Showing papers in "Phytopathology in 1984"

Studies on the in vitro and in vivo antifungal activity of fosetyl-Al and phosphorous acid

Abstract: Fenn, M. E., and Coffey, M. D. 1984. Studies on the in vitro and in vivo antifungal activity of fosetyl-A1 and phosphorous acid. Phytopathology 74:606-611 In a low-phosphate medium fosetyl-A1 showed a much higher activity in vitro against Phytophthora than previously reported in the literature. Both fosetyl-Al, and more particularly phosphorous acid (HjPO,), were highly inhibitory in vitro against several species of Phytophthora. Phosphorous acid was much less inhibitory in vitro against Pythium and had only low activity against a selection of non-oomycetous fungi. The ECso values for an isolate of Phytophthora cinnamomi, cultured on a low phosphate medium, were 0.05 PO3 meq of H3PO3 (4 pg/ mi) and 0.45 PO3 meq of fosetyl-A1 per liter (54 pg/ ml). An increase in the level of phosphate reduced the inhibition of mycelial growth due to fosetyl-Na, but there was little or no effect of phosphate on the inhibition caused by HjPOx. In vivo, either 12.7 PO3 meq of &PO3 (1.0 g/ L) or 12.7 PO:! meq of fosetyl-A1 per liter (1.5 g a.i.1 L), applied as a foliar spray or soil drench, gave equivalent control of root rot caused in seedlings of Persea indica by Phytophthora cinnamomi. Compared to fosetyi-Al, H3PO3 had a similar, though generally higher efficacy, in reducing stem infection of Persea indica seedlings by Phytophthora citricola. The ECm values for inhibition of stem infection were 0.09 Po3 meq of H3P03 (8 pg/ ml) and 0.22 PO3 meq of fosetyl-A1 per liter (26 pg a.i.1 ml). Additional key words: aluminum tris-0-ethyl phosphonate, sodium ethyl phosphonate. Fosetyl-A1 (aluminum tris-0-ethyl phosphonate) is the active ingredient of a formulated systemic fungicide, known as AlietteB, developed by RhGne-Poulenc Phytosanitaire in France (28,29,38,40). Fosetyl-A1 has high efficacy against some diseases caused by members of the Peronosporales, particularly the downy mildew fungi and several Phytophthora species (2,3,6-9,11,14,15, 18,20-24,26-30,32,33,36,38-41). Previous reports have indicated that fosetyl-A1 prevented in vitro fungal growth only a t concentrations of 1,000 pg/ ml or greater (9,12,29-3 1,34,36,37,39). Since fosetyl-A1 was found to have low activity against mycelial growth in vitro, it has been proposed that rather than exerting a direct effect on the pathogen it may act indirectly by triggering a host resistance response (4,10,13,19,24,29,35,37,39,40). Fosetyl-A1 has been reported to cause a stimulation of host defense responses in detached tomato leaves infected with Phytophthora capsici (4,10,13,19,35,37) and in detached grape leaves infected with Plasrnopara viticola (1 9,24). Fosetyl-A1 is degraded to H3PO3 in plant tissue (4,35,37,38). In this paper we report on the in vitro and in vivo activity of fosetyl-A1 and H3P03. The influence of the phosphate level of the culture medium on the in vitro activity of fosetyl-Al, fosetyl-Na, and HjPO3 is also investigated. MATERIALS AND METHODS Phytophthora root rot control with fosetyl-A1 and H3P03. Nineweek-old Persea indica seedlings growing in UC mix (50% blow sand, 50% peat moss, plus 2.2 kg dolomite, 1.5 kg superphosphate, 148 g KN03, and 148 g KzS04 per cubic meter (1) in 6-cm-diameter peat pots