The relationship between antifungal diene levels and fungal inhibition during quiescent infection of unripe avocado fruits by Colletotrichum gloeosporioides

Quantitative changes in the antifungal compound, 1-acetoxy-2-hydroxy-4-oxo-heneicosa-12.15-diene, in freshly harvested avocado fruits during the initial stages of fungal development were investigated to determine the possible involvement of the compound in quiescent infections of Colletotrichum gloeosporioides. The concentration of the antifungal compound in the peel decreased to subfungitoxic concentrations 16 h after harvest. Fifty-six hours later the antifungal diene had increased to c . 3800 μg/g fresh weight. At this stage, germinated appressoria had penetrated the cuticle to the epidermal cells but no fungal development was observed until 7 days later when the concentration of the diene had decreased to 100-110μg/g fresh weight. Following a dip treatment at 55°C for 5 or 10 min, the antifungal diene concentration decreased as in the controls, but it remained at subfungitoxic concentrations for a longer period enabling fungal development and early symptom expression.
The concentration of the diene in the flesh of freshly harvested fruit decreased to 120 μg/g fresh weight 24 h after harvest. Inoculation of peeled fruits with spores of C. gloeosporioides showed germination without appressoria formation and symptom expression occurred 24-48 h later. Symptom expression was delayed if fruits were inoculated after coating the flesh with epicuticular wax extracts or if the flesh was inoculated 3 days after harvest when the antifungal diene had regained a fungitoxic concentration. Disease symptoms were expressed in soft fruits containing subfungitoxic concentrations of the diene.
We conclude that the diene in unripe avocado fruits inhibits fungal development of germinated appressoria or conidia. The quiescent structure of C. gloeosporioides in unripe avocado fruit is a subcuticular hypha.     

Development of Colletotrichum gloeosporioides Restriction Enzyme-Mediated Integration Mutants as Biocontrol Agents Against Anthracnose Disease in Avocado Fruits

ABSTRACT Reduced-pathogenicity mutants of the avocado fruit pathogen Colletotrichum gloeosporioides isolate Cg-14 (teleomorph: Glomerella cingulata) were generated by insertional mutagenesis by restriction enzyme-mediated integration (REMI) transformation. Following seven transformations, 3,500 hygromycin-resistant isolates were subjected to a virulence assay by inoculation on mesocarp and pericarp of cv. Fuerte avocado fruits. Fourteen isolates showed a reduced degree of virulence relative compared with wild-type Cg-14. Two isolates, Cg-M-142 and Cg-M-1150, were further characterized. Cg-M-142 produced appressoria on avocado pericarp similar to Cg-14, but caused reduced symptom development on the fruit's pericarp and mesocarp. Isolate Cg-M-1150 did not produce appressoria; it caused much reduced maceration on the mesocarp and no symptoms on the pericarp. Southern blot analysis of Cg-M-142 and Cg-M-1150 showed REMI at different XbaI sites of the fungal genome. Pre-inoculation of avocado fruit with Cg-M-142 delayed symptom development by the wild-type isolate. Induced resistance was accompanied by an increase in the levels of preformed antifungal diene, from 760 to 1,200 mug/g fresh weight 9 days after inoculation, whereas pre-inoculation with Cg-M-1150 did not affect the level of antifungal diene, nor did it delay the appearance of decay symptoms. The results presented here show that reduced-pathogenicity isolates can be used for the biological control of anthracnose caused by C. gloeosporioides attack.     

