Peltier A J, Hatfield R D, Grau C R
Department of Plant Pathology, University of Wisconsin - Madison; 1630 Linden Dr., Madison, WI 53706.
U.S. Dairy Forage Research Center, 1925 Linden Dr., Madison, WI 53706.
Plant Dis. 2009 Feb;93(2):149-154. doi: 10.1094/PDIS-93-2-0149.
Sclerotinia stem rot, caused by Sclerotinia sclerotiorum, is an economically important disease of soybean (Glycine max) in the north-central United States and other temperate regions throughout the world. The occurrence and severity of Sclerotinia stem rot in the field is highly dependent upon prevailing environmental conditions, which can prove problematic when evaluating soybean accessions for resistance. The identification of an environmentally stable plant trait associated with resistance to S. sclerotiorum could be used to indirectly screen for resistance and would prove useful in the identification and development of resistant germplasm. Observations of the soybean-S. sclerotiorum interaction suggest a role for preformed stem lignin content in disease resistance. Although S. sclerotiorum produces numerous enzymes that degrade plant cell wall components, no lignin-degrading enzymes have been reported. Despite a hypothesized direct relationship between preformed lignin content and disease resistance, previous studies on soybean have correlated lignin content to nutritional value and not to disease resistance. We hypothesized that plants with low stem lignin are more susceptible and exhibit greater Sclerotinia stem rot severity than plants with high lignin concentrations. Six soybean accessions that varied in response to S. sclerotiorum were selected for study in a series of field experiments. Soybean stems were sampled at reproductive developmental stages that correspond to specific events in both soybean plant development and the Sclerotinia stem rot disease cycle. The lignin concentration of stem component samples was quantified. Soybean accessions expressed statistically different disease phenotypes in both 2004 and 2006. Lignin concentrations differed among accessions, growth stages, and plant parts. Results were contrary to our hypothesis, with positively ranked correlations observed between accession Sclerotinia stem rot severity and lignin concentration for all nodes and internodes assayed. For the R3 growth stage, lignin concentration of the internode between the fourth and fifth trifoliate leaves correlated best with disease severity data from each year (P = 0.005). These results indicate that resistance is related to low stem lignin concentration and that soybean stem lignin concentration can be used as a biological marker to select for resistance to S. sclerotiorum.
由核盘菌（Sclerotinia sclerotiorum）引起的菌核病是美国中北部以及世界其他温带地区大豆（Glycine max）的一种具有重要经济影响的病害。田间菌核病的发生和严重程度高度依赖于当时的环境条件，这在评估大豆种质资源的抗性时可能会带来问题。鉴定与抗核盘菌相关的环境稳定型植物性状可用于间接筛选抗性，并且在抗性种质资源的鉴定和培育中会很有用。对大豆与核盘菌相互作用的观察表明，茎中预先形成的木质素含量在抗病性中起作用。尽管核盘菌产生多种降解植物细胞壁成分的酶，但尚未有木质素降解酶的报道。尽管预先形成的木质素含量与抗病性之间存在假设的直接关系，但之前关于大豆的研究将木质素含量与营养价值相关联，而非与抗病性相关联。我们假设茎木质素含量低的植物比木质素浓度高的植物更易感病，并且菌核病严重程度更高。选择了六个对核盘菌反应不同的大豆种质资源，在一系列田间试验中进行研究。在与大豆植株发育和菌核病病害循环中的特定事件相对应的生殖发育阶段采集大豆茎样本。对茎成分样本的木质素浓度进行定量。大豆种质资源在2004年和2006年都表现出统计学上不同的病害表型。木质素浓度在种质资源、生长阶段和植物部位之间存在差异。结果与我们的假设相反，在所检测的所有节和节间中，种质资源的菌核病严重程度与木质素浓度之间观察到正相关。对于R3生长阶段，第四和第五片三出复叶之间节间的木质素浓度与每年的病害严重程度数据相关性最好（P = 0.005）。这些结果表明抗性与低茎木质素浓度相关，并且大豆茎木质素浓度可作为选择抗核盘菌的生物学标记。