were transplanted into 3.8-L metal containers with soil naturally infested with P. cinnamomi from an avocado grove on the campus at the University of California, Riverside (UCR). In the control treatment the soil was treated with aerated steam for 1 hr a t 60 C to destroy propagules of Phytophthora. On the day following transplanting, one set of the plants was given a foliar spray until run-off, with either distilled water or aqueous solutions of fosetylThe publication costs of this article were defrayed in part by page charge payment. This article must therefore be hereby marked "advertisement" in accordance with 18 U.S.C. tj 1734 solely to indicate this fact. @I984 The American Phytopathological Society A1 (1.5 g a.i./L) or H3P03 (1.0 g/L). At these concentrations fosetyl-A1 and H3P03 contained 12.7 PO3 m e q / L . T h e concentration of fosetyl-A1 needed to give consistent control of root rot was determined in preliminary greenhouse experiments. Paper towels were used to cover the soil to prevent any run-off solution from contacting the soil. The same solutions were applied as 25-ml soil drenches to each pot. The foliar spray and soil drench treatments were repeated at 7 days, and at 8 days a third foliar spray was applied. Treatments were replicated five times. All solutions contained 0.027 M MES buffer (2-[N-morpholinolethane sulfonic acid) adjusted to a pH of 6.2. Plants were grown in the greenhouse and watered with tap water and dilute Hoagland's solution. Six weeks after transplanting, the increase in plant height was measured, the soil was washed from the roots, and the extent of root rot assessed visually. Roots and shoots were placed in separate paper bags, and dried at 65 C for 2 days to obtain their dry weights. Control of stem infection by P, indica by Phytophthora citricola with fosetyl-A1 and H, PO,. Nine-week-old P. indica seedlings were placed in 946-ml styrofoam cups containing 650 ml of distilled deionized water, to which were added 2 X lo4 motile zoospores per plant of P. citricola, isolate P1273 from the Phytophthora collection at UCR. Twenty-seven hours after inoculation, seedlings of P. indica were transferred to solutions containing different concentrations of H3P03 or fosetyl-A1 in0.03 M MES buffer a t pH 6.2. Five days later, the stems were cut into 12-14 pieces 0.7 cm in length, the number of pieces depending upon stem length, dipped in 70% ethanol, blotted, and plated onto PARP medium (17) modified by the substitution of 125 pg,'ml ampicillin trihydrate (85%, Bristol Laboratories, Syracuse, NY 1320 1) for 250 p g sodium ampicillin per milliliter. On the first, second, and third day alter plating, the stem pieces from which Phytophthora was recovered were marked and the percentage of stem pieces infected was calculated. There were six replicates of each treatment. Expression of PO, concentrations. To avoid confusion, the concentration of all PO3-containing compounds (H3PO3, fosetylNa, and fosetyl-Al) are expressed as either PO3 meq/ L or pg/ ml. The former expression allows for a comparison of compounds on the basis of their PO3 content. Fosetyl-Na and &Po3 have one Po3 group per molecule, while fosetyl-A1 has three PO3 groups due to the trivalency of aluminum. Values expressed as PO3 meq/ L can be converted to micrograms per milliliter by multiplication with the

