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17AGRICULTURAL SCIENCES
RESEARCH PROGRESS ON IDENTIFICATION OF WHEAT MAIN DISEASES AND INSECT PESTS, POWDERY MILDEW AND PATHOGEN
Tao Ye
Henan Institute of Science and Technology, Xinxiang, China Sumy National Agrarian University, Sumy, Ukraine ORCID: 0000-0002-4675-1294 Vlasenko V.
Doctor (Agricultural Sciences), Professor, Department of plant protection, Sumy National Agrarian University, Sumy, Ukraine ORCID: 0000-0002-5535-6747 Wu Liuliu
Henan Institute of Science and Technology, Xinxiang, China Sumy National Agrarian University, Sumy, Ukraine ORCID: 0000-0001-2345-6789
ABSTRACT
Wheat is one of the most widely planted food crops in the world, and at least 1/3 of the world's population feeds on wheat as the staple food. With the progress and development of society, the requirements for agricultural quality are getting higher and higher, especially for wheat cultivation. Wheat is an important crop related to the economic benefits of local agriculture. Wheat fruit is one of the most common foods and the main source of carbohydrates for people. However, wheat is very susceptible to diseases in the process of planting, and in severe cases, it may even lead to a reduction in wheat production and no harvest. In this article, the main diseases faced in wheat planting are analyzed, and the research progress of crop powdery mildew and pathogen identification is described, in order to provide a theoretical reference for the research on wheat powdery mildew and its control.1. Main diseases in wheat cultivation.
Keywords: Wheat; Powdery mildew; Fusarium head blight; Pathogen identification.
China has a long history of planting wheat, and wheat planting occupies an important position in the development of China's agricultural economy. In order to improve the yield and quality of wheat and increase the economic income of farmers, it is necessary to improve the prevention and research of wheat-related diseases, so as to further optimize disease prevention and control technologies.
1.1 Powdery mildew of wheat
Powdery mildew of wheat can injure some organs of wheat plant and do great harm to wheat yield. At the beginning of the disease, the leaves appeared 2 ~ 3mm pale gray mildew spots, with the passage of time expanded to nearly round to oval white mildew spots. Mildew surface will produce white powder, when the wind or external vibration will fly away. The white powder is called conidia, and in this way it spreads to other wheat. In the later stage, the mildewing layer of the disease turned to grayish white to light brown, and small black dots about the size of needles were scattered on the disease spots, forming an obturator shell (Li Juan, 2019).Powdery mildew of wheat mainly occurred in spring in the winter wheat area, and powdery mildew pathogen mainly came from the local area, and also from the neighboring areas with early disease. The onset of powdery mildew was slow when the temperature was below 12°C, and it was easy to cause the spread of powdery mildew when the relative humidity was above 75%, which seriously affected the yield and quality of wheat. If there is little rain in the local environment, the disease will be severe if there is more rain that year. If it is a rainy area, rainy days, excessive rainfall,
wheat powdery mildew situation will be alleviated to a certain extent. Continuous rainfall washes away the surface conidia, preventing widespread spread of the pathogen. In the process of planting, we should also pay attention to fertilizer management, reduce the utilization rate of nitrogen fertilizer, to avoid the situation of green wheat. If there are problems in field management during the planting process, insufficient water and fertilizer for wheat, coupled with dry land, weak growth and low resistance to disease, powdery mildew can also cause large-scale transmission.
