Incidence Of White Rot Research Articles

Sclerotinia resistance in sunflower. II. Combining ability and midparent heterosis for reaction to ascospore infections at flowering

In Argentina, susceptibility of the sunflower crop to Sclerotinia sclerotiorum capitulum attacks can cause significant yield losses. We reported earlier two hybrids among a series obtained from crosses between inbred lines following a factorial mating design that had a sufficient level of resistance to be adapted to the main Argentina sunflower growing area. Results concerning the per se behavior of the parental lines involved in these crosses and the combining ability and heterosis effects of such parental genotypes are presented in this article. The lines showed different responses to white rot incidence and relative incubation period. There were significant effects for general and specific combining ability and also for midparent heterosis, for the two variables evaluated. Preponderance of additive gene effects on genetic control white rot resistance level was shown. The development of sunflower inbred lines to be used as parents in the production of hybrids for areas requiring moderately resistant hybrids is an important phase in breeding programs. To optimize the use of resources and time, our results suggest that testing general combining ability at early generations of selfing followed by testing of hybrids may be considered as an adequate strategy in breeding for white rot resistance.

Evaluation of Arbuscular Mycorrhizal Fungi and Trichoderma Species for the Control of Onion White Rot (Sclerotium cepivorum Berk)

The present study was carried out to evaluate the indigenous Arbuscular Mycorrhizal Fungi (AMF) and Trichoderma species isolated from rhizosphere soils of onion cultivated fields at Ambo and Toke Kutaye districts of West Showa, Ethiopia, and their effect on plant growth, and their biocontrol against onion white rot caused by Sclerotium cepivorum Berk. Five species with twenty isolates of Trichoderma were isolated and screened in vitro for the inhibition of S. cepivorum. Out of these, four isolates of Trichoderma spp viz. T. harzianum (ATh1), T. viride (ATv1), T. hamatum (NThm3), and T. koningii (QTk2), were found potent antagonists with mean percent inhibition of the pathogen, 65.4, 64.8, 54.3 and 53.5, respectively. Altogether, 10 AMF species representing four genera viz. Acaulospora, Gigaspora, Glomus, and Scutellospora, were isolated and identified. Six dominant species of AMF were selected and mass multiplied by using Sorghum vulgare Pers. as the compatible host plant. Among six AMF species, the potential efficient strain, Glomus aggregatum (Awaro isolate), was selected for using as bio control agent. The bio-control potential of these bio-agents against white rot pathogen was carried out under pot culture condition, using G. aggregatum alone or in combination with four isolates of Trichoderma spp. Incidence of S. cepivorum was significantly reduced in bulbs of onion (66.19%), and also improved plant growth was observed in plants inoculated with combined inoculation of G. aggregatun and T. harzianum (ATh1 isolate), followed by the combined inoculation of G. aggregatum and T. viride (ATv1) with pathogen (59.75%). Plants inoculated with S. cepivorum alone showed pronounced disease symptoms with mean disease incidence of 90.5%. The overall reduction in the incidence of white rot was 56.22% in the treatment of T. harzianum ATh1 isolate with pathogen, followed by 53.72% for G. aggregatum with pathogen. These results clearly pointed out that G. aggregatum and T. harzianum ATh1 isolate can block the severity of disease caused by S. cepivorum in onion. Use of these bio-control agents could be promoted as an active component of bio-intensive Integrated Disease Management Program (IDMP), under organic mode.

THE CORELATIONS BETWEEN WHITE ROT (RIGIDOPORUS LIGNOSUS L.) INCIDENCE AND SOIL CHARACTERS OF RUBBER ECOSYSTEM IN PENUMANGAN BARU, LAMPUNG

The corelations between White Rot (Rigidoporus lignosus L.) incidence and soil characters of rubber ecosystem in Penumangan Baru, Lampung. A study was conducted to evaluate the corelation between soil characters and white rot incidence. The study was done in Penumangan Lampung from June 2007 to July 2008. Seven sites were observed on the incidence of white rot of indicator plants (cassava). Physical, chemical, and biological soil characters were correlated and regressed with white rot incidence. The results showed that there were correlation between white rot incidence and soil characters such as pH KCl, number of fungal genus (fungal diversity), Ca+, total cation, CEC, and saturation base. Ion Ca+, total cation, saturation base correlated positively with white rot incidence, on the contrary, fungal diversity, cation exchange capacity, and pH KCl correlated negatively with white rot incidence. Thus, efforts to increase fungal diversity, cation exchange capacity, and pH (in acidic soil) could be used as basic strategies to develope intergrated control of white rot disease.

