Morphological, Pathogenic, and Molecular Characterization of Alternaria Isolates Associated with Alternaria Late Blight of Pistachio

Abstract

Alternaria isolates were obtained from various pistachio tissues collected in five orchards in California. For all isolates, morphological characteristics of the colony and sporulation apparatus were determined and compared with those of representative isolates of A. alternata, A. tenuissima, A. arborescens, and A. infectoria. A selection of the pistachio isolates and the representative Alternaria isolates were evaluated for pathogenicity to pistachio. Molecular characteristics of these isolates were determined using random amplified polymorphism DNA (RAPD) analysis, polymerase chain reaction restriction fragment length polymorphism (PCR-RFLP) analysis of nuclear intergenic spacer rDNA, and sequence analysis of nuclear internal transcribed spacer (ITS) rDNA. Based on morphological characteristics, the pistachio isolates were grouped as identical or very similar to either A. alternata, A. tenuissima, A. arborescens, or A. infectoria. Isolates from the alternata, tenuissima, and arborescens species-groups were pathogenic to pistachio and no significant differences in pathogenicity were observed. Isolates from the infectoria species-group were only weakly pathogenic to pistachio. Based on cluster analysis of RAPD and PCR-RFLP data, three distinct clusters were evident; the infectoria cluster, the arborescens cluster, and a combined alternata/tenuissima cluster. Based on analysis of ITS sequence data, the infectoria species-group was phylogenetically distinct from the other species-groups. Isolates of the alternata, tenuissima, and arborescens species-groups comprised a monophyletic clade in which the three species-groups could not be further resolved.

AFLP analysis of Russian Alternaria tenuissima populations from wheat kernels and other hosts

“…Many researchers have found this fungus to be a common pathogen on a number of plants in different parts of the world. It can, for example, induce late blight of pistachio in the USA (Pryor and Michailides 2002), and was established as a major cause of apple dry core rot in South Africa (Serdani et al 2002).…”

Genetic differences in Alternaria alternata isolates associated with brown spot in tangerine cultivars

“…Many researchers have reported that differentiation of the small-spored Alternaria spp. is difficult due to lack of variation in nuclear ribosomal ITS and β-tubulin sequences, two genomic regions typically used in fungal systematic 17,27 . The A. alternata population of tangerine in Jahrom region orchards showed high morphological and genetic diversity, which may provide information on genetic differences among tangerine isolates from different cultivars.…”

“…Much research has focused on identification of genetic differences among citrus-associated Alternaria spp. 11,[15][16][17] but little is known about genetic differences among Alternaria isolates from individual citrus species. The objective of this study was to clarify that Alternaria isolates collected from tangerine cultivars had genetic differences (based on ITS sequences).…”

Determination of mycotoxin profiles characteristic ofAlternariastrains isolated from Malbec grapes

“…A wide variety of Alternaria strains was isolated from different hosts including grapes [3][4][5][6]. Species such as Alternaria alternata, A. arborescens and A. tenuissima have frequently been isolated from grapes during development in the vineyard or postharvest storage [4,[7][8][9].…”