Molecular Pathogens, 2025, Vol.16, No.3, 121-133 http://microbescipublisher.com/index.php/mp 123 brassicae in acidic heavy soils or poor drainage fields is more likely to occur. In the field of sickness, nodules may appear in the seedling stage of rapeseed. The incidence rate and condition index will increase rapidly as the growth period advance, often resulting in large-scale seedling shortages. Due to the diverse transmission channels of dormant spores (irrigation water, agricultural machinery, bacterial fertilizers, etc.) and lastingly survive, Plasmodiophora brassicae is difficult to eradicate in the fields once it is colonized. At present, China has promoted anti-Plasmodiophora brassicae rape varieties in some serious wards, and has taken measures such as lime regulating soil acidity and rotating crops with rice to reduce the occurrence of diseases (Figure 1) (Zhu et al., 2020). Figure 1 Colony morphology and gram staining of the F85 and T113. Both strains strained purpled, identifying them as Gram-positive bacteria. The cells were rod-shaped. The F85 colonies were khaki, the edges were clearcut, and the surface was dry and opaque. The colony of T113 had a dull color and a smooth, translucent surface(Adopted from Zhu et al., 2020) 2.3 Blackleg of rapeseed (Brassica napus) Rapeseed Leptosphaeria maculans is a global disease caused by fungal microcosm infection, also known as stem-based ulcer disease. The bacteria include two species: Leptosphaeria maculans and L. biglobosa. They are infected individually or in mixed manner on Brassica crops such as rapeseed, causing dark-brown necrotic lesions at the base of the plant, causing dryness and collapse of the stem base, and eventually causing serious yield reductions. Black shin disease is extremely prevalent in major rapeseed countries such as North America, Europe and Australia, and is one of the rapeseed diseases with the largest production losses in these regions (Balesdent et al., 2020). Historically, the toxic Leptosphaeria maculans bacteria have caused a sharp decline in rapeseed production in Canada and Australia, and the near devastating epidemic has forced the local area to rely on disease-resistant varieties and improved crop rotation to resume production. In China, Leptosphaeria maculans was not common for a long time, but since the end of the 20th century, the suspected Leptosphaeria maculans has been detected in 16 provinces including the Yangtze River Basin, southwest and northwest. After investigation and identification, a considerable range of rapeseed fields in China has found a strain of black shin disease, but the main pathogen is the attenuated L. biglobosa (Cheng et al., 2023), which causes relatively mild harm. Leptosphaeria maculans overwinters on the previous rapeseed residues in a sexual stage, and produces ascospores in spring, infecting new season crops. The disease can be felt from the seedling stage to the bolting stage. At first, gray-brown lesions are formed on cotyledons or leaves. The bacteria can lurk to the base of the stem, and the stem base often rots and breaks after flowering and pods. The mild and rainy winter and spring climate, the retention of bacterial residues and the continuous planting of dense crops will aggravate the prevalence of black shin disease. In terms of prevention and control, the key measures are to strictly prevent the invasion of bacteria in non-ward areas, implement quarantine and monitoring in areas that may be infected, and adopt strategies such as crop rotation to avoid diseases, timely removal of disease-resistant bodies, and transplantation of disease-resistant varieties in the areas where disease occurs.
RkJQdWJsaXNoZXIy MjQ4ODYzNA==