Morphological and pathogenic characterization of Pestalotiopsis spp. pathogen of hazelnut in Serbia

Hazelnut (Corylus avellana L.) is an economically very important fruit species cultivated in many countries. The world's largest producer and exporter of hazelnuts is Turkey. In Serbia, compared to other types of fruit, hazelnuts are grown on significantly smaller areas. In the last decade, hazelnut has become more interesting for the producers and there is a growing trend of increase of areas under this crop. Hazelnut is the host of numerous pathogens and pests that can cause significant economic damage in orchards. To date, there has been no comprehensive research on the causes of hazelnut diseases in Serbia, and the goal of our work was to determine the causes of some fungal diseases. In the period from 2017 to 2020, samples of hazelnut leaves and branches with symptoms of necrotic spotting were collected from a large number of plantations in Serbia. A large number of isolates were isolated from the collected samples for further determination. Based on the morphological and pathogenic properties of the isolates, the presence of phytopathogenic fungi from the genus Pestalotiopsis was determined.

First Report of Tomato spotted wilt virus in Hosta in Florida

In spring 2003, symptoms similar to thrips-vectored spotted wilt disease caused by Tomato spotted wilt virus (TSWV) were observed on outdoor-grown hosta in Florida. Symptoms observed included leaf necrosis and stunting, chlorotic and necrotic spotting, and distinctive ring patterns. This is the first report of TSWV on hosta in Florida. Accepted for publication 29 September 2003. Published 24 October 2003.

The Role of Ethylene in the Development of Constant-light Injury of Potato and Tomato

The role of tehylene in the development of constant-light injury of potato (Solanum tuberosum L.) and tomato (Lycopersicon esculentum Mill.) was investigated. In one study, silver thiosulfate (STS) was applied to the foliage of four potato cultivars growing under constant light. Leaf area and shoot dry mass of `Kennebec' and `Superior', cultivars normally injured by constant light, were greater (P<0.05) than those of control plantsgiven foliar applications of distilled water. Examination of STS-treated `Kennebec' leaflets revealed significantly less injury (necrotic spotting and reduced starch content) than the water-treated controls. `Norland' and `Denali', cultivars tolerant of constant light, exhibited no differences in growth between treatments. In a second study, injury (necrotic spotting and reduced starch content) was induced in leaflets of `Denali' when exposed to spray applications of 0.5 mmol·L-1 ethephon or air containing 0.5 to 0.8 μL·L-1 ethylene. In a third study, three genotypes of `Ailsa Craig' tomato were grown under constant light. Leaves of the normal `Ailsa Craig' exhibited epinasty, reduced chlorophyll concentration, and reduced starch content. Leaves of a mutant `Ailsa Craig', containing the Never ripe mutation, did not exhibit epinasty but exhibited the same amount of reduced chlorophyll concentration and starch content as normal plants. Leaves of a transgenic `Ailsa Craig', containing an antisense gene of 1-aminocyclopropane 1-carboxylate (ACC) oxidase, were epinastic, but chlorophyll concentration and starch content were greater than in leaves of normal and mutant plants. These results suggest that transgenic plants were more tolerant of constant light than the other genotypes. Evidence from these studies indicates that ethylene, combined with constant light, has an important role in the development of constant-light injury.

Size of Tuber Propagule Influences Injury of `Kennebec' Potato Plants by Constant Light

Chlorosis and necrotic spotting develop on the foliage of particular cultivars of potato (Solanum tuberosum L.) when grown under constant light. `Kennebec', a cultivar severely injured by constant light when propagated from tissue-cultured plantlets, also was injured when plants were propagated from small tuber pieces (≈1 g). However, plants did not develop injury when propagated from large tuber pieces (≈100 g). Plants from large tuber pieces grew more rapidly than plants from small tuber pieces. The role of plant vigor and carbohydrate translocation in controlling injury development is discussed.

125 THE ROLE OF ETHYLENE IN THE DEVELOPMENT OF CONSTANT-LIGHT INJURY OF POTATO

Chlorosis and necrotic spotting develop on expanding leaves of particular cultivars of potato (Solanum tuberosum L.) when grown under constant light and temperature conditions. Plantlets of a constant-light sensitive cultivar, Kennebec, were planted into peat:vermiculite and established at 18C for 10 d under a 12 h light: 12 h dark photoperiod. Plants were then exposed to constant light and sprayed with 1 ml of either 0.5 mM silver thiosulfate (STS), an ethylene-action inhibitor, or water (as a control) every 2 days. Specific `target' leaflets, 5-10 mm in length at the beginning of the constant-light period, were harvested on days 5-9 of constant light, during injury development, and placed in bags made of Teflon film for IO-15 minutes to collect ethylene. Ethylene release and necrotic spotting increased as days of constant light increased for both water and STS-treated leaves, though STS-treated leaves produced slightly less ethylene and significantly less necrotic spotting than water-treated leaves. Ethylene release was correlated with extent of necrotic spotting. STS-treated plants exhibited greater dry weight and leaf area then water-treated plants. The results indicate that ethylene is not only produced by injured leaf tissue but, in addition, that ethylene may have a role in the development of constant-light injury symptoms.

