Combined application of antagonist Bacillus amyloliquefaciens and essential oils for the control of peach postharvest diseases

Bacillus amyloliquefaciens PPCB004 was selected as a potential antagonist to control Botrytis cinerea, Penicillium expansum and Rhizopus stolonifer on peach fruit. The HPLC data of PPCB004 indicated the lipopeptides iturin A, fengycin and surfactin as secondary metabolites. The GC/MS analysis of PPCB004 showed 3-hydroxy-2-butanone as the dominant compound (97.52% of relative peak area). Thyme (TO) and lemongrass (LO) oils showed over 50% and 25% inhibition of radial mycelial growth respectively with 8 μl oil per plate for all pathogens. Combination treatment with both oils failed to increase the percentage inhibition of radial mycelial growth of the pathogens. Combined application of PPCB004 with TO or LO was tested to assess the effectiveness in the control of these pathogens during postharvest storage. The biofilm formation of PPCB004 was significantly higher in LO than TO. LO (6 μl plate⁻¹) and PPCB004 completely inhibited the mycelial growth of the pathogens. Fruit inoculation trials with PPCB004 + LO in NatureFlex™ modified atmosphere packaging (MAP), showed lower disease incidence and severity at 25 °C for 5 d than treatments with PPCB004 + MAP, PPCB004 + TO + MAP, LO + MAP, TO + MAP or stand-alone MAP. On naturally infected fruit, PPCB004 + LO + MAP and LO + MAP treatments retained the total soluble solids/titratable acidity ratio and flesh firmness but failed to stimulate the levels of total phenolic content, phenylalanine ammonia-lyase, β-1,3-glucanase and chitinase activities. Combination of PPCB004 (spray treatment) + LO (in pad delivery system) in NatureFlex™ MAP showed absence of disease and off-flavour development, retained the overall appearance and increased the overall acceptance at market shelf conditions (20 °C for 2 d) after cold storage at 4 °C for 14 d.     

Effect of pre-harvest calcium chloride applications on fruit calcium level and post-harvest anthracnose disease of papaya

Anthracnose disease of papaya, caused by Colletotrichum gloeosporioides Penz, can cause extensive postharvest losses. The goal of this research was to use pre-harvest calcium applications to reduce anthracnose disease. Six pre-harvest foliar calcium sprays were applied biweekly to papaya trees in experimental orchards at Universiti Putra Malaysia. Additional in vitro and in vivo tests were carried out to test the effect of calcium on fruit calcium content, spore germination, mycelial growth and disease severity. Calcium chloride at 1%, 1.5% and 2.0% concentrations significantly decreased spore germination. Calcium content of papaya fruit was significantly increased by calcium sprays at a concentration of 2.0% in 2012 and 2013. In vivo studies showed that increasing calcium content in fruit by calcium sprays at 1.5 and 2.0% concentrations significantly reduced anthracnose incidence of fruits during five weeks storage at 12 ± 2 °C, and delayed initiation of disease symptoms by four weeks.     

The efficacy of combined application of edible coatings and thyme oil in inducing resistance components in avocado (Persea americana Mill.) against anthracnose during post-harvest storage

Avocado fruit has high economic value; however, major post-harvest losses are encountered throughout the supply chain mostly due to anthracnose disease caused by the fungus Colletotrichum gloeosporioides. Increasing consumer concern regarding food safety and demand for organically produced fruits makes it necessary to search for natural environmentally friendly alternative products and processes for the fruit industry; particularly in disease control. Antifungal effects of Gum Arabic (GA) (10%), Aloe vera (AL) (2%), chitosan (CH) (1%) alone or in combination with thyme oil (1%) were investigated in vitro. CH + thyme oil and AL + thyme oil [1:1 or 3:1 v/v] showed fungicidal effects while AL, CH, GA and GA + thyme oil [3:1 v/v] showed fungistatic effects on mycelial growth of C. gloeosporioides in vitro. CH and AL coatings alone or in combination with thyme oil [3:1 v/v], either as preventative or curative treatments in comparison with commercial treatment (prochloraz, 0.05%) and untreated control were evaluated on incidence and severity (lesion diameter) of anthracnose in vivo. Preventative CH + thyme oil treatments significantly reduced the severity of anthracnose (8.9 mm) compared to thyme oil (12.7 mm), AL + TO (14.4 mm), CH (17.8 mm), AL (20.6 mm), PZ (18.3 mm) and untreated samples (34.8 mm). As curative method, the CH + thyme oil combination also reduced the severity of anthracnose by at least 4 mm compared to the other treatments. The total phenols, polyphenol oxidase, phenylalanine ammonia-lyase, β-1,3-glucanase, chitinase, catalase and superoxide dismutase activities, firmness and flesh colour were also determined. Results showed an increase in peroxidase, phenylalanine ammonia-lyase, β-1,3-glucanase, chitinase, catalase and superoxide dismutase activities and total phenolics with reduced loss of firmness and flesh colour following CH + thyme oil treatments. This investigation recommends CH + thyme oil [3:1 v/v] combination treatment as a suitable alternative to the currently adopted prochloraz applications in controlling anthracnose disease in avocado fruit during storage.     

