Whole wheat rot disease affects both the seedling and adult stages of the plant, with symptoms becoming most apparent as the plants approach maturity. During the seedling stage, the pathogen primarily infects the roots and lower stem, causing them to darken and rot. Secondary roots may also be affected. Infected seedlings show yellowing leaves, leaf curling, reduced tillering, and stunted growth, which can lead to death in severe cases. The plants are often delayed, sparse, and exhibit darkened roots. Once the plant reaches the jointing stage, the base of the first or second internode and the stem surface develop dark brown mycelium under moist conditions, a condition known as "black foot." This is a key symptom distinguishing full rot from other root rots. Severely infected plants may become dwarfed, especially in later growth stages, and their stems may develop "white spikes." In the field, diseased plants often appear in clusters or patches, and in extreme cases, entire plants may die.
The disease cycle begins with the survival of pathogenic mycelia in soil debris, particularly during summer or winter, serving as the initial source of infection for the following season. Diseased plant residues in uncomposted organic fertilizers can also act as primary infection sources. Pathogens can persist in wheat seedlings, weeds, or other crops, spreading to subsequent crops. While ascospores can germinate and cause disease, their impact is far less significant compared to the mycelium present in infected plant material. The pathogens are soil-borne, and their survival time varies depending on environmental conditions and testing methods, ranging from 1–2 years to 3–5 years. Crop rotation is an effective strategy to reduce disease incidence.
The disease spreads through contaminated manure, irrigation, and farm equipment, which can transfer pathogens over short distances. There has been debate about whether seeds can carry the disease. Although seed contamination can occur, the presence of pathogens in commercial seeds is typically low, and disease transmission through seeds has not been consistently confirmed. Therefore, disease-free areas often restrict the movement of seeds from infected regions.
Environmental and agricultural factors significantly influence disease occurrence. Continuous cropping of wheat followed by corn increases pathogen buildup in the soil, leading to higher disease incidence. Proper crop rotation can reduce the problem, while improper practices may have little effect. No-tillage or reduced tillage can help control the disease by limiting soil aeration. Early sowing is generally more favorable than late planting.
Nutritional imbalances, such as nitrogen deficiency, promote disease development, while balanced nutrient application—especially increased organic matter—can suppress it. Phosphorus deficiency or an imbalance between nitrogen and phosphorus can worsen the disease. Applying phosphorus fertilizer improves root development and reduces disease severity. Other nutrients, like calcium, also play a role in disease resistance.
Soil type, temperature, and moisture levels affect disease progression. Sandy soils, which retain less moisture and nutrients, are more prone to disease, whereas clay soils tend to be less affected. Alkaline soils favor disease development compared to neutral or acidic soils. Winter wheat is more susceptible when there is heavy rainfall in autumn and spring, and irrigated fields are more vulnerable than dry land. High summer temperatures and rain help decompose diseased plant material, reducing bacterial populations and disease incidence.
Currently, no wheat varieties are fully resistant to full rot, and resistance sources within the wheat and barley genera are limited. However, some varieties show varying degrees of tolerance.
To manage the disease, farmers should implement rational crop rotation, avoiding continuous wheat cultivation. Rotating with non-host crops like peanuts, tobacco, tomatoes, sugar beets, castor, or green manures can effectively reduce pathogen buildup. Balanced fertilization is essential, with emphasis on organic matter and proper ratios of nitrogen, phosphorus, and potassium. Applying around 6,000 kg of organic fertilizer per acre helps improve soil health and reduce disease risk.
Biological control methods, such as rotating with legumes or corn, can maintain beneficial soil microorganisms that suppress the pathogen. Chemical treatments, including seed treatments with 12% triadimenol at 0.02–0.03% of seed weight or using 2.5% Siye seed coating agent at 1:1000 dilution, offer some protection. For foliar applications, 20–30 grams of 12.5% wolfberry fruit or 500 grams of 50% carbendazim per mu mixed with 200 kg of water can be sprayed along the stem base during the seedling stage. These integrated strategies help minimize the impact of whole wheat rot disease.
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