Bacterial biocontrol agents against diseases caused by <i>Rhizoctonia solani</i> in sugar beet

Rhizoctonia solani, the fungal pathogen that causes damping-off, and root and crown rot, is a significant concern for sugar beet growers. Chemical control is the most common approach, but it leads to other problems including environmental pollution, the development of pathogen resistance, disruption of beneficial microbial communities, and the potential for residue accumulation in the crop. Thus, alternative strategies are required. This study examined the efficacy of 21 biocontrol bacterial strains against 4 virulent R. solani isolates (AG 4 HGI, AG 4 HGII, AG 4 HGIII, and AG 2-2 IIIB). In-vitro tests measured fungal growth diameter and inhibition in dual culture, while liquid media were used to evaluate both dry and wet mycelium growth of the fungus. Effective agents from in-vitro tests were tested in-vivo, measuring seed germination and infection severity rates in pots. In dual culture tests, biocontrol agents inhibited the pathogen by 15.19-54.43%. Pseudomonas fluorescens FDG-37 was effective against all R. solani isolates, with the highest efficacy against AG 2-2 IIIB. Additionally, liquid medium experiments showed that these bacteria inhibited fungal growth by approximately 100%. In pot experiments, Pseudomonas fluorescens FDG-37 increased seed germination rates for AG 4 isolates, ranging from 48.89 to 68.89%, compared to the control application, which showed germination rates between 13.33% and 15.56%. Additionally, it reduced disease severity ranging from 01.23 to 05.09%, while the control application had severity levels ranging from 33.33 to 51.85%. Bacillus amyloliquefaciens TV-17 C showed superior results with a germination rate of 57.78% with AG 4 HGIII. Regarding the AG 2 isolate, B. subtilis QST-3 exhibited a seed germination rate of 82.22%, while the control had 40%. Moreover, it reduced disease severity by 11.75% compared to 57.41% in the control application. Overall, P. fluorescens FDG-37, B. subtilis QST-3, B. subtilis SRND, B. pumilus TV-3D, B. amyloliquefaciens TV-17 C, and Brevibacillus choshinensis TV-53D demonstrated significant biological control capabilities against the tested R. solani isolates (AG 4 HGI, AG 4 HGII, AG 4 HGIII, and AG 2-2 IIIB) in sugar beet.

Journal

INDIAN PHYTOPATHOLOGY

Year

2024

Volume

77

Issue

1

Pages

211-217

ISSN

0367-973X

eISSN

2248-9800

DOI

10.1007/s42360-023-00697-8

WoS UID

WOS:001570528700010