Applications of ionizing radiation for the control of postharvest diseases in fresh produce: recent advances

Postharvest diseases cause considerable losses to harvested fruits and vegetables worldwide. In addition to various treatments to control postharvest losses caused by pathogens, the global trend is shifting toward more ecofriendly alternatives safer to human health. Thus far, the main approach to postharvest disease control has mostly relied on the use of chemicals. However, the intense use of chemical fungicides has caused side effects such as environmental issues and evolution of fungicide‐resistant isolates. With increasing demand for the use of non‐chemicals, ionizing radiation has been investigated for application in many aspects of postharvest treatment, especially as an approach with significant potential for the control of postharvest disease. Recently, a number of more or less technologically advanced methodologies, e.g. irradiation combined with other types of treatments and induced disease‐resistance, have been developed to control postharvest diseases as well as to increase the quality and storage life of fresh commodities. Challenges for future application of irradiation in fresh produce are the cost, lack of irradiation facilities, lack of knowledge about optimal conditions for different commodities, and lack of acceptance of irradiated fresh produce. This review aims to document the advances in understanding of the effects of irradiation on postharvest disease, the possible modes of action, and the perspectives in commercial use.     

Long‐lasting β‐aminobutyric acid‐induced resistance protects tomato fruit against Botrytis cinerea

Minimizing losses to pests and diseases is essential for producing sufficient food to feed the world's rapidly growing population. The necrotrophic fungus Botrytis cinerea triggers devastating pre‐ and post‐harvest yield losses in tomato (Solanum lycopersicum). Current control methods are based on the pre‐harvest use of fungicides, which are limited by strict legislation. This investigation tested whether induction of resistance by β‐aminobutyric acid (BABA) at different developmental stages provides an alternative strategy to protect post‐harvest tomato fruit against B. cinerea. Soil‐drenching plants with BABA once fruit had already formed had no impact on tomato susceptibility to B. cinerea. However, BABA application to seedlings significantly reduced post‐harvest infection of fruit. This resistance response was not associated with a yield reduction; however, there was a delay in fruit ripening. Untargeted metabolomics revealed differences between fruit from water‐ and BABA‐treated plants, demonstrating that BABA triggered a defence‐associated metabolomics profile that was long lasting. Targeted analysis of defence hormones suggested a role of abscisic acid (ABA) in the resistance phenotype. Post‐harvest application of ABA to the fruit of water‐treated plants induced susceptibility to B. cinerea. This phenotype was absent from the ABA‐exposed fruit of BABA‐treated plants, suggesting a complex role of ABA in BABA‐induced resistance. A final targeted metabolomic analysis detected trace residues of BABA accumulated in the red fruit. Overall, it was demonstrated that BABA induces post‐harvest resistance in tomato fruit against B. cinerea with no penalties in yield.     

外源油菜素甾酮处理水稻对褐飞虱取食和产卵选择性等行为的影响

为了解经油菜素甾酮处理后水稻对褐飞虱Nilaparvata lugens的抗性,通过在水稻培养液中添加不同浓度的油菜素甾酮,观察水稻对褐飞虱取食和产卵、若虫生长发育、羽化等行为的影响,评估油菜素甾酮在水稻抗虫防御反应中的作用。结果表明,水稻培养液中的油菜素甾酮可被水稻有效吸收并产生生理活性。经0.01～10μmol/L油菜素甾酮处理后水稻叶片弯曲程度均显著增加,其叶角分别为对照的3.3～11.0倍。褐飞虱取食和产卵嗜好性与油菜素甾酮处理浓度密切相关,经较低浓度0.005～0.05μmol/L油菜素甾酮处理的水稻能显著降低褐飞虱雌成虫的取食和产卵嗜好性,其产卵量为对照的35.0%～73.9%;而较高浓度0.1～5μmol/L油菜素甾酮处理则增加褐飞虱雌成虫的取食和产卵嗜好性,其产卵量为对照的1.3～1.8倍。0.01、1、5、10μmol/L油菜素甾酮处理的水稻显著降低褐飞虱若虫的羽化率,为对照的32.5%～53.3%。0.1～10μmol/L油菜素甾酮处理显著缩短褐飞虱若虫发育历期,仅为对照的94.1%～96.9%。褐飞虱若虫存活数和初羽化雌成虫体重分别仅在0.1、10μmol/L油菜素甾酮处理下显著降低。表明油菜素甾酮处理水稻可对水稻抗虫防御反应产生影响,其具有作为生态功能分子用于褐飞虱田间防控的潜力。     

