Pathogenic, cultural, morphological and molecular variability among eight isolates of Alternaria solani, causing early blight of tomato

Abstract

Among the fungal diseases infecting tomato crops, early blight caused by Alternaria solani (Ellis and Martin) Jones and Grout is one of the most catastrophic disease causing accountable losses. Further, all of the tomato cultivars presently under cultivation have succumb more or less to early blight disease. Therefore, the present studies were undertaken for the pathogenic, cultural, morphological and molecular variability among the isolates of A. solani. The results reveal all of the eight isolates of A. solani as pathogenic to tomato (Cv. Pusa Ruby) and showed variability amongst them. The test isolates could grow better on the basic culture medium potato dextrose agar; however, highest mycelial growth was recorded on the isolate AsLt (88.50 mm), followed by AsBd (82.36 mm) and AsHl (78.40 mm), with excellent sporulation. All of the eight test isolates exhibited a wide range of variability in respect of their mycelial and conidial dimensions and septation. RAPD-PCR analysis of the four most virulent A. solani isolates, using 13 OPA primers revealed that the isolates AsBd (Beed) and AsLt (Latur) were closely related with 85% genetic similarity whereas, the isolates AsHl (Hingoli) and AsJl (Jalna) were closely related with 50% genetic similarity, but distinct from that of AsLt and AsBd isolates.

Green Synthesis of Silver Nanoparticles Using Pomegranate and Orange Peel Extracts and Their Antifungal Activity against Alternaria solani, the Causal Agent of Early Blight Disease of Tomato

“…Many investigators in various countries [29][30][31][32][33] have tried the morphological and molecular characterization of A. solani. Moreover, in the present study, the molecular investigation confirmed the morphological characteristics of the pathogen isolates that were suspected to be A. solani.…”

Morphological and Molecular Variability of Alternaria solani and Phytophthora infestans Causing Tomato Blights

“…Few isolates grew fast within the first four days, others increased growth in days 6-7, while another lot increased its growth on the last days of the experimental period [ 32 ]. Nikam et al [ 33 ] investigated the radial growth of eight A. solani isolates and reported radial growth ranging between 65.80 mm and 88.50 mm. Similarly, Nafisa and Javed [ 34 ] evaluated seven isolates of A. solani and reported their growth to range between 50 mm and 88 mm within a period of seven days.…”

“…Among the 19 fungal isolates studied by Mugao et al [ 36 ], majority of them (12) had a growth margin that was irregular, while the others (7) had a circular growth margin. Among eight isolates studied by Nikam et al [ 33 ], the growth margins were either circular or regular and either smooth or rough. Some had zonation, while others were without zonation.…”

“…Similar results were reported by Mugao et al [ 36 ], and after evaluating nineteen isolates, the colony colour varied from being greenish brown, dark brown, grey, to being greyish brown. Nikam et al [ 33 ] evaluated the morphology of eight A. solani isolates, and only two out of the eight isolates had a similar colony colour which was brownish black. The other six isolates had different colony colours (black, dark grayish, olivaceous black, pinkish red, light grey, and creamish white).…”

“…Six of the isolates had slender, short, unbranched beaks, while one had an elongated branched beak. The report of Nikam et al [ 33 ] also showed that the beak sizes also varied with some having elongated beaks, while others had short beaks. Seven strains of A. solani studied by Nafisa and Javed [ 34 ] revealed a beak size ranging between 10 and 50 μ m. According to Loganathan et al [ 37 ], the beak length of the 5 isolates studied ranged between 60 and 89.3 μ m. Rotem [ 8 ] reported that the length of the beak size of A. solani conidia ranged between 139 and144 μ m and the beak width ranged between 12–20 μ m. According to Simmsons [ 42 ], the conidial sizes were 120–296 μ m length and 12 and 20 μ m width.…”