Phytopathology. 1997 Apr;87(4):440-5. doi: 10.1094/PHYTO.1997.87.4.440.
ABSTRACT The interactive effects of concomitant infection by the nematode Pratylenchus penetrans and the fungus Verticillium dahliae on symptom expression in Russet Burbank potato was studied in growth chamber experiments. Treatments were P. penetrans at three initial densities, V. dahliae at one inoculum density, the combination of the nematode at these three densities and the fungus, and a noninfested control. Gas exchange was measured nondestructively in leaf cohorts of different ages, one to three times weekly, with a LI-COR portable photosynthesis system. The single-pathogen treatments had no effect on assimilation or transpiration rates, but joint infection had a significant impact. In concomitant infection, photosynthesis was impaired more than transpiration, so estimates of leaf health were based on carbon assimilation rates only. Reductions in assimilation rate were apparent before the onset of visual symptoms. Assimilation rates decreased as much as 44% in the top, and newest, leaves of concomitantly infected plants, compared to rates in control plants. Even so, the health of newly produced leaves did not become progressively worse through time. With light use efficiency less than 0.20 mol of CO(2) fixed per mol of photosynthetically active radiation used as the criterion for disease incidence, disease progressed acropetally from the oldest to the youngest leaves. In plants infected with P. penetrans (0.8 nematodes per cm(3) of soil) in combination with V. dahliae, all leaves in cohorts 1 and 2 were symptomatic by 45 days after planting, and leaves in cohorts 3 to 6 became symptomatic at weekly intervals thereafter. For the control and single-pathogen treatments, the first time that light use efficiency fell below 0.20 in all leaves in cohort 1 was 71 days after planting. Concomitant infection reduced leaf life span by about 3 weeks. Both visual and physiological symptom expression were invariant to differences in initial nematode inoculum densities ranging from 0.8 to 2.5 nematodes per cm(3) of soil in one experiment and from 1.3 to 4.1 nematodes per cm(3) of soil in a second experiment.
摘要 在生长室实验中，研究了线虫旋纹潜蝇和真菌黄萎轮枝菌共同感染对 Russet Burbank 马铃薯症状表达的交互影响。处理方法为线虫旋纹潜蝇在三个初始密度下，真菌黄萎轮枝菌在一个接种密度下，线虫在这三个密度下与真菌组合，以及非侵染对照。每周一到三次，使用 LI-COR 便携式光合作用系统对不同年龄的叶群进行非破坏性气体交换测量。单一病原体处理对同化率或蒸腾率没有影响，但联合感染有显著影响。在共同感染中，光合作用受到的损害大于蒸腾作用，因此叶片健康的估计仅基于碳同化率。在出现视觉症状之前，同化率的降低就已经很明显了。与对照植株相比，共同感染植株顶部和最新的叶片同化率下降了 44%。即便如此，新产生的叶片的健康状况并没有随着时间的推移而逐渐恶化。当用光效率小于 0.20 摩尔 CO(2)固定/摩尔光合作用有效辐射作为发病标准时，疾病从最老的叶片向最年轻的叶片进行向顶性进展。在感染旋纹潜蝇（每厘米(3)土壤中有 0.8 条线虫）与黄萎轮枝菌组合的植株中，所有叶片在种植后 45 天内出现症状，而叶片在第 3 至 6 组则以每周一次的间隔出现症状。对于对照和单一病原体处理，在第 1 组所有叶片的光效率首次降至 0.20 以下是在种植后 71 天。共同感染使叶片寿命缩短了大约 3 周。在一个实验中，线虫初始接种密度从每厘米(3)土壤 0.8 到 2.5 条不等，在另一个实验中，线虫初始接种密度从每厘米(3)土壤 1.3 到 4.1 条不等，视觉和生理症状表达均不变。
