Wheat resistance to leaf blast mediated by silicon

Abstract

Blast, caused by Pyricularia grisea, is one of the most important diseases of wheat. The effects of silicon (Si) on this wheat disease were studied. Plants of wheat cultivars Aliança and BH-1146 were grown in plastic pots containing Si-deficient soil amended with either calcium silicate (+Si) or calcium carbonate (−Si). The content of Si in leaf tissue was significantly increased by 14.8% for the +Si treatment. There were no significant differences between Si treatments for calcium content, so variations in Si only accounted for the observed differences in the level of blast resistance. The incubation period was significantly increased, on average, by 28.2% for the +Si treatment. The area under blast progress curve and the number of lesions per cm 2 of leaf area significantly decreased by 31 and 45%, respectively, for the +Si treatment. There was no significant effect of Si on final disease severity. The concentration of total soluble phenolics observed in both cultivars supplied with Si did not apparently play any role in the increased blast resistance. The highest content of lignin-thioglycolic acid derivatives was found in plants from both cultivars with Si during the time period evaluated. Chitinase activity was high at the intermediate stages of fungal infection in both cultivars supplied with Si. Peroxidase activity was found to be high at the late stage of fungal infection for both cultivars supplied with Si and seemed to play a role in enhancing wheat blast resistance. Polyphenoloxidase activity also apparently had no effect on resistance for any of the treatments. These overall results revealed the potential of Si to decrease wheat susceptibility to blast.

Microscopic aspects of the colonization of Pyricularia oryzae on the rachis of wheat plants supplied with silicon

“…Massive wheat yield losses due to blast occur when P. oryzae infects the rachis at the base of the spike, thereby limiting grain development and filling in addition to destroying the spikes completely (Goulart et al, 2007;Kohli et al, 2011). The ability of Si to decrease the intensities of several diseases on many crops is well known (Datnoff et al, 2007), including blast on wheat Perez et al, 2014;Rios et al, 2014;Sousa et al, 2013;Xavier et al, 2011). In rice, Datnoff et al (1991) found reductions in both incidence and severity of neck blast on the panicles of rice plants growing in a Si-deficient Histosol amended with calcium silicate.…”

“…Xavier et al (2011) showed that the incubation period of blast on the leaves of wheat plants increased with the use of Si, whereas the area under the blast progress curve and the number of lesions per cm 2 of leaf area significantly decreased. The authors reported that high concentrations of lignin-thioglycolic acid derivatives and high activities of chitinases and peroxidases contributed to the increase in wheat resistance to blast.…”

“…Although Si is not considered an essential nutrient for plants, it has been important in reducing the intensities of diseases in many economically important crops, such as banana, barley, beans, cucumber, oats, rice and wheat (Bélanger et al, 2003;Dallagnol et al, 2009;Fortunato et al, 2012Fortunato et al, , 2014Polanco et al, 2012;Xavier et al, 2011). Xavier et al (2011) showed that the incubation period of blast on the leaves of wheat plants increased with the use of Si, whereas the area under the blast progress curve and the number of lesions per cm 2 of leaf area significantly decreased.…”

Wheat blast research: Status and imperatives

“…They found that at histochemical level, Si is involved in the potentiation of the biosynthetic pathway of flavonoids that increases wheat resistance to blast. Silicon application reduced area under blast progress curve by 31% in an experiment reported by Filha et al (2011). Several substances like jasmonic acid (JA), deacetylated chitosan (DC), potassium silicate (PS), potassium phosphate (PP), tebuconazole (TE) etc.…”

“…Ever since its first report, blast pathogen was variously named by researchers for example, Pyricularia oryzae Oliveira et al, 2015;Cruz et al, 2015a;Silva et al, 2015), Pyricularia grisea (Filha et al, 2011;Kohli et al, 2011;Rocha et al, 2014), Magnaporthe grisea (Urashima and Kato, 1994;Peng et al, 2011;Pagani et al, 2014) and M. oryzae Triticum (Cruz et al, 2015a). Blast pathogen has shown capability to evolve fast to adapt to new climates.…”