Morphology, phylogeny and pathogenicity ofAlternariaspecies, involved in leaf spot disease of sunflower in northern Iran

Abstract

Leaf spot disease of sunflower is one of the most important foliar diseases on this crop worldwide. Several fungal groups are known to cause leaf spot disease on sunflower. Species of the genus Alternaria are the most common and serious leaf spot causing fungi on this crop. Leaf spot disease is the most destructive foliar diseases on sunflower in northern Iran; however, the identity of the causal agent remains unknown. The present study was aimed to characterise the identity of the causal agent of the disease by means of morphological and molecular data as well as to evaluate the pathogenicity of the responsible species. For this purpose, a total number of 97 fungal isolates were recovered from sunflower leaves with leaf spot disease symptoms from the sunflower fields in northwestern zone of Iran. All of the isolates were identified as Alternaria alternata based on cultural and morphological characteristics. A subset of isolates was subjected to phylogenetic analysis using sequence data from ITS-rDNA region, gpd and rpb2 genes. Sequence data from ITS-rDNA and gpd did not discriminate A. alternata from the other small-spored Alternaria species. A phylogeny inferred using sequence data from rpb2 gene clustered our isolates in several sub-clades within a single monophyletic clade. Sequence data for the type strain of the other small-spored Alternaria species has to be included in phylogenetic analysis, in order to make sure, whether the observed variations in rpb2 gene sequences are an indication for the population variation in sunflower isolates of A. alternata or define species boundaries among the small-spored Alternaria species. The results of pathogenicity assay on sunflower plants (cultivar Euroflor) under greenhouse condition revealed that A. alternata is pathogenic on sunflower.

First Report of Curvularia Lunata and Alternaria Alternata Causing Leaf Blights on Tomatoes in Sindh, Pakistan

“…Although molecular studies also revealed the distinction between small and large-spored species of the Alternaria genus (Andrew et al, 2009;Peever et al, 2004). The first or second conidia in every chain often slightly longer, however, 2ndary chains were septate or without septums and the tip of conidia are unbranched with brown in color are diagnostic characteristic feature to identify the Alternaria alternata plant fungal pathogen (Khodaei and Arzanlou, 2013). Subsequently, isolates (S6, S15, S17) appeared in their cultural and morphological features including; culture dark or olivaceous brown color, mycelium septate and branched, long chains of conidia with tapered apices identified as Alternaria alternata species (Figure 9,10 and 11) (Akhtar et al, 2004;Simmons, 2007;(Ramjegathesh and Ebenezar, 2012;Khodaei and Arzanlou, 2013).…”

“…The conidia were light brown in colour having tapered apices mostly formed in chains but sometimes singly with muriform shape (Ramjegathesh and Ebenezar, 2012). Conidia were long ellipsoid, obclavate, moderate in size, divided into septums, straight conidia, and dark brown to olivaceous green and smooth as suggested by (Khodaei and Arzanlou, 2013). Sometimes secondary conidiophores may be formed with one or a few conidiogenous lociapically or laterally (Figure 5).…”

“…Symptoms arise from the tips and margins of leaves which move towards the central areas resulting blighted leaves (Akhtar et al, 2004). Morphology of cultures/ Nature of growth: The fungal cultures in petri plates inoculated with leaf samples S6, S15 and S17 appeared with dark olivaceous brown to dark blackish brown on the surface of PDA media (Khodaei and Arzanlou, 2013).…”

Genetic Diversity of Trichoderma harzianum Isolates in Sunflower Rhizosphere: The Application of the URP Molecular Marker

“…Oil imports account for a significant part of the sunflower oil supply in Iran and Italy. Improving sunflower production is a promising approach for offsetting vegetable oil shortages [1]. Sunflower cultivation is hampered by several phytopathogens.…”