Carrot ( Daucus carota L.) of the plant Alternaria disease (review)

. Nowadays, fungi-related illnesses are widespread in all nations that cultivate vegetables, which lowers output. Carrots are harmed by pathogenic fungus both during the growing season and while they are in storage, which reduces both the amount and quality of the crop. From this perspective, it is critical to investigate the bioecological characteristics of the fungus that cause illnesses in carrots and to carry out research on the creation of effective and ecologically friendly countermeasures. Alternaria diseases Daucus carota L. is one of the most common diseases of the carrot plant and often has a significant impact on the yield of carrots. Carrot Alternaria several fungi belonging to the genus are harmful and the symptoms of the disease are manifested in the form of leaf spotting, black crown and black rot of roots. Protecting carrots from these diseases is one of the main tasks facing field experts. Therefore, this research intends to make a summary of literature data on Alternaria leaf spotting, root rot and black rot of young seedlings caused by Alternaria fungi. The results showed that the most stable yielding carrot hybrid was F1 Santa Cruz taken as the control variant, which showed the highest yield, accounted for 113.7, however, its resistance to alternariosis was slightly lower, which was 2.3. In this regard, it is recommended to continue research on other new hybrids.


Introduction
Most of the world's agricultural crops are vegetable crops. According to FAO data, carrots and turnips are grown on an average of 1,491,529.0 hectares in the world, and an average of 41,753,738.46 tons are harvested from them [1][2][3][4][5]. Today, fungal diseases are common in all vegetable-growing countries of the world, causing a decrease in productivity in vegetable cultivation. Pathogenic fungi damage carrots during the growing season and during storage, causing a decrease in the quantity and quality of the harvest [4][5][6][7][8][9]. From this point of view, it is important to study the bioecological characteristics of the fungi that cause diseases in carrots and to conduct scientific research on the development of environmentally friendly and effective measures against it.
Clearly, carrots are damaged by various phytopathogens both during the growing season and during storage in warehouses. Diseases affecting fruits during storage are highly harmful and can significantly reduce the number of stored products [10,[12][13][14][15][16][17]. According to experts, the number of losses is on average 25-30% of the cultivated crop, and in some years, it can exceed 40%. However, these losses are caused by phytopathogenic microorganisms that are well adapted to spread and develop in cold storage facilities at 0-1 °C and 90-95% relative humidity [11][12][13][14]. These pathogens often develop together, which increases the pathological process of root rot, causing mixed (wet and dry) rot [1,5]. Furthermore, fungi are one of the main pathogens of plant diseases. Pathogenic fungi use a variety of methods to reproduce, spread, and cause disease in plants. Some fungi kill the host plant and feed on dead matter (necrotrophs), while others thrive on living tissue (biotrophs). Fungi use a variety of virulence factors to reproduce and spread within the host plant. Depending on the method of infection, virulence factors perform different functions. While almost all pathogens disrupt the primary defenses of plants, necrotrophs produce toxins to kill plant tissues [22][23][24][25].
According to the literature data, it became clear that most of the celery related plants (carrot, celery, parsley, spinach and chives) are less susceptible to disease in the first year of cultivation, but can be severely damaged by various pathogens during winter storage and in the second year for seed production [6][7][8][9][10]. Alternaria disease is considered one of the most common diseases of carrots, and the disease is caused by Alternaria caused by several fungi belonging to the genus. Clearly, it is possible to observe the manifestations of Alternaria in carrots, such as leaf spotting, black spot and black rot of roots. Alternaria belongs to the genus Alternaria and belongs to the Dematiaceae family.
The life cycle of these species is saprophytic, but several species are pathogenic for a specific host plant range [13,24]. Alternaria leaf spotting: alternaria rot is also observed in carrots, the disease is caused by the Alternaria radicina Meier fungus [17][18][19][20][21][22][23]. The disease is widespread in all areas where carrots are grown, and affects the plant at different ages and during storage of roots. The pathogen can cause complete death of young plants from germination to the 3-4 leaf phase. In this case, alternariosis manifests itself as a "black thigh". In the later stages of development, it causes the leaves to dry up and die, as a result of which the yield of root crops is sharply reduced. The greatest damage is observed during storage of root crops. The disease affects the quantity, quality and seed loss of the crop. By spring, with a strong spread of the disease, stored seeds can rot up to 100% [4][5][6][7][8].
Alternaria radicina (Meier et al.) Neerg. (syn. Stemphylium radicinum) is one of the common pathogens of carrots in Europe and North America. The fungus is known to cause black root rot of carrots during the growing season and during storage, hence its common name "black rot". At the same time, the pathogen is known to cause carrot leaf spotting, seed germination, and root rot. The fungus primarily infects carrot roots and causes dry, black, necrotic spots on carrot roots and roots. As a result of the expansion and fusion of these spots, the root of the carrot can completely rot [17][18][19][20]. This research intended to comprehensively review characteristics of Carrot (Daucus carota L.) of the plant Alternaria disease towards getting better insight about type of disease and its impact on lifespan of carrot (Daucus carota L.)