肉桂精油复合壳聚糖涂膜对采后番木瓜炭疽病的防治效果及作用机制分析

番木瓜是我国著名的热带、亚热带水果之一,但番木瓜属于呼吸跃变型果实,采后不耐贮运,其中由炭疽病引起的腐烂损失最为严重。因此,如何防治番木瓜采后炭疽病,降低番木瓜腐烂损失,延长贮藏保鲜期,成了制约番木瓜产业健康发展的瓶颈问题。本文以‘大青’番木瓜为试验材料,以绿色环保的肉桂精油-壳聚糖复合保鲜液为处理手段,研究其对采后番木瓜炭疽病的防治效果及作用机制,为我国番木瓜采后贮运保鲜产业发展提供理论依据和应用参考。分别用0.5%壳聚糖、0.5%壳聚糖+0.3%肉桂精油、0.5%壳聚糖+0.5%肉桂精油、0.5%壳聚糖+0.7%肉桂精油溶液对采后番木瓜果实进行喷雾处理,清水处理作为对照,处理后的番木瓜分为2组,其中一组处理后置于25℃下恒温贮藏,定期测定果实病情指数;另一组处理后置于25℃下恒温贮藏24 h后,在果面刺伤接种番木瓜炭疽菌,定期调查果实病斑直径,并对果皮进行取样,测定不同处理果实的抗病相关物质含量和抗病相关酶活性的变化情况。番木瓜炭疽菌的离体抑菌实验采用含药PDA平板抑菌法进行测定。研究结果表明:0.5%壳聚糖+0.3%肉桂精油处理对番木瓜炭疽病的防治效果最好,复合处理可完全抑制离体番木瓜炭疽菌的生长和产孢,复合处理显著降低了番木瓜果实的病斑直径,提高了抗病相关物质木质素、总酚(TP)和过氧化氢(H₂O₂)的含量,提高了抗病相关酶苯丙氨酸解氨酶(PAL)、过氧化物酶(POD)和β-1,3葡聚糖酶(β-1,3-GA)的活性,但对几丁质酶(CHI)活性影响不大。由此可见,肉桂精油复合壳聚糖涂膜对番木瓜炭疽菌有较好的防控效果,一方面是由于复合处理抑制了番木瓜炭疽菌的生长,另一方面是复合处理诱导番木瓜果实提高了抗病性。因此,适宜浓度的肉桂精油复合壳聚糖涂膜处理为防控番木瓜采后炭疽病提供了一种绿色新途径。     

