Ben Naim Yariv, Mattera Robert, Cohen Yigal, Wyenandt C Andrew, Simon James E
New Use Agriculture and Natural Plant Product Program and Department of Plant Biology, Rutgers University, 08901, New Brunswick, NJ, US.
Faculty of Life Sciences, Bar Ilan University, 5290002, Ramat Gan, Israel.
Planta. 2025 May 29;262(1):10. doi: 10.1007/s00425-025-04703-3.
A model predicting the level of resistance of basil to downy mildew was developed. The model integrates plant age, genetic background, sporulation, disease intensity, pathogen races, and environmental data at an early stage of disease. These results can be used to select and develop new basil cultivars and accelerate the time needed in breeding for basil downy mildew resistance. Basil downy mildew (BDM) caused by the oomycete Peronospora belbahrii emerged as a global threat, rapidly becoming the most devastating disease of sweet basil (Ocimum basilicum) and other Ocimum spp. worldwide. Despite advancements in understanding its biology and epidemiology, and the availability of approved fungicides and management strategies, BDM remains economically destructive and an ongoing risk to basil production worldwide. Recently, the development and introduction of resistant cultivars have emerged as crucial tools in BDM management and the emergence of new BDM races creates new challenges to controlling this disease. The present study aimed to provide growers and breeders with insights into the survival capabilities of resistant basil cultivars under varying genetic backgrounds, pathogen races, growth stages, and various environmental conditions. Through a series of lab and field experiments, we evaluated the response of multiple resistant sources and their lineages to various isolates of P. belbahrii across different locations, using multiple indices to assess their resistance. Entries carrying the R genes Pb1/Pb2 exhibited complete resistance across all races, growth stages, and environmental conditions. Those harboring the R-gene Pb2 showed similar resistance levels, with minor variability due to growth stage. Responses of Pb1 plants varied with pathogen race, displaying full resistance to race 0 at all growth stages but displaying susceptibility to race 1. Plant cultivars possessing MRI resistance genes and their recombinant inbred lines (RIL's) exhibited variable responses to pathogen attacks, ranging from high tolerance to complete susceptibility. Some MRI RIL's showed high resistance similar to Pb2 entries. Pb0 cultivars and 'Eleonora' (unknown background) were susceptible to all races and growth stages in all experiments. Comprehensive analysis across all genetic backgrounds revealed a significant correlation (R = 0.73) between disease intensity (D.I) at the seedling stage under controlled conditions and D.I in adult plants under field conditions. Principal Component Analysis (PCA) across six experiments indicated that the primary components influencing disease outcomes were the accession, race, and growth stage, explaining 65%, 22%, and 7% of the variability, respectively. A prediction model based on the statistical parameters residual (%) and root-mean-square error (RMSE) demonstrated strong predictability, particularly regarding pathogen sporulation and daily disease development rates. The model predicted resistance probabilities with R values of 0.81, 0.91, and 0.93 at the second, third, and final disease score readings, respectively, significantly earlier (~ 14-21 days post-infection) than traditional assessments (~ 42 days). These findings demonstrate that resistance in basil entries against current pathogen races can be effectively assessed within weeks of disease onset, facilitating more timely and informed management decisions for growers and providing an important tool for plant breeders in search of improved BDM resistance.
开发了一个预测罗勒对霜霉病抗性水平的模型。该模型整合了植株年龄、遗传背景、产孢量、病害严重程度、病原菌小种以及病害早期的环境数据。这些结果可用于选择和培育新的罗勒品种，并缩短罗勒抗霜霉病育种所需的时间。由卵菌纲的佩罗霉引起的罗勒霜霉病已成为全球威胁，迅速成为甜罗勒（罗勒属）和全球其他罗勒属物种最具毁灭性的病害。尽管在了解其生物学和流行病学方面取得了进展，并且有了获批的杀菌剂和管理策略，但罗勒霜霉病在经济上仍然具有破坏性，并且对全球罗勒生产构成持续风险。最近，抗性品种的开发和引入已成为罗勒霜霉病管理的关键工具，而新的罗勒霜霉病菌株的出现给控制这种病害带来了新的挑战。本研究旨在为种植者和育种者提供关于抗性罗勒品种在不同遗传背景、病原菌小种、生长阶段和各种环境条件下的存活能力的见解。通过一系列实验室和田间试验，我们使用多个指标评估抗性来源及其谱系对不同地点的多种佩罗霉分离株的抗性反应。携带R基因Pb1/Pb2的材料在所有小种、生长阶段和环境条件下均表现出完全抗性。携带R基因Pb2的材料表现出相似的抗性水平，仅因生长阶段存在轻微差异。携带Pb1基因的植株对病原菌小种的反应不同，在所有生长阶段对小种0表现出完全抗性，但对小种1表现出易感性。具有MRI抗性基因的植物品种及其重组自交系（RIL）对病原菌攻击表现出不同的反应，从高耐受性到完全易感性不等。一些MRI RIL表现出与携带Pb2基因的材料相似的高抗性。在所有实验中，Pb0品种和“埃莱奥诺拉”（背景未知）对所有小种和生长阶段均易感。对所有遗传背景的综合分析表明，在受控条件下幼苗期的病害严重程度（D.I）与田间条件下成株期的D.I之间存在显著相关性（R = 0.73）。对六个实验进行主成分分析（PCA）表明，影响病害结果的主要成分是材料、小种和生长阶段，分别解释了65%、22%和7%的变异性。基于统计参数残差（%）和均方根误差（RMSE）的预测模型显示出很强的预测能力，特别是在病原菌产孢量和每日病害发展速率方面。该模型在第二次、第三次和最终病害评分读数时预测抗性概率的R值分别为0.81、0.91和0.93，比传统评估（约42天）显著提前（感染后约14 - 21天）。这些发现表明，在病害发生几周内就能有效评估罗勒材料对当前病原菌小种的抗性，有助于种植者更及时、明智地做出管理决策，并为寻求提高罗勒霜霉病抗性的植物育种者提供重要工具。