1.2 Fusarium head blight
Fusarium head blight is the main disease affecting wheat growth quality and quantity. When it occurs, it is easy to cause seedling blight, ear rot, stem base rot, stem rot and ear rot, and wheat from seedling to heading can be affected. The buds turn brown, then the root crowns rot. In mild cases, the seedlings are yellow and thin, and in severe cases, it can kill a lot of wheat. The withered seedlings produced a large amount of red mildew, and the late wheat produced dense bacterial asco-cysts. Touch with the hand, there is a distinct sense of protuberance. Bacteria can live and winter on other crops, spread effectively by wind and air currents in the second year, sputtering on the withered anthers of flower vessels to germinate, first living saprophytic, then infusing spikelets, and a few days later producing a large number of pink mildew layers. Wheat suffers the highest infection rate of fusarium graminearum during flowering, especially to the full flowering stage of wheat. However, after the main body of the wheat spike is formed, the conidia's influence on the field will be
reduced to some extent, but with the wind or other means of transmission, they will infect the surrounding wheat field. The gibberellum can survive both winter and summer inside the seed as mycelium. Fusarium graminearum is widely spread mainly through wind and rain, among which rain water plays a very important role in virus transmission. When the ambient temperature is above 7°C, the water content in the soil is more than 50%, and the virus will form shells, and the ambient temperature is above 15 °C, the formation of transmitting ascospores. In the rainfall environment, the ascospores will mature rapidly, and under the influence of the environment, the virus scattered on the anther, the amount of bacteria in the field of disease and residual body, serious disease; Topographic reasons are mainly due to the low-lying rural terrain and poor drainage, which leads to the deposition of precipitation in the field. Moreover, the high density of wheat planting is not conducive to the field management of planters, which makes fusarium graminearum more serious.
2. Research progress of powdery mildew
Erysiphales are a very important group of bio-trophic pathogens, mainly parasitizing the aboveground parts of cruciferous plants. Can cause harm to a variety of crops (Ellingham et al., 2019) (Ellingham O, David J, Culham A. Enhancing identification accuracy for powdery mildews using previously underexploited DNA loci[J]. Mycologia, 2019, 111(2): 1-15.) Since the first scientific name of Powdery mildew was first identified by Linnaeus, they have played an important role in the history of plant pathology for more than 280 years (Yao Yijian, 1988). The morphological characteristics of white, powdery surface mycelium, conidia and dark brown tea spore make Powdery Mildew become one of the most famous and easily recognized plant pathogens (Yang Li, 2013). Powdery mildew fungi often develop in a relatively humid environment, and their high water content of conidia, compatibility with host and sensitivity to chemical fungicides make them significantly different from other plant pathogens (Gay et al., 2010). Powdery mildew will become endemic in a relatively short time after landing on the host surface in the field and can be identified and managed by culture of different crops, chemistry, biology, and host resistance (Burie and Ducrot, 2015). Powdery mildew can cause disease in many angiosperms. In fact, most of them harm dicotyledons, except for Erysiphe graminis and Blumeria graminis, which cause disease in monocotyledons. The conidia and conidia of powdery mildew are white and powdery, and the diseased plant can be identified from a distance (Qi Peikun, 2007).The most obvious characteristic of Powdery mildew is that it has two different growth stages. The first stage is asexual reproduction or conidia stage, which forms a large number of white conidia on the diseased host plants. These conidia are easily transmitted by air flow and become the source of secondary inoculation. The second is the stage of sexual reproduction, in which sexual spores are formed in the later asexual stage. The spores in the ascus are called perithecia in the mature stage. These fruitoids are cephalic, small, globular at first, and yellowish brown, dark brown, brown, or black. The obturator shell has distinct appendages,
which are filiform and branching, bulbous at the base and curved or spiky at the apex. The appendages are of great value to the classification and identification of this genus. Ascus are sac-like structures, mostly oval in shape, and contain 2 to 8 ascospores at maturity, depending on the fungus species (Braun, 1981).