The role of phytoalexins in resistance to fusarium wilt in pigeon pea (Cajanus cajan)

Mechanisms of resistance to fusarium wilt (Fusarium udum) were investigated in pigeon pea cultivars from Malawi. Wilt-susceptible (Malawi local) and wilt resistant (ICP 9145) plants were stem-inoculated with a spore suspension containing 2·10⁶ conidia/ml of the pathogen. Occlusion of a small proportion of infected vessels was observed, but the resistant reaction appeared to depend mainly on rapid phytoalexin synthesis. Four fungitoxic isoflavonoid phytoalexins—hydroxygenistein, genistein, cajanin and cajanol-were isolated from plants 15 days after inoculation. Cajanol was identified as the main antifungal compound. The concentration of cajanol was 329·4 μg/g in the resistant cultivar as against 88·6 μg/g in the susceptible cultivar 15 days after inoculation. Crude extract from the resistant plants sampled at 24 h after inoculation contained 34·8 μg ml of cajanol. The LD₅₀ value of cajanol for spore germination was determined as 35μg/ml. The cajanol content of fungus-infected ICP 9145 10 days after inoculation totally inhibited conidial germination of F. udum.     

大黄酚对黄瓜白粉病菌的抑制作用研究

 采用子叶喷雾法分别测定了大黄酚(chrysophanol)对黄瓜白粉病菌(Sphaerotheca fuliginea)的保护和治疗生物活性。结果表明,大黄酚能有效降低黄瓜白粉病的病情指数,其保护和治疗作用的EC₅₀分别为0.23μg/mL和25.88μg/mL,对照药剂50%硫磺悬浮剂保护作用的EC₅₀为59.75μg/mL,10%苯咪甲环唑可湿性水分散粒剂治疗作用的EC₅₀为13.55μg/mL。在此基础上,利用2.4μg/mL大黄酚溶液处理黄瓜子叶24h后接种白粉病菌,在不同时段对病组织进行透明染色观察白粉病菌的变化情况。结果发现,大黄酚可有效降低黄瓜白粉病菌分生孢子的萌发率和萌发芽管个数,并能抑制菌丝的生长以及降低新生分生孢子的个数。接菌后24h,清水对照萌发率为66.6%,而大黄酚处理后的孢子不萌发;接菌后48h,对照菌丝的平均长度为414.7μm,大黄酚处理的菌丝平均长度为40.1μm;接菌后144h,对照的新生分生孢子串最多为8个孢子,大部分为6-7个,而大黄酚处理后的新生分生孢子串孢子个数最多为2个,大部分为1个。接菌7d后对照的病情指数为72.2,大黄酚处理组的病情指数仅为2.1,其保护作用防治效果达到97.1%,远高于50%硫磺悬浮剂65.4%的防效。     

毒死蜱在梨果实不同部位的残留及消解动态

为探明毒死蜱在梨果实不同部位的残留及消解规律,以20 a生鸭梨（Pyrus bretschneideri Rehd.cv.Yali）为试材,于果实生长期在套袋后向整株喷施48%毒死蜱乳油500倍液（有效成分960 mg/L）,分析毒死蜱向果实中的运输及分配规律;于果实成熟期在采收前向果面喷施48%毒死蜱乳油1 000倍液（有效成分480 mg/L）,分析采后毒死蜱在梨果实不同组织中的分布特征。采用乙腈萃取和GC-NPD检测方法,测定不同处理试材中的毒死蜱含量。结果表明,在果实套袋情况下,整株喷施毒死蜱后72 h内果实不同部位（果心除外）毒死蜱含量均呈现先逐渐上升而后下降趋势,其中果柄、果皮和果梗洼中毒死蜱最高含量值及其出现的时间分别为6.66 mg/kg（12 h）、2.42 mg/kg（24 h）和0.09 mg/kg（12 h）,表明套袋果实毒死蜱来源于枝叶运输,经果柄进入果实后易向果皮累积;而未套袋果施药后24和72 h果皮中毒死蜱含量分别为套袋果的12.56和7.29倍,表明套袋可有效降低果实中毒死蜱的残留量。于果实成熟期向果面喷施毒死蜱后7、14和25 d,果皮中毒死蜱残留量分别为15.54、13.70和12.81 mg/kg,占全果含量的100%,而果肉中毒死蜱残留量低于本检测方法的最低检出浓度（0.05 mg/kg）,因此果皮为果实中毒死蜱主要残留部位,且贮藏期果皮中毒死蜱不易向果肉扩散。     

