Sensitivity of the Pyrenophora teres Population in Algeria to Quinone outside Inhibitors, Succinate Dehydrogenase Inhibitors and Demethylation Inhibitors

Abstract

Net blotch of barley caused by Pyrenophora teres (Died.) Drechsler, is one of the most destructive diseases on barley in Algeria. It occurs in two forms: P. teres f. teres and P. teres f. maculata. A total of 212 isolates, obtained from 58 fields sampled in several barley growing areas, were assessed for fungicide sensitivity by target gene analysis. F129L and G137R mitochondrial cytochrome b substitution associated with quinone outside inhibitors (QoIs) resistance, and succinate dehydrogenase inhibitors (SDHIs) related mutations (B-H277, C-N75S, C-G79R, C-H134R, and C-S135R), were analyzed by pyrosequencing. In vitro sensitivity of 45 isolates, towards six fungicides belonging to three chemical groups (QoI, demethylase inhibitor, and SDHI) was tested by microtiter technique. Additionally, sensitivity towards three fungicides (azoxystrobin, fluxapyroxad, and epoxiconazole) was assessed in planta under glasshouse conditions. All tested isolates were QoI-sensitive and SDHI-sensitive, no mutation that confers resistance was identified. EC 50 values showed that pyraclostrobin and azoxystrobin are the most efficient fungicides in vitro, whereas fluxapyroxad displayed the best disease inhibition in planta (81% inhibition at 1/9 of the full dose). The EC 50 values recorded for each form of net blotch showed no significant difference in efficiency of QoI treatments and propiconazole on each form. However, in the case of fluxapyroxad, epoxiconazole and tebuconazole treatments, analysis showed significant differences in their efficiency. To our knowledge, this study is the first investigation related to mutations associated to QoI and SDHI fungicide resistance in Algerian P. teres population, as well as it is the first evaluation of the sensitivity of P. teres population towards these six fungicides.

Ten decadal advances in fungal biology leading towards human well-being

“…Recently, some countries have replaced azole antifungals in agriculture by alternatives, but nevertheless, azole resistance has increased rapidly all over the world (Van der Linden et al 2015 ; Howard et al 2009 ). Importantly, there are not so many alternatives on the market neither in human medicine, nor in agriculture, where azoles represent the key fungicides, especially, when also other fungicides lost approval (succinate dehydrogenase inhibitors) or face resistance (e.g., quinone outside and sterol demethylation inhibitors) of important plant pathogens (Birr et al 2021 ; Lammari et al 2020 ; Pan et al 2020 ) and fungicides in mixtures with azoles seems to be the only option to avoid famines. Such a situation is mainly because of lack of innovations caused by insufficient financial incentives due to undervaluation of the critical situation.…”

Management of Pyrenophora teres f. teres, the Causal Agent of Net Form Net Blotch of Barley, in A Two-Year Field Experiment in Central Italy

“…Some of these active ingredients are well known to be very effective also when used singularly. In fact, even if in this study a mixture of fluxapyroxad and pyraclostrobin (Priaxor) was tested, fluxapyroxad (an SDHI fungicide) alone was recently defined as the best P. teres inhibitor [ 31 ]. Similarly, the very high efficacy of pyraclostrobin (QoI) alone towards this pathogen has been previously demonstrated [ 30 , 56 ].…”

“…In addition, different groups of foliar fungicides are used for the control of this disease: succinate dehydrogenase inhibitors (SDHIs), demethylation inhibitors (DMIs), and quinone-outside inhibitors (QoIs) [ 27 , 28 , 29 ]. In particular, in many barley growing areas, QoIs show excellent efficacy and are registered for the control of net blotch [ 30 ] with SDHI and DMI fungicides also largely used in Europe [ 28 ] and worldwide [ 31 ]. The effectiveness of disease control using foliar fungicides depends on different factors, such as disease pressure, application rate, mode of action of the active ingredient, timing and number of treatments, and application rate [ 29 ].…”

SDHI resistance in Pyrenophora teres f teres and molecular detection of novel double mutations in sdh genes conferring high resistance

“…Afterwards, to distinguish between the teres and maculata forms, specific SNPs in the sdhB gene sequence were used to differentiate between Ptt and Ptm isolates. The alignment of the sdhB gene between Ptt and Ptm shows around eight SNPs between the two forms 45–47 …”