Phytotoxic and cross-protective effects of culture filtrates of Rhizoctonia solani isolates on Zea mays

Authors: SINGH, VIMLA - Icar-Indian Institute Of Maize Research; KARJAGI, CHIKAPPA - Icar-Indian Institute Of Maize Research; Lakshman, Dilip; KUMAR, AUNDY - Indian Agricultural Research Institute; MEHRA, RAKESH - Haryana Agricultural University; SHEKHER, MEENA - Icar-Indian Institute Of Maize Research

Submitted to: Annals of Plant Protection Sciences
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/20/2018
Publication Date: 3/31/2018
Citation: Singh, V., Karjagi, C.G., Lakshman, D.K., Kumar, A., Mehra, R., Shekher, M. 2018. Phytotoxic and cross-protective effects of culture filtrates of Rhizoctonia solani isolates on Zea mays. Annals of Plant Protection Sciences. 26:153-159. https://doi.org/10.5958/0974-0163.2018.00033.2.
DOI: https://doi.org/10.5958/0974-0163.2018.00033.2

Interpretive Summary: Rhizoctonia solani is a soil borne fungus which causes the highly destructive banded leaf and sheath blight disease of maize. The present study was undertaken to examine the phytotoxic effects of culture filtrates of several isolates of the pathogen on maize seed germination and seedling growth. In addition, cross protection by weak pathogenic isolates against the most pathogenic isolates was examined. The study demonstrated that culture filtrates of two of the tested isolates were highly pathogenic, and prior seed treatment with the culture filtrates of four weakly pathogenic isolates could subsequently protect maize seeds against the pathogenic effects of severe isolates. Moreover, this study highlights the use of toxins from culture filtrates as biotic stressor for screening of resistant germplasm, which can save manpower, expenses, and time. This information will be useful to scientists developing disease control strategies for the important soilborne plant pathogen Rhizoctonia solani.

Technical Abstract: Rhizoctonia solani is a soil borne fungus causing the highly destructive banded leaf and sheath blight disease on Zea mays. The disease is emerging as a major biotic constraint for maize production in India. Management strategies often yield inconsistent results due to the highly variable nature of the fungus. The present study was undertaken to examine the phytotoxic effects of culture filtrates of the R. solani isolates Udm, Del, Dho, Rch, Mtp and Bpn on maize seed germination and seedling growth. Cross protection by weak pathogenic isolates was also examined against the most pathogenic isolates in the study. Our findings reveal significant variability in phytotoxicity of the culture filtrates of the 6 isolates on seed germination, seedling growth and severity of disease symptoms, with the isolates Udm and Del being the most aggressive on the host and also in macroscopic interactions with the other 5 isolates. However, when maize seeds were pretreated with culture filtrates of the 6 isolates, the severity due to challenge inoculation with culture filtrates of Udm and Del was reduced. The severity of Del was most effectively reduced compared to that of Udm. The Mtp isolate showed the best result in cross protection, reducing the severity of symptoms to 53% for Udm and 50% for the Del isolate. However, seeds pretreated with Udm and Del isolates also showed a slight reduction in the severity of symptoms. This reveals that pretreatment of maize seeds with culture filtrate of a pathogenic isolate may also provide cross protection against challenge inoculation of the same R. solani isolate. The study highlights the use of culture filtrates of R. solani as biotic stressor for screening of resistant germplasm, which can save manpower, expenses, and time.