Control and prevention of contact infection of brown rot disease with fosetyl-aluminium,and residue levels in post-harvest-treated citrus fruits

The effect of fosetyl-aluminium on the control and spread of brown rot disease Phytophthora citrophthora in post-harvest citrus fruit was studied in laboratory and semi-commercial experiments. Aqueous solutions of fosetyl-aluminium at 5 to 10 g a.i. litre^?1 controlled the fungus even when applied 3 days after inoculation at 17°C. No mycelia developed on the peel surface of treated fruit. The fungicide exerted a good prophylactic effect on healthy fruit, protecting them during storage from contact inoculation. Fosetyl-aluminium also showed a fungitoxic effect in vitro and in vivo on other fungi which developed in harvested citrus fruits. Residue levels of phosphoric acid in the treated fruit were higher when the fungicide was incorporated in the wax coating the fruit than when applied in aqueous solution, and levels were lower in the pulp than in the peel. It is concluded that fosetyl-aluminium is a suitable commercial post-harvest treatment for control of brown rot in citrus fruits.     

Involvement of antifungal compounds from rockmelon fruit rind (<Emphasis Type="Italic">Cucumis melo</Emphasis> L.) in resistance against the fruit rot pathogen <Emphasis Type="Italic">Fusarium oxysporum</Emphasis> f. sp. <Emphasis Type="Italic">melonis</Emphasis>.

Fusarium rot caused by Fusarium oxysporum f. sp. melonis, causes significant postharvest losses in rockmelon crops. Although latent infection is often present in the field, symptoms of the disease may not appear until fruit maturity. The susceptibility of different-aged rockmelon fruit cv. “Colorado” was determined by inoculating fruit at different stages of development with a spore suspension of F. oxysporum f. sp. melonis. Disease symptoms appeared first and were more severe in older fruit compared to younger fruit. Disease symptoms on fruit 35 DAA (Days After Anthesis) and 42 DAA appeared within 3 days of inoculation and rapidly covered the fruit within 5 days. In contrast, disease symptoms on fruit 7 DAA appeared 6 days after inoculation and grew slowly. Extraction of antifungal compounds without involving acid hydrolysis from 7 DAA fruit rind did not show antifungal activity on TLC plates. However, hydrolysis of the ethyl acetate fraction resulted in a strong fungal inhibitory zone on agar plates against colonies of F. oxysporum f. sp. melonis. Separation of the hydrolysed crude extracts on TLC plates indicated the presence of two distinct antifungal zones with R_f 0.36 and 0.13 in young fruit 7, 14 and 21 DAA. The area of fungal inhibition of compound R_f 0.36 was greater than that of R_f 0.13 on the TLC plate. Extracts from mature fruit of 35 and 42 DAA did not have detectable levels of antifungal compounds. The decrease in the susceptibility of rockmelon fruit during maturity may be correlated to a decrease in the antifungal compounds in the fruit with maturity.     

Evaluation of the systemic activity of simeconazole in comparison with that of other DMI fungicides

The systemic activity of simeconazole (RS-2-(4-fluorophenyl)-1-(1H-1,2,4-triazol-1-yl)-3-trimethylsilylpropan-2-ol) in plants was compared with those of eight other sterol demethylation inhibitor (DMI) fungicides. Simeconazole prevented the infection of Blumeria graminis (DC) Speer f sp hordei Marchal on barley leaves within a radius of several centimeters from the edge of local treatment on the leaves when the compound was separated from the leaves by glass coverslips. This reveals that simeconazole has prominent vapour-phase activity. Simeconazole showed excellent curative activity against barley powdery mildew when treated 1-3 days after inoculation. Furthermore, this indicates that simeconazole has notable translaminar activity because, when the compound was applied onto either the adaxial or abaxial leaf surface, it showed excellent efficacy against powdery mildew on the opposite side of the leaf surface of barley and cucumber. Simeconazole also showed excellent efficacy against barley powdery mildew by soil drench 24h after inoculation. This suggests that simeconazole was absorbed very quickly into the barley plant after treatment. The permeability of the compound through cuticular membranes prepared from tomato fruits was about 20% at 22 h after the treatment and was much superior to that of the other DMI fungicides tested.     

