莧菜自銹病之感染源與其病勢之進展

Inoculum Sources of Amaranth White Rust and Its Disease Development

李敏郎( M.L Lee) ； 謝文瑞( W.H Hsieh)

《植物病理學會刊》 12卷3期 (2003/09) Pp. 163-172

https://doi.org/10.6649/PPB.200309_12(3).0004

摘要

During July-August in 2001 and 2002, disease development of amaranth white rust caused by Albugo bliti were investigated continuously in amaranth monoculture fields at Hsilo in the central Taiwan. During the experimental periods, the recorded temperatures and relative humidities were 25-31℃ and 80-100% respectively, and duration of optimal temperature and relative humidity for sporangial germination lastec 11-14 hr and 9-12 hr everyday, respectively, were the suitable conditions for the disease development. Increase of plant height and leaf numbers of amaranth exhibited the exponential and logistic growth model, respectively, during 2001's trial. Relationship between leaf numbers and amaranth white rust showed the linearity (R2 ＞ 0.9). Before trials, the primary inoculum densities of A. bliti in soil varied between 220 and 260 sporangia/g soil were detected and no sporangium was trapped from the air. Based on the analysis of sporangial density in the air, the infected cotyledons and diseased leaves of seedlings were the main sources of the secondary inocula which produced maximally at 3-4 leaf stage. Disease development of white rust exhibited the Gompertz model with an asymmetric sigmoid curve. The accumulated frequencies of diseased leaf numbers on the 4th to 8th leaf order from the top were varied between 47-75%. Indices of dispersion, vanance-to-mean ratio (VM) and Lloyd's index of patchiness, both were used in spatial analysis of white rust in the field. Spatial pattern of white rust in the field. Spatial pattern of white rust in the field was random at cotyledon and one leaf stage (VM= I, LIP= I), and quickly became regular pattern (VM=O.OO6-0.96, LIP=O.OOO8-0.68). The results obtained from the disease incidenee inferred the optimal sample size needed at least 300 samples to decide whether white rust was occurred when the precision level was set at 0.2-0.25 and disease incidence was at 10% after seeds were sowed 14 days later.

關鍵字

莧菜 ； 白銹病 ； 感染源 ； 病勢進展 ； 空間分布 ； 最適取樣數

並列摘要

During July-August in 2001 and 2002, disease development of amaranth white rust caused by Albugo bliti were investigated continuously in amaranth monoculture fields at Hsilo in the central Taiwan. During the experimental periods, the recorded temperatures and relative humidities were 25-31℃ and 80-100% respectively, and duration of optimal temperature and relative humidity for sporangial germination lastec 11-14 hr and 9-12 hr everyday, respectively, were the suitable conditions for the disease development. Increase of plant height and leaf numbers of amaranth exhibited the exponential and logistic growth model, respectively, during 2001's trial. Relationship between leaf numbers and amaranth white rust showed the linearity (R2 ＞ 0.9). Before trials, the primary inoculum densities of A. bliti in soil varied between 220 and 260 sporangia/g soil were detected and no sporangium was trapped from the air. Based on the analysis of sporangial density in the air, the infected cotyledons and diseased leaves of seedlings were the main sources of the secondary inocula which produced maximally at 3-4 leaf stage. Disease development of white rust exhibited the Gompertz model with an asymmetric sigmoid curve. The accumulated frequencies of diseased leaf numbers on the 4th to 8th leaf order from the top were varied between 47-75%. Indices of dispersion, vanance-to-mean ratio (VM) and Lloyd's index of patchiness, both were used in spatial analysis of white rust in the field. Spatial pattern of white rust in the field. Spatial pattern of white rust in the field was random at cotyledon and one leaf stage (VM= I, LIP= I), and quickly became regular pattern (VM=O.OO6-0.96, LIP=O.OOO8-0.68). The results obtained from the disease incidenee inferred the optimal sample size needed at least 300 samples to decide whether white rust was occurred when the precision level was set at 0.2-0.25 and disease incidence was at 10% after seeds were sowed 14 days later.

並列關鍵字

edible amaranth ； white rust ； inoculum ； disease development ； spatial pattern ； optimal sample size