Methods and materials
In fact, the species A.radicina is closely related to A. petroselini (Neerg.) Simmons and A. carotiincultae Simmons. Therefore, this and other species Alternaria sect. Radicina is generalized to A. radicina conidia, which have a short elliptical or ovoid shape (Fig. 1). Conidiophores were simple or branched, forming single apical conidia or, rarely, single conidia balls [13][14][15][16][17][18][19]. Alternaria, which is fungi of the phylum Fungi, are a morphologically diverse collection of taxa that can be found in almost all ecosystems worldwide. The number of species varies from about 150 to several hundred [19][20][21]. Most species are saprotrophic and can be associated with different substrates or plant debris from different sources. In addition, many of these species are serious plant pathogens that cause significant yield losses in agriculture every year [15][16][17][18][19][20][21][22][23][24]. In addition, many species of this genus are highly pathogenic during postharvest and storage of agricultural products, and they contribute significantly to the annual loss of agricultural products [15]. If the fungus spreads along with the seed, it can usually damage the seedlings and cause them to rot or cause damage to the stem. But often, especially during heavy dew and frequent rains, abundant spores are formed and damage many cultivated plants and weeds. The germinating spores penetrate the plant tissue directly or through injuries and form new conidia that are soon dispersed by wind, rain [7,24].
Leaf spot disease was first reported in Germany in 1855. At that time, the causative agent of the disease was Sporidesmium exitiosum Kühn v. dauci Kühn. described as a fungus. Over the next 90 years, the disease did not play a significant role in carrot cultivation in Europe. In the USA, the disease was first recorded in Louisiana in 1890 and the causative agent was identified as Macrosporium carotae Ellis & Langlois [5,10]. Obviously, the disease is the most economically important carrot disease in the world. As a result of the Alternaria epidemic, the complete loss of the crop was recorded in some farms [5,9]. The disease is due to Alternaria dauci caused by fungus. This fungus damage to photosynthetic tissue in plant leaves and weakening or death of leaves causing severe damage. Clearly, 40-60% of the crop, sometimes up to 100%, is affected by the disease can be lost [8,16]. Furthermore, the disease affects the carrot plant in the first and second years of carrot cultivation. This disease reduces the storage quality of carrot roots during storage in warehouses, causes a decrease in the number of seeds and a decrease in germination in carrots planted for seed. Depending on weather conditions and the phytosanitary status of crops, the spread of the disease can reach 70-80%, and the yield of root crops can decrease to 35-50% [2,5,6]. In fact, a favorable temperature range for the development of the disease is 20-28 °C, and the optimum is 24 °C [11,25].