Saccharin-induced protection against powdery mildew in barley: effects on growth and phenylpropanoid metabolism

Treatment of barley ( Hordeum vulgare ) with 3 m m saccharin, applied as a foliar treatment to the first leaf or as a soil drench, provided significant control of powdery mildew ( Blumeria graminis f.sp. hordei ) on first and second leaves. This was unlikely to be the result of a direct effect of saccharin on the fungus, as application of the chemical to first leaves 2 h before inoculation did not affect conidial germination or formation of appressoria. Saccharin treatment had no significant effect on plant growth, except for a reduction in total leaf area in plants treated with a saccharin drench 14 days before inoculation with mildew. Phenylalanine ammonia-lyase activity was reduced significantly in second leaves 18 and 48 h after inoculation in plants treated with saccharin 14 days earlier. Peroxidase activity increased significantly in plants challenged with mildew within 6 days of saccharin application, although changes were not apparent until 48 h after pathogen challenge. On these occasions, treatment with saccharin resulted in a 33% increase in peroxidase activity compared with controls. In plants inoculated 10 or 14 days after saccharin application, cinnamyl alcohol dehydrogenase (CAD) activity increased prior to, and 18, 24 and 48 h after, inoculation of the barley plants with mildew. CAD activity increased approximately twofold compared with controls. However, in contrast to peroxidase, CAD activity was significantly higher in saccharin-treated plants prior to and after inoculation with powdery mildew, suggesting that saccharin primes CAD activity prior to pathogen challenge.     

茚嗪氟草胺及其代谢物在柑橘和土壤中的残留及消解动态

为明确茚嗪氟草胺及其代谢物indaziflam-diaminotriazine(IND-D),indaziflam-carboxylic acid(IND-C),indaziflam-triazine-indanone(IND-T),indaziflam-hydroxyethyl(IND-H),indaziflam-o...     

A new method for inoculation of fruit with <Emphasis Type="Italic">Guignardia citricarpa</Emphasis>, the causal agent of citrus black spot

Citrus black spot (CBS) is a fungal disease, caused by Guignardia citricarpa, that has a high economic impact on citrus. Although G. citricarpa has been associated with black spot of citrus, an adequate pathogenicity test is still not available. Thus, our objective was to develop and evaluate a simple, safe, and practical pathogenicity test. We used fruits from Pera-Rio and Valencia sweet orange trees from two different orchards, located in the State of São Paulo, Brazil. Inoculation was performed by placing six disks colonized by G. citricarpa, onto the peel of healthy fruits, previously bagged. In the Pera-Rio sweet orange grove, initial symptoms of the false melanose type resulting from the inoculations were observed 55 days after inoculation (dai). In the Valencia grove, initial symptoms also of the false melanose type resulting from the inoculations occurred 73 dai. A total of 92.8% and 86.6% of the Pera Rio and Valencia fruits inoculated, respectively, showed symptoms of CBS. Citrus black spot symptoms were not observed in any of the control fruits.     

Concentrations of constitutive alk(en)ylresorcinols in peel of commercial mango varieties and resistance to postharvest anthracnose

