DESTROYER PATHOGEN OF POTATO ( SOLANUM TUBEROSUM ) IN GEORGIA

O. Shainidze*, Sh. Lamparadze, A. Murvanidze and J. Diasamidze.  Batumi Shota Rustaveli State University, Faculty of Technology, Department of Agroecology and Plant protection, Ninoshvili str. 35, Batumi, 6010 Georgia. ...................................................................................................................... Manuscript Info Abstract ......................... ........................................................................ Manuscript History


ISSN: 2320-5407
Int. J. Adv. Res. 4 (9), 235-247 236 Late blight was a major culprit in the 1840s European, the 1845 Irish and 1846 Highland potato famines. The organism can also infect tomatoes and some other members of the Solanaceae. In the world, this disease causes about $ 6 billion damage to crops each year (Chand, Sudeep, 2009;et al., 2011. Direct cash costs of efforts to control and production losses are estimated only Potata> $ 3 billion / year worldwide CIP, 1996). In this regard, at least, have a bad situation in Georgia. In the Georgian Republic under favorable cold and wet conditions and without any corresponding levels of regulation against the pathogen, P. infestans can lead to almost 100% reduction in crop yields; therefore, potatoes can not be controlled without frequent fungicide applications for the effective control of the disease.
Even now, more than 170 years after it was first associated with the potato late blight disease in Europe and in North America, P. infestans remains a major problem in agriculture and recalcitrant to low-input, stable disease suppression.
Despite the fact that considerable progress has been made in the understanding of its basic biology, ecology and pathogenicity (Coffey, Wilson, 1983;Bourke,1991;Andrivon, 1996 (Dowley et al., 1995), thousands of scientific articles and thousands of popular reports, as well as many historical processes (Turner, 2005); etc., P. infestans is still a serious problem in agriculture. In Georgia, a considerable amount of research has been devoted to date on various aspects of relations P. infestans potato (Kanchaveli, 1978I;Shainidze, , 2000Shainidze, , 2013and et al.). Here we look at the current state of the patogena.

Research objectives:-
The objectives of this study was to identify and determine the composition of pathogenic fungi that propagate in the Solanum tuberosum weight agrocenoses Georgia; among them to clarify and examine the most common potato destructor; to establish the scope of its development -the spread under favorable and enabling environment. In addition, the aim of this study was to evaluate the resistance of varieties of potatoes Phytophtora infestans in relation to the effectiveness and stable yields.

Materials and methods:-
The object of the study were different varieties of potato plants (Solanum tuberosum) and pathogenic fungi which inhabit agrocenoses weight Georgia. Materials were collected using well known methods (Bilai et al, 1982;Giants et al, 1980;Dudka et al, 1982;Foster et al., 2004). Routing and stationary methods were used to study the field of research. Symptoms such as rot, mummification, wilting, spotting, necrosis, mold, Gauls, ulcer, deformation, chlorosis, mosaic, etc., were recorded. The study upper and lower parts of infected plants were collected and labeled. The following procedures, such as off-site and laboratory treatment, collection of preserved plant specimens, assembly, storage, assessment of the infected plants have been carried out for processing the collected samples. We analyzed the distribution and development of disease. Identification of fungi was carried out using modern identification guides (Hawksworth, 1974;Khokhryakov et al, 1984;Watanabe, 2000).
Collections of the new species have been examined by standard light microscopy (Pereval, Carl Zeiss, Jena and Olympus, BX 50, Hamburg,Germany). The SEM micrographs have been prepared by means of a JSM-35 (Japan) SEM microscope. The specimens examined are deposited at HAL, KW and TGM (Holmgren et al., 1990). Collections were examined by standard light microscopy (Pass, Carl Zeiss, Jena, and Olympus, BX 50, Hamburg, Germany). SEM photomicrographs were prepared using DSM-35 (Japan) SEM microscope. Samples were deposited on Hal, KW and TGM (Holmgren et al., 1990).