Application of thymol and iprodione to control garlic white rot (Sclerotium cepivorum) and its effect on soil microbial communities

The effect of different dosages of thymol alone, iprodione alone and combinations of thymol and iprodione on white rot disease of garlic and its impact on soil microbial community structure were investigated under greenhouse conditions. Thymol alone or in combination with the fungicide iprodione did not appear to reduce either white rot incidence or soil sclerotia density as compared to an infected control. However, iprodione alone or in combination with thymol reduced soil fungal biomass. In addition, iprodione alone decreased soil microbial activity as estimated by fluorescein diacetate (FDA). Soil bacterial community structure as estimated by phospholipid fatty acid (PLFA) profiles was also was affected by both thymol and iprodione applications. The correlation biplot of the individual PLFAs and biocide treatment indicated that the treatments with thymol alone increased cyclopropyl fatty acid (cy17:0 and cy19:0), while the treatments with iprodione alone increased some saturated and branched fatty acids (principally i16:0, a15:0 and 18:0). In addition, taking into account PLFA biomarkers, thymol applications reduced Gram-negative bacteria in soil. To our knowledge, this research is the first report about the effect of a monoterpene (thymol) on soil microflora.

Powder formulations of Bacillus subtilis, Trichoderma spp and Coniothyrium minitans for biocontrol of Onion White Rot

In vitro, B. subtilis, T. harzianum, T. viride, T. spirale and C. minitans isolates showed different inhibitory effects against the growth of S. cepivorum. T. harzianu. While T. spirale showed the greatest antagonistic effect to the pathogen, followed by T. viride and B. subtilis isolates. However, isolates of C. minitans showed a slight antagonistic effect. In greenhouse experiments, the application of the tested powder formulations of bacteria and fungi to infested soil at the time of planting and two weeks before transplanting, significantly reduced the incidence of white rot on Giza 6 onion cultivars. The application of bacterial antagonists two weeks before transplanting resulted in the highest reduction of disease incidence. However, a similar reduction in disease severity was detected when the tested fungal antagonists were applied at the time of transplanting or two weeks later. The use of these bioagents in the form of powder formulations as soil treatment could be recommended for the control of white rot in onion.

Integration of soil solarization and chemical sterilization with beneficial microorganisms for the control of white root rot and growth of nursery apple

White root rot ( Dematophora necatrix (Mart.)) is a serious disease of apple ( Malus domestica Borkh) in nurseries and orchards in India. In 2002 and 2003, field experiments were conducted to integrate soil solarization with native isolates of Azotobacter chrococcum and vesicular–arbuscular mycorrhizal fungi and observe its effect on the incidence of white root rot and growth of the saplings. Apple seeds coated with two native isolates of A. chrococcum (AZUHF 1 and AZUHF 2) were sown in plots inoculated with 4 native isolates of va-mycorrhiza, i.e. AMUHF 1 ( Glomus fesiculatum), AMUHF 2 ( Glomus macrocarpum), AMUHF 3 ( Glomus mosseae) and AMUHF 4 ( Gigaspora sp.) in 14 different combinations and these plots were solarized with transparent polyethylene mulch (25 μm thick) for 40 days in summer months. Soil solarization resulted around 9 °C higher temperature with average maximum temperature of 38–39 °C. Inoculation of saplings with AMUHF 1 isolate of va-mycorrhiza and AZUHF 1 isolate of A. chrococcum and then their planting in solarized soil was found most effective with no incidence of white root rot in comparison to 33.6–35.4% in control accompanied with 78–113% increase in shoot length and 81.6–84.3% increase in root length. Shoot and root length of the saplings was 9.6–10.6 and 9.2–16.0% higher, respectively, in solarized plots in comparison to sterilized plots.

