Legume Genomics and Genetics 2025, Vol.16, No.6, 297-312 http://cropscipublisher.com/index.php/lgg 301 deficiency symptoms and growth stagnation, and cannot provide sufficient nutrition for the pods, resulting in poor development or shedding of young pods. Long-term excessive moisture in the soil can also induce pea root diseases, such as root rot and wilt, which infect the root system and weaken the plant's absorption function, exacerbating physiological drought and nutritional disorders. The study compared waterlogging-tolerant and waterlogging-intolerant soybean varieties. Under flooding conditions, the root biomass and number of beneficial rhizosphere bacteria of waterlogging-tolerant varieties were significantly higher than those of sensitive varieties, which enabled the former to maintain good nutrient absorption in waterlogging (Schillaci et al., 2023). Similarly, different pea genotypes also have differences in root adaptability under waterlogging stress. Some moisture-tolerant varieties can form more aeration tissue to alleviate the problem of insufficient oxygen. But in general, peas are relatively intolerant to waterlogging, and continuous 14 days of flooding can cause peas to almost fail. The excessive moisture in the soil caused by continuous rain has a huge impact on the pea pod setting rate: impaired root function means that the water and nutrient supply required for the flower pods cannot be guaranteed, and the result is that a large number of flower pods will wither and fall off, and the pod setting rate will drop sharply. In terms of management, measures such as digging ditches to drain waterlogging and adding organic matter to improve soil permeability should be taken to minimize the inhibitory effect of field waterlogging on the pea root system. 3.3 Increased pathogens causing pollination and fertilization issues High humidity environment provides a breeding ground for the growth and spread of a variety of pathogenic microorganisms. In continuous rainy weather, the pea population is closed and humid, and diseases such as gray mold, sclerotinia, and rust are prone to outbreaks, which directly infect the floral organs and young pods of peas, thereby interfering with the pollination and fertilization process. Gray mold (infection by gray mold) is particularly common under continuous rainy conditions. Gray mold can infect the stems, leaves, flowers, and pods of peas. Its spores are most likely to germinate at a relative humidity of more than 95%. Once they invade the flowers, they will cause petals to rot, and then destroy the pistil and ovule tissues, making it impossible for the flower to complete normal fertilization. Field observations show that a gray mold layer is often seen on pea flowers after continuous rainy days. This is a sign of massive reproduction of gray mold. The affected flowers then wither and fall off, and the pod setting rate is significantly reduced (Long et al., 2022). Sclerotinia disease (such as pea sclerotinia disease) is also prone to spread in humid environments. The ascospores of its pathogen can attach to flowers, causing floral rot and producing white sclerotia. In years with continuous rain, sclerotinia disease often occurs on a large scale, causing peas to "flower without fruit". Rust, downy mildew, etc. also spread rapidly under high humidity conditions, and severe infection can terminate the reproductive growth of plants prematurely. Continuous rain can also indirectly affect the activities of insect pollinators (although peas are mainly self-pollinated, some insects help to increase the pod setting rate). The attendance rate of pollinating insects on rainy days is reduced, which may cause a decrease in pollination efficiency. However, in comparison, the disease poses a greater threat to pea pod setting, because peas are mainly self-pollinated by closed pollination, and the impact of insect vectors is limited, while the damage of pathogens to the flower is devastating. A monitoring of rapeseed in Hunan showed that continuous rain and low light led to a large outbreak of sclerotinia disease during the flowering period of rapeseed, and the number of pods decreased by more than 30% in severe cases. It can be inferred that flowering diseases caused by continuous rain on peas will also cause significant yield reduction. Therefore, during continuous rainy weather, we must be particularly vigilant against diseases such as gray mold and sclerotium, and take preventive measures on pea flower pods, such as spraying protective fungicides and promptly removing diseased and residual parts, to reduce the interference of pathogens on pollination and fertilization. 4 Varietal Differences in Response to Continuous Rain 4.1 Characteristics of sensitive vs. tolerant cultivars There are obvious differences in the tolerance of pea varieties to environmental stress. Some varieties have a sharp
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