Walcott R R, McGee D C, Misra M K
Seed Science Center and Department of Plant Pathology, Iowa State University, Ames 50011.
Seed Science Center and Department of Agricultural and Biosystems Engineering, Iowa State University, Ames 50011.
Plant Dis. 1998 May;82(5):584-589. doi: 10.1094/PDIS.1998.82.5.584.
Different levels of asymptomatic, seed-borne infection by storage fungi (Aspergillus and Penicillium spp.) or Phomopsis seed decay (PSD) (Phomopsis longicolla, Diaporthe phaseolorum var. sojae, and D. phaseolorum var. caulivora) were induced in sub-lots of separate soybean seed lots by incubation of seeds or pods, respectively, for different times at 25°C and at a relative humidity >95%. Seeds were then air-dried to a constant moisture content in the laboratory atmosphere, and each sub-lot was tested for incidence of infection, germination, and moisture content. Individual seeds in each sub-lot also were dropped 10 cm onto a transducer in an ultrasound analyzer. The average peak value of the ultrasound signals for each sub-lot, which indicates the weight of seeds, decreased linearly as the incidence of seed infection by storage fungi (r = 0.85) or PSD (r =0.82) increased. The slope and width of the signal, which indicates seed softness, increased as seed infection increased for both groups of fungi, although coefficients of determination were lower (r ranged from 0.42 to 0.59). Germination values, which decreased as seed infection for both pathogens increased, showed similar but inverse relationships to ultrasound parameters. Peak values of ultrasound signals decreased, and slope and width increased, as seed moisture content increased for sub-lots of soybeans at three levels of infection by Phomopsis seed decay. The potential for ultrasound technology to identify soybean seeds with asymptomatic infections of seed-borne pathogens was thus established.
通过分别将种子或豆荚在25°C、相对湿度>95%的条件下培养不同时间，在单独的大豆种子批次的子批次中诱导出不同水平的无症状、种传真菌（曲霉属和青霉属）感染或拟茎点霉种子腐烂（PSD）（长喙拟茎点霉、大豆荚腐壳囊孢和菜豆荚腐壳囊孢）。然后将种子在实验室环境中风干至恒定水分含量，并对每个子批次进行感染发生率、发芽率和水分含量测试。每个子批次中的单个种子也被从10厘米高处掉落至超声分析仪中的换能器上。每个子批次超声信号的平均峰值表示种子重量，随着种传真菌（r = 0.85）或PSD（r = 0.82）引起的种子感染发生率增加而呈线性下降。信号的斜率和宽度表示种子柔软度，随着两组真菌引起的种子感染增加而增加，尽管决定系数较低（r范围为0.42至0.59）。发芽率随着两种病原体引起的种子感染增加而降低，与超声参数呈现相似但相反的关系。在拟茎点霉种子腐烂三种感染水平下，随着大豆种子子批次水分含量增加，超声信号峰值降低，斜率和宽度增加。因此，确立了超声技术识别无症状种传病原体感染大豆种子的潜力。
