Browsing by Author "LATORRE, BA"

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    COMPARATIVE PROTEIN ELECTROPHORETIC AND ISOENZYMIC PATTERNS OF PHYTOPHTHORA-CRYPTOGEA ISOLATES FROM CHILEAN KIWIFRUIT AND NORTH-AMERICAN DECIDUOUS FRUITS
    (1995) LATORRE, BA; PEREZ, GF; WILCOX, WF; TORRES, R
    Isolates of Phytophthora from fruit crops, previously identified as P. cryptogea on the basis of standard morphological criteria, were compared using electrophoretic patterns of total soluble mycelial proteins and isozyme analysis. According to these criteria, all 33 isolates recovered from kiwifruit in Chile were similar or identical to isolates from California recovered from kiwifruit, apple, and cherry. In contrast, the Chilean and California isolates appeared no more related to New York isolates of P. cryptogea than they were to isolates of P. cactorum, P. cinnamomi, and P. megasperma that were similarly examined. Isolates identified as P. cryptogea from deciduous fruit crops in New York appear to belong to a different taxon than isolates of P. cryptogea from fruit crops in Chile and California.
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    DEVELOPMENT OF AN INFECTION MODEL FOR BOTRYTIS BUNCH ROT OF GRAPES BASED ON WETNESS DURATION AND TEMPERATURE
    (AMER PHYTOPATHOLOGICAL SOC, 1995) BROOME, JC; ENGLISH, JT; MAROIS, JJ; LATORRE, BA; AVILES, JC
    Grape berries were dipped in conidial suspensions of Botrytis cinerea and incubated for 4, 8, 12, 16, or 20 h of wetness at temperatures ranging from 12-30 C. Berries were infected after 4 h of wetness at all temperatures tested. Incidence of berry infection increased with increasing wetness duration at all temperatures. A multiple regression model described the legit of infection as a function of the interaction of wetness duration and temperature (R(2)=0.75). This model was incorporated into an infield environmental monitoring station and evaluated for two seasons on Thompson Seedless table grapes in the central valley of Chile. Applications of captan (3.2 kg/ha a.i.) or vinclozolin (1 kg/ha a.i.) were made according to the Botrytis model or a standard phenological spray program that consisted of four sprays (at bloom, cluster thinning, veraison, and preharvest) plus additional sprays after major rain events. Disease incidence and severity at harvest were similar whether applications were made according to a standard program (six to nine applications in 1991-1992, four to five in 1992-1993) or according to the Botrytis model (two to four applications in 1991-1992, zero to five in 1992-1993). In some vineyards, postharvest disease was significantly less when sprays were made according to the Botrytis model recommendations compared with the standard spray program.
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    DICARBOXIMIDE-RESISTANT ISOLATES OF BOTRYTIS-CINEREA FROM TABLE GRAPE IN CHILE - SURVEY AND CHARACTERIZATION
    (AMER PHYTOPATHOLOGICAL SOC, 1994) LATORRE, BA; FLORES, V; SARA, AM; ROCO, A
    Two 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.
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    EFFECT OF POTATO VIRUS-Y ON GROWTH, YIELD, AND CHEMICAL-COMPOSITION OF FLUE-CURED TOBACCO IN CHILE
    (1984) LATORRE, BA; FLORES, V; MARHOLZ, G
    The 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.
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    FACTORS AFFECTING RELEASE OF ASCOSPORES BY THE PEAR SCAB FUNGUS (VENTURIA-PIRINA)
    (1985) LATORRE, BA; YANEZ, P; RAULD, E
    Ascospores of V. pirina were monitored under field conditions [Chile] in 1982 and 1983 with a Burkard 7-day recording spore trap adjusted to sample about 8 m3 of air/h at 55 cm above the ground. Ascospore productivity was determined weekly by sampling partially decomposed pear leaves near the spore trap. Ascospore emissions occurred mainly during daylight hours and fluctuated daily and seasonally (associated with period of free moisture). The first mature ascospores were found when pear trees were in the green tip stage of fruit bud development (late Aug. and early Sept.). Maximum ascospore catches were recorded in Sept. (white cluster to full bloom stage of fruit bud development), then progressively decreased until Dec. The lack of later liberation under Chilean conditions is apparently due to the absence of free moisture periods.
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    ISOLATION OF PSEUDOMONAS-SYRINGAE PV SYRINGAE FROM CANKERS AND EFFECT OF FREE MOISTURE ON ITS EPIPHYTIC POPULATIONS ON SWEET CHERRY TREES
    (1985) LATORRE, BA; GONZALEZ, JA; COX, JE; VIAL, F
    Frequency of isolation of P. syringae pathovar syringae (Pss) from bacterial cankers on 3- to 4-yr-old sweet cherry trees [Prunus avium] (cultivar Napoleon) was highest between late winter (Aug.) and early spring (Sept.). Large, abrupt changes in epiphytic populations of Pss were found on dormant buds of ''Napoleon'' cherry shoots under field conditions. These changes closely followed the presence or absence of free moisture resulting from rainfall or dew. Populations of Pss greater than 104 colony-forming units/gram of buds were only recorded during wet periods; otherwise, populations remained low or undetectable. Field observations were corroborated by greenhouse experiments on detached, dormant cherry shoots where 10-fold or higher fluctuations in bacterial populations occurred in response to 24 h of wetness or dryness.
