Pathogenic and molecular variation of Fusarium species causing head blight on barley landraces

Abstract

Fusarium head blight (FHB) is consistently one of the most important barley diseases worldwide. This study aimed to evaluate the pathogenicity of 16 isolates of four Fusarium species under controlled conditions and their genetic variability using 22 random amplified polymorphic DNA (RAPD) markers. Pathogenic variation was characterized based on disease development rates and disease index on two Syrian barley landraces with varying resistance to FHB, Arabi Aswad (AS) and Arabi Abiad (AB). Significant differences in intra- and inter-Fusarium species pathogenicity and in susceptibility between the above-mentioned cultivars were highlighted. Overall, the two barley landraces showed moderately susceptible to moderately resistance levels to fungal infection and FHB spread within the head. Quantitative traits showed significant correlation with previous data generated in vitro and under field conditions, suggesting that growth chamber indices can predict fungal pathogenicity and quantitative disease resistance generated under various experimental conditions. Based on PCR amplification with seven different primers, the isolates showed genetic variation. Dendrogram generated by cluster analysis based on RAPD markers data showed two main groups, suggesting that a possible clonal origin could exist in the four Fusarium species. RAPD fingerprints are not useful to distinguish the 16 Fusarium isolates with different levels of pathogenicity.

In vitro variation in pathogenicity of Fusarium species causing head blight in relation to their isolation from barley head

“…These fungal cultures, referred herein as original isolates, were collected during the 2015 growing season from naturally infected wheat kernels exhibiting FHB symptoms from Ghab Plain with a history of head blight epidemics, one of the principal Syrian wheat production areas. Recently, the 16 Fusarium species causing FHB isolates were molecularly analyzed by random amplified polymorphic DNA (Sakr and Shoaib, 2021). Field findings at the Deir Al-Hajar Agricultural Experiment Station, located south east of the countryside of Damascus, Syria (33820 0 N, 36826 0 E, altitude 600 m) during 2018/19 and 2019/20 confirmed pathogenic and resistance data generated under in vitro and growth chamber conditions (Sakr, 2020a;Sakr and Shoaib, 2021).…”

“…Arabi Aswad (AS, moderately resistant) as ranked from previous in vitro, growth chamber and field observations (Sakr, 2018a(Sakr, , 2018b(Sakr, , 2019(Sakr, , 2020a(Sakr, , 2020bSakr and Shoaib, 2021). Sixteen single-spore derived cultures of four FHB species, i.e., F. culmorum (F1, F2, F3, F28 and F30), F. solani (F7, F20, F26, F29, F31 and F35), F. verticillioides (synonym Fusarium moniliforme) (F15, F16, F21 and F27) and F. equiseti (F43) were selected for their contrasting pathogenicity (based on previously several experimental observations (Sakr, 2018a(Sakr, , 2018b(Sakr, , 2019(Sakr, , 2020a(Sakr, , 2020bSakr and Shoaib, 2021). The above-cited barley cultivars were individually and artificially inoculated to assess disease incidence for Type I resistance, resistance to initial penetration of the pathogen, as indicator of the cultivar's resistance and pathogenicity of 16 FHB isolates.…”

“…Recently, the 16 Fusarium species causing FHB isolates were molecularly analyzed by random amplified polymorphic DNA (Sakr and Shoaib, 2021). Field findings at the Deir Al-Hajar Agricultural Experiment Station, located south east of the countryside of Damascus, Syria (33820 0 N, 36826 0 E, altitude 600 m) during 2018/19 and 2019/20 confirmed pathogenic and resistance data generated under in vitro and growth chamber conditions (Sakr, 2020a;Sakr and Shoaib, 2021). In brief, the spikes of AB and AS were sprayed during anthesis (Zadok stage 69) with a spore suspension at 5 3 10 4 spores/ml of 16 Fusarium isolates.…”

A simple and reliable assay to quantify host resistance and aggressiveness of the pathogen in the Fusarium head blight-barley pathosystem

“…Recently, Sakr (2020b) noted that four in vitro components (seed germination, coleoptile length, coleoptile weight and root weight) in the coleoptile infection assay predicted resistance and aggressiveness occurring at the earliest and latest barley development stages during FHB infection. Under controlled and field conditions, there were significant differences in aggressiveness intraand inter-species and in susceptibility between AS and AB; aggressiveness values over the two growing seasons in the field and in the growth chamber were significantly correlated with aggressiveness traits previously obtained in vitro (Sakr, 2020a;Sakr and Shoaib, 2021).…”

“…In addition to F. graminearum, causal agents of barley-FHB are Fusarium culmorum, Fusarium avenaceum, Fusarium tricinctum, Fusarium langsethiae, Fusarium sporotrichioides and Fusarium poae (Parry et al, 1995;Bottalico and Perrone, 2002;Bai and Shaner, 2004;Xue et al, 2006;McMullen et al, 2012;Becher et al, 2013;Dahl and Wilson, 2018). It is known that under diverse experimental conditions, Fusarium isolates show strong variability in aggressiveness (Xue et al, 2006;Hestbjerg et al, 2002;Opoku et al, 2011;Garmendia et al, 2018;Sakr, 2018aSakr, , 2019bSakr, , 2020aSakr and Shoaib, 2021), defined as the degree of damage caused by the pathogen to the host (Lannou, 2012). Diverse aggressiveness of several isolates of the same species might influence disease response (Janssen et al, 2018).…”