Browsing by Author "FLORES, V"
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- ItemDEFORMATIVE DISEASE IN IRIDAEA-LAMINARIOIDES (RHODOPHYTA) - GALL DEVELOPMENT ASSOCIATED WITH AN ENDOPHYTIC CYANOBACTERIUM(1993) CORREA, JA; FLORES, V; SANCHEZ, PThis study is the first report of an algal disease, developed in close association with an endophytic organism, documented for the southeastern Pacific. We describe a disease affecting wild populations of the red alga Iridaea laminarioides Bory in central Chile, characterized by gall developments on the surface of sporophytic, cystocarpic, and immature thalli. These abnormal growths result in severe morphological alterations of the affected thalli. Diseased fronds display an aggregated spatial distribution and occur throughout the year, with a maximum in summer followed by a decline in winter. The presence of galls was not associated with broken or torn fronds. Although causality has not been unequivocally demonstrated, our field and laboratory observations indicate a strong association of the galls with infections by an endophytic cyanobacterium, probably belonging to the genus Pleurocapsa.
- ItemDICARBOXIMIDE-RESISTANT ISOLATES OF BOTRYTIS-CINEREA FROM TABLE GRAPE IN CHILE - SURVEY AND CHARACTERIZATION(AMER PHYTOPATHOLOGICAL SOC, 1994) LATORRE, BA; FLORES, V; SARA, AM; ROCO, ATwo to four applications annually of the dicarboximide (DC) fungicides iprodione and vinclozolin have been used widely for 10-15 yr to control gray mold, caused by Botrytis cinerea, of grapes in Chile. Control failures attributable to field resistance to DC fungicides have not been reported, although the frequency of low-level resistant (LLR) isolates increased from 2 to 74.9% between the 1987-1988 and 1993-1994 growing seasons; 0.3 and 0.6% of the isolates tested during 1992-1993 and 1993-1994, respectively, were highly resistant based on mycelial growth inhibition on PDA amended with 10 mg/L of vinclozolin. The EC50 for mycelial growth varied from 2.51 to 9.02 and from 2.00 to 18.16 mg/ L of vinclozolin among isolates from commercial plantations during 1992-1993 and 1993-1994, respectively. The resistant factor (RF) for the most resistant LLR isolate was 60.13, although most LLR isolates had RF values of <30. Cross-resistance among DC fungicides and to dicloran and PCNB was demonstrated. Although resistant isolates lost some fitness attributes, e.g., higher osmolarity sensitivity, they were virulent and equally inhibited when inoculated nectarine fruit were treated with commercial rates of iprodione, procymidone, and vinclozolin. Conidial germination and mycelial growth of highly sensitive (HS) isolates (EC50 for mycelial growth = less-than-or-equal-to 0.5 mg/L) collected from grapevines never exposed to DC fungicides were completely inhibited by 10 mg/L of iprodione or vinclozolin. Conidial germination of LLR isolates (EC50 for mycelial growth = 2-5 mg/L) was inhibited by only 0.7-9.7%, whereas mycelial growth was arrested by 89.0-91.6%. Inhibition of growth of LLR isolates by iprodione or vinclozolin may partially explain the relatively high degree of control of gray mold of table grape that is still possible with DC fungicides after 10-15 yr of continuous use.
- ItemEFFECT OF POTATO VIRUS-Y ON GROWTH, YIELD, AND CHEMICAL-COMPOSITION OF FLUE-CURED TOBACCO IN CHILE(1984) LATORRE, BA; FLORES, V; MARHOLZ, GThe effect of potato virus Y (PVY) on growth, yield and chemical composition of flue-cured tobacco cultivars Coker 86 and NC-744 was primarily determined by the time of inoculation. On Coker 86, early inoculations (15 and 28 days after transplanting) caused height reductions of 37.0 and 34.7% and yield reductions of 71.5 and 74.8%, respectively. Effects were less detrimental on NC-744, suggesting this cultivar possesses a degree of tolerance to the Chilean necrotic strain of PVY. Nevertheless, plant height and dry weight were reduced 9.9 and 16.3% and 36.9 and 38.9%, respectively, by inoculations 15 and 28 days after transplanting. PVY also modified the chemical composition of cured leaves. Total nicotine content was always higher in cured leaves from diseased plants than in those from healthy controls. Because early inoculations caused the most detrimental effects, the 1st mo. after transplanting should be considered the most critical period for PVY infection.
