University of Florida-NFREC, USA.
Phytopathology. 2012 Aug;102(8):794-803. doi: 10.1094/PHYTO-10-11-0294.
Soybean rust (SBR), caused by Phakopsora pachyrhizi, is a damaging fungal disease of soybean (Glycine max). Although solar radiation can reduce SBR urediniospore survival, limited information is available on how solar radiation affects SBR progress within soybean canopies. Such information can aid in developing accurate SBR prediction models. To manipulate light penetration into soybean canopies, structures of shade cloth attenuating 30, 40, and 60% sunlight were constructed over soybean plots. In each plot, weekly evaluations of severity in lower, middle, and upper canopies, and daily temperature and relative humidity were recorded. Final plant height and leaf area index were also recorded for each plot. The correlation between amount of epicuticular wax and susceptibility of leaves in the lower, middle, and upper canopies was assessed with a detached leaf assay. Final disease severity was 46 to 150% greater in the lower canopy of all plots and in the middle canopy of 40 and 60% shaded plots. While daytime temperature within the canopy of nonshaded soybean was greater than shaded soybean by 2 to 3°C, temperatures recorded throughout typical evenings and mornings of the growing season in all treatments were within the range (10 to 28.5°C) for SBR development as was relative humidity. This indicates temperature and relative humidity were not limiting factors in this experiment. Epicuticular wax and disease severity in detached leaf assays from the upper canopy had significant negative correlation (P = 0.009, R = -0.84) regardless of shade treatment. In laboratory experiments, increasing simulated total solar radiation (UVA, UVB, and PAR) from 0.15 to 11.66 MJ m(-2) increased mortality of urediniospores from 2 to 91%. Variability in disease development across canopy heights in early planted soybean may be attributed to the effects of solar radiation not only on urediniospore viability, but also on plant height, leaf area index, and epicuticular wax, which influence disease development of SBR. These results provide an understanding of the effect solar radiation has on the progression of SBR within the soybean canopy.
大豆锈病（SBR）由 Phakopsora pachyrhizi 引起，是大豆（Glycine max）的一种破坏性真菌病。虽然太阳辐射可以降低 SBR 担孢子的存活率，但关于太阳辐射如何影响大豆冠层内 SBR 进展的信息有限。这些信息可以帮助开发准确的 SBR 预测模型。为了控制太阳辐射进入大豆冠层，在大豆田上构建了遮阳网结构，分别衰减 30%、40%和 60%的阳光。在每个地块中，每周评估下部、中部和上部冠层的严重程度，并记录每日温度和相对湿度。每个地块还记录了最终植物高度和叶面积指数。用离体叶片测定法评估了下、中、上部叶片表皮蜡质含量与叶片易感性之间的相关性。所有处理中下部冠层的最终病情严重度比未遮荫大豆高 46%至 150%，40%和 60%遮荫处理的中部冠层也较高。虽然未遮荫大豆冠层内的日间温度比遮荫大豆高 2 至 3°C，但在整个生长季节的典型傍晚和清晨，所有处理的温度都在 SBR 发展的范围内（10 至 28.5°C），相对湿度也是如此。这表明温度和相对湿度不是本实验的限制因素。无论遮荫处理如何，上部冠层的离体叶片测定中表皮蜡质含量和病情严重度都有显著的负相关（P=0.009，R=-0.84）。在实验室实验中，将模拟总太阳辐射（UVA、UVB 和 PAR）从 0.15 增加到 11.66 MJ m(-2)，可将担孢子的死亡率从 2%增加到 91%。早期种植的大豆中冠层高度不同的病害发展的可变性可能归因于太阳辐射不仅对担孢子活力，而且对植物高度、叶面积指数和表皮蜡质的影响，这些因素影响 SBR 的病害发展。这些结果提供了对太阳辐射在大豆冠层内 SBR 进展中影响的理解。