Incidência de podridão-branca em frutos de macieira com e sem ferimentos

Este estudo teve como objetivo avaliar a incidência da podridão-branca (Botryosphaeria dothidea) em frutos de dois genótipos de macieira submetidos à inoculação artificial, na ausência e na presença de ferimentos provocados pela mosca-das-frutas (Anastrepha fraterculus) e por estilete. O experimento foi conduzido no laboratório de Entomologia da Epagri/Estação Experimental de Caçador, na safra 2005/2006. No estudo, foram utilizados frutos da cv. Catarina (grupo 'Fuji') e da seleção M-13/00 (grupo 'Gala'). Os tratamentos foram os seguintes: (1) frutos feridos por mosca-das-frutas; (2) frutos feridos com estilete; (3) frutos sem ferimentos, e (4) frutos sem ferimentos pulverizados com água destilada (testemunha). Os tratamentos 1; 2 e 3 foram inoculados com B. dothidea. O delineamento experimental foi inteiramente casualizado, com quatro repetições, de quatro frutos por parcela. Na cv. Catarina, o número de lesões de podridão-branca foi maior em relação à M-13/00. Os ferimentos nos frutos favoreceram o estabelecimento e o desenvolvimento de lesões da doença.

Association of white rot ( Sclerotium cepivorum) of garlic with environmental factors and cultural practices in the North Shewa highlands of Ethiopia

Field surveys were conducted in North Shewa highlands, Amhara state, Ethiopia during 2003 and 2004 main cropping seasons to determine the distribution, prevalence and the association of garlic white rot ( Sclerotium cepivorum) incidence with environmental factors and cultural practices. In both years a total of 385 garlic fields were surveyed in four districts, and 96.6% of the fields were infested with white rot. Disease incidence varied among districts and between years, altitude range, soil type and field management practices. The mean disease incidence in 2 years ranged from 21% in Lalo Mama Mider to 42% in Basona and Werena district, where it was significantly higher. The incidence in 2004 cropping season was higher by 37.28% than in 2003. Logistic regression was used to analyse the association of white rot incidence with environmental factors and cultural practices as independent variables. District, cropping year, soil type and weed management practices were significantly associated with white rot incidence in a multiple variable model. Higher incidence of white rot was significantly associated with Basona and Werena district. Lower incidences had a high probability of association with Angolela and Asagirt and Lalo Mama Mider (2003) cropping year and good weed management practices. In a reduced multiple variable model, year and weed management practice were significantly associated with lower white rot incidence. In garlic intercropped with Brassica there was very low disease incidence. The survey revealed high occurrence and distribution of white rot in the study area and effective and feasible management options need to be developed.

Rhizosphere competent Mesorhizobiumloti MP6 induces root hair curling, inhibits Sclerotinia sclerotiorum and enhances growth of Indian mustard (Brassica campestris)

The bacterial strain Mesorhizobium loti MP6, isolated from root nodules of Mimosa pudica induced growth and yield of Brassica campestris. The isolate MP6 secreted hydroxamate type siderophore in Chrom-Azurol Siderophore (CAS) agar medium. Production of hydrocyanic acid (HCN), indole acetic acid (IAA) and phosphate solubilizing ability was also recorded under normal growth conditions. Root hair curling was observed through simple glass-slide technique. In vitro study showed a significant increase in population of M. loti MP6 in rhizosphere due to root exudates of B. campestris. In dual culture technique the strain showed a strong antagonistic effect against Sclerotinia sclerotiorum, a white rot pathogen of Brassica campestris. The growth of S. sclerotiorum was inhibited by 75% after prolonged incubation. Efficient root colonization of mustard seedlings was confirmed by using a streptomycin-resistant marker M. loti MP6strep+. The M. loti MP6 coated seeds proved enhanced seed germination, early vegetative growth and grain yield as compared to control. Also, a drastic decline (99%) in the incidence of white rot was observed due to application of M. loti MP6.