肉桂精油复合壳聚糖涂膜对采后番木瓜炭疽病的防治效果及作用机制分析

番木瓜是我国著名的热带、亚热带水果之一,但番木瓜属于呼吸跃变型果实,采后不耐贮运,其中由炭疽病引起的腐烂损失最为严重。因此,如何防治番木瓜采后炭疽病,降低番木瓜腐烂损失,延长贮藏保鲜期,成了制约番木瓜产业健康发展的瓶颈问题。本文以‘大青’番木瓜为试验材料,以绿色环保的肉桂精油-壳聚糖复合保鲜液为处理手段,研究其对采后番木瓜炭疽病的防治效果及作用机制,为我国番木瓜采后贮运保鲜产业发展提供理论依据和应用参考。分别用0.5%壳聚糖、0.5%壳聚糖+0.3%肉桂精油、0.5%壳聚糖+0.5%肉桂精油、0.5%壳聚糖+0.7%肉桂精油溶液对采后番木瓜果实进行喷雾处理,清水处理作为对照,处理后的番木瓜分为2组,其中一组处理后置于25℃下恒温贮藏,定期测定果实病情指数;另一组处理后置于25℃下恒温贮藏24 h后,在果面刺伤接种番木瓜炭疽菌,定期调查果实病斑直径,并对果皮进行取样,测定不同处理果实的抗病相关物质含量和抗病相关酶活性的变化情况。番木瓜炭疽菌的离体抑菌实验采用含药PDA平板抑菌法进行测定。研究结果表明:0.5%壳聚糖+0.3%肉桂精油处理对番木瓜炭疽病的防治效果最好,复合处理可完全抑制离体番木瓜炭疽菌的生长和产孢,复合处理显著降低了番木瓜果实的病斑直径,提高了抗病相关物质木质素、总酚(TP)和过氧化氢(H₂O₂)的含量,提高了抗病相关酶苯丙氨酸解氨酶(PAL)、过氧化物酶(POD)和β-1,3葡聚糖酶(β-1,3-GA)的活性,但对几丁质酶(CHI)活性影响不大。由此可见,肉桂精油复合壳聚糖涂膜对番木瓜炭疽菌有较好的防控效果,一方面是由于复合处理抑制了番木瓜炭疽菌的生长,另一方面是复合处理诱导番木瓜果实提高了抗病性。因此,适宜浓度的肉桂精油复合壳聚糖涂膜处理为防控番木瓜采后炭疽病提供了一种绿色新途径。     

1-MCP处理对‘油木奈’果实采后生理和品质的影响

研究1.2 μL/L的1-甲基环丙烯（1-methylcyclopropene,1-MCP）处理对在（25±1）℃下贮藏的‘油木奈’（Prunus salicina Lindl. cv. Younai）果实采后生理和品质的影响。结果表明,与对照果实相比,1-MCP处理可有效降低‘油木奈’果实呼吸强度、呼吸峰值和乙烯释放量,延缓果实细胞膜相对渗透率升高和果实表面色调角h°值的下降,保持较高的果实硬度、可滴定酸和果皮叶绿素含量,延迟果实外观颜色转变,减少果实失重和腐烂。经1-MCP处理的果实在（25±1）℃下贮藏15 d时的好果率为80％,而对照果实只有58％。因此认为,1-MCP处理可以延缓采后‘油木奈’果实后熟衰老和保持果实品质,延长果实保鲜期。     

预冷前后1-MCP处理对杨梅采后贮藏品质的影响

本研究以‘硬丝’杨梅为试材,比较预冷前后进行1-MCP处理,及贮藏温度对杨梅采后贮藏品质及货架期的影响。预冷结合1-MCP处理,可延缓贮藏期间杨梅果实单果重、硬度的下降,抑制膜脂过氧化产物MDA含量和呼吸强度的上升,延缓贮藏6 d内果实可溶性糖、可滴定酸含量的降低,但对延缓花色苷含量降解效果不明显。预冷前或后进行1-MCP处理,在延缓果实品质劣化方面并无显著差异。预冷处理可有效降低果实入库时的呼吸强度,但需结合1-MCP处理才能有效维持贮藏期间果实呼吸强度处于较低水平。预冷后1-MCP处理,杨梅果实可贮藏于7 ℃中5 d,出库后,货架期可达5 d,腐烂率<10%,与贮藏于4 ℃中无显著差异,可有效降低冷库能耗成本,贮藏效果优于预冷前1-MCP处理。考虑生产实际,杨梅采后处理应及时装箱,加冰壶,置于4 ℃预冷处理,冷藏运输应控制在5 h以内。入库前使用7 μL/L的1-MCP于4 ℃冷库中熏蒸18 h。贮藏期可置于4~7 ℃冷库中贮藏5 d,于第6天上架销售,货架期可达5 d,具有较好的应用前景。     

亚精胺处理对采后番木瓜果实质地及成熟衰老的影响

为探讨亚精胺处理对采后番木瓜果实质地变化及成熟衰老的影响,以‘日升’番木瓜为试材,采用质构仪质地多面分析（texture profile analysis, TPA）法,对亚精胺处理后番木瓜果实贮藏期间呼吸速率和色泽的变化、果实各项质地参数进行测定。结果表明：适当浓度的亚精胺处理可有效延缓番木瓜果实的软化。其中5 mmol/L的亚精胺处理效果最佳,其次是1 mmol/L亚精胺处理。果实的硬度、咀嚼性、胶着性、黏聚性、回复性较之蒸馏水处理组均有所提高,并显著降低果实的呼吸速率,延缓果实色泽的转变。而10 mmol/L的亚精胺处理加速了果实的软化及成熟衰老。相关性分析表明,果实硬度、咀嚼性、胶着性、黏聚性、回复性之间均呈现极显著的正相关性,弹性与其他质构参数间呈现较差的相关性（P<0.519）。综上所述,TPA测试可用于评价采后番木瓜果实质地的变化。     

