Department of Plant, Soil, and Microbial Sciences, Michigan State University, East Lansing, MI 48824.
Department of Horticulture, Michigan State University, East Lansing, MI 48824.
Plant Dis. 2021 Jun;105(6):1843-1850. doi: 10.1094/PDIS-07-20-1469-RE. Epub 2021 May 6.
We assessed the effect of three antibiotics (streptomycin, oxytetracycline, and kasugamycin) on populations of the fire blight pathogen on apple flower stigmas during three field seasons. Application timing relative to presence on flower stigmas had little impact on population dynamics and subsequent disease incidence. Although populations on water-treated flowers increased to 10 cfu flower after 4 to 5 days during each experiment, the antibiotics streptomycin and kasugamycin caused statistically significant reductions in stigma populations by as many as 4 to 5 logs over a 4- to 5-day period during two of the three experiments. In contrast, the effect of oxytetracycline on populations on stigmas was more variable, with reductions in populations only observed during one of the three experiments. In agreement with the population data, the disease incidence was significantly higher for oxytetracycline-treated flowers compared with the other antibiotic treatments during 2 of 3 years. Statistical analyses of the effects of weather parameters on antibiotic activity revealed that solar radiation and temperature negatively impacted the activity of both kasugamycin and oxytetracycline. We further assessed the potential for photodegradation of formulated kasugamycin (Kasumin 2L) and found that Kasumin 2L was susceptible to degradation in vitro after exposure to a 16-h photoperiod of daily light integrals (DLIs) varying from 6 to 35 mol⋅m⋅d. We further determined that exposure to three consecutive 16-h photoperiods of DLIs of 23 or 35 mol⋅m⋅d reduced the available concentration of Kasumin 2L (assessed using a bioassay) from 100 μg⋅ml to 10 to 20 μg⋅ml. Our results correlate the superior blossom blight control efficacy of kasugamycin and streptomycin with significant population reductions in on apple flower stigmas but indicate that, similar to oxytetracycline, kasugamycin is vulnerable to photodegradation, which would suggest that further considerations are necessary when applying this antibiotic.
我们评估了三种抗生素（链霉素、土霉素和井冈霉素）在三个田间季节对苹果花柱头火疫病病原菌种群的影响。与花柱头存在时间相关的施药时间对种群动态和随后的发病率影响很小。尽管在每个实验中，经过 4 至 5 天处理的花上水处理花朵上的种群增加到 10 cfu 花，但在三个实验中的两个实验中，链霉素和井冈霉素在 4 至 5 天内使柱头种群数量减少了多达 4 至 5 个对数。相比之下，土霉素对柱头种群的影响更为多变，仅在三个实验中的一个实验中观察到对种群的减少。与种群数据一致的是，在 3 年中的 2 年中，与其他抗生素处理相比，土霉素处理花朵的发病率明显更高。对天气参数对抗生素活性影响的统计分析表明，太阳辐射和温度对井冈霉素和土霉素的活性均有负面影响。我们进一步评估了制剂井冈霉素（Kasumin 2L）光降解的可能性，发现 Kasumin 2L 在暴露于每日光照积分（DLIs）从 6 到 35 mol·m·d 的 16 小时光周期后，在体外容易降解。我们进一步确定，暴露于 3 个连续的 16 小时光周期，DLIs 为 23 或 35 mol·m·d，会使 Kasumin 2L 的可用浓度（通过生物测定评估）从 100 μg·ml 降低到 10 到 20 μg·ml。我们的结果表明，井冈霉素和链霉素对苹果花柱头病原菌的出色花腐病控制效果与苹果花柱头病原菌种群数量的显著减少有关，但表明与土霉素类似，井冈霉素易光降解，这表明在应用这种抗生素时需要进一步考虑。
