Context or problem

Root rots, a major factor contributing to yield loss in chickpea, often occur in disease complexes.

Objective or research question

Plant responses to disease complexes are not well elucidated. We sought a clear understanding of a newly identified disease complex in chickpea, dry root rot (DRR)–wilt disease complex, in the field and studied the effect of drought on the severity of the complex and its effect on yield. We compared plant responses to DRR alone and the disease complex under drought and determined the phytohormones involved in plant defense against the disease complex.

Methods

We compared the effect of 14 environments (two soil moisture regimes at seven locations) on the incidence of the disease complex and yield loss in four chickpea genotypes. We also studied the effect of drought on rhizospheric and root endo-microbial communities by whole-genome and metagenomic sequencing and performed LC-MS-based phytohormonal profiling of chickpea roots.

Results

Soil moisture and plant genetic variability were critical in modulating disease incidence in field conditions. DRR was the primary driver of the disease complex under drought stress. Drought aggravated the yield reductions caused by the disease complex from 35% to 60% in susceptible genotypes. Further, drought-tolerant genotypes performed better under combined disease complex infection and drought stress and exhibited lesser yield losses than susceptible genotypes. Pathogenic fungi such as Macrophomina phaseolina, Fusarium oxysporum, and Rhizoctonia solani were enriched in the chickpea rhizosphere, and M. phaseolina was predominant in infected chickpea roots under both well-watered and drought conditions. Symbiotic associations of chickpea with nitrogen-fixing bacteria were suppressed under drought stress. Abscisic acid, jasmonic acid, and salicylic acid were found to be involved in defense against the disease complex across various stages of plant growth.

Implications or significance

We highlight the interaction between drought and soil pathogens affecting chickpea yield and suggest the utilization of drought-tolerant root traits as donor traits for improving combined stress resistance. We also demonstrate growth stage–dependent phytohormonal responses elicited by DRR and the DRR–wilt disease complex. The identification and management of root rots is essential, and our findings offer valuable new insights into a lesser-known but highly significant disease complex of chickpea.

Data availability statement

Manuscript data is available at Supplementary File S1. The soil microbe whole-genome and metagenome and root-microbe 16 S and ITS sequencing data are available at NCBI PRJNA871091 and PRJNA895851.

中文翻译：

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干旱减弱植物对多种根际病原体的反应：一项关于鹰嘴豆田干根腐病相关疾病综合症的研究

上下文或问题

根腐病是导致鹰嘴豆产量下降的一个主要因素，通常发生在疾病综合体中。

目标或研究问题

植物对疾病复合体的反应尚未得到很好的阐明。我们在田间寻求对鹰嘴豆中一种新发现的病害综合症——干根腐病 (DRR)- 枯萎病综合症的清晰了解，并研究了干旱对综合症严重程度的影响及其对产量的影响。我们比较了植物对单独的 DRR 和干旱条件下的疾病复合体的反应，并确定了参与植物防御该疾病复合体的植物激素。

方法

我们比较了 14 种环境（七个地点的两种土壤水分状况）对四种鹰嘴豆基因型的复杂疾病发生率和产量损失的影响。我们还通过全基因组和宏基因组测序研究了干旱对根际和根内微生物群落的影响，并对鹰嘴豆根进行了基于 LC-MS 的植物激素分析。

结果

土壤水分和植物遗传变异性对于调节田间条件下的疾病发病率至关重要。DRR 是干旱胁迫下疾病复合体的主要驱动因素。在易感基因型中，干旱加剧了由疾病复合体引起的减产，从 35% 增加到 60%。此外，耐旱基因型在综合疾病复杂感染和干旱胁迫下表现更好，并且表现出比易感基因型更小的产量损失。Macrophomina phaseolina、Fusarium oxysporum和Rhizoctonia solani等致病真菌在鹰嘴豆根际富集，而M. phaseolina在充分浇水和干旱条件下，在受感染的鹰嘴豆根中占优势。在干旱胁迫下，鹰嘴豆与固氮细菌的共生关系受到抑制。脱落酸、茉莉酸和水杨酸被发现参与防御植物生长各个阶段的疾病复合体。

影响或意义

我们强调了影响鹰嘴豆产量的干旱和土壤病原体之间的相互作用，并建议利用耐旱根性状作为供体性状来提高综合抗逆性。我们还展示了由 DRR 和 DRR-枯萎病复合体引起的生长阶段依赖性植物激素反应。根腐病的识别和管理至关重要，我们的研究结果为鹰嘴豆鲜为人知但非常重要的疾病综合症提供了有价值的新见解。

数据可用性声明

手稿数据可在补充文件 S1 中获得。土壤微生物全基因组和宏基因组以及根微生物 16 S 和 ITS 测序数据可在 NCBI PRJNA871091 和 PRJNA895851 获得。