A GENETICALLY-CONTROLLED NECROTIC SPOTTING OF CORN LEAVES

Corn plants of several cultivars were found in the field in 1972 and 1973 with a prominent pattern of small whitish necrotic spots on their leaves. No organisms could be isolated from the lesions. They start as water-soaked spots, and certain environmental conditions favor their appearance. The condition was shown to be seed-transmitted. Self-pollinating affected plants and cross-pollinations between affected and healthy plants resulted in genetically significant ratios of affected and healthy plants which supported the hypothesis that the condition is controlled by a single dominant gene. It very closely resembles a genetically-controlled necrotic leaf spotting produced by Neuffer and Calvert with a mutagen acting on pollen grains.

Cercospora elaeidis. [Descriptions of Fungi and Bacteria].

A description is provided for Cercospora elaeidis. Information is included on the disease caused by the organism, its transmission, geographical distribution, and hosts. HOSTS: Elaeis guineensis. DISEASE: Freckle of oil palm. In the nursery areas of leaf infection show as groups of dull brown spots (each rarely exceeding 0.5 mm diam.); the spots coalesce, necrosis spreads and the surrounding tissue becomes orange; heavily infected areas of the lamina die. The final development of the symptoms is particularly noticeable on the older leaves. Necrotic spotting also occurs on field palms and it is usually most severe on the older fronds. The small brown spots have a small water-soaked halo; both the spots and halo (becoming yellow and then orange) enlarge; fully developed spots are round to oval, 3-4 mm diam. with the halo c. 10 × 4 mm; spots may coalesce and parts of the lamina become desiccated. GEOGRAPHICAL DISTRIBUTION: Central, E. and W. Africa (CMI Map 487, ed. 1, 1972). There is a later record from Australia (NT) on Carpentaria acuminata. A record from Surinam is considered doubtful (51, 4761). TRANSMISSION: No studies reported.

Nonspecificity of the necrosis-inducing toxin of Sclerotium bataticola

Sclerotium bataticola produces a translocatable toxin which induces necrotic spotting in sunflower leaves. The toxin is not host specific, and does not induce symptoms on all susceptible host species. Virulence of four isolates of S. bataticola is not correlated with their toxin production in culture.

Alternaria padwickii. [Descriptions of Fungi and Bacteria].

A description is provided for Alternaria padwickii. Information is included on the disease caused by the organism, its transmission, geographical distribution, and hosts. HOSTS: Oryza sativa. DISEASE: Stackburn, seedling blight and leaf spot of rice (Oryza sativa). Necrotic spotting on the roots and coleoptile leads to death of seedlings. Leaf spots are circular or oval, up to 1 cm diam., with a dark margin; the centre becomes pale and bears the black sclerotia. Spotting occurs on the glumes, the kernels are invaded and become discoloured and shrivelled. Sclerotia are formed in all infected areas (27: 447). GEOGRAPHICAL DISTRIBUTION: Widespread in S.E. Asia and parts of Oceania but not reported from Australia; it also occurs in Egypt, Malagasy Republic, Nigeria and Surinam (CMI Map 314, ed. 3, 1972). TRANSMISSION: By seed, up to 79% infection of seed samples has been found (25: 182). The pathogen probably survives between crops on the straw.

Mechanisms of pathogenesis in Sclerotium bataticola on sunflowers. 1. Production and translocation of a necrosis-inducing toxin

Necrotic spotting of leaves is an early symptom of attack by Sclerotium bataticola on sunflowers. Spots appear after invasion of vascular tissues by the pathogen, which does not spread appreciably from the point of inoculation.Inoculation of one stem of plants split apically to give twin stems on one root system resulted in necrotic spotting of leaves first on the inoculated, and later on the uninoculated stem. Introducing cell-free filtrates of cultures of S. bataticola into sunflower plants or detached leaves resulted in production of the same type of necrotic spots. Introduction of eosin dye, which is translocated in the vascular system, into whole plants and detached leaves produced patterns of coloration similar to the patterns of necrotic spotting. The necrosis may be attributed to a translocatable toxin produced by the fungus.It is indicated that the toxin is neither an enzyme nor a protein. It has not been eluted after adsorption by activated carbon.