He Liyuan
Plant diseases caused by pathogenic bacteria. Up to now, there are more than 500 kinds of recorded plant bacterial diseases. Some plants have several bacterial diseases, the most of which is about 10, but many plants have not found bacterial diseases.
Distribution and harm
Bacterial diseases are distributed everywhere where plants grow, but the types of diseases are different according to different climatic zones or different ecological zones. Some kinds of plant pathogens have strong specificity of parasitism, which can only infect one plant, and some kinds have a wide range of parasitism, which can infect more than 200 kinds of plants, such as Ralstonia solanacearum. Bacterial diseases are harmful to plants in many ways, such as affecting the normal growth and development, nutritional metabolism or photosynthesis of plants. , thus causing huge economic losses to crops. For example, according to the report of H.W.Kennedy et al. (1980), the economic losses caused by 43 kinds of bacterial diseases in 3/kloc-0 states in the United States in 1976 amounted to more than 206 million dollars; It is reported that cotton yield has decreased by 30% due to Xanthomonas campestris. Mal-vaccaerum dye. In China, Xanthomonas campestris. In the early 1970s, rice diseases were prevalent in the Yangtze River basin for three consecutive years, with an annual incidence area of about 133.3 hectares, and seriously ill rice fields were burnt. It is recognized by academic circles that bacterial blight of rice is an important bacterial disease in the world, which mainly occurs in China, Japan and Southeast Asian countries. Plant bacterial wilt (Psendmonas solanaceareum Smith) occurs in all continents, but it is seriously harmful in tropical, subtropical and some temperate regions under warm, hot, humid and rainy conditions. Both the Yellow River basin and its southern provinces occur in China, but the south of the Yangtze River basin is the most harmful. Plant soft rot is a disease caused by several Erwinia, which mainly harms cruciferous crops, Gramineae and other cultivated plants, and occurs all over the world and in the north and south of China. Pear fire blight (Erwinia amyloviora (Burrill) Winslow, etc.) mainly occurs in Western Europe and North America, and harms pears and apples. Known as "bacterial fire", it is a devastating bacterial disease, but it has not been found in China. Plant root cancer, also known as Agrobacterium tumefaciens Conn, is distributed in all continents and has a wide range of hosts, which is particularly harmful to stone fruit trees. In recent years, peach, grape, hops and other cultivated plants have been seriously affected in some areas of China. Potato ring rot Sepedonium Davis, etc.) is widely distributed in Europe and North America. Occurred in the main potato planting areas in China, especially in the single-cropping rice areas in the north and the alpine mountainous areas in the south. However, since 1980s, with the continuous establishment of non-toxic seed potato production system and the implementation of whole potato sowing, the harm of this disease has decreased year by year. There are also several dangerous bacterial diseases spread by seeds or planting materials. Such as corn wilt (Erwinia staining), bean wilt (Bacillus wilsonii PV. Pyrus pyricularis, Fusarium wilt of alfalfa. In-sidiosum Davis, etc.), banana bacterial wilt (P.sola-nacearum race 2) and sugarcane gummosis (x. campestris PV. vascuorum Dye) are seriously harmful in some countries, and have not been found in China or only occurred in some areas, so they have not been found in some areas.
Types and characteristics of symptoms
Plant bacterial diseases have the following symptom types. ① Tissue necrosis. It usually occurs in leaves, stems, fruits or seeds of plants, showing local necrosis of tissues, with brown, yellow or other colors of round, oval, polygonal or irregular spots, and the diseased spots are often oil-soaked or water-soaked. Sometimes there is colloidal pus on the surface of the lesion. Many species of Xanthomonas and Pseudomonas, and some species of Erwinia and Corynebacterium can cause this symptom. ② Rot. It mostly occurs in tubers, tubers, bulbs and fruits, and sometimes in stems and petioles. Tissue rot, bacterial disintegration, can spread from the surface to deep tissue, sometimes soft rot or wet rot. Some species of Erwinia, Xanthomonas and Corynebacterium can cause this symptom. 3 wilting. Due to systemic infection, leaves wither, change color, wither and even die, and sometimes plants shrink and turn yellow. The vascular bundles of main roots, stems and even branches change color, and mucus often overflows from the cross section of vascular bundles. Some species of Pseudomonas, Corynebacterium and Erwinia can cause this symptom. Four burns. It usually occurs in the blade, starting from the edge of the blade and gradually expanding until the whole blade. Leaves turn yellow, dry and curly, and burn. Some bacteria that are difficult to cultivate, as well as some Corynebacterium and Erwinia often cause this symptom. ⑤ ulcer. Generally occurs in stems, fruits and other parts. Plant tissue is necrotic or ulcerated, with large lesion and irregular shape, but it is mostly limited to surface tissue. A few species of Xanthomonas and Pseudomonas can cause this symptom. Scab. It is more common in root tuber, tuber and other parts, but also in fruits and leaves. The lesion is prominent, like sore 7 16649, round or irregular. Individual species of Streptomyces and Xanthomonas can cause this symptom. ⑥ Tissue hyperplasia. Generally occurs in stems, branches and roots. Plant cells proliferate or swell, showing cancer-like, tumor-like, ribbon-like or hair-like. All individual species of rhizobia and Pseudomonas in soil can cause this symptom.
control
For diseases with multiple transmission routes, comprehensive control measures are often taken. Many plant pathogens can overwinter or overwinter in seedlings or other propagation materials, and are important sources of infection. The disease spreads with the transportation of seeding materials with bacteria. Disease-free seedlings and seed potatoes can be selected through seedling quarantine or seed treatment to prevent the spread of diseases. Diseases spread through the soil, and pathogenic bacteria can survive in the soil for a long time, especially in plant residues in the soil. As a source of infection, these bacteria are often difficult to eliminate. Therefore, planting disease-resistant varieties is an effective measure to prevent and control such diseases. Pesticides can be used to treat seedlings and other propagation materials and soil, and can also be sprayed on the surface of plants to protect plants from infection or alleviate diseases. In addition to chemical agents, there are biological agents, and biological control is mainly used to prevent soil-borne diseases.
philology
Agrois, Journal of Plant Pathology, 2nd Edition. , Academ Press, new york, 1978.