Medicinal Plant Notoginseng (Tianqi) Fusarium Root Rot Explained in Detail

The scientific name of notoginseng is Panax notoginseng (Burk.) F.H.Chen, with the synonym Panax pseudo-ginseng Wall. var. notoginseng (Burkill) Hoo & Tseng. Also known as tianqi. It is a perennial herb of the Araliaceae family, using its rhizome, flowers and leaves as medicine, and has the functions of invigorating blood and removing stasis, reducing swelling and relieving pain, stopping bleeding and lowering blood pressure. It is a specialty of Guangxi and Yunnan in China, and in recent years many counties south of the Yangtze River and in Guangdong also produce it.

Symptoms Also called root rot disease, chicken-dropping rot, stinking notoginseng, etc. This disease can occur on one-year-old to three- or four-year-old notoginseng, but it mainly harms one- and two-year-old notoginseng. When the disease occurs, the leaves above ground turn yellow and the growth vigor is poor. In the early stage, when the temperature is high at noon, the leaves droop slightly, and they can still recover in the morning and evening. When diseased plants are dug out, the roots are infected and turn yellow-brown or rot. The main, lateral and fibrous roots can all be affected, with the main root being the most common. Rot starting at the sheep-gut part of the rhizome is the most common. If only one side of the root rots, sometimes the leaves on the corresponding side above ground turn yellow. In the late stage, the diseased roots all become dark brown or grayish white and mushy, hence the name "chicken-dropping rot," which may be related to subsequent bacterial invasion. The disease is severe in the high-temperature and high-humidity season from May to August each year.

Pathogen Fusarium solani (Mart.) Sacc. f. sp. radicicola (Wr.) Snyd. & Hans., called the root disease specialized form of Fusarium solani, is a fungus of the Deuteromycotina. On PSA, the aerial hyphae are relatively well developed, and the colony has streaks and is dense and thick; it is grayish white, and later the reverse side of the culture dish turns blue-green. Microspores are produced early and abundantly; they are borne singly on small phialides and have diverse shapes, mostly curved oval. Macrospores are produced on highly branched conidiophores, and the spore-producing cells are phialide-like; the macrospores are inequilateral fusiform, slightly curved, relatively broad and short; with 2-4 septa, those with 3 septa accounting for the vast majority, and the basal foot cell is not obvious; generally the second cell from the base is the widest; the apical cell is slightly beak-shaped. Macrospores with 3 septa measure 26-40 x 5-6 (μm). Besides infecting the roots of notoginseng, this fungus can also infect potato tubers or stem bases, tulip bulbs, konjac tubers, etc.

Transmission routes and disease conditions The pathogen overwinters in seeds, seedlings, diseased soil and diseased residues. In the field, heavy clay soil, poor drainage and many underground pests easily induce this disease. Especially after two-year-old notoginseng is transplanted, if watering is uneven or not timely, the roots become shriveled and soft, the soil moisture becomes saturated, root hairs are prone to suffocation and death, and the pathogen invades and easily causes disease. It occurs as early as the seedling emergence period in March; in April and May, when the temperature rises and it is dry, the disease stagnates; from June to September, with high temperature and abundant rain, it enters the peak incidence period. The occurrence of this disease is also related to excessive water loss or heat exposure during the transport of seedlings. Field soil that is too clayey leads to poor plant growth, causing the root tissue to have weak disease resistance and making the disease likely; in production, excessive application of nitrogen fertilizer makes the disease severe.

Control methods (1) Select disease-free and healthy seeds and seedlings. (2) Choose plots with good drainage and loose soil for planting notoginseng. (3) Implement crop rotation of more than 5 years; generally, continuous cropping of notoginseng should not exceed 3 years. (4) Manage the notoginseng garden well, promptly remove diseased plants or diseased roots, and disinfect diseased holes with lime or chemicals. In winter and spring, prevent alternating dryness and wetness; water timely in the dry season and drain promptly after rain; advocate applying compost fermented with effective microorganisms. (5) In the early stage of disease, irrigate the roots with 1:2:250-300 Bordeaux mixture or 12% green copper emulsifiable concentrate at 600 times dilution, which has a certain effect.