International Crops Research Institute for the Semi-Arid Tropics (ICRISAT), Patancheru, 502324, India.
Acharya NG Ranga Agricultural University, Guntur, Andhra Pradesh, 522034, India.
BMC Plant Biol. 2024 Nov 5;24(1):1042. doi: 10.1186/s12870-024-05706-0.
Stem rot, caused by the soil-borne pathogen Sclerotium rolfsii, pose a serious challenge in the groundnut (Arachis hypogaea L) cultivation. Although this disease is widespread globally but had most adverse impact in groundnut growing regions of United States, India, and Australia. The pathogen primarily targets the crown region of the plant, resulting in systemic collapse and potentially leading to yield losses up to 80%. Effective genetic control measures are essential to mitigate the impact of this disease on groundnut production. Realizing the time and resource-consuming complex field-based phenotyping, the availability of easy and repeatable phenotyping methods may fasten the process of donor and gene discovery efforts.
Multi-season phenotyping was performed for stem rot on 184 minicore germplasm accessions, including checks, under two conditions: sick field screening and response to oxalic acid assay. This study demonstrated medium to high heritability (52-63% broad-sense heritability) and significant environmental influence (36%). The response to the oxalic acid assay showed a high proportion of similarity (approximately 80%) with the percent mortality observed in the sick field indicating an easy way of performing precise phenotyping. Notably, seven genotypes-ICG163, ICG721, ICG10479, ICG875, ICG11457, ICG111, and ICG2857-exhibited stable resistance, with less than 30% mortality against stem rot disease. Among these, ICG163, ICG875, and ICG111 displayed low mortality and consistent stability across multiple seasons in both the sick field and controlled conditions of the oxalic acid assay.
The oxalic acid assay developed in this study effectively complements field phenotyping, as a reliable method for assessing stem rot resistance. Seven resistant genotypes identified through this assay can be utilized for the introgression of stem rot resistance into elite genotypes. Given the significant influence of the environment on stem rot resistance, it is essential to implement multi-season phenotyping to obtain precise results. Furthermore, the response to oxalic acid serves as a valuable supplement to traditional field phenotyping, since maintaining uniform disease pressure during field screenings is often challenging.
土传病原菌立枯丝核菌引起的茎腐病对花生（Arachis hypogaea L）种植构成严重威胁。尽管这种疾病在全球范围内广泛存在，但对美国、印度和澳大利亚的花生种植地区影响最为严重。病原菌主要针对植物的冠部，导致系统崩溃，可能导致产量损失高达 80%。有效的遗传控制措施对于减轻这种疾病对花生生产的影响至关重要。意识到基于田间的表型复杂且耗时耗力，容易且可重复的表型鉴定方法的可用性可能会加速供体和基因发现工作的进程。
对包括对照在内的 184 份微核心种质资源进行了茎腐病多季节表型鉴定，在两种条件下进行：田间病圃筛选和草酸测定的响应。本研究表明，茎腐病的表型具有中到高度的遗传力（52-63%广义遗传力）和显著的环境影响（36%）。草酸测定的响应与田间病圃观察到的死亡率有很高的相似性（约 80%），表明这是一种进行精确表型鉴定的简便方法。值得注意的是，有七个基因型——ICG163、ICG721、ICG10479、ICG875、ICG11457、ICG111 和 ICG2857——表现出稳定的抗性，对茎腐病的死亡率低于 30%。其中，ICG163、ICG875 和 ICG111 在田间和草酸控制条件下的多个季节中，死亡率低且稳定性一致。
本研究中开发的草酸测定方法有效地补充了田间表型鉴定，是一种评估茎腐病抗性的可靠方法。通过该测定方法鉴定的七个抗性基因型可用于将茎腐病抗性导入到优良基因型中。鉴于环境对茎腐病抗性的显著影响，有必要进行多季节表型鉴定以获得准确的结果。此外，由于在田间筛选期间保持均匀的疾病压力通常具有挑战性，因此，草酸的响应可以作为传统田间表型鉴定的有价值的补充。