Strategies for management of Sclerotium cepivorum Berk. in garlic.

The impact of incorporation of onion, broccoli or carrot crop residues, followed by soil solarization and by incorporation of chicken manure-Trichoderma harzianum (Ch-T) at garlic planting, on sclerotium density and viability of Sclerotium cepivorum, white rot incidence and garlic yield was evaluated in the field in a 3 x 3 x 2 factorial arrangement. Planting and incorporation of broccoli significantly reduced sclerotium density and viability (53 and 14%, respectively) and increased the yield of garlic (18%) compared with incorporation of onion (control). Soil solarization significantly reduced inoculum density (75%), viability (84%) and disease incidence (88%), and increased garlic yield by up to 152%, compared with non-solarized treatments. Incorporation of broccoli in combination with soil solarization was the strategy, which gave the greatest reduction in sclerotium density and viability, the lowest white rot incidence, and the highest yield of garlic.

Management of white rot ( Sclerotium cepivorum) of garlic using fungicides in Ethiopia

Four field experiments were conducted at the Debre Zeit and Bakelo areas of North Shewa, Ethiopia in 2003/2004 and 2004/2005 to determine the effects of five fungicides on epidemics of white rot ( Sclerotium cepivorum), and to identify effective fungicides for its management. Five fungicides: tebuconazole as a clove treatment and supplemented basal spray, benomyl, mancozeb, captan and thiram as a clove treatment were applied to Tseday (G-493) and local garlic cultivars. The treatments were arranged in a randomized complete block design with three replications. There was an untreated control for each cultivar. The trials were conducted in fields naturally infested with S. cepivorum. Treatment of garlic cloves with tebuconazole at the rate of 2.1 ml kg −1and spray at 0.25 l ha −1 at stem bases resulted in a significant reduction in initial and final white rot incidence, progress rate, and severity on bulbs. Captan at the rate of 4.17 g kg −1and benomyl at 5.2 g kg −1gave a significant reduction in final disease incidence and the disease was reduced by 16% and 24%, respectively, over the control at Bakelo. At Debre Zeit these fungicides decreased final disease incidence by 40–44%. The highest increase in marketable yield was obtained from garlic treated with tebuconazole (43–73%), captan (48–77%) and benomyl (42–64%) more than the control. Thiram reduced the disease initially, but subsequently did not prove effective. Garlic yield of both cultivars were improved by fungicide application. On average marketable yield increased 27–44.1% at Debre Zeit and 33–70% at Bakelo over the untreated control plots. Differences existed between seasons and locations and these could be due to differences in environment and inoculum levels.

HEAT TREATMENTS TO CONTROL WHITE ROT (BOTRYOSPHAERIA DOTHIDEA) ON ´FUJI´ APPLES

The need to prolong shelf-life after harvest having reduced losses of fruits due to rot incidence resulted in an increased use of agrochemicals over the past few years. Nevertheless, consumer concerns with regards to pesticide residues and the fact that these widely-applied chemicals after harvest have shown some lack of control effectiveness encouraged the search for alternative methods to minimize postharvest decay. Heat treatments to control postharvest pathogens have been tested in many fruit species. In the present work the objective was determine the effect of heat applied with a hot water brush system on the incidence of white rot (B. dothidea (Moug.) Ces. & DeNot) on cv. Fuji apples. The apples were artificially inoculated with a 5% potato dextrose solution containing 106 conidia/ml. After inoculation the apples were maintained for 48 h at 28°C and thereafter brushed with hot water at 50, 55 or 58°C for 30 s. After the treatments, the apples were transferred for 17 days to 20°C. The effects of the treatments were determined by visual analysis of the number of decayed fruit and number of lesions on each individual fruit. Applying heat for 30 s on apples with the hot water brush system reduced the percentage of apples showing typical symptoms of white rot as well as reduced the number of lesions on each fruit. Best results were obtained with water at 55 or 58°C.

