Effect of Septoria Leaf Blotch and its Control with Commercial Fungicides, on arbuscular-mycorrhizal-Fungal Colonization, Spore Numbers, and morphotype Diversity

Abstract

Arbuscular-mycorrhizal internal structures (i.e. total root colonization, arbuscules, vesicles) and external structures (i.e. spore density), and Glomeromycota spore morphotypes, were evaluated in wheat severely infected with Mycosphaerella graminicola - the causal agent of Septoria leaf blotch. Plots in which the infection was controlled with a commercial fungicide at recommended field doses, were also examined. The commercial fungicide used was an admixture of trifloxistrobin and tebuconazole. No negative effects of the fungicide application on arbuscular-mycorrhizal fungi (AMF) were found. The M. graminicola fungicidal treatment actually favoured the formation of arbuscules and AMF spores, as there was a selective increase in the density of spores belonging to the glomoid morphotype. Arbuscular-mycorrhizal fungi have an absolute dependence on the carbon provided by the plant. A severe foliar disease leading to a diminished carbon supply to the roots would generate decreases in carbon availability. Such decreases would strongly affect mycorrhizal associations and development. Furthermore, the change in the green-leaf area produced by a severe foliar disease and/or a reversal of that condition through fungicide treatment could result in shifts in the composition of the AMF community so as to favour glomoid morphotypes. Glomoid species have been previously considered as r-strategists

Micorrización en Capsicum annuum L. para promoción de crecimiento y bioprotección contra Phytophthora capsici L.

“…This coincides with that reported by Schalamuk et al (2014), where on wheat plants (Triticum sp.) That were severely affected by septoria caused by Mycosphaerella graminicola the spore density was higher than in plants selectively with lower disease damage.…”

“…Esto coincide con lo reportado por Schalamuk et al (2014), donde en plantas de trigo (Triticum sp.) que se encontraban severamente afectadas por septoriosis causada por Mycosphaerella graminícola, la densidad de esporas fue selectivamente mayor que en plantas con menor daño de la enfermedad.…”

Fungicides With Contrasting Mode of Action Differentially Affect Hyphal Healing Mechanism in Gigaspora sp. and Rhizophagus irregularis

“…Unfortunately, these molecules may also affect soil plant-beneficial microorganisms such as AM fungi ( Jin et al, 2013 ; Buysens et al, 2015 ). Their impact on these belowground microorganisms have been investigated under field (e.g., Schalamuk et al, 2014 ; Rivera-Becerril et al, 2017 ), greenhouse (e.g., Jin et al, 2013 ; Channabasava et al, 2015 ; Rabab and Reda, 2019 ) and growth chamber ( de Novais et al, 2019a ) conditions as well as in vitro on root organs (e.g., Campagnac et al, 2008 ; Zocco et al, 2008 ) or whole plants (e.g., Zocco et al, 2011 ).…”

Seleção de fungicidas visando à preservação de fungos micorrízicos arbusculares nativos no cultivo do feijoeiro

“…O tebuconazol é mencionado como não impactante a este tipo de endófito (Burrows & Ahmed, 2007;Reis et al, 2010), o que pode ter atenuado o estresse quando aplicado em mistura. Schalamuk et al (2014) verificaram aumento na densidade de esporos e arbúsculos de FMAs a partir da aplicação de tebuconazol + trifloxistrobina no controle da septoriose no trigo.…”