Mature green mango fruits of commercially important varieties were screened to investigate the levels of constitutive antifungal compounds in peel and to assess anthracnose disease after inoculation with Colletotrichum gloeosporioides. High-pressure liquid chromatography was used to quantify the levels of 5-n-heptadecenylresorcinol and 5-n-pentadecylresorcinol in the peel extracts. The fruit peel of the varieties ‘Kensington Pride’ and ‘Keitt’ were observed to have the highest levels of both 5-n-heptadecenylresorcinol (107.3–123.7 and 49.9–61.4 μg/g FW, respectively) and 5-n-pentadecylresorcinol (6.32–7.99 and 3.30–6.05 μg/g FW, respectively), and the fruits of the two varieties were found to have some resistance to postharvest anthracnose. The varieties ‘Kent’, ‘R2E2’, ‘Nam Doc Mai’, ‘Calypso’ and ‘Honey Gold’ contained much lower concentrations of resorcinols in their peel and three of these varieties were found to be more susceptible to anthracnose. Concentrations of 5-n-heptadecenylresorcinol were significantly lower at the ‘sprung’ and ‘eating ripe’ stages of ripening compared to levels at harvest. Concentrations of 5-n-pentadecylresorcinol did not differ significantly across the three stages of ripening. The levels of these two resorcinols were found to be strongly inter-correlated (P<0.01, r²=0.71), with concentrations of 5-n-heptadecenylresorcinol being an average 18 times higher than those of 5-n-pentadecylresorcinol. At the ‘eating ripe’ stage, significant relationships were observed between the concentrations of each type of alk(en)ylresorcinol and anthracnose lesion areas following postharvest inoculation, P<0.001, r²= 0.69 for 5-n-pentadecylresorcinol, and P<0.001, r²= 0.44 for 5-n-heptadecenylresorcinol.     

Stress on avocado fruits regulates Δ9-stearoyl ACP desaturase expression,fatty acid composition,antifungal diene level and resistance to Colletotrichum gloeosporioides attack

The expression of the avocado homologue avfad9 encoding Δ⁹-stearoyl-ACP desaturase was enhanced by multiple stimuli: inoculation with Colletotrichum gloeosporioides, exposure to ethylene or CO₂, low temperature (4 °C) and fruit wounding. This enhanced expression was correlated with an increase in the preformed antifungal (Z, Z)-1-acetoxy-2-hydroxy-4-oxo-heneicosa-12,15-diene. Treatments of fruits with ethylene that enhanced the up-regulation of avfad9 also increased the concentration of 18:2 fatty acid and the incorporation of ¹⁴C-linoleate into the antifungal diene. Fruits with enhanced Δ⁹stearoyl-ACP desaturase expression were more resistant to C. gloeosporioides. It is suggested that the enhanced Δ⁹stearoyl-ACP desaturase expression is involved in elevation of unsaturated 18:2. It is also concluded that similar treatments enhance the incorporation of labeled 18:2 into the antifungal diene and elicit the concurrent enhanced resistance to fungal attack.     

多羟基双萘醛提取物WCT抗病毒的生理病理学研究

 本文研究了多羟基双萘醛提取物WCT处理西葫芦后,对西瓜花叶病毒的防效和抗病毒相关酶活性及超微结构变化。结果发现,先喷WCT 24 h后接种的相对预防效果为83.7%,高于先喷病毒A 24 h后接种的预防效果和先接种24 h后喷WCT的治疗效果。WCT预防处理能在喷药后第3 d或第9 d相对于接种未喷药处理的PPO、POD和PAL的活性显著提高,且3种酶活性随时问推移都有一个上升-下降-上升的交替起伏的变化趋势;能诱导西葫芦在Rf值为0.33、0.36、0.43处多出3条新的PPO同工酶带,能增强2条在Rf值为0.73和0.79的POD同工酶带。WCT治疗处理酶活性变化规律与接种未喷药处理的对照相近,对寄主植物没有诱导作用。在西葫芦发病初期,相对于接种未喷药处理的对照,WCT预防处理的西葫芦叶肉细胞内病毒内含体数量减少,内含体的形状主要以风轮状为主,叶绿体和线粒体没有解体现象,且叶绿体中淀粉粒膨大积累,叶绿体附近嗜锇颗粒增多。WCT治疗处理与接种未喷药处理的几乎没有明显差异。     

Concentrations of constitutive alk(en)ylresorcinols in peel of commercial mango varieties and resistance to postharvest anthracnose

