Molecular Plant Breeding 2025, Vol.16, No.5, 294-302 http://genbreedpublisher.com/index.php/mpb 296 (Liu et al., 2021; Wen et al., 2022; Islam et al., 2023; Song et al., 2023). Environmental stress and exogenous inducers (such as nano-selenium and chitosan) can also activate defense signals and enhance disease resistance (Kabita et al., 2020; Li et al., 2020). 2.3 Interactions between nutrient availability and secondary metabolite production Nutrient supply (nitrogen, selenium, etc.) can affect photosynthesis, soluble sugar accumulation and hormone levels, thereby indirectly influencing the synthesis of capsaicin and other secondary metabolites. When nutrients are sufficient, the supply of precursor substances and energy is better, the activity of phenylpropane and fatty acid pathways is enhanced, and the contents of antioxidant substances such as capsaicin, flavonoids, and polyphenols will also increase. Nutritional status can also regulate hormone signals (such as jasmonic acid, ethylene), thereby affecting the expression of transcription factors and altering the types and contents of secondary metabolites (Sun et al., 2019; Li et al., 2020; Islam et al., 2023). In organic cultivation, reasonable fertilization management can optimize the quality of chili peppers and enhance their disease resistance. 3 Fertilization Regimes in Organic Hangjiao Pepper Production 3.1 Organic fertilization sources: compost, manure, green manure, and biofertilizers Common organic fertilizers include compost, livestock and poultry manure (such as chicken manure), green manure and bio-fertilizers. Studies have found that the combined use of chicken manure and corn stalks can significantly increase the yield and disease resistance of Hangjiao pepper, improve the microbial structure in the soil, enhance soil functionality, and reduce continuous cropping obstacles and soil-borne diseases (Gao et al., 2020). Amino acid water-soluble fertilizer is a kind of bio-fertilizer. When used at a low concentration, it can increase the content of capsaicin and dihydrocapsaicin in the fruit of Hangjiao pepper, make the pungency stronger and the quality better (Bakpa et al., 2021). 3.2 Nutrient release dynamics and soil microbial interactions The nutrients of organic fertilizer are released relatively slowly. It can provide crops with elements such as nitrogen, phosphorus and potassium for a long time and also promote the reproduction of beneficial microorganisms. The combined use of chicken manure and straw can not only increase the diversity of soil microorganisms, especially the dominant bacterial groups such as Proteobacteria and Ascomycota, but also enhance the disease resistance of the soil and reduce soil-borne diseases (Gao et al., 2020). Amino acid fertilizers can improve the physiological conditions and root activity of plants and help maintain the micro-ecological balance of the soil (Bakpa et al., 2021). 3.3 Comparative characteristics of balanced vs. targeted nutrient application Balanced fertilization refers to the reasonable proportion of different nutrients to ensure the all-round growth of crops. Targeted fertilization is to adjust the nutrient ratio based on the specific needs of crops, such as increasing pungency or enhancing disease resistance. Studies have shown that low-concentration amino acid fertilizer (1.8 kg/ mu) can significantly increase capsaicin and protein content while ensuring yield, which helps to enhance pungency and quality (Bakpa et al., 2021). Chicken manure combined with straw is more suitable for improving soil quality and enhancing disease resistance, especially for plots with severe continuous cropping obstacles (Gao et al., 2020). However, if some fertilizers are used in excessive amounts, such as high-dose alkaline conditioning fertilizers, although the yield may increase, the benefits will gradually decrease (Ding, 2021). 4 Effects of Fertilization Regimes on Pungency 4.1 Influence of nitrogen, potassium, and microelements on capsaicinoid levels The amounts of nitrogen, potassium and trace elements will directly affect the amount of capsaicin in Hangjiao peppers. Research has found that applying 1.8 kg per mu of amino acid water-soluble fertilizer can increase the capsaicin content of Hangjiao peppers to 5.80 mg/g and the dihydrocapsaicin content to 1.08 mg/g. At the same time, the levels of protein and vitamin C also increase, and the fruit quality is better. However, if the fertilizer concentration is too high, it does not necessarily lead to more capsaicin; instead, it may increase soluble sugar (Bakpa et al., 2021). This indicates that the dosage of nitrogen, potassium and trace elements should be reasonable in order to make the pungency of Hangjiao peppers better.
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