菠萝蜜果实PG基因的克隆与表达分析

为明确PG基因在菠萝蜜果实后熟软化过程中的作用,本研究以‘海大2号’菠萝蜜果实为材料,采用0.5 mg/L 1-MCP和1000 mg/L ETH处理,研究了室温（20℃）条件下果实成熟过程中硬度和果胶的动态变化,克隆获得4个PG基因,并对其进行了生物信息学和表达分析。结果表明：随着菠萝蜜果实的成熟,果肉硬度快速下降,可溶性果胶和离子型果胶不断增加,共价态果胶有所下降;ETH处理促进了果实WSP和ISP含量的上升,加速了软化进程,1-MCP处理抑制了贮藏前期果肉硬度的下降,推迟了软化进程,但明显提高了3种果胶的含量。AhePG1~AhePG4基因的开放阅读框（ORF）长度1221~1434 bp,编码406~477个氨基酸。AhePG1蛋白含有4个保守结构域（Ⅰ~Ⅳ）,AhePG2和AhePG3只含结构域Ⅰ和Ⅱ,AhePG4缺失结构域Ⅲ;AhePG基因分别与桃（AF095577.1）、菜豆（XM_007162208.1）、葎草（MN971583.1）、菜豆（XM_007151391.1）PG基因编码的氨基酸序列的亲缘关系较近,相似度分别达75.63%、73.11%、79.71%、70.75%。qRT-PCR分析结果显示：AhePG1基因在果实成熟前期表达量低,在后期高表达,而AhePG2/3/4基因的表达量在果实成熟过程中总体较低。ETH处理抑制了AhePG1基因的表达量,而1-MCP处理延缓了4个AhePG基因表达量的增加,但增加了成熟后期AhePG2、AhePG3、AhePG4基因的表达。相关性分析发现,果肉硬度与水溶性果胶含量和AhePG1基因表达呈显著和极显著负相关,而水溶性果胶含量又与AhePG1基因表达呈显著正相关。本研究说明,菠萝蜜果实的软化与果胶降解有关,AhePG1可能是菠萝蜜果实果胶降解和果实软化的关键PG基因之一,控制着果实成熟后期的软化;1-MCP处理能延缓菠萝蜜果实的成熟,但并不影响果实后期成熟时的软化,AhePG1、AhePG2、AhePG3、AhePG4基因可能对其软化均有作用。     

Effects of ethylene and 1-methylcyclopropene on potato tuber sprout control and fry color

The study examined the efficacy of 1-methylcyclopropene (1-MCP), an anti-ethylene compound, as a preventative treatment for ethylene-induced fry color darkening in potato (Solanum tuberosum L.) tubers, without reducing the effectiveness of ethylene as a tuber sprouting control agent. The experiment was conducted for two years with ‘Shepody’ and ‘Russet Burbank.’ Tubers of each cultivar from four separate growers received one of the following treatments: Air (control), Air + 1-MCP (1 (μL.L^-1 for 48 h), isopropyl N (3-chlorophenyl) carbamate (chloropropham; CIPC; 1% a.i. [v/v]); continuous ethylene (4 μL.L^-1) in air; continuous ethylene pre-treated with 1-MCP once; continuous ethylene pre-treated with 1-MCP and repeated monthly; and continuous ethylene pre-treated with 1-MCP and repeated bi-monthly. Treatment started after suberization and cooling to 9 C, and samples were evaluated at 3-wk (year 1) or 4-wk (years 2 and 3) intervals thereafter until April (Shepody) or June (Russet Burbank). Sprout growth (sprout fresh weight per tuber), fry color (Agtron reflectance units), tuber weight loss, incidence of disease infection and internal disorders were evaluated. Weight loss, tuber infection, and the occurrence of disorders were not affected by any of the treatments. Sprout growth was controlled by the continuous ethylene supply in both cultivars, and single or multiple additions of 1-MCP to the ethylene treatment did not affect the ethylene control of sprouting. As expected, ethylene treatment alone enhanced fry color darkening in both cultivars. In Russet Burbank tubers, fry color was not darkened in any of the ethylene + 1-MCP (once, monthly, or bimonthly) treatments. In Shepody, fry color was not darkened in the ethylene + 1-MCP monthly or bimonthly treatments, but started darkening 4 wk after exposure in the single ethylene + 1-MCP treatment. It is concluded that 1-MCP can be used to control fry color darkening induced by ethylene without blocking ethylene control of tuber sprouting. However, the number of 1-MCP applications required may vary with the cultivar, e.g., one application was sufficient in Russet Burbank but not in Shepody.     

