Plant Extracts and Bacterial Filtrates Curb Chickpea Anthracnose Fungus, Toxin Signal Study Finds

Chickpea anthracnose, caused by the fungus Ascochyta rabiei, remains a major constraint to chickpea production, and a new open-access study in BMC Plant Biology reports that biological treatments can suppress the pathogen’s growth while also altering the apparent levels of solanapyrone A, a phytotoxic secondary metabolite associated with toxin-mediated plant damage. The work, published on 27 October 2026 by Djihane Bouzid, Mohamed Mihoub Zerroug and Hamama Bouriche, argues that visible fungal growth inhibition alone may be an insufficient criterion for selecting biological control candidates, because treatments can also modify toxin-associated responses.

The study evaluated Ruta montana and Carthamus caeruleus plant extracts together with cell-free filtrates of the bacteria Bacillus megaterium and Pseudomonas fluorescens, measuring both fungal growth and a spectrophotometrically estimated solanapyrone A-associated signal. The researchers found that this signal was strongly influenced by the culture medium, reaching its highest estimated level in Czapek Dox medium supplemented with metal cations, an observation that underscores how strongly assay conditions shape apparent toxin readings.

Solanapyrone A itself inhibited chickpea hypocotyl elongation in a genotype-dependent manner, with the cultivar FLIP 97-220 C showing the lowest sensitivity.

On the antifungal side, both plant extracts inhibited A. rabiei growth, with R. montana showing stronger activity than C. caeruleus. Live bacterial antagonism reduced fungal growth by 43.17 percent for B. megaterium and 50.31 percent for P. fluorescens.

Crucially, the authors report that fungal growth inhibition and the apparent solanapyrone A-associated signal did not follow parallel profiles. High treatment concentrations often produced visible antifungal activity but did not necessarily reduce the 327 nm signal used to estimate the toxin.

Against that backdrop, selected bacterial filtrate dilutions stood out. B. megaterium filtrate diluted to one quarter and P. fluorescens filtrate diluted to one eighth of the crude preparation combined residual visible inhibition of fungal growth with lower apparent solanapyrone A-associated levels than the untreated control. These dilutions therefore represent the most promising dual-response candidates identified under the tested conditions.

The authors are careful about interpretation. Because solanapyrone A was estimated spectrophotometrically at 327 nm, the observed decrease should be read cautiously as an apparent reduction in a solanapyrone A-associated signal rather than a confirmed drop in the toxin itself. They state that chromatographic confirmation by HPLC-DAD, HPLC-MS or LC-MS/MS is required to determine whether the decrease reflects reduced biosynthesis, conversion, degradation, binding or metabolization of solanapyrone A.

Even with that caveat, the study’s central proposal is actionable: a dual-response screening approach for biological control candidates against chickpea anthracnose, combining fungal growth inhibition with evaluation of toxin-associated responses. As the article is shared early as a citable, peer-reviewed accepted version subject to further edits, follow-up work confirming the toxin findings chromatographically will be the key test of whether these bacterial filtrate dilutions can move from culture-dish promise toward practical protection of chickpea crops.

Subject of Research: Effects of plant extracts and bacterial filtrates on Ascochyta rabiei growth and apparent solanapyrone A levels in chickpea anthracnose

Article Title: Biological treatments affect Ascochyta rabiei growth and apparent solanapyrone A levels in chickpea anthracnose

Article References: Bouzid, D., Zerroug, M. M., & Bouriche, H. (2026). Biological treatments affect Ascochyta rabiei growth and apparent solanapyrone A levels in chickpea anthracnose. BMC Plant Biology. https://doi.org/10.1186/s12870-026-10223-3

Image Credits: AI Generated

DOI: 10.1186/s12870-026-10223-3

Keywords: chickpea anthracnose, Ascochyta rabiei, solanapyrone A, biological control, Bacillus megaterium, Pseudomonas fluorescens, Ruta montana, Carthamus caeruleus, plant extracts, bacterial filtrates, phytotoxin, spectrophotometry