长期咸水灌溉对土壤酶活性及反应动力学的影响

为了探讨咸水灌溉导致土壤质量下降的原因,研究了5个含盐量水平(1.25(对照)、2.50、5.00、7.50d S·m~(-1)和10.00 d S·m~(-1))的咸水长期田间污染对0~20 cm和20~40 cm土壤水解酶活性及酶促反应动力学性质的影响。结果表明:咸水灌溉导致土壤脲酶、β-葡糖苷酶和碱性磷酸酶活性呈现不同程度的降低,与对照相比,10d S·m~(-1)咸水灌溉下0~20 cm土壤层三种酶活性分别下降45.5%、50.8%和24.9%,20~40 cm土壤层三种酶活性分别下降37.44%、32.1%和21.8%;咸水灌溉改变了土壤酶的催化动力学特性,与对照相比,10 d S·m~(-1)咸水灌溉下脲酶、β-葡糖苷酶和碱性磷酸酶的最大反应速度V_(max)分别下降47.77%、44.62%和15.01%,Km分别下降57.12%、保持不变和下降14.64%,β-葡糖苷酶V_(max)/K_m下降39.63%,脲酶和碱性磷酸酶的V_(max)/K_m没有显著变化。数据表明咸水灌溉对不同的酶抑制机制不尽相同。     

夏玉米蒸散优化参数模型及参数敏感性分析

分别采用2种不同的冠层阻力模型和土壤阻力模型,组合成4种Shuttleworth-Wallace(S-W)模型,模拟夏玉米农田灌浆期的逐时蒸散量,以涡度相关法观测蒸散量为实测值检验模型改进的效果,找出最优冠层阻力模型和土壤阻力模型,并分析最优S-W模型对各阻力参数的敏感性。结果表明:李俊改进型有效叶面积指数冠层阻力模型和Sellers土壤阻力模型组合的S-W模型模拟效果最好,S-W模型估算玉米田蒸散的精度显著提高,蒸散发模拟值与实测值的相关系数、一致性指数更接近1,蒸散发模拟的相对误差和均方根误差变小。敏感性分析表明,在计算各个阻力参数模型中,S-W1模型估算蒸散发对冠层阻力最敏感,其次是土壤阻力和有效叶面积指数;采用改进型有效叶面积指数冠层阻力模型和Sellers土壤阻力参数模型组合后,在一定程度上提高了模型精度,提高了计算准确率。     

宁夏南部山区冬小麦抗旱指标鉴定研究

为了更快速有效地利用现有资源,选育适宜宁南山区旱地种植的冬小麦新品种,本试验通过抗旱系数、主成分分析、相关分析及聚类分析等方法对8个品种12个性状进行研究。结果表明:8个品种根据抗旱系数不同,可分为抗旱性强、中、弱3个等级;12个性状的主要信息主要集中在4个主成分中,累积贡献率达93.40%,这4个主成分因子主要反映产量、抗旱系数、穗长、穗粒数、千粒重、单株粒重、株高、不实小穗数、颖花结实率9个性状。产量、穗下节长和株高与抗旱系数间为显著或极显著正相关。通过聚类分析将8个品种聚为3类,第一类包含3个品种,分别是Z0217-3,Z0231-3和对照中引6号,这三个品种的产量、抗旱系数、穗下节长、千粒重及株高等主要指标在第三类和第二类之间,但穗长、穗粒数及单株粒重在三类中平均值最低。第二类包含2个品种,分别是98-5808-1和Z0228-2-1,这两个品种的穗粒数、单株粒重和不实小穗数三个指标平均值最高,但产量、抗旱系数、穗下节长、千粒重等指标平均值最低。第三类包含3个品种,分别是Z0349-4,08AWS089和晋太0509,这三个品种平均产量高,抗旱系数高,平均穗长最大,平均穗下节长最长,平均结实小穗数最多,千粒重最大、株高最高。     

