Fruit Spot Disease Research Articles

Occurrence of a Fruit Spot Disease of Pear Caused by Septoria pyricola in Tyrnavos Larissa, Northern Greece

Pear tree (Pyrus communis) is an important crop in Greece. In 2012, fruits of the pear cv. Kontoula were observed in commercial fields located in Tirnavos, Prefecture of Larrisa, Greece, with symptoms of well-defined brown angular margins and their grayish white centers in which a few pycnidia (about 180 × 150 μm) were produced within the spots. Pycnidia were dark, separate, and globe-shaped with an ostiole (opening at the apex) from which conidia (about 40 to 60 × 3 μm) were extruded, and erupted through the surface of the infected tissue. Conidia were produced on short conidiophores. They were clear, narrowly elongated to filiform, and several-celled. The pathogen was isolated on acidified-PDA (2.5 ml 85% lactic acid per liter of nutrient medium) and incubated at 23°C for 7 days. The pathogen was identified as Septoria pyricola Desm. based on morphological characteristics. Koch's postulates were completed in the laboratory by placing a 40-μl drop of suspension (4 × 105 conidia ml-1 of water) on a wounded area of healthy fruits of cv. Kontoula. Fruits were surface sterilized with dipping in 0.1% chlorine solution, allowed to dry in a laminar flow hood. There were 15 inoculated and 15 control fruits (similarly inoculated with sterile distilled water) in a randomized design. Fruits were covered with perforated polythene bags to maintain a high humidity necessary for infection and these bags were removed 48 h after inoculation and maintained at room temperature (23 ± 2°C). Lesion development was recorded daily for each fruit. Koch's postulates were satisfied after re-isolating the fungus from inoculated fruit that developed symptoms similar to those observed on fruits collected from fields. Symptoms of this disease were found in all pear orchards cultivating the cv. Kontoula located in Tyrnavos (a municipality in the Prefecture of Larissa). Symptoms of septoria leaf spot were also observed in the above pear orchards. In contrast, no symptom of septoria fruit spot and septoria leaf spot was observed in apple orchards of the above regions. To our knowledge, this is the first report of the occurrence of S. pyricola as causal agent of fruit spot of pears in Greece. Fruit spotting is relatively uncommon; nevertheless, Sivanesan (3) gives two reports of conidia infecting pear fruits from Italy and South Africa (1,2).

Pseudocercospora leaf and fruit spot disease of citrus: Achievements and challenges in the citrus industry: A review

Citruses are the worlds’ second fruit crops by volume next to banana. It is one of the most important commodity in tropical Africa as source of foreign currency, raw material for agro-industries and source of employment. The production and productivity of citrus in tropical Africa including Ethiopia are critically threatened by a number of diseases. Among others, pseudocercospora leaf and fruit spot of citrus caused by a fungus Pseudocercospora angolensis is the most destructive disease of citrus. Literature reviews have been made by searching the available information on leaf and fruit spot of citrus. Journal articles, research papers, workshop proceedings, Thesis research, manuals, and quarantine regulations were among the information sources of the review. The disease is widespread in 22 African countries including Ethiopia with a single report around Yemen in the Arabian Peninsula. Scattered research efforts have been made by different researchers in Africa mainly dealing with its geographic distribution, biology, and management practices. Fungicides, plant extracts/essential oils, and host resistance are among the research efforts made for the control of P. angolensis. Even though the disease is not yet reported to the rest of the world, it becomes a serious concern as an important quarantine pest thereby critically affecting the world trade and germplasm exchange of the citrus industry. Therefore, the purpose of this paper is to compile the scattered information on various aspects of leaf and fruit spot of citrus mainly to avail the information for researchers, development workers and policy people. Moreover, this review will suggest future research and development direction towards better understanding and sustainable management practices of the disease.

Asperisporium and Pantospora (Mycosphaerellaceae): epitypifications and phylogenetic placement.

The species-rich family Mycosphaerellaceae contains considerable morphological diversity and includes numerous anamorphic genera, many of which are economically important plant pathogens. Recent revisions and phylogenetic research have resulted in taxonomic instability. Ameliorating this problem requires phylogenetic placement of type species of key genera. We present an examination of the type species of the anamorphic Asperisporium and Pantospora. Cultures isolated from recent port interceptions were studied and described, and morphological studies were made of historical and new herbarium specimens. DNA sequence data from the ITS region and nLSU were generated from these type species, analysed phylogenetically, placed into an evolutionary context within Mycosphaerellaceae, and compared to existing phylogenies. Epitype specimens associated with living cultures and DNA sequence data are designated herein. Asperisporium caricae, the type of Asperisporium and cause of a leaf and fruit spot disease of papaya, is closely related to several species of Passalora including P. brachycarpa. The status of Asperisporium as a potential generic synonym of Passalora remains unclear. The monotypic genus Pantospora, typified by the synnematous Pantospora guazumae, is not included in Pseudocercospora sensu stricto or sensu lato. Rather, it represents a distinct lineage in the Mycosphaerellaceae in an unresolved position near Mycosphaerella microsora.

