Spatial distribution of Phytophthora cactorum in New York apple orchard soils
Spatial distribution of Phytophthora cactorum in New York apple orchard soils
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纽约苹果园土壤中坏疽疫霉的空间分布
DOI：
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发表时间：
1996
期刊：
影响因子：
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通讯作者：
W. Wilcox
中科院分区：
文献类型：
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作者：
I. Horner;W. Wilcox
苹果果园土壤中恶疫霉休眠孢子的种群分布有3个明显的梯度。种群在坡底相对较高，随着距离的增加而下降，并与土壤含水量密切相关。种群数量随着离树干距离的增加而减少，在树木行除草剂带外接近于零。随着深度的增加，P. cactorum种群数量也急剧下降，约50%和70%的繁殖体分别位于土壤顶部3和6 cm处。在没有有机基质的情况下，繁殖体数量显着下降18个月后，在土壤表面或附近，但保持不变，在7至10厘米的深度，表明不断更新的表面种群，以保持陡峭的深度梯度。苹果落叶、落果和落花都能自然地被P. cactorum侵染。在秋季接种叶片的表面修正导致土壤种群的大幅增加，测量第二年春天，无论是在微区和直接下成熟的苹果树。从苹果树下土壤表层采集到大量的腐殖酸，5 ~ 9月平均为1.45kg/m2。这些土壤中含有相对较高的P. cactorum种群，其密度与土壤表层的密度相当，可能是造成所观察到的陡峭垂直梯度的原因。
Population assessments of dormant spores of Phytophthora cactorum in apple orchard soils yielded three clear distribution gradients. Populations at the bottoms of slopes were relatively high, declined with increasing distance up slopes, and strongly correlated with soil moisture content. Populations decreased with increasing distance from the tree trunk, becoming close to nil outside the tree-row herbicide strip. There was also a sharp decline in P. cactorum populations with increasing depth with approximately 50 and 70% of propagules in the top 3 and 6 cm of soil, respectively. In the absence of organic substrates, propagule numbers declined significantly after 18 months at or near the soil surface, but remained constant at 7- to 10-cm depth, indicating continual renewal of surface populations to maintain the steep depth gradient. Fallen apple leaves, fruit, and petals were all naturally colonized by P. cactorum in the field. Surface amendments with inoculated leaves in the fall resulted in a substantial increase in soil populations measured the following spring, both in microplots and directly beneath mature apple trees. Large quantities of earthworm castings (1.45 kg/m 2 from May to September) were collected from the soil surface beneath apple trees. These contained relatively high populations of P. cactorum at densities comparable with those in the surface layers of soil and were likely to have contributed to the steep vertical gradient observed.