온도와 토양습도가 마늘 흑색썩음균핵병 발생에 미치는 영향

파속채소에 발생하여 큰 피해를 주는 흑색썩음균핵병균을 대상으로 외국 도입균주와 국내 분리균주간의 유전형을 UP-PCR을 이용하여 Tyson 등이 보고한 방법으로 조사한 결과, 국내에서 분리되는 Sclerotium cepivorum은 UP-PCR그룹 b에 속하는 것으로 확인되었으며, 대균핵 형성균과 DNA profile에 있어서 현저한 차이를 보였다. 두 가지 병원균의 균핵 표면구조를 전자현미경을 이용하여 확인한 결과, S. cepivorum은 대균핵 형성균에 비해 잔주름이 적고 내부에 포자와 유사한 구조가 관찰되었다. 흑색썩음균핵병을 일으키는두 가지 병원균은모두 <TEX>$10\~25^{\circ}C$</TEX>에 범위에서 생장되었고 생장 최적온도는 <TEX>$20^{\circ}C$</TEX>이었으며, <TEX>$28^{\circ}C$</TEX> 이상에서는 전혀 자라지 않았다. 두 가지 병원균의 균핵 형성정도는 <TEX>$20^{\circ}C$</TEX>에서 배양시 가장 높았고 균핵 발아정도는 <TEX>$20\~24^{\circ}C$</TEX> 범위에서 높았다 처리온도를 달리하여 처리일수별로 휴면중인 병원균 균핵의 발아정도를 조사한 결과, <TEX>$35^{\circ}C$</TEX>에서 7일간 전처리한 후 <TEX>$10^{\circ}C$</TEX>에서 7일간 배양했을 때 발아가 가장 잘 되었으며 S. cepivorum은 <TEX>$70\%$</TEX>,대균핵 형성균은 <TEX>$100\%$</TEX>발아되었다. 담수기간 및 처리온도가 병원균의 생존에 미치는 영향을 조사한 결과 처리온도가 높아질수록 균핵 발아 정도가 감소되는 것으로 나타났다. 흑색썩음균핵병을 일으키는 두 가지 병원균은 토양습도에 따라 발병정도에 있어서 큰 차이를 보였다. 마늘흑색썩음균핵병은 토양습도가 <TEX>$15\%$</TEX>(-300 mb)일 때 가장 높은 발병을 보였으며 <TEX>$17\%$</TEX> 이상되거나 <TEX>$13\%$</TEX> 이하로 되었을 때에는 토양습도가 <TEX>$15\%$</TEX>일 때에 비해 병 발생이 현저히 감소되었다. This study was conducted to elucidate effect of environmental factors on the development of white rot. In order to identify the causal agents causing white rot of Allium crops, we compared DNA profiles of a representative isolate, Sclerotium cepivorum, introduced from foreign country with Korean isolates using UP-PCR. As a result, Sclerotium isolates forming round-shaped sclerotia were identified as Sclerotium cepivorum pertaining in UP-PCR b group and Sclerotium isolates farming anamorphic-shaped sclerotia presumed to be a novel species of Sclerotium based on DNA profiles of UP-PCR. There was a big difference in DNA band pattern between two species of Sclerotium isolated in Korea. Electron micrographs of scanning electron microscope and transmission electron microscope showed morphological differences in sclerotial surface structure and rind layers between two species of Sclerotium. There were more wrinkles and pore spaces on sclerotial surface of Sclerotium sp. forming anamorphic-shaped sclerotia than that of Sclerotium cepivorum forming round-shaped sclerotia. Both of two white rot pathogens grew well at the temperature range of <TEX>$10-25^{\circ}C$</TEX> with optimal temperature of <TEX>$20^{\circ}C$</TEX>. Sclerotia of the two pathogens were well formed at <TEX>$20^{\circ}C$</TEX> and well germinated at the temperature range of <TEX>$20-24^{\circ}C$</TEX>, Effect of pre-incubation of sclerotia on destruction of sclerotial dormancy of two pathogens was evaluated through storing sclerotia under different temperature condition. The sclerotia of the two pathogens showed an increased capacity to germinate on potato dextroise agar when the sclerotia were incubated for 7 days at <TEX>$10^{\circ}C$</TEX> after pre-treatment at <TEX>$35^{\circ}C$</TEX> for 7 days. At that time, germination rate of Sclerotium sp. and 5. cepivorum was <TEX>$100\%\;and\;70\%$</TEX>, respectively. Flooding period and treatment temperature had an effect on sclerotial survival rate of the two pathogens. As flooding period and treatment temperature increased, sclerotial germination rate of the two pathogens decreased. It was confirmed that soil humidity played an important role on development of white rot. It was the highest disease incidence of garlic white rot when garlic were sown at potted soils infested with the two pathogens and adjusted soil humidity to <TEX>$15\%$</TEX> (field moisture capacity, about -300 mb). As soil humidity increase or decrease based on <TEX>$15\%$</TEX> of soil humidity, disease incidence decreased move and more.

