冰核细菌在我国北方玉米上的消长动态规律

Dynamic changes of ice nucleation active bacterial population inhabiting on corn in Northern China

研究证明,菠萝欧文氏菌(Erwinia ananas)为我国北方玉米上优势冰核细菌种类,占总体INA细菌95 %以上。采用定量定性和定期取样分离方法,首次研究INA细菌在玉米上的消长动态规律。结果表明:玉米不同生长发育阶段是影响INA细菌在玉米上数量分布和消长动态变化的重要因素,以抽雄至成熟期间分布INA细菌数量最多,高达10 7～10 8CFU/ g,比拔节至抽雄期高出2～3个数量级,比苗期至拔节期高出4～5个数量级;同时还指出,玉米不同播期,对INA细菌数量分布影响显著,差异很大,其中INA细菌分布数量消长变化,以正常播种(1.9×10 7CFU / g) >中期播种(7.9×10 5CFU/ g) >晚期播种(5 .0×10 4 CFU/ g) ;研究指出,处于抽雄至成熟期间的玉米上分布的INA细菌数量最多,因此期间(8月上旬至9月下旬) ,气温逐渐降低,昼夜温差大,田间结露多,加上玉米处于成熟阶段,抗INA细菌能力弱,这些因素有利于低温(5～2 0℃范围内生长)型INA细菌生长繁殖。

As reported in previous research, Erwinia ananas was the predominant ice nucleation active (INA) bacterial species, which covered over 95% of all INA bacteria inhabiting on corn in northern China. The dynamic changes of its population were first researched in this paper. The population of E. ananas inhabiting on corn in Datong and Jilin was checked periodically. The bacterial population varied greatly on different growing stages of corn. In Datong, during the period of heading to ripening, the bacterial population was most abundant with a population of 2.32×10~7CFU/g, while during the period of elongation to heading, the population decreased to 2.85×10~5CFU/g, and decreased further to 8.5×10~2CFU/g during the period of seedling to elongation. In Jilin, the population fluctuations of E. ananas exhibited a similar pattern, having a population of 1.2×10~8, 6.9×10~5, and 5.25×10~3CFU/g, respectively, for the 3 above-mentioned growing stages. This result demonstrated that growing stage of corn was an important factor influencing the population of E. ananas inhabiting on corns. During the period of heading to ripening, the population was at its maximum, being as high as 10~7～10~8CFU/g, 2～3 and 4～5 magnitude orders, respectively, higher than the period of elongation to heading and seedling to elongation. When the period of heading ripening meets the occurrence of early frost, the large population of INA bacteria will induce and worsen the frost damage to corn at -2℃ to -3℃. This study will be beneficial to predicting and relieving frost damage through monitoring and controlling INA bacteria. In Datong, three batches of corn were sowed with an interval of 30 days. The population of E. ananas inhabiting on corn was checked on Sept. 10th, displaying a population size of 1.9×10~7CFU/g, 7.9×10~5CFU/g, and 5.0×10~4CFU/g, respectively, for the three batches. The results showed that the sowing time affected the population size. The earlier sowing is, the higher population of E. ananas is. The population of E. ananas inhabiting on corn in Datong was about one magnitude order lower than that in Jilin. The higher altitude, stronger ultraviolet radiation and less rainfall in Datong than in Jilin might account for this result.