Aggressiveness and physiological specialization of Septoria tritici Rob. isolates

Abstract

Pathogenicity tests verifying the behavior of Septoria tritici isolates should be considered as a priority in the selection of resistant wheat materials to this pathogen, since the aggressiveness of each isolate can vary significantly, causing problems in the evaluation and selection of resistant genotypes. The objective of this work was to determine whether physiologic specialization exists among Argentinean and American Septoria tritici isolates, through the analysis of their pathogenicity on cultivars and lines of bread wheat (Triticum aestivum L.). The experiments were carried out in Castelar-Argentina and in Davis-USA. In Castelar, a split plot design (n = 4) was used. The cultivars or lines were randomized in the plots and the isolates in the subplots. Each subplot consisted of three plants belonging to a cultivar or line. In Davis, a strip split plot design (n = 6) was used. A pot containing three plants of each cultivar or line constituted the experimental plots. In both sites, the inoculation was made at the flag leaf phenological stage through foliar aspersion of a conidial suspension adjusted to 10 6 -10 8 conidia mL -1. Evaluations were made by recording the leaf area covered with pycnidia (LACP) at the flag leaf stage with the use of rating scales. Differences (P ≤ 0.0001) in LACP were detected among cultivars or lines. Isolate effects and the interaction cultivar × isolate were significant (P ≤ 0.0001). Variations in aggressiveness and virulence were found among the isolates, indicating the presence of horizontal and vertical resistance in the host cultivars. Cada subparcela foi composta por três plantas pertencentes a um determinado cultivar. Na segunda localidade, foi adotado um delineamento em blocos casualizados e arranjo em faixas, com seis repetições, onde as parcelas experimentais foram constituídas por um vaso contendo três plantas de cada cultivar. A inoculação foi feita no estádio fenológico de folha bandeira em ambas localidades com uma suspensão de conídios ajustada a uma concentração de 10 6 -10 8 esporos mL -1 , empregando a técnica de inoculação por aspersão foliar. As avaliações foram feitas registrando-se a área foliar coberta por picnídios (AFCP) no estádio de folha bandeira com auxílio de escalas de notas. Em ambas localidades foram detectadas diferenças significativas (P ≤ 0,0001) em AFCP entre cultivares. Foram também detectados efeitos significativos de isolados e da interação cultivares x isolados (P ≤ 0,0001). Foram detectadas variações na agressividade e virulência dos isolados sugerindo a presença de resistência horizontal e vertical no material vegetal testado. Testes de patogenicidade destinados a verificar o comportamento de isolados de Septoria tritici devem ser considerados como uma prioridade na seleção de materiais de trigo resistentes a este patógeno. Palavras-chave: Mycosphaerella graminicola, Triticum aestivum, mancha foliar, resistência vertical, resistência horizontal Aggressiveness and physiological specialization of S. tritici isolates 415

Association between Septoria tritici Blotch, Plant Height, and Heading Date in Wheat

“…The cultivars differed in plant height, heading date, and resistance to Septoria tritici blotch, and represented the range in these characteristics for cultivars grown in Argentina in 1998. ‘Klein Toledo’, an old cultivar, also was included because it is moderately resistant to Septoria tritici blotch (Gieco et al, 2004).…”

Virulence and pathogenic variability of wheat leaf blotch (Zymoseptoria tritici) isolates in Oromia, Ethiopia

“…Pathogenicity assays showed the action of Zt isolates should be regarded as a priority in the selection of resistant wheat materials to this disease (Brian 1976; Ghaffary 2011). Therefore, several studies have indicated that different wheat genotypes interact differently with different Zt isolates, indicating that the pathogen has physiological speci city (Ababa et al 2022;Ballantyne 1989;Boughalleb and Harrabi 1997;Brading et al 2002;Brian 1976; Dalvand et al 2018;Ghaffary 2011;Gieco et al 2004;Grieger 2001;Hosseinnezhad et al 2014;Jlibene et al 1993; Kema et al 1995;Kema and Vansilfhout 1997;Makhdoomi et al 2015;Mekonnen et al 2020;Saadaoui 1987). Hence, understanding the population diversity and pathogen virulence pattern is critical for developing the most effective and long-lasting resistance breeding strategies (Brading et al 2002;Dalvand et al 2018;Ghaffary 2011;Grieger 2001; Gri ths and Ao 1980; Makhdoomi et al 2015).…”