3. Research progress of pathogen identification
The ability to identify organisms that cause specific crop diseases is the cornerstone and prerequisite for preventing crop diseases and understanding and controlling them. Traditional methods of identifying fungal plant pathogens rely on interpretation of visual symptoms and/or isolation, culture and laboratory identification of pathogens. The accuracy and reliability of these methods largely depend on the experience and skills of diagnosers (Gong Meng, 2006). New methods such as immunological methods, DNA/RNA probes and PCR amplification techniques are increasingly applied to the diagnosis of plant pathogens. The greatest advantage of these techniques over traditional diagnostic methods may be their high specificity. They can tell the difference between different fungal species, A single species can also be identified (Bailey et al., 2002).It provides new opportunities for studying and understanding the biology of plant pathogenic fungi, the structure and dynamics of pathogen population, host/pathogen interaction, gene flow in pathogen population and inoculant movement. As more information becomes available on fungal genomics and gene function, The range of application of molecular diagnostic techniques will also expand (Heath and Geitmann, 2000). Pcr-based methods are sensitive and can detect traces of pathogen DNA, which is useful for studying systemic infections or early detection of disease before symptoms develop. Compared with culture method, PCR method is faster and results can be obtained within 1-2 days after sampling. Is more reliable than visual symptom recognition because they do not rely on the skills required to distinguish the nuances of disease symptoms (Li Fenglan et al., 2010) .The combination of morphological and molecular identification will greatly accelerate and improve the identification speed and accuracy of pathogenic bacteria, and provide technical support for disease prevention and monitoring in wheat production.
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MECHANISMS OF DETOXIFICATION TOLERANCE TO HEAVY METALS IN WHEAT
Wu Liuliu
PhD student
Sumy National Agrarian University, Sumy, Ukraine ORCID: 0000-0001-2345-6789 Tao Ye PhD student
Sumy National Agrarian University, Sumy, Ukraine ORCID: 0000-0002-4675-1294 Zhatova H.
PhD (Agricultural Sciences), Professor Sumy National Agrarian University, Sumy, Ukraine ORCID: 0000-0002-8606-6750
ABSTRACT
As a non-essential nutrient element, cadmium in soil and water can be absorbed and accumulated by crops, affecting the normal growth and development of plants, and then causing serious phytotoxic reactions in a variety of physiological levels, thus affecting the health of animals and humans through the food chain, causing great harm to human health. This paper discusses the mechanism of plant resistance to heavy metal detoxification, studies the molecular mechanism of cadmium absorption, transport and exportation of wheat, reduces the accumulation of cadmium in crops, the treatment of cadmium pollution and the creation of wheat varieties with low accumulation of cadmium, which is of great significance to ensure food safety and food safety.
Keywords: wheat, cadmium, absorption, transport, distribution, tolerance mechanism, molecular mechanisms.
Soil contains excessive or harmful heavy metals, absorbed by plant roots to the plant, in the process of long-term heavy metal stress, plants through various resistance mechanisms and regulatory mechanism to reduce or avoid heavy metal poisoning, allow it to grow in the high concentration of heavy metals in the environment to complete its development process, this defense mechanism is called detoxification tolerance mechanism. Since it is difficult to control the accumulation of heavy metals in soil environment, it is necessary to master the detoxification mechanism and defense system of plants to heavy metals, and to understand the way that plants absorb, transport and accumulate heavy metals, so as to better avoid the heavy metal stress of plants [1-2]. Tolerance and detoxification mechanisms in plants can be divided into two categories: internal tolerance and external rejection. The internal tolerance mechanism is the complexation and chelation of some substances in plants with heavy
metals[3], Limiting heavy metals to some specific tissue parts of plants can reduce the effectiveness of heavy metals and alleviate the toxic effects of heavy metals on plants. The mechanism of external rejection is that plants prevent heavy metal ions from entering the plant cells or expel excessive heavy metals from the cells to avoid accumulation in the cells. These detoxification mechanisms are not independent, but mutually rein-forcing[3]. So the patient detoxification mechanism of heavy metals by plants, separation and accumulation of cadmium absorption or cloning of functional genes, reveal the accumulation of low accumulation or not of grain crops cultivated on the molecular mechanism of the absorption, transport and accumulation of cadmium, can clear the key process plants absorb cadmium, cadmium accumulation in the crop resistance control, reduce the consumption risks of heavy metals.
Detoxification of plant root exudates
