Effects of azoxystrobin, difenoconazole, polyoxin B (polar) and trifloxystrobin on germination and growth of Alternaria alternata and decay in red delicious apple fruit

Alternaria alternata is the predominant fungal pathogen responsible for moldy-core in red delicious strains of apple. In this study, we report on the effects of the polyoxin B compound Polar, the strobilurin fungicides, azoxystrobin and trifloxystrobin, and the sterol inhibitor difenoconazole on spore germination, mycelial growth and fruit decay on detached fruits caused by A. alternata. Germination was most sensitive to polyoxin B and trifloxystrobin among the tested compounds. The 50% and 95% effective concentration (EC₅₀, and EC₉₅), values for in vitro inhibition of conidial germination of the fungus were lowest for polyoxin B and trifloxystrobin, ranging from <0.01 to 0.15 μg/ml and 180 μg/ml, respectively. Germination was least sensitive to difenoconazole and azoxystrobin (EC₅₀ and EC₉₅ values ranging from 25 to 72 μg/ml and 720 μg/ml, respectively). Mycelial growth in vitro of A. alternata was most sensitive to difenoconazole (EC₅₀ and EC₉₅ values of 0.8 and 12 μg/ml, respectively) and least sensitive to both strobilurin fungicides (EC₉₅>1000 μg/ml). Decay formation by A. alternata on mature detached fruits was most affected by trifloxystrobin and azoxystrobin (EC₅₀ and EC₉₅ values of 0.015–0.087 μg/ml and 8 μg/ml, respectively), intermidiate in sensitivity to Polyoxin B (EC₅₀ and EC₉₅ from 1 to 33 μg/ml, respectively), and difenoconazole was the least effective (EC₅₀ and EC₉₅ from 20 to 490 μg/ml, respectively). Polyoxin B applied at 24 or 48 h post-inoculation inhibited fruit decay development. Difenoconazole and trifloxystrobin were less effective and azoxystrobin was ineffective when applied at 48 h post inoculation. The activity of azoxystrobin, difenoconazole, Polyoxin B and trifloxystrobin on one or more stages of the life cycle of A. alternata and on decay development in fruits suggests that these compounds potentially could provide control of moldy-core disease in apple.     

河南太行山南方红豆杉种子催芽研究

应用变温层积和激素处理,探讨打破太行山南方红豆杉种子休眠的技术。结果表明,高温处理时间与红豆杉的裂口数呈正相关;激素处理对种子萌发有明显促进作用;低温处理并非是种子裂口的必要条件。     

饲料中添加维生素E对不同养殖密度鲤鱼生产性能的影响

以建鲤为研究对象,采用2×3双因子试验设计,在基础饲料中分别添加0、62.5、187.5mg/kg维生素E,分别在两个养殖密度(15g/L和60g/L)下进行饲喂,探讨饲料中添加不同水平维生素E对不同养殖密度鲤鱼生产性能的影响。试验期为8周。结果表明:(1)养殖密度对鲤鱼的生长、摄食率和重量变异系数具有显著影响(P0.05)。高密度各组的特定生长率和摄食率均显著低于低密度组(P0.05),但是高密度组重量变异系数显著高于低密度组(P0.05)。(2)维生素E显著影响特定生长率(P0.05),对摄食率和重量变异系数无显著影响(P0.05)。同一养殖密度下,维生素E对低密度各组的生长无显著影响(P0.05);在高密度下,维生素E组的生长显著高于对照组。(3)维生素E和养殖密度的交互作用对鲤鱼的生长、饲料系数和重量变异系数影响显著(P0.05)。可见,在本试验条件下,随着鲤鱼养殖密度的增加,应适当增加维生素E的添加量来调控其摄食,进而促进生长和降低个体分化。