Results and discussion
It was observed that A. radicina was the formation of yellow pigments in acidic potatodextrose (APDA) as a result of the production of a toxin radical (Fig. 2) . A. radicina was also able to produce small amounts of toxic metabolites radicinol and epi-radicinol. Radicin produced by A. radicina was associated with the pathogenicity of A. radicina in carrots and can be detected in naturally infected carrots [13,23]. In wet weather, especially in autumn, the affected leaves were rotted and covered with a weak greenish-brown mold. During storage, dry spots formed on the side or top of the tubers. When the rhizome was cut, the affected tissue turned black, which was in sharp contrast to the healthy rhizome (Fig. 2).
Sources of infection were infected seeds, plant debris, infected root crops planted for seed and soil. Clearly, the pathogen can be stored in the soil for up to 8 years. Wet, warm weather favors development of the disease in the field. It was found that in years with dry and cold autumn, the harmfulness of black rot was reduced [4][5][6][7]. Noteworthy, there are various ways to protect carrots from Alternaria, but none of them may be effective, especially when the disease is strongly developed. Agronomic practices such as seed and foliar treatments, crop rotation, and post-harvest disposal of crop residues help control the disease. Fields were heavily sprayed with fungicides, but this approach was expensive and not always effective [16]. The development of genetic control of carrot diseases offers a promising alternative method. Breeders have developed carrot varieties with partial resistance to carrot leaf spot, but although varying degrees of disease control have been achieved, complete resistance to this disease has not been observed [16][17][18][19][20][21][22].
It was reported that chemical protection of crops and cleaning of seeds with hot water were methods implemented in practice, but sometimes these methods were ineffective [13,18]. Clearly, increasing the resistance of carrot varieties through selection was the most effective way to control the fungus A. radicina. All approaches to increase active resistance are based on the introduction of the pathogen into plants or plant tissues. An elementary requirement is the relevance and pathogenicity of the pathogen isolates used. Therefore, it is necessary to isolate current authentic strains for repeated surveillance of pathogens in the field and for seeding approaches [20][21][22][23][24][25]. In addition, isolates must be taxonomically welldescribed, genetically identical, which can be done using monoconidial lines, and must show sufficient virulence. In order to potentially assess plant resistance, it has become clear that the obtained isolates need to be characterized not only by cultural, morphological or molecular characters, but also by pathogenicity and aggressiveness [13].
Alternaria disease is primarily combated by chemical means with resistant varieties, healthy seeds, and appropriate fungicides. Adequate nitrogen fertilization usually reduces the rate of development of Alternaria disease. Crop rotation, removal and burning of infested plant debris, and weed control can help reduce infestation when susceptible crops are planted the following year [7]. Regarding the determination of the resistance of carrot hybrid varieties to alternariosis, information was provided by Yu. Zemskova. It was found that the most stable yielding carrot hybrid was F1 Santa Cruz taken as the control variant, which showed the highest yield, accounted for 113.7, however, its resistance to alternariosis was slightly lower, which was 2.3. In this regard, it is recommended to continue research on other new hybrids ( Table 1). The lowest damage score was observed in F1 Abaco (1.8), followed by F1 Baltimore and F1 Cardiff, of which were 2.0 and 2.1, respectively. Noteworthy, the highest damage score was reported in F1 Cordoba, accounted for 2.4. Besides, one of the most important indicators was productivity, and accordingly, F1 Cardiff was dominant one with 78% among others. However, the lowest productivity was observed in F1 Abaco, which had 72% (Table 1). It was reported that for good storage of carrot roots, storage in sand was widely used, which protects the roots from moisture evaporation, wilting and damage. Fertilization with chalk (200-250 g/10 kg) created a slightly alkaline environment on the surface of root crops and prevents the development of phytopathogenic fungi. It was found that the development of diseases can be stopped by increasing carbon dioxide in the environment by 3-4%, includes cleaning and disinfection of warehouses for storage of root crops. Whitening the walls and ceilings ( 2-3 kg of freshly slaked lime with the addition of 200-300 g of copper sulfate per 10 liters of water with a working solution of 0.5 l/m 2 ). It was identified that the optimum temperature regimes were ranged in between 0-1 °C, meanwhile the high air humidity was around 90-95%, which should not be violated during the entire storage period [1].

Conclusions
Alternaria diseases are considered the most dangerous diseases of carrots and can damage the plant at all stages of vegetation. Considering that pathogenic fungi are transmitted through seeds, obtaining seeds from healthy plants and treating the seeds before planting will help to reduce the disease.
The lowest damage score was observed in F1 Abaco (1.8), followed by F1 Baltimore and F1 Cardiff, of which were 2.0 and 2.1, respectively. Besides, one of the most important indicators was productivity, and accordingly, F1 Cardiff was dominant one with 78% among others.
In order to keep root crops well, it is important to store them in sand, which protects them from moisture evaporation, wilting and damage. In addition, pollination with chalk (200-250 g/10 kg) creates a slightly alkaline environment on the surface of root crops and prevents the development of phytopathogenic fungi.