Mature green mango fruits of commercially important varieties were screened to investigate the levels of constitutive antifungal compounds in peel and to assess anthracnose disease after inoculation with Colletotrichum gloeosporioides. High-pressure liquid chromatography was used to quantify the levels of 5-n-heptadecenylresorcinol and 5-n-pentadecylresorcinol in the peel extracts. The fruit peel of the varieties ‘Kensington Pride’ and ‘Keitt’ were observed to have the highest levels of both 5-n-heptadecenylresorcinol (107.3–123.7 and 49.9–61.4 μg/g FW, respectively) and 5-n-pentadecylresorcinol (6.32–7.99 and 3.30–6.05 μg/g FW, respectively), and the fruits of the two varieties were found to have some resistance to postharvest anthracnose. The varieties ‘Kent’, ‘R2E2’, ‘Nam Doc Mai’, ‘Calypso’ and ‘Honey Gold’ contained much lower concentrations of resorcinols in their peel and three of these varieties were found to be more susceptible to anthracnose. Concentrations of 5-n-heptadecenylresorcinol were significantly lower at the ‘sprung’ and ‘eating ripe’ stages of ripening compared to levels at harvest. Concentrations of 5-n-pentadecylresorcinol did not differ significantly across the three stages of ripening. The levels of these two resorcinols were found to be strongly inter-correlated (P<0.01, r²=0.71), with concentrations of 5-n-heptadecenylresorcinol being an average 18 times higher than those of 5-n-pentadecylresorcinol. At the ‘eating ripe’ stage, significant relationships were observed between the concentrations of each type of alk(en)ylresorcinol and anthracnose lesion areas following postharvest inoculation, P<0.001, r²= 0.69 for 5-n-pentadecylresorcinol, and P<0.001, r²= 0.44 for 5-n-heptadecenylresorcinol.     

新烟碱类杀虫剂在苹果果实不同部位中的残留

为了明确噻虫嗪、烯啶虫胺、吡虫啉、啶虫脒、噻虫胺和呋虫胺6种新烟碱类杀虫剂在苹果果实不同部位中的迁移转化规律,以10年生红富士苹果树为试材,分别于蚜虫发生期 (7月10日) 和果实采收前1 d (9月25日) 通过整株喷雾施药,随机取样,采用高效液相色谱仪测定,外标法定量,分析各杀虫剂在生长期套袋果实和不套袋果实及储藏期果实不同部位中的残留量及迁移规律。结果表明:在果实套袋情况下,施药后72 h内果实不同部位各新烟碱类杀虫剂的含量均呈现先逐渐上升而后下降的趋势,且在果皮中的残留量最低 (均低于0.08 mg/kg),其中烯啶虫胺和吡虫啉在果皮中的残留量低于最低检测浓度,而在果柄和果肉中的残留量明显高于果皮中的,表明套袋果实中药剂主要来源于枝叶运输,经果柄进入果实后易向果肉累积;在果实未套袋情况下,施药后72 h 6种杀虫剂在果肉中的含量均高于套袋果实果肉中的,分别是套袋果实果肉中含量的7.75、3.52、3.36、6.57、2.92和3.06倍,表明套袋可有效降低果实中该类药剂的残留量。储藏试验结果表明:直接向果面喷施6种新烟碱类杀虫剂后,药剂主要存在于果皮中,施药后14和21 d在果肉中的含量均低于最低检测浓度,表明储藏期果皮为该类药剂的主要残留部位,且不易向果肉中转移。     

Efficacy of oxolinic acid and other bactericides in suppression ofErwinia amylovora in pear orchards in Israel