Integrated management of postharvest banana anthracnose (Colletotrichum musae) through plant extracts and hot water treatment

The aim of the present study was to determine the integrated effect of plant extracts and hot water treatment on postharvest anthracnose and banana fruit quality. Artificially inoculated banana fruit were dipped in 10% and 20% (w/v) extracts of four plant species, viz. Acacia albida, Argemone mexicana, Dovalis abyssinica and Prosopis juliflora at room temperature (20 °C), 45 °C and 50 °C. Fruit treated separately with 20% extracts of A. albida and P. juliflora at 50 °C had reduced anthracnose incidence and severity. These treatment combinations also had the highest percentage of marketable ripe banana fruits. In conclusion, applying aqueous plant extracts at 50 °C enhanced the antifungal activity of extracts without affecting the physico-chemical properties of banana.     

Control of postharvest anthracnose of banana using a new edible composite coating

Anthracnose is a postharvest disease of banana caused by the fungus Colletotrichum musae that results in major economic losses during transportation and storage. For the management of banana anthracnose, antifungal effects of Arabic gum (AG) (5, 10, 15 and 20%), chitosan (CH) (1.0%), and the combination of AG with CH were investigated in vitro as well as in vivo. CH at 1.0% and 1.5% had fungicidal effects on C. musae. AG alone did not show any fungicidal effects while the combination of 1.0% CH with all tested AG concentrations had fungicidal effects. However, the potato dextrose agar (PDA) medium amended with 10% AG incorporated with 1.0% CH showed the most promising results among all treatments in suppressing the mycelial growth (100%) and conidial germination inhibition (92.5%). In vivo analysis also revealed that 10% AG incorporated with 1.0% CH was the optimal concentration in controlling decay (80%), showing a synergistic effect in the reduction of C. musae in artificially inoculated bananas. The 10% AG incorporated with 1.0% CH coatings significantly delayed ripening as in terms of percentage weight loss, fruit firmness, soluble solids concentration and titratable acidity. The results showed the possibility of using 10% Arabic gum incorporated with 1.0% chitosan as a biofungicide for controlling postharvest anthracnose in banana.     

番木瓜NAC转录因子的克隆与表达分析

为探究番木瓜NAC转录因子的序列特征及功能,以‘大庆7号’番木瓜果肉为试验材料,采用RTPCR克隆出2个不同的NAC类基因,命名为CpNAC1(Gene Bank KT364871)和CpNAC2(Gene Bank KT372241),其开放阅读框(ORF)长度分别为609 bp和805 bp,分别编码202个和268个氨基酸,其N端含有NAM保守结构域。采用实时荧光定量PCR研究其在乙烯利及清水对照处理后果实不同成熟时期中的表达情况,结果发现,CpNAC1和CpNAC2基因随着处理后时间的增加,表达量呈先下降后缓慢上升的趋势,且均与果实成熟呈负相关。但CpNAC1表达趋势与果实成熟过程中乙烯的表达量相反,受乙烯抑制降低表达量,从而参与了番木瓜果实的成熟衰老进程,而CpNAC2基因在乙烯处理后番木瓜果实中表达量与对照处理相比没有显著变化,说明CpNAC2基因不是通过乙烯信号传导途径来调控果实成熟。     

