2 while a fraction with Rf 0.20 was seen only in race 3. A fraction with Rf value 0.64 was characteristic of race 4. All the four races has common patterns of catalases, esterases and peroxidases, except race 1 which exhibited one extra peroxidase band.

Biocontrol of Rhizoctonia solani in cotton by fluorescent pseudomonads

Abstract: Isolates of fluorescent pseudomonads were tested for their ability to suppress the root rot and damping off pathogen of cotton, Rhizoctonia solani. Forty four per cent of the isolates suppressed the growth of the pathogen very strongly. The disease intensity was reduced from 52.6 per cent (with non - bacterized seeds) to zero (with seeds bacterized with isolates F-13, F-14 and F-11) in pot experiements.

Entomogenous fungi from north-east India.

Abstract: Field survey in rice ecosystem on rainfed rice recovered 240 cadavers of rice hispa, Dieladispa armigera (Olivier) (Coleoptera, Chrysomelidae). The entomogenous association was formed/established by the fungi on the insects are Beauveria bassiana (Bals.) Vuill., Aspergillus flavus Link., Fusarium heteroporum Nees ex Fr., Penicillium eyelopium Westling, Geotrichum sp. and Mucor sp. The former three were found as entomopathogenic while the remaining two are of opportunistic in association. B. bassiana and A. flavus showed their potentiality as biocontrol agents.

Predisposing factors for Phytophthora blight of pigeonpea.

Abstract: A pigeon pea plot at the ICRISAT Centre, Patancheru, India, was observed daily during the 1987 and 1988 rainy seasons for blight infection (caused by P. drechsleri f.sp. cajani). Disease onset occurred on Jul. 10 and on Aug. 4 in 1987 and 1988, respectively. In both years, infection and subsequent disease development occurred when day temp. were <28°C. Rain was recorded on 7 consecutive days prior to disease onset in 1987 and on 5 of 7 days in 1988. An increase in soil inoculum levels was also associated with a decrease in day temp., higher rainfall and cloudy weather

Effect of homoeopathic drugs on respiration of germinating fungal spores

Abstract: Effect of a number of homeopathic drugs on the respiration of germinating spores of eight fungal pathogens was investigated. Majority of drugs suppressed the respiration but the magnitude of suppression varied with the drugs, their potencies and the pathogens. A significant con-elation between inhibition of spore germination and rate of respiration was recorded. Changes in the organic acid pool of the spores during germination were also affected by the drugs.

Races of Fusarium oxysporum causing wilt in chickpea: biochemical variability

Abstract: Four physiologic races of Fusarium oxysporum f. sp. ciceri (Foc), which cause wilt of chickpea (Cicer arietinum], differed significantly in their total sugars, proteins and amino acids. Total sugars were maximum in race 3 (93.3 ppm) and minimum in race 1 (23.2 ppm). Noticeable differences were recorded among the four races in their total protein content. When analysed for amino acids, race 3 showed less quantities of arginine (2.9 g), glycine (2.8 g), histidine (2.1 g), and methionine (0.7 g) 100g-1 protein than the other three races.

Metabolic changes in groundnut leaf due to infection by leaf spot pathogens

Abstract: Changes in specific activities of polyphenol oxidase (PPO) peroxidase (PO), catalase and levels of total phenols, total soluble sugars and mineral elements in the healthy and diseased leaves of susceptible (MH-l, JL-24) and tolerant (MH-2, C-333) cultivars of groundnut were studied. Total phenols were markedly higher in tolerant than in susceptible cultivars. Amount of phenol decreased after infection in all the cultivars, conversely, total soluble sugar increased after infection. The specific activities of PPO remained higher while that of PO was lower in tolerant cultivars than in susceptible ones. In response to infection, the activities of both the enzymes increased sharply. However, this increase was more associated with susceptibility. Catalase activity, however, was observed only in healthy leaves and comparatively higher in tolerant cultivars. Nitrogen (N) content was lower in tolerant than in susceptible cultivars and it decreased after infection. Following infection, phosphorus (P), zinc (Zn) and manganese (Mn) were found to decrease while potassium (K) and iron (Fe) increased in all the cultivars. These changes were quite considerable in susceptible compared with tolerant cultivars.

New species of Cercospora, Mycovellosiella and Phaeoisariopsis

Abstract: Cercospora pteridigena sp. nov. on Adiantum venustum, Mycovellosiella urariae sp. nov. and Phaeoisar iop sis fabacearum sp. novo on Uraria hamosa and Phaeoisariop sis woodfordiae sp. novo on Woodfordia fructicosa are described, illustrated and compared with closely related species.

Mycobial deterioration in strychnine and brucine of Strychnos nux-vomica seeds

Abstract: Two major indolic alkaloids, viz., strychnine (0.87%) and brucine (0.06%) contained in Strychnos nux- vomica L. seeds showed considerable change due to artificial inoculation with the spore suspensions of Aspergillus flavus Link: ex. Fries., A. niger van Teigh. and Penicillium citrinum Thorn. recorded as dominant fungal flora on the seeds during storage.

Jeerasannidhi Award Lecture - VA-Mycorrhiza - Dimensions of its application

Abstract: Mushrooms were known to mankind since the early phase of civilization but the German botanist Frank (1885) was the first to coin the term 'Mycorrhiza' for designating a symbiotic relationship between fungi and plant roots. Initially his contention that the mycorrhiza represents a beneficial symbiosis between trees and fungus was challenged by his contemporaries but later researches during the first half of the present century established that the mycorrhizal colonization is responsible for increased growth and nutrient uptake in the forest trees. A great bulk of information regarding mycorrhiza accumulated during later period and it became known that many other types of mycorrhiza are of common occurrence in nature. Scientists started exploiting them for the welfare of the human beings. Many ways were devised to use them as tools for improving the productivity in plants or making them resistant against the vagaries of nature or pathogens.

Effect of inorganic fertilizers on the development of foot rot disease of soybean caused by Sclerotium rolfsii

Abstract: The effect of soil amendments with chemical fertilizers on the rhizosphere micro flora and on the development of foot rot disease of soybean was studied in-vivo. The fertilizers significantly increased bacteria but reduced fungi (excepting rock phosphate at 0.10 and 0.25%) and actinomycete in soybean rhizosphere. Rock phosphate (0.25%) and urea (0.5%) increased Aspergilli while Znso 4 (0.10 and 0.25%) increased Penicillia in the rhizosphere. Soil amendments initially increased Sclerotium rolfsii population in soil resulting in increased pre-ernergence seed rot. Seedlings which escaped seed rot, delayed symptom expression. Higher concentration (0.5%) of most of the fertilizers used were found to be toxic to the growth and yield of soybean. In field, urea (80 kg/ha) and Znso 4 (10 kg/ha) initially increased S. rolfsii population which decreased slightly at a later stage. A significant reduction in the disease .was recorded with all the fertilizers used, of which Znso 4 produced the best result. Urea (80 kg/ha) and ZnS0 4 (10 kg/ha) stimulated plant growth, which was reflected on the increased plant height and yield as compared to others.