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    OCCURRENCE AND RELATIVE SUSCEPTIBILITY OF APPLE CULTIVARS TO BOTRYOSPHAERIA CANKER IN CHILE
    (1984) LATORRE, BA; TOLEDO, MV
    A canker disease initially observed on the trunks of Red King Oregon apple trees was caused by Botryosphaeria dothidea, a fungus not previously reported on apples in Chile. Trunk symptoms were characterized by the presence of flat, sunken cankers. Initially, the surface of the bark turned orange to pink, developed a papery appearance, and sloughed away. Abundant black pycnidia extruded through the outer layer of the bark. All B. dothidea isolates tested caused fruit rot on apple cv. Granny Smith, Starking Delicious and Richared Delicious and produced cankers after 8 wk on the trunks of artificially inoculated 1-yr old Red King Oregon apple trees. Trunk susceptibility was dependent (P = 0.01) on cv., isolate and inoculation position. Red King Oregon was the most susceptible cv., followed by Red Spur and Starkrimson. Granny Smith, Granny Smith Spur and Golden Spur were the most resistant cultivars. Differences in virulence among fungal isolates were observed. At present, Botryosphaeria canker of apple is considered of minor importance but is a potential threat to the Chilean apple industry.
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    PHYTOPHTHORA ROOT-ROT OF KIWIFRUIT IN CHILE
    (1991) LATORRE, BA; ALVAREZ, C; RIBEIRO, OK
    Kiwifruit (Actinidia chinensis) has become a major fruit crop for exportation in Chile totalling about 30,000,000 t each year. A decline associated with a severe root rot has frequently appeared in 1- to 5-yr-old kiwifruit vines in the central zone of Chile. Our results demonstrate the presence of pathogenic isolates of Phytophthora cryptogea and P. citrophthora associated with diseased plants. This is the first report of these pathogens affecting kiwi in Chile. They are a potential threat for kiwi production, particularly in poorly drained soils.
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    ROOT-ROT OF RED RASPBERRY CAUSED BY PHYTOPHTHORA-CITRICOLA AND P-CITROPHTHORA IN CHILE
    (AMER PHYTOPATHOLOGICAL SOC, 1993) LATORRE, BA; MUNOZ, R
    Outbreaks of root rot on red raspberry occur frequently in Chile and often are related to excess soil moisture. Aerial symptoms, including leaf chlorosis, wilting of primocanes and floricanes, poor growth of floricanes, and poor emergence of primocanes, are always associated with root necrosis. Diseased plants eventually die. Phytophthora citricola and P. citrophthora were consistently recovered from the roots of symptomatic plants of the cultivars Willamette and Glen Clova. These pathogens were identified on the basis of morphological features of sporangia and sex organs and mycelial growth at different temperatures. P. citricola has been previously associated with root rots and decline of red raspberry, but this is the first report of P. citrophthora as a pathogen on red raspberry and the first confirmed report of any Phytophthora species causing root rot of red raspberry in South America.
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    STRAIN IDENTIFICATION AND CROSS-PROTECTION OF POTATO VIRUS-Y AFFECTING TOBACCO IN CHILE
    (1985) LATORRE, BA; FLORES, V
    Necrosis 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.
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    VERTICILLIUM WILT, A LIMITING FACTOR FOR TOBACCO PRODUCTION IN CHILE
    (1989) LATORRE, BA; LOLAS, M; MARHOLZ, G
    A wilt and orange-to-yellow discoloration observed in recent years in burley types of tobacco [Nicotiana tabacum] in Chile was confirmed to be caused by Verticillium dahliae. Disease incidence as high as 25.6% had occurred. Significant yield losses were estimated in nine of 11 selected plots during the 1987-1988 growing seasons. Quality also was significantly affected in diseased versus symptomless cultivar Burley-49 tobacco plants. Isolates of V. dahliae from tobacco were pathogenic to plants of tobacco cultivar Burley-21. However, only mild symptoms occurred in cultivar Coker-86; flue-cured lines V-1 and V-3 appeared to be resistant. All isolates were pathogenic to the susceptible tomato cultivar Earlypak-7, and some isolates caused symptoms on tomato seedlings of the resistant cultivars San Remo, Flora Dade, and Cal-Ace. Lower disease incidence was observed in the latter cultivars. Consequently, isolates from tobacco appeared to be race 1 of V. dahliae.