不同浓度 1-MCP 处理对采后安溪油柿果实的保鲜效应

本研究探讨了不同浓度纸片型 1-甲基环丙烯（1-MCP）（0、0.45、0.90、1.35、1.80 μL/L）处理对安溪油柿果 实在(25±1) ℃、相对湿度 85%贮藏条件下的保鲜效应。贮藏期间测定了果实呼吸强度，果实硬度，果皮色差 a*、b*、 L*值和色调角 h 值，果皮转红率，以及感官品质等指标的变化。结果表明：与对照安溪油柿果实比较，不同浓度纸片 型 1-MCP 处理 12 h 均可抑制采后安溪油柿果实呼吸强度，延迟呼吸高峰出现，保持较高的果实硬度，抑制果皮色差 a*、b*、L*值和色调角 h 值的变化，延迟果实转红，保持果实原有风味，减少果实腐烂。其中 1.35 μL/L 1-MCP 处理效 果最佳。因此，1.35 μL/L 纸片型 1-MCP 处理 12 h 可作为在(25±1) ℃、相对湿度 85%贮藏条件下安溪油柿果实的适宜 处理条件，以延长贮藏寿命和保持果实品质。     

1-MCP延缓采后台湾青枣果实衰老及其与能量代谢的关系

研究1-甲基环丙烯(1-MCP)处理对采后‘中青’台湾青枣果实贮藏品质与烟酰胺腺嘌呤二核苷酸激酶(NADK)活性、烟酰胺腺嘌呤二核苷酸(NAD)、烟酰胺腺嘌呤二核苷酸磷酸(NADP)、还原型烟酰胺腺嘌呤二核苷酸(NADH)、还原型烟酰胺腺嘌呤二核苷酸磷酸(NADPH)、能量物质[三磷酸腺苷(ATP)、二磷酸腺苷(ADP)、一磷酸腺苷(AMP)]及能荷(EC)的关系。采后台湾青枣果实用1.8μL/L的1-MCP处理12 h后在(15±1)℃下贮藏,定期测定能量物质、NAD、NADP、NADH和NADPH含量、NADK活性及细胞膜透性,并在贮藏前后测定果实品质指标和腐烂率。结果表明:1-MCP处理保持‘中青’台湾青枣果实较高的ATP、NADP、NADPH含量,NADK活性和能荷值,较低的NAD和NADH含量,延缓贮藏期间细胞膜透性的增加;保持较高的果实硬度、可溶性固形物(TSS)、有机酸(TA)和维生素C含量,延缓果皮叶绿素含量下降,降低腐烂率。据此认为,1-MCP处理延缓采后台湾青枣果实衰老降低腐烂率可能与细胞保持较高的能荷水平有关。     

Effect of electrolyzed oxidizing water and continuous ozone exposure on the control of Penicillium digitatum on tangerine cv. ‘Sai Nam Pung’ during storage

The effect of electrolyzed oxidizing (EO) water in combination with ozone to control postharvest decay of tangerine cv. “Sai Num Pung” was investigated. The spore suspension containing 10⁵ conidia ml⁻¹ of Penicillium digitatum was prepared. EO water was generated by electrolysis of various concentrations of NaCl solution (5, 25, 50% and saturated NaCl). The spore suspension was inoculated into EO water and incubated at 27 °C for 1, 2, 4, 8 and 32 min. It was found that the EO water with saturated NaCl completely inhibited the spore germination of the fungus within 1 min. When the fruits inoculated with P. digitatum were washed in EO water at the same concentrations as previous experiment for 4, 8 and 16 min and stored at 5 °C for 18 days, it was found that immersion of the fruit in EO water for 8 min was the most effective to reduce disease incidences. Moreover, washing fruit in EO water and kept in a refrigerated chamber at 5 °C with continuous ozone exposure at a concentration of 200 mg l⁻¹ for 2 h day⁻¹ to extend storage life suppressed the disease incidence until 28 days. However, none of the treatments had any effect on the quality of fruit such as total soluble solids, titratable acidity, percent weight loss and peel color. Therefore EO water may be useful for surface sanitation and ozone has potential to control the recontamination of postharvest diseases in tangerine fruit in storage room.     

HXKs基因在香蕉果实后熟过程中功能初探

香蕉是世界主要水果之一,对乙烯非常敏感,属于呼吸跃变型果实。目前,香蕉果实后熟机理还未完全探明,后熟过程中己糖激酶(HXK)与乙烯的关系还不清楚。通过BLAST比对从香蕉基因组数据库中发现HXK基因家族的11个成员,经克隆获得这些基因的序列,并研究HXKs基因在香蕉果实自然后熟过程中的转录表达谱,重点研究乙烯利、甘露糖、NAG和1-MCP对HXKs基因表达、HXK酶活和内源乙烯生物合成的影响。结果表明:在香蕉果实后熟过程中HXKs基因呈现差异性表达,乙烯利上调大多数HXKs基因的表达和HXK酶活,1-MCP的作用正好相反,这表明外源乙烯正作用于HXK。另一方面,甘露糖加快内源乙烯生物合成,NAG却推迟内源乙烯生物合成,这说明HXK正作用于内源乙烯生物合成。所以,在香蕉果实后熟过程中乙烯和HXK之间存在相互促进的关系。这将为进一步阐明香蕉果实后熟机制提供理论依据,也将为香蕉果实保鲜新技术的挖掘提供新思路。     