- ItemGREEN PATCH DISEASE IN IRIDAEA-LAMINARIOIDES (RHODOPHYTA) CAUSED BY ENDOPHYTON SP (CHLOROPHYTA)(1994) CORREA, JA; FLORES, V; GARRIDO, JA green mottled coloration, or green patch disease, develops in the red alga Iridaea laminarioides Bory when it is infected by the algal endophyte Endophyton sp. The disease is widespread in host populations along the coast of central and southern Chile (33-degrees-17' S to 40-degrees-33' S) and affects both gametophytic and sporophytic fronds. It is characterized by green areas, usually located at the base of the thalli, which become soft in texture in fully developed infections. The softening of the host tissue is caused by cellular destruction resulting from endophyte-mediated compaction of the cells, followed by secondary bacterial infections. Bacteria gain access to the host through openings left in the host thallus during spore release from mature sporangia of Endophyton. Both life-history phases of L laminarioides were successfully infected by unialgal isolates of Endophyton in laboratory trials. Infection was achieved only by germlings from newly settled spores and the process of penetration was completed within 3 d. Softening of laboratory-infected thalli became evident about 8 wk after penetration and thallus destruction was complete after 3 to 4 mo of culture.
- ItemSTRAIN IDENTIFICATION AND CROSS-PROTECTION OF POTATO VIRUS-Y AFFECTING TOBACCO IN CHILE(1985) LATORRE, BA; FLORES, VNecrosis severa, caused by potato virus Y (PVY), severely affects flue-cured, burley, and oriental tobaccos in Chile. PVY populations consisted of necrotic and nonnecrotic strains distinguished on the basis of the symptoms produced. Most Chilean isolates were identified as race I (MsMr) or race 3 (NsNr). However, a few were identified as race 2 (MsNr) on the basis of reactions they induced on tobacco cultivars susceptible and resistant to the root-knot nematode. PVY isolates were also distinguishable by their reactions on tobacco Virgin A Mutant, a noncompatible (apparently immune) reaction or compatible reactions that were either necrotic or nonnecrotic symptoms incited on veins or stems. The presence of necrosis did not necessarily appear to be associated with symptom severity. Most nonnecrotic PVY isolates exerted partial protection against a challenge inoculation with a necrotic strain, demonstrating the ocurrence of this phenomenon among PVY isolates and suggesting cross-protection as a possible mechanism for PVY control. Cross-protection may also play a significant role in the epidemiology of PVY diseases.
- ItemWHITENING, THALLUS DECAY AND FRAGMENTATION IN GRACILARIA-CHILENSIS ASSOCIATED WITH AN ENDOPHYTIC AMEBA(1995) CORREA, JA; FLORES, VWhitening of Gracilaria chilensis, accompanied by tissue softening and thallus fragmentation, was found to be associated with the presence of an endophytic amoeba. Although the symptoms developed originally in green mutant thalli, subsequent infections in the laboratory also affected normal, wild-type G. chilensis. Ultrastructural evidence indicates that the amoebae perforate the host cell walls of both cortical and medullary cells and digest their protoplasm. Feeding by the amoeba appears to involve both phagocytosis and enzymatic digestion of the host tissue. Destruction of the host tissue resulted in large cavities first, followed by thallus fragmentation. No other organism was found during the early stages of thallus invasion by the amoeba, although bacteria may appear once the amoeba reaches the inner tissues of the host.