甘薯采后生理、主要病害及贮藏技术研究

Study on Postharvest Physiology, Main Diseases and Storage Technology of Sweet Potato

【目的】中国种植甘薯约670万hm2,年产量1亿t,因贮藏不当,霉烂变质15%左右。论文研究甘薯采后呼吸类型、贮藏温度和贮藏期主要病害,探讨不同贮藏方法对主要病害和采后生理的影响,为甘薯贮藏保鲜提供理论依据和技术参数。【方法】以陕西省主栽品种秦薯5号为试材,采用气流法测定呼吸强度,分别在(10±0.5)、(11±0.5)、(12±0.5)、(13±0.5)℃温度下贮藏,通过比较腐烂指数确定贮藏温度。对病原菌进行科赫氏验证、ITS序列分析和形态学鉴定,根据病原菌孢子繁殖情况确定噻苯咪唑(TBZ)熏蒸用量,以目前采用的甘薯杀菌剂甲基托布津粉剂作对照。贮期用DNS比色法测定多聚半乳糖醛酸酶(PG)活性,用试剂盒法测定淀粉酶和超氧化物歧化酶(SOD)活性,抗坏血酸含量测定用2,6-二氯酚靛酚滴定法,淀粉含量测定用酸水解法,还原糖含量测定用DNS比色法,原果胶含量测定用咔唑比色法。研究经过TBZ熏蒸、贮前低温(3、4、5℃)处理、塑料袋包装,秦薯5号贮期SOD、淀粉酶、PG的活性,分析淀粉、还原糖、抗坏血酸、原果胶的含量变化,计算贮藏后期腐烂指数和商品率。试验数据采用Excel 2010统计软件整理分析,多重比较采用Duncan新复极差测验。【结果】甘薯为呼吸跃变型,最适贮藏温度为11℃,贮藏期间主要病害黑斑病病原菌为暗梗孢科砖隔孢亚科(Dietyosporoideae of Dematiaceae)交链孢霉属(Alternaria Nees ex Wallr.)甘薯交链孢霉菌(A.bataticolaIkata),TBZ抑制病原菌孢子繁殖作用明显。甘薯采后经室温愈伤,贮前低温处理,TBZ熏蒸,塑料袋包装,11℃下贮藏,能够显著抑制淀粉酶、PG酶活性,保持SOD酶较高活性,从而降低了淀粉转化成糖的速率,使抗坏血酸含量维持较高水平,延缓了甘薯采后生理衰老进程,保持了甘薯原有良好品质。【结论】甘薯采收以后在自然条件下放置5 d,使其愈伤,然后转入冷库在4℃下低温处理2 d,再将冷库缓慢升温,每天升温1℃,直至11℃下长期贮藏。在冷库升温期间用含量为4.5%的TBZ熏蒸剂按6 g·m-3用量处理3 h,塑料袋包装,贮藏210 d,腐烂指数0.185,商品率93%。甘薯贮前经愈伤、低温处理,TBZ熏蒸结合塑料袋包装,在适宜的温度下贮藏,保鲜效果理想,食用安全卫生。

【Objective】The planting area of sweet potato is 6.7 million square hectometer and its annual output is 100 million tons in China. However, the mildew deterioration rate of sweet potato production is about 15% due to the improper storage. The respiration type, storage temperature and main storage diseases of postharvest sweet potato were studied. To provide a theoretical basis and technical parameters for sweet potato storage, the effects of different fresh-keeping technologies on storage physiology and mainly diseases of sweet potato were investigated in the paper.【Method】Qinshu5 sweet potato as a main cultivated variety in Shaanxi was stored at （10±0.5）, （11±0.5）, （12±0.5） and （13±0.5）℃, respectively. The respiration intensity was evaluated by air flow method, the storage temperature was determined by comparing the decay index, the storage disease pathogen was identified by Koch＇s validation, ITS sequence analysis and morphological characteristics, and the dosage of thiabendazole （TBZ） fumigation was determined by comparing the spore breeding situation. The common sweet potato fungicide mildothane powder was used as the control. The polygalacturonase （PG） activity was measured by DNS colorimetry, amylase activity and superoxide dismutase （SOD） activity were determined by reagent kit, ascorbic acid content was determined by 2, 6-dichloro phenol indophenol titration, starch content was determined by acid hydrolysis method, reducing sugar content was determined by DNS colorimetry, and original pectin content was determined by carbazole colorimetry. The changes of SOD activity, amylase activity, PG activity, starch content, reducing sugar content, ascorbic acid content and original pectin content of Qinshu 5 sweet potato treated with TBZ fumigation, pre-storage low temperature （3, 4, 5℃）, plastic bag packaging during storage were measured. Decay index and commercial percentage were calculated during the late period of storage. The statistical software Excel 2010 was used to analyze the test data and Duncan’s method was applied for the multiple comparison. 【Result】 The respiration type of sweet potato was climacteric variant and the optimum storage temperature was 11℃. Alternaria bataticola Ikata was the main pathogen that led to black spot disease during storage. TBZ could inhibit the spore reproduction obviously. The treatment that postharvest sweet potato callused at room temperature, being pre-cooled at low temperature, fumigated by TBZ, packaged with plastic bags, and then stored at 11℃ can significantly restrained the activities of amylase and PG, kept the activity of SOD in a highly active state, reduced the rate of starch convert into sugar, maintained the ascorbic acid content at a high level, delayed the physiological aging process of postharvest sweet potato, and kept the original quality of sweet potato well.【Conclusion】The postharvest sweet potato was placed to callus for 5 days under natural conditions, treated with low temperature at 4℃ for 2 days, then the storage temperature went up slowly with 1℃ every day, until it came to 11℃ the long-term storage started. During the storage temperature rising, the sweet potato was treated with 4.5% TBZ fumigant at the dosage of 6 g·m-3 for 3 hours and stored in plastic bags, with the rotten index being 0.185 and the commercial percentage being 93% after 210 days of storage. Under the suitable temperature, the sweet potato was preserved well by the callus before storage, low temperature treatment, TBZ fumigation combined with plastic package. Meanwhile it had a good safety and hygiene.