热处理复合香茅精油处理对番木瓜保鲜效果及软化相关酶活性的影响

本文以‘美中红’番木瓜为试材,研究了热处理复合香茅精油处理对番木瓜果实采后保鲜效果及软化相关酶的影响,测定了贮藏过程中果实失重率、硬度、颜色、可溶性固形物（TSS）、可滴定酸（TA）、维生素C（Vc）和呼吸速率,还测定了多聚半乳糖醛酸酶（PG）、果胶甲酯酶（PE）、纤维素酶（CL）和β-半乳糖苷酶（β-GAL）等软化相关酶的活性。结果表明：热处理复合香茅精油处理可显著降低番木瓜果实病情指数和失重率,延缓果实硬度下降和颜色的转黄,提高果实中的TSS和Vc含量和果实固酸比,降低果实呼吸速率,延迟呼吸高峰的出现;复合处理可降低果实PG酶、PE酶和β-GAL酶活性,延迟PE酶峰值的出现,对CL酶活性影响不显著。可见,复合处理对番木瓜果实有较好的保鲜效果,复合处理延缓果实硬度下降与降低呼吸速率以及降低PG酶、PE酶和β-GAL酶活性密切相关。     

Induction of lignin and pathogenesis related proteins in dragon fruit plants in response to submicron chitosan dispersions

Chitosan is capable of triggering the induction of defence responses of the plants. This study was carried out to investigate in vitro and in vivo antifungal activity of submicron chitosan dispersions and also to determine the mechanism of induced resistance in dragon fruit plants by strengthening of cell wall and production of pathogenesis related proteins. Highest inhibition in radial mycelial growth (90.2%) was obtained by 600 nm droplet size at 1.0% chitosan concentration. None of the emulsifiers showed any antifungal effect during in vitro studies. Field studies showed the reduction of 22% disease incidence and 66% disease severity in anthracnose on dragon fruit plants treated with 600 nm droplet size as compared to control plants after one month of assessment. Lignin contents in cell wall of dragon fruit plants increased 2 folds in plants treated with 1.0% chitosan at 600 nm droplet size while 11 and 10 folds increase in β-1,3-glucanase and chitinase activity, respectively was also recorded in the plants inoculated with Colletotrichum gloeosporioides. The accumulation of lignin and higher level activity of pathogenesis related proteins in response to submicron chitosan dispersions may bolster in mounting effective resistance against the devastating disease of anthracnose.     

Agronomic and economic assessment of intensive pest management of dry bean (Phaseolus vulgaris)

Two common production constraints of dry bean (Phaseolus vulgaris) in Ontario are annual weeds and anthracnose (caused by Colletotrichum lindemuthianum). Dry bean is not considered a competitive crop and weed interference can result in substantial yield losses, while anthracnose is considered one of the most devastating diseases in dry bean production. A study conducted in Ontario Canada, examined the effect of two herbicide programs on weed management, thiamethoxam insecticide treatment on plant enhancement and three fungicide programs on anthracnose development in a navy bean cv. ‘OAC Rex’. The premium herbicide program (s-metolachlor + imazethapyr) reduced percent weed ground cover relative to the economic herbicide program (trifluralin) in five of six locations. Thiamethoxam increased emergence and vigour at only one location, which contradicts reported benefits of thiamethoxam on plant health. The herbicide or thiamethoxam treatments did not affect anthracnose disease severity, visible seed quality, net yield or economic return. The fungicide seed treatment was often superior to the untreated control, for a number of the parameters measured. The application date of the foliar fungicide, relative to the onset of disease, varied between site-years. This dramatically influenced the fungicide’s effectiveness. Foliar fungicides increased seed quality and net economic return compared to the control when applied prior to disease development. The combination of fungicide seed treatment followed by a foliar fungicide provided the largest reduction in anthracnose severity.