Occurrence of a Fruit Spot Disease of Pomegranates Caused by Colletotrichum gloeosporiodes in the Prefecture of Komotini, Greece.

Pomegranate (Punica granatum L.) is an important crop in Greece. In 2010, fruits of the pomegranate cv. Wonderful, in commercial fields located in the Prefecture of Komotini in eastern Greece, were observed to have symptoms of distinct dark brown spots. The waxy acervuli observed in infected tissue were subepidermal, typically with setae and simple, short, erect conidiophores. Conidia were hyaline, one celled, ovoid to oblong, slightly curved or dumbbell shaped, and 10 to 15 μm long and 5 to 7 μm wide. The pathogen was isolated on acidified potato dextrose agar (PDA) (2.5 ml of 85% lactic acid per liter of nutrient medium) and incubated at 23°C for 7 days. The pathogen was identified as Colletotrichum gloeosporiodes (Penz) Sacc. on the basis of morphological characteristics and internal transcribed spacer (ITS) sequence (100% identity to AJ301912, C. gloeosporioides species complex) (3) by CBS Fungal Biodiversity Centre, Identification Service, Utrecht, the Netherlands, (CG-1 isolate deposited in CBS Collection; Accession No. CBS 129372). Koch's postulates were completed in the laboratory by placing a 40-μl drop of suspension (4 × 105 conidia ml-1 of water) on a wounded area of healthy fruits of cv. Wonderful. Fruits were surface sterilized by dipping in 0.1% chlorine solution and allowed to dry in a laminar flow hood. There were 15 inoculated and 15 control fruits (similarly sprayed with sterile distilled water) in a randomized design. Fruits were covered with perforated polythene bags to maintain a high humidity necessary for infection that were removed 48 h after inoculation and the fruits were maintained at room temperature (23 ± 2°C). Lesion development was recorded daily for each fruit. Koch's postulates were satisfied after reisolating the fungus from inoculated fruit that developed symptoms similar to those observed on fruits collected from fields. To our knowledge, this is the first report of the occurrence of C. gloeosporioides as a causal agent of fruit spot of pomegranates in Greece. Fruit spots caused by C. gloeosporioides have been reported in pomegranate fields of other countries around the world (1,2).

Altitude, tree species and soil type are the main factors influencing the severity of Phaeoramularia leaf and fruit spot disease of citrus in the humid zones of Cameroon

In Cameroon and most countries of tropical Africa where Phaeoramularia leaf and fruit spot disease of citrus is reported, a total yield loss of 50–100% is common. For effective control of this disease, it is imperative to understand how it originates, and which factors contribute to its development. To this end, the environmental and biological characteristics of each tree from 39 sites located in 13 citrus production basins in the humid zones of Cameroon were collected by means of a survey. Information was collected by interviewing heads of households, and by visual inspection of trees and their environment. The independent variable was severity of the disease while the dependent variables were environmental and biological characteristics. Climatic characteristics varied from one basin to another. The 13 citrus production basins were regrouped in five categories based on disease severity. Altitude, tree species and soil type were the main factors influencing the disease severity. Thus the higher is the altitude, the more important is the disease severity. Also, disease severity increased with increasing number of grape fruit, orange and pummelo trees. However, disease severity was lower on trees growing on volcanic soils as compared with the other soil types. Further analysis of these factors could lead to the development of a risk assessment model for Phaeoramularia leaf and fruit spot of citrus.

Comparison of Molecular Procedures for Detection and Identification of Guignardia citricarpa and G. mangiferae.

Citrus black spot, caused by Guignardia citricarpa, is a serious fruit spot disease and is widely distributed in Asia, southern Africa, and South America, but does not occur in North America or the Mediterranean region. A nonpathogenic species, G. mangiferae, is cosmopolitan with a wide host range and can colonize citrus fruit and leaves saprophytically. Detection and identification of Guignardia spp. on citrus fruit is necessary for epidemiological, management, and regulatory purposes. In this study, we compared published and unpublished polymerase chain reaction primer sets for their specificity and sensitivity in the detection and differentiation of the two Guignardia spp. All primers evaluated successfully identified the two species using purified DNA from fungal cultures or mycelia as source materials. However, some primer sets were not highly effective in detecting G. citricarpa when DNA was extracted directly from single characteristic black spot lesions on fruit. Thus, new primer pairs for both species were designed from the internal transcribed spacer region that were highly sensitive and specific for detection of G. citricarpa using DNA recovered from single lesions on fruit by a rapid DNA extraction procedure.