Biological control effects of a new isolate of Trichoderma harzianum on Pythium aphanidermatum

Abstract: On tente divers substrats comme milieu de base pour T. spp. Des applications generalisees et des traitements de semences sont experimentees

Biological control of Meloidogyne javanica with Bacillus penetrans

Abstract: Mode d'action de l'agent sur plants de tomate et etude de son efficacite. Presence naturelle sur la vigne. Etude en pots et au champ

Effects of microwave oven treatment on microorganisms in soil

Abstract: Recherche des effets des conditions de traitement (duree, quantite de sol, humidite, type de sol) sur l'elimination des microorganismes. Effets particuliers sur Pythium, Fusarium, Heterodera, Rhizoctonia, champignons mycorhiziens. Comparaison avec l'autoclavage et les fumigants

Manganese accumulation in wood decayed by white rot fungi

Abstract: Black regions and flecks in wood decayed by several white rot fungi ( Cerrena unicolor , Dichomitus squalens , Ganoderma applanatum , G. tsugae , Heterobasidion annosum , * 2Ischnoderma resinosum*1, and Perenniporia medulla-panis ) contained large concentrations of manganese. Two types of decay patterns occurred in wood degraded by these fungi: a selective delignification resulting in the removal of lignin and hemicellulose and a typical white rot causing simultaneous removal of all cell wall components. Atomic emission spectrometry and X-ray microanalyses detected manganese and determined its spatial relationship within selectively delignified wood. Black regions in eastern hemlock wood decayed by G. tsugae showed over a 100-fold increase of manganese when compared with sound wood. When black regions were compared with surrounding delignified wood and adjacent white-rotted wood, the increases of manganese were 24-fold and 51-fold, respectively. In contrast to the other decays examined, manganese deposits were found in white-rotted wood attacked by Fomes fomentarius . Micromorphological characteristics of decayed wood and manganese deposits were observed with scanning electron microscopy. Leucoberbelin blue reagent confirmed the presence of manganese oxides within the black regions.

Evaluation of Trichoderma koningii and Trichoderma harzianum from New York soils for biological control of seed rot caused by Pythium spp..

Abstract: Isolement, caracterisation et test d'agents de lutte biologique. On recherche l'efficacite de divers materiaux adhesifs pour le traitement des semences ou comme gelifiants en semis direct fluide

The Controlled Experiment in the Scientific Method with Special Emphasis on Biological Control

Abstract: The experimenter questions, manipulates, alters, controls, and the raw untreated soil is an appropriate control-this is the element forces nature to reveal herself. An experiment is a game in which "observed without interference"; but what is the nature of the phenomena are carefully Watched, at a particular time and place, in "peat-bran control" in this case? The sterile peat-bran medium not relation to an intentional disturbance occurring in them and infested with the biological control agent is a candidate. Yet, it is around them. According to Egler (6), "a controlled experiment is not the same substrate as that acted upon by the agent during one where two or more situations are watched, where one is incubation. Further, the addition of previously undigested organic observed without interference, and where the others are matter to soil can induce increased disease severity and/or toxin manipulated in known ways. The changes are then related to this production resulting from the activity of soil microflora leading to known manipulation." plant damage (15) or, alternatively, can lead to biological control The control is such an integral factor in the scientific method that (2,3). Sterile peat-bran medium has its own "interference" and is it is taken for granted and treated only briefly, if at all, in the not an appropriate control. philosphical literature and is only rarely defined. Indeed, in most Elimination of the biocontrol agent after growth. To allay these disciplines, a control is readily identifiable; for plant pathologists, difficulties, perhaps the agent could be grown in the sterilized however, establishing controls is complicated by the multitude of peat-bran medium and then autoclaved or fumigated to remove the interacting factors in the classic disease triangle. The experiments living portion of the substrate. Much of the nutrient in the peatinvolve pathogens; therefore, there can be inoculated and bran would be utilized by the microorganism prior to the second uninoculated controls. When plant pathologists study biological sterilization; however, the dead cells, stable products extracted by control, they add a new set of parameters (3) involving the the fungus during growth, and any residual unutilized nutrients

Possible mechanisms by which postharvest calcium treatment reduces decay in apples.

Abstract: Mise en evidence du role indirect du Ca dans le phenomene de resistance des pommes a l'infection par Penicillium expansum, par la formation de constituants, au niveau de la paroi cellulaire, qui s'opposent a la penetration de la moisissure

Fungi associated with several developmental stages of heterodera glycines from an alabama usa soybean field soil

Abstract: An examination of young, swollen, cream-colored cysts of Heterodera glycines Ichinohe attached to root surfaces and of white, newly exposed females partly immersed within roots of Alabama-grown soybeans [Glycine max (L.) Merr.] revealed the presence of a number of fungal pathogens. Fungi most frequently isolated from these stages of development were: Chaetomium cochliodes Palliser, Exophiala pisciphila McGinnis & Ajello, Fusarium oxysporum Schlecht, F. solani (Mart.) Sacc., Phytophthora cinnamoni Rands, Pythium sp., a sterile mycelium, and Trichosporon beigelii (Kuchenm. & Rabenh.) Vuill. Fifty percent of the cream-colored cysts were infected as compared to 20 percent of the younger white, lens-shaped females. An examination of sausage-shaped females within roots and brown cysts from soil indicated that two and 70 percent respectively were invaded by fungi. Results indicated that a progressive increase in fungal colonization occurred with nematode development. Some overlapping of the