Flavor Precursor [S-alk(en)yl-L-cysteine sulfoxide] Concentration and Composition in Onion Plant Organs and Predictability of Field White Rot Reaction of Onions

Breeders have found field screening for white rot (Sclerotium cepivorum Berk.) resistance in onion (Allium cepa L.) to be unreliable since consistently moderate to high disease levels that significantly differentiate cultivars do not occur over field sites and years. The objective was to determine if differences in onion white rot resistance levels were associated with differing S-alk(en)yl-l-cysteine sulfoxide (ACSO) levels. A collection of onion breeding lines and hybrids were evaluated in field trials at six sites in 1999-2001. High performance liquid chromatography was used to analyze ACSOs in onion plant organs. Four main cysteine-sulfoxides exist in Allium L. species: methyl (MCSO), 2-propenyl (2-PeCSO), 1-propenyl (1-PeCSO), and propyl (PCSO). 1-PeCSO was predominant in onion leaves, bulbs, and roots. 2-PeCSO was found in trace amounts in onion leaves and roots. There was significantly more 2-PeCSO and total ACSO (roots only) and 1-PeCSO (roots and bulbs) in accessions that were more susceptible to white rot in the field trials. This is the first report of significant differences in ACSO contents among white rot susceptible and resistant onions. A covariance analysis was used to determine if the ACSO levels that significantly distinguished among accessions could predict field onion white rot reaction. 1-PeCSO from both roots and bulbs was the best predictor of field disease incidence in field sites that had low, moderate, and high disease levels. Although the ACSO concentrations were not assessed on an individual plant basis, breeders may be able to screen onions for resistance to S. cepivorum by comparing onion root or bulb 1-PeCSO levels based on the results from this research. White rot incidence in the field should be higher in those plants whose roots and bulbs have the highest levels of 1-PeCSO.

Suppression of Allium white rot (Sclerotium cepivorum) in different soils using vegetable wastes

Mixtures of wet vegetable wastes (Brassica, carrot or onion) and dry onion waste were composted at 50 °C for 7 days. The incorporation of the raw or composted vegetable waste mixtures into sandy loam, silt and peat soils reduced the viability of sclerotia of S. cepivorum in glasshouse pot bioassays. The reduction in viability was dependent on waste type, rate of incorporation, duration of exposure and soil type. Onion waste was the most effective waste type in reducing sclerotia viability in all three soils. The Brassica and carrot wastes were as effective as the onion waste in silt soil but less effective in sandy loam and peat soil. A 50% w/w incorporation rate of the wastes gave the largest reduction in viability, with an increase in reduction over time. Composted onion waste reduced sclerotia viability under glasshouse and field conditions although the effect was smaller in the field. Composted onion waste incorporated into soil at 50% w/w reduced the incidence of Allium white rot on onion seedlings in glasshouse pot tests. Incidence and control of the disease differed with soil type. The most consistent control was achieved in peat soil whereas no control was observed in silt soil. Incorporation of the waste 2 months prior to sowing or transplanting reduced seedling emergence in sandy loam soil and growth in all three soil types. The potential for field application of composted vegetable wastes as a sustainable method for control of Allium white rot and waste disposal is discussed.