Distribution and management ofPhaeoramularialeaf and fruit spot disease of citrus in Ethiopia

Introduction. Citrus is the most important fruit crop widely grown by small-scale and commercial farms in Ethiopia. However, productivity of citrus in many parts of the country is threatened by Phaeoramularia leaf and fruit spot disease caused by Phaeoramularia angolensis. Surveys and field experiments were conducted to map the geographical distribution, and to study the efficacy of different fungicides for the control of this disease. Materials and methods. Surveys were conducted in the major citrus-growing areas (south, south-west and north-west) of Ethiopia. Random sampling techniques were used for sample collection. The efficacy of different fungicides against P. angolensis was studied under a hot-spot area, based on disease incidence and severity, and marketable fruit yield. Results and discussion. Phaeoramularia leaf and fruit spot disease of citrus has been widespread throughout the south, south-west, and north-west of Ethiopia, cau- sing complete crop failure. This disease was more severe in smallholder farmers' fields as compared with the commercial orchards. The severity of P. angolensis was varied between different citrus species and areas with different agro-ecologies. The south and south-west part of the country, cha- racterized by high and frequent rainfall with high humidity, were severely affected by the disease. Field application of Benlate, Score and Cuproxat significantly reduced the incidence and severity of the disease and, thereby, increased marketable fruit yield. Conclusion. Phaeoramularia leaf and fruit spot disease of citrus has become widespread in many parts of Ethiopia within a short period. Further investigation on P. angolensis biology and detailed epidemiological studies are mandatory to develop a model, and, thereby, to facilitate forecasting systems for effective and sus- tainable management of leaf and fruit spot disease of citrus in Ethiopia. Ethiopia / Citrus / plant diseases / blotches / Phaeoramularia angolensis / geographical distribution / disease control

Effect of Essential Oils from Citrus Varieties on in vitro Growth and Sporulation of Phaeoramularia angolensis Causing Citrus Leaf and Fruit Spot Disease

Citrus leaf and fruit spot disease caused by Phaeoramularia angolensis is a serious production constraint in tropical Africa. In previous studies, essential oils extracted from fruit peels of two tolerant varieties exhibited a strong antifungal activity in vitro against P. angolensis as compared to oils from susceptible ones. In order to investigate if the susceptibility of citrus varieties is associated with the antifungal activity of their essential oils, some 22 varieties of different susceptibility levels (tolerant, susceptible and highly susceptible) and belonging to different botanical groups were studied. Oils extracted from fruit peels were evaluated for their activity against radial growth and sporulation using the poisoned food technique. The optimal doses for growth inhibition and conidial reduction were 2500 and 1000 ppm, respectively. At these doses, radial growth and sporulation exceeded the untreated control respectively for four and nine varieties suggesting that oils from these varieties promote fungal development. In general, oils from the tolerant group were most effective in reducing radial growth irrespective of dose. The highly susceptible group ranked first in reducing sporulation at dose 1000 ppm (45.93%) while at higher doses of about 2000–2500 ppm, oils from the tolerant varieties could reduce sporulation up to 100%. The marked dose effect in reducing sporulation suggests that there may be different compounds acting with changing dose. Botanically, oils from pummelo (Citrus maxima, tolerant group), were best in reducing radial growth (>87% inhibition) while those from grapefruits (C. paradisi, highly susceptible group) were most effective in reducing sporulation (>64% reduction).

Control of Alternaria Spot Disease on Loquat (Eriobotrya japonica Lindl.) Using Detached Fruits and Leaf-disk Assay

Treatments with four types of new, slightly toxic and non-residual fungicides and two preparations of Trichoderma harzianum were applied against Alternaria alternata, causal organism of Alternaria leaf and fruit spot disease of loquat. Preventive and curative effects of the above-mentioned treatments were bioassessed by measuring lesion diameter of A. alternata and its sporulation density on detached loquat fruits and leaf discs. Results indicated that preventive and curative effects of the treatment with difenoconazole (Score®) and cyprodinil+flodioxonil (Switch®) applied at a rate of 0.35% (V/V) and 0.20% (W/V), respectively, significantly reduced the lesion diameter of A. alternata on treated fruits and leaf discs compared to the untreated control fruits and leaf discs. Also, application of the above-mentioned fungicides at the same rates completely inhibited the sporulation of A. alternata at preventive and curative treatment with Switch® and at curative treatment with Score® on treated leaf discs compared to the untreated control organs. Conidia of T. harzianum (strain Th2) formulated in invert emulsion and applied at a concentration of 1.3X108 conidia/ml of the preparation, significantly suppressed lesion diameter of A. alternata and its sporulation density on treated fruits compared to treatment with conidial suspension of T. harzianum in sterile distilled water, and the control (blank formulation of invert emulsion or sterile distilled water only). These results should be confirmed under field conditions before large scale application.

A New Storage Disease of Chillies (Capsicum annuum L.)

Chillies or Green peppers (Capsicum annuumL.) are extensively grown in this country during rainy and winter seasons. The crop brings good profit for the grower as it is widely used in green as well as in dried condition. A fruit spot disease of this valuable vegetable was noticed during the cold months of 1962 at Phule Market, Poona, on the sweet variety (which is usually bigger in size), stored in bamboo baskets and crates. On microscopical examination of such spots the fungus appeared to be a species of Helminthosporium. The pungent varieties of chilies such as‘Gauran’(long in size) and‘Dharwar round’wert; found to be free from infection. Affected fruits incubated in moist chambers gave abundant sporulation of the causal organism. Ripened and red chili-fruits were free from such infection in the markets. The present paper gives an account of the etiology of the disease, pathogen city and cultural behaviour of the fungus.