不同根瘤菌菌株对盐胁迫下甘农9号苜蓿生长及生理特性的影响

以已筛选的与甘农9号苜蓿匹配效果较好的5株根瘤菌株为研究对象,研究不同浓度NaCl(0、0.4%、0.8%、1.2%)胁迫下,不同根瘤菌株对甘农9号苜蓿生长及生理特性的影响。研究结果表明,在非接菌情况下,随NaCl浓度提高,对苜蓿的生长抑制作用增大,而接菌以后,不同菌株均通过其固氮作用、根瘤菌与苜蓿共生对其生长及生理应答特性的改变来提高苜蓿抗盐胁迫的能力。但是不同菌株与苜蓿匹配对盐的耐受程度不一。经隶属函数综合分析表明,非盐胁迫下,接菌后,对苜蓿生长及生理特性影响较明显的菌株是Da99、DL58及QL31B,而菌株Ga66、Wa32与对照比较差异不显著;在不同盐胁迫处理下,所有菌株相比对照都明显促进苜蓿的生长及提高其抗盐性。在0.4%盐浓度下与甘农9号苜蓿匹配效应最好的菌种是Ga66、QL31B,其隶属函数值较对照分别提高了53.8%和58.6%;在0.8%盐浓度下所有参试菌株均与甘农9号苜蓿匹配效应较好;在1.2%盐浓度下与甘农9号苜蓿匹配效应最好的菌种是Ga66、QL31B;在任何盐浓度下与甘农9号苜蓿匹配效应均好的菌种是QL31B。     

花铃期干旱胁迫对不同棉花品种光合特性影响及抗旱性评价

以28份抗旱性不同的棉花品种为材料,通过大田花铃期水分胁迫,以抗旱系数和主成分分析综合评价各个棉花品种的抗旱水平,并对其评价和等级进行划分。结果表明,各个棉花品种在花铃期干旱胁迫下,各指标反应程度不同,其中叶绿素、净光合速率、水蒸汽压亏缺、气孔导度变化较明显,通过RI值聚类分析,将材料分成4个大类,第Ⅰ类为高抗型品种有C1470、ND359-5、新炮1号、新陆中39等18份品种;第Ⅱ类为中抗型的包括天合995、吉扎81、大铃棉、TM-1、10615-1、塔什干7号;第Ⅲ类为敏感型的包括新陆早1号、新石K7、鲁棉28;第Ⅳ为极敏感型的新陆早26。进一步利用逐步回归建立回归方程D=-1.496+0.775Ci+0.160Gs-0.020VPD+0.719Pn+0.799Tr-0.241WUE+0.663Chl(R2=0.996),筛选出7个指标,分别为Ci、Gs、VPD、A、Tr、WUE、Chl,各材料估计精度大于97.55%。     

大豆品种鼓粒期田间抗旱鉴定

大豆鼓粒期缺水是制约大豆产量形成的重要因素之一。在鼓粒期对大豆品种进行抗旱性鉴定,可为大豆抗旱育种和抗旱节水栽培提供依据。选取不同地区育成的代表性品种（品系）46份,在鼓粒期田间干旱与灌水条件下,分析其产量、产量性状、生育期与形态性状、籽粒品质性状等指标,并且对其进行抗旱性鉴定。结果表明,干旱区46份材料平均产量1 759.6 kg/hm²,灌水对照区平均产量2 223.1 kg/hm²,46个品种平均耗水系数1.079 t/kg。干旱对三粒荚影响显著,对单株荚数、单株粒数、生物产量、单株粒重、百粒重影响极显著。干旱区的平均蛋白质含量极显著高于灌水区,比对照区提高幅度4.47 %;平均脂肪含量极显著低于灌水区,比正常灌水区降低幅度4.19 %。干旱条件下品种百粒重下降,生育期提早均属于品种抗旱性的适应反映,与抗旱性无关。适于呼伦贝尔的品种推荐为北豆14、黑河50、黑河43、华疆3、登科1号、蒙豆15、北豆37、黑河36、北豆38等。     

油菜与核盘菌互作分子机理研究进展

菌核病是由核盘菌（Sclerotinia sclerotiorum (Lib.) de Bary）引起的真菌性病害,每年导致油菜（Brassica napus L.）产量损失10%-20%,是制约我国油菜生产最主要的病害。培育抗（耐）病油菜品种是防治油菜菌核病最为经济有效的途径。本文主要综述了近五年油菜-核盘菌互作分子机制的研究进展。研究表明：（1）核盘菌侵染寄主早期存在活体营养型阶段;（2）草酸提供的酸性pH,而非草酸本身,是核盘菌的必需致病因子;（3）核盘菌有效地利用效应蛋白抑制寄主的抗病反应或者诱导寄主细胞坏死以帮助其侵染;（4）油菜对菌核病的抗性具有中等遗传力,为数量抗性;（5）病原相关分子模式（pathogen-associated molecular pattern, PAMP）引发的免疫反应（PAMP-triggered immunity, PTI）是油菜对核盘菌产生数量抗性的主要根源;（6）功能基因组学研究表明抗（耐）病油菜材料防卫反应更加剧烈,能有效调控细胞内的氧化还原平衡状态,及时清除过量活性氧（reactive oxygen species,ROS）的积累,抑制细胞死亡。核盘菌-油菜互作分子机制的研究将有助于指导油菜抗菌核病育种。