Results and Discussion:-
A total of 50 species (including 13 species of virus and viroid, 5 -bacteria, 32 -the fungus) have been identified in Solanum tuberosum (Tabel 1), as a result of phytopathological and mycological studies carried out in different places (agrocenosis Georgia) in industrial regions. Among the total microbiota, late blight is one of the most devastating potato diseases Sometimes, during storage, infected tubers may be covered with different colored mycelia (Figure 1), which includes 11 species of fungi (Alternaria solani, Aspergillus Niger, Botritis cinerea,
Some are plant pathogens causing root and stem rot, vascular wilt or fruit rot. Other species cause storage rot and are important mycotoxin producers. Several species, notably Fusarium moniliforme, F. oxysporum, and F. solani, are recognized as being pathogenic to man and animals (Kriek, Kellerman and Marasas,1981;Kriek, Marasas and Thiel, 1981).
It should be noted that a wide range of microbiota tubers (Consortium, Association) marks the first time in Georgia (maybe all over the world).
Observations have shown that the formation of a consortium of home begins when the temperature reaches -20°C, and the optimum temperature is about 22 °C. High air humidity (90-95%) accelerates the formation of the consortium. Currently, research is ongoing to discover the initiator of the fungus, taking part in the creation of the consortium and to determine the relationship between the fungi involved in it. Common symptom of the disease is the "Leaf Blight", which is found everywhere.
Lesions on leaf blades can be extended to the shell sheet. Defeat increases in length and width, and may also have wavy edges.
Long-term monitoring showed that in Georgia potato rot is identified by black or brown lesions ( Figure 2) on the leaves and stems, which at first glance it may seem that small and watery or have chlorotic borders, but soon quickly expand and become necrotic.
Infected tubers occur when sporangia are washed from the leaves into the soil. Infections generally begin in tuber cracks, eyes or lenticels.

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In humid conditions, late blight produces sporangia and sporangiophores on the surface of infected tissue. This leads to a significant increase in white sporulation at the forefront of defeats on the abaxial (lower) surfaces of the leaves and stems (Figure 3).
Sporangiophores grow out of diseased tissue. Sporangia are released into the atmosphere for aerial dispersal during a drop in relative humidity, or they can be dispersed in water splashes. Indirect germination releases zoospores, which, after encystment and germination on host tissue, produce lesions visible after 2-4 days. It has been found that in humid areas (Ajara) Georgia sporangia are formed, when the relative humidity is 89%, and in mountainous areas -90-91%. Sporulation can occur from 3,5 -26,5°C, but the optimum range is 18-22°C. Sporangia germinate directly via a germ tube at 21-26°C. Below 18° C, sporangia produce 6 to 8 zoospores which require water for swimming.
Each zoospore is able to initiate an infection, which explains why the disease is more severe in cool, moist conditions.
After colonization leaf tissue Sporangiophores exit stomata thousands forming sporangia which can be moved by wind or rain, and eventually infect plants close or distant range. Almost similar findings were made by foreign researchers (Pristou and Gallegly, 1954;Gees and Hohl, 1988;Coffey and Wilson, 1983).

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Solanum tuberosum as a host, the asexual life cycle of P. infestans can be completed rapidly with production of massive numbers of sporangia that are readily dispersed-explaining why whole fields can be transformed from slightly diseased to nearly completely destroyed within just a few days.
Late blight struck the growing plants as a frost in summer. It spread faster than other dangerous diseases.
The leaves, stems and tubers are all susceptible (Figure 4), so that the potato late blight pathogen, certainly deserves the name Phytophthora, "plant destroyer." The test of 12 varieties of potatoes (Table 1)  Very high incidence of potato (100%) was observed in 2015 on Russian variety Nevsi and Picaso.
This year Warm days, and extended wet conditions with rain and fog led to a late blight epidemic, which in less than two weeks, destroyed all the potato.
It was found that every year the loss of potato late blight reached from 5 to 92 percent, depending on location, time of year, weather conditions and cultivars. Disease control:-Eco-friendly and economically sound tactics to suppress late blight is the immediate goal of many researchers and this objective is also an incentive for a wide range of fundamental research by many scientists. At present, the most reliable approach for integrated management, using an array of tactics, including planting healthy seed tubers, eliminating the source of the pathogen farm, using "resistant" varieties and fungicide application in response to a real need as determined by scouts or forecast.
The biological method used against Phytophtora infestans proved to be the most effective among the agro-technical, sanitaryhygienic, chemical and o ther types of controls. In particular, the antagonist fungus Trichoderma viride (Trichoderma lignorum) was used against pathogens. Soil was tilled with 4% of the suspension (400 gm of T. viride per 10 Lin 5 m 2 area) prior to planting the potatoes. In this case, the percentage of infection of plant was 7.2 % in a field. The biological efficiency was equal to 83.2. In the control variant, the percentage of infection of plant (without introducing the antagonist into it) was 92.3%. The experimental results have shown that the harvest and economic efficiency respectively are increasing, which were equal to 29.3% in a field.