Reaction of some sunflower accessions to Albugo tragopogonis and Sclerotinia sclerotiorum infections

Sunflower is attacked by several pathogens that reduce both the quantity and quality of harvested grains. It is necessary to keep evaluating the germplasm of this oil crop in order to detect new resistance sources to be included in breeding programs. Different accessions from North Central Regional Plant Introduction Office, Ames, IA, were evaluated for reaction to A. tragopogonis and S. sclerotiorum infections on levaes and capitula, respectively. Under our conditions, statistical analysis showed differential responses to white rust severity, white rot incidence and relative incubation period. Accessions were classified according to their level of resistance to each infection type. A general and favorable association between white rust and white rot performances was absent in the evaluated genetic material. The accession PI 343790 had the highest level of resistance to each quantified variable while the accessions Ames 3224, Ames 4040 and Ames 4050 had the lowest levels of resistance. Applicability of these results in sunflower genetic improvement for resistance to the studied diseases is discussed.

Armillaria Species Infesting Vineyards in Northwestern Spain

Twelve vineyards in northwestern Spain were studied to assess the incidence of white root rot during 1995 and 1997. In both years, diseased plant material was collected and the Armillaria species responsible was identified on the basis of compatibility testing. Subsequently, restriction fragment length polymorphism (RFLP) analysis of the intergenic spacer region of the nuclear ribosomal RNA gene cluster was used to identify Armillaria species in another 45 symptomatic samples submitted for diagnosis from this area. During 1995, 9 of the 12 vineyards showed white root rot, although in eight cases less than 2% of plants were affected; in the remaining vineyard 17% of plants were diseased. During 1997, 10 of the 12 vineyards were affected and three showed a marked increase in the number of plants with white root rot (to 43%, in the vineyard in which 17% were affected in 1995). The compatibility method detected Armillaria mellea in samples from 10 of the 12 vineyards, and Armillaria gallica in samples from two vineyards. RFLP–PCR analysis detected four restriction patterns corresponding to A. mellea, A. gallica and Armillaria cepistipes: patterns mel 1 (A. mellea, 71% of samples), mel 2 (A. mellea, 18%), gal 1 (A. gallica, 9%), and cep 1 (A. cepistipes, 2%, i.e. a single sample). This is the first report of A. gallica and A. cepistipes infecting Vitis spp. The presence of these two Armillaria species may be related to the fact that the vineyards from which they were isolated were located on cleared forestry sites.

Effect of Inoculum Concentration and Calcium Salts on Infection of Apple Fruit by Botryosphaeria dothidea.

The objective of this study was to determine the effects of calcium salts on growth of Botryosphaeria dothidea and incidence of white rot. The relative virulence of five B. dothidea isolates was determined using the apple cultivars Fuji, Gala, Golden Delicious, Liberty, and York. Cultivar and isolate differences in lesion diameter were significant. Cultivar differences occurred between Fuji, which was most susceptible, and Gala, which was least susceptible. Isolates PA-1 and PA-2 were most virulent. Isolate PA-4 was used at conidia concentrations of 1 × 104, 1 × 105, 1 × 106, and 1 × 107 conidia per ml on Golden Delicious fruit to test the effects of four inoculum concentrations on fruit infection by B. dothidea. Incidence of infection on detached, nonwounded fruit increased as inoculum concentration increased. The effects of four calcium salts on infection of wounded fruit by conidia were examined in field and laboratory experiments. In the field experiments, lesion size was slightly reduced on fruit treated with either calcium hydroxide or calcium silicate after wounding and prior to inoculation with conidia of B. dothidea, whereas lesions that developed at wounds treated with calcium chloride or calcium propionate were similar to those of the control. In the laboratory experiments, in several instances supplementation with calcium salts resulted in increased lesion diameter relative to the control. Two of five isolates tested showed increased percent germination with all four calcium salts, and one isolate showed increased germination in the presence of two of the four calcium salts. Germ tube elongation was not affected by calcium salts for four out of five isolates tested. There was significant variation among isolates and calcium salts on the growth of B. dothidea in liquid culture. Calcium chloride and calcium hydroxide enhanced the growth of three isolates and had no effect on the other three isolates. Calcium propionate inhibited the growth of four isolates and had no effect on the other two isolates. Calcium silicate inhibited the growth of one isolate and had no effect on the other five isolates.

