Effect of inoculum density of Stromatinia cepivora on the amount of white rot reduced by Trichoderma species in garlic

Abstract

Background: White rot, a garlic disease caused by the soil-borne fungus Stromatinia cepivora (Berk.) Whetzel, is a serious problem of garlic productions in Egypt. This study examines the potential of controlling the disease biologically by using three Trichoderma species, i.e., Trichoderma harzianum, Trichoderma koningii, and Trichoderma virens employed either alone or in combination. Results:In in vitro assays, three Trichoderma species, i.e., Trichoderma harzianum, Trichoderma koningii, and Trichoderma virens and tebuconazole, were compared for their ability to suppress S. cepivora isolate (Sc8). In greenhouse experiments, the chemical treatment was the most effective, with the lowest incidence of garlic white rot compared with the control. The antagonistic fungi tested either individually or in combination significantly reduced the incidence of white rot on garlic. In general, dual and triple combinations of the fungal isolates were more effective than these isolates used individually. The combination of the three Trichoderma species was the most effective treatment, decreasing disease incidence by 50.0% in 2016/2017 season and 40.0% in 2017/2018 season, respectively. The three Trichoderma species employed alone or in combinations and tebuconazole were evaluated under low and high disease pressures in field trials to determine which situation (s) provided the best control of garlic white rot. Under low (40 sclerotia/kg of soil) and high (600 sclerotia/kg of soil) inoculum density, the standard fungicide programme (dipping of garlic cloves in tebuconazole (1 ml of Folicur 25% l −1 of water) plus spraying garlic stem bases with the same concentration of tebuconazole) gave statistically significant disease control, decreasing disease incidence by 67.7 and 29.4% in 2016/2017 season and 72.6 and 31. 1% in 2017/2018 season, respectively. Under low disease pressure, significant control, equal to the fungicide treatment, was achieved with the trip combination of three Trichoderma species. However, Trichoderma species employed alone gave insignificant control of garlic white rot under high disease pressure. The triple combination of three Trichoderma species decreasing disease incidence by 65.6 and 15.5% in 2016/2017 season and 74.2 and 18.6% during 2017/2018 season, under low and high inoculum density, respectively. The activities of defense enzymes, i.e., peroxidase, polyphenoloxidase, and chitinase due to application of Trichoderma species, were enhanced in garlic plants either grown under low or high disease pressures. Reduction of white rot disease incidence was accompanied by increased growth parameters and bulbs yield of garlic plants grown under field conditions. Conclusions: These results indicated that the performance of three Trichoderma species may be influenced as much by the absolute disease pressure. It was concluded that, at the low disease pressure site, the low level of inoculum and disease incidence enabled three Trichoderma species to bring about disease control.

Role of Purpureocillium lilacinum Cultural Filtrate in Controlling Onion White Rot

“…Culture filtrates significantly boosted onion yields compared to the non-amended control in the two field trials. These results are in concordance with the pervious findings of Davis et al (2007) and Elshahawy et al (2019b). This was also supported by Harman et al (2004) who found that after colonization of bioagent, Trichoderma spp.…”

“…Hence, growers still depending on chemical control to eradicate the pathogen (Fullerton and Stewart, 1991;Fullerton, et al, 1995;Melero-Vara, et al, 2000). Different previous safety strategies have been applied for controlling white rot including biological and physical measurements such as soil fumigation (Entwistle, 1990), soil solarization (Melero-Vara, et al, 2000), the compost of Allium crops waste (Elshahawy et al, 2019a), crop rotation with non-Allium crops (Banks and Edgington, 1989), plant extracts (Montes-Belmont and Prados-Ligero, 2006), biological control agents and /or bioagents culture filtrates (Clarkson et al, 2006;Dilbo et al, 2015;Elshahawy et al, 2017 a,b;Elshahawy et al, 2018 a,b andElshahawy et al, 2019b).…”

Anaerobic soil disinfestation with ethanol or sucrose reduces the viability of Meloidogyne javanica and Stromatinia cepivora

“…The number of resistant cultivars to root-knot nematodes is limited and, in Brazil, all commercial cultivars of garlic and onion are susceptible to S. cepivora (Lourenço Júnior et al, 2018). Solarization, biofumigation, and the application of biocontrol agents may be valuable options for the management of nematodes and S. cepivora, especially when used in an integrated approach (Fuga et al, 2012;Elshahawy, Saied, Abd-El-Kareem, & Morsy, 2019;Forghani & Hajihassani, 2020).…”