The efficacy of oxolinic acid (at 200 and 300 μg a.i./l) and of several antibiotic compounds (streptomycin sulfate at 100 μg a.i./l, glycocide B at 700 μg a.i./l, kasugamycin at 80 μg a.i./l and gentamicin sulfate at 30 and 60 μg a.i./l) againstErwinia amylovora, the causal agent of fire blight in pears, was evaluated in 43 orchard experiments in 1997–2000 in Israel. In addition to the above orchard experiments, the efficacy of the bactericides was tested in live experiments with artificial inoculation. Natural fire blight symptoms were observed in 16 of the 43 experiments; in 13 of them, disease intensity and its distribution among the experimental plots provided a basis for data analysis, leading to reliable conclusions concerning the efficacy of the tested bactericides. Oxolinic acid at 300 μg a.i./l was highly effective againstE. amylovora and reduced disease severity significantly in all experiments, as compared with the untreated plots; however, a concentration of 200 μg a.i./l was not effective in some cases. Among the tested antibiotics, only gentamicin sulfate was as effective as oxolinic acid. Results of the artificial inoculation experiments corroborated those obtained in the naturally infected orchards. The pre-infection activity of oxolinic acid was determined on blossom clusters that were sprayed with the bactericide before inoculation. Control efficacy on blossom clusters sprayed 1–4 days before inoculation ranged from 68% to 80%, a level which did not differ significantly from that observed on blossom clusters sprayed on the day of inoculation (80% control). The postinfection activity of oxolinic acid was determined on blossom clusters that were sprayed with the compound after inoculation. Oxolinic acid was as effective when applied 1 or 2 days after inoculation as when it was applied on the day of inoculation; however, application of the bactericide 3 days after inoculation no longer resulted in significant disease suppression. Oxolinic acid has been used commercially in Israel since 1998 with appreciable success. Contribution No. 533-00 from the Agricultural Research Organization     

Effect of GRAS compounds on Aspergillus rot of wood-apple (Feronia limonia)

Fruit rot caused by Aspergillus niger is a major postharvest problem in wood-apple, Feronia limonia Swingle (syns. F. elephantum Correa; Limonia acidissima L.; Schinus limonia L. [Rutaceae]). The effect of four Generally Recommended As Safe (GRAS) compounds—sodium bicarbonate, calcium chloride, citric acid and sodium benzoate—in different concentrations was evaluated on mycelium growth and spore germination. The effectiveness of the compounds was investigated on inoculated and naturally infected fruits. Sodium bicarbonate (4%) completely inhibited the mycelial growth and spore germination. Fruits that were first inoculated and then treated with 4% sodium bicarbonate, or the reverse, gave 53.6% and 98.4% disease reduction, respectively. Non-treated control fruits were diseased completely 3 days after inoculation. Sodium bicarbonate treatment on naturally infected fruits controlled the disease by 100% and extended the storage life up to 28 days at 27?±?2°C and 65–70% r.h. Sensory attributes of the treated fruits did not change during storage.     

杧果炭疽菌拮抗细菌的筛选鉴定及其防病效果

为寻找对杧果炭疽菌Colletotrichum gloeosporioides有效的生防菌株,从瓜叶白粉病病斑上分离得到104株细菌,通过平板对峙培养筛选出16株拮抗细菌,分别测定其在8种不同培养基中的抑菌活性,筛选出有较强抑菌作用的9A、26A和4N菌株进行室内、果园防病试验,并对具有较好防治作用的9A、26A菌株进行了鉴定。结果显示,拮抗菌9A、26A和4N分别在南瓜汁、红薯汁和马铃薯汁培养基上的抑菌活性最高,对杧果炭疽菌菌丝生长抑制率分别为88.83%、87.83%和85.87%;室内9A、26A和4N菌株菌液处理离体果实,24 h后接种炭疽菌分生孢子液,对杧果炭疽病的防治效果均达100%,与咪鲜胺对照组相同;在果园9A和26A的防病效果分别为98.4%和90.5%,显著高于对照组的防效78.8%,而4N的防效只有58.2%。根据形态、生理生化特征及16S rDNA 序列分析结果,将菌株9A和26A鉴定为枯草芽胞杆菌Bacillus subtilis。研究表明,菌株9A和26A具有较好的生防利用价值。