2001년 농작물 병해 발생개황

2001년 기상의 특징은 3월부터 5월까지 계속된 극심한 가뭄과 생육기간 내내 계속된 고온현상 그리고 별다른 태풍의 내습 없이 9, 10월 수확기 맑은날의 지속으로 요약할 수 있다. 벼는 순조로운 기상 때문에 잎, 이삭도열병, 세균성벼알마름병, 흰잎마름병, 잎집무늬마름병의 발생이 예년에 비해 경미하였으나, 감비추진 정책에 의해 생육후기 깨씨무늬병이 발생하여 전국적으로 문제시되었으며 그동안 발생이 적었던 줄무늬잎마름병이 경기, 충청, 호남 서해안지역을 중심으로 많이 발생하였다. 고추는 생육기 비가 많이 왔던 전남북 지역에서 역병 발생이 심하였으며 토마토와 오이는 대부분 예년에 비해 병발생이 적었다. 수박의 경우는 꽃자리 부분이 썩는 푸른곰팡이병이 전국적으로 발생하였으며 CGMMV는 전년에 비해 상당폭 발생면적이 감소하였고 노지재배의 경우 탄저병 발생이 예년에 비해 심하였다. 참외와 딸기도 전년에 비하여 병발생이 경미하였으며 예년에 발생이 많았던 참외의 급성위조증상도 발생이 대폭 감소하였다. 마늘·양파의 흑색썩음균핵병은 봄철의 가뭄과 고온현상으로 병발생의 전년의 절반수준으로 감소하였다. 감자의 풋마름병은 발병포장이 증가하는 경향이었으며 고구마의 덩굴쪼김병도 발생이 감소하였다. 사과의 경우 전반적으로 병 발생이 예년에 비해 경미하였으며 배는 흰가루병이 많이 발생하였다. 맥류의 붉은곰팡이병은 예년처럼 거기 발생이 없었다. Climate in the year of 2001 could be summarized as severe drought from March to May, unusually high temperature in whole plant growth periods and clear weather condition especially in harvesting time of September and October without any typoons. In rice, major diseases such as leaf and panicle blast, bacterial blight, sheath blight and bacterial grain rot developed little due to unfavorable weather conditions, however, brown spot occurred severely due partly to the reduced use of N-fertilizer, Rice stripe virus infection was unusually high mainly in the west coast areas with four times more diseaseD area campared to the previous year, In pepper phytophthora blight was extremely severe in Cheonnam and Cheonbuk provinces, where had frequent rainfalls during growing period. Incidence of major diseases of tomato and cucumber in 2001 was relatively mild. In watermelon, penicillium fruit rot, one of the peculiar disease, spread over major production areas, whereas CGMMV, usually severe in every years was much reduced. Watermelon plants growing in open-fields were more severely diseased than those in plastic houses. Major diseases of chinese melon and strawberry occurred slightly and in particular, sudden wilt syndrome of chinese melon which was severe in 2000 showed mild infections in 2001. Incidence of white rot of garlic and onion was much lower unlike other years due mainly to spring drought and high temperature in the growing period. Infected area of potato bacterial wilt tended to increase in 2001 while fusarium wilt of sweetpotato was decreased. Apple diseases were generally mild, but powdery mildew of pear increased sharply. Barley scab was not severe as seen in other years.

Use of diallyl disulphide for the commercial control of &lt;i&gt;Sclerotium cepivorum&lt;/i&gt;

Soil treatment with diallyl disulphide (DADS) for the control of Allium white rot (Sclerotium cepivorum Berk) was studied in two trials under commercial growing conditions In the 19961998 trial two applications of DADS gave a 79 increase in yield when compared with the untreated control; the addition of three tebuconazole applications gave no extra yield One application of DADS gave a 33 increase in yield In the 19982000 trial various DADS application rates were tested All DADS treatments resulted in a large reduction in Allium white rot incidence compared with the untreated control Application of DADS gave a 57 increase in yield relative to the untreated control