Field Crop 2025, Vol.8, No.3, 126-138 http://cropscipublisher.com/index.php/fc 130 3.3 Variety materials and cultivation management measures There are a total of 20 genotypes in this material, including 6 for soybeans, 5 for peas, 4 for mung beans, and 5 for peanuts. Both conventional varieties and new strains with stronger drought resistance are included. The key points to consider when making a selection are that the regional adaptability and drought tolerance differences should be more obvious. Among soybeans, Zhonghuang 13 is the control, Heinong 44 has relatively weak drought resistance, while Sili Hong is more drought-resistant. The peas were controlled with Kewan No. 3 and also with Ningwan No. 4. There are two types of mung beans: "Green Star" from Gansu Province and "Jilu No. 2" from Jilin Province. The peanuts include HO-1, which is high in oleic acid (with good drought tolerance), and Luhua 11. Before sowing, the germination rate of all seeds was measured and they were uniformly coated. Cultivation and management should be kept as consistent as possible, but there are still some differences in details among various regions. For instance, in Inner Mongolia and Gansu, soil moisture retention is achieved through compaction, while in Henan, no tillage and stubble retention are adopted. Sowing should be uniformly carried out using precision seeders, with the depth controlled between 3 and 5 centimeters. The seeding rate should be based on the basic number of seedlings, approximately 10 kilograms per mu for soybeans and 15 kilograms per mu for peas. Standardize the application of fertilizers, applying 20 kilograms of N, 60 kilograms of P₂O₅ and 30 kilograms of K₂O per hectare at one time. Field management was also carried out in accordance with uniform requirements, including replanting, pest and disease control, and chemical weeding. Additional supports were set up for the peas to prevent them from lodging. Throughout the entire growth period, there was basically no irrigation. It relied on natural precipitation, and no extreme cases occurred. During the experiment, phenology and weather conditions were also recorded. Protective rows were set up around the plot to reduce marginal interference, making the obtained data more reliable (Wang et al., 2020). 4 Phenotypic Traits and Data Collection 4.1 Yield and constituent trait indicators Yield and its composition indicators are the key to measuring drought tolerance, but the harvest times for different crops are not the same. For instance, soybeans and mung beans should be harvested only when over 80% of the pods have turned yellow. Peas are usually harvested in the middle to late July, and peanuts need to be picked before the frost. When collecting, remove the edge rows and only calculate the weight of the effective area in the middle. In addition to the total output, we also measured the constituent factors such as the number of pods per plant, the number of grains, and the weight per hundred grains. The peanuts also recorded the number of full and unfull fruits. Randomly select 10 samples from each plot and calculate the average value to represent them. These indicators respectively record the values under drought and normal conditions, and then uniformly convert them into relative yields and reduction rates to analyze the drought resistance of varieties (El-Nabarawy et al., 2016; Yan et al., 2020). In terms of results, the differences in yield reduction among different varieties are quite significant: some pea varieties only have a 10% reduction in yield during severe drought, but others can exceed 40%. Among the soybeans, the output of Heinong 44 has decreased by more than 30%, while that of Silihong and Suinong 28 is less than 15%, remaining relatively stable. From the perspective of traits, generally speaking, varieties with better drought resistance have less reduction in the number of pods or grains, indicating that the flowering and podding period is less affected by drought. These measurements provide a basis for the subsequent quantitative evaluation of drought tolerance. 4.2 Physiological characteristics and root system characteristics indicators To understand the differences in drought tolerance mechanisms among various varieties, we measured some physiological and root system indicators during the period when drought was more obvious. For instance, in terms of leaf moisture, the relative moisture content (RWC) and leaf water potential were measured during the flowering period. Generally speaking, the RWC of drought-tolerant varieties is higher than that of sensitive ones-some drought-tolerant peas can even maintain a RWC of over 80%, but sensitive varieties are less than 70%. Photosynthesis and gas exchange were also measured by instruments. It was found that the photosynthetic rate (Pn) of drought-tolerant varieties decreased less, the stomatal opening degree (Gs) decreased appropriately, and the
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