S.S.Wagh, A. P. Suryawanshi and P. G. Chavan
Department of Plant Pathology, College of Agriculture, VNMKV, Parbhani – 431 402 (M.S.), India.
Cultural, morphological and pathogenic studies revealed a wide range of variability of among the 20 isolates of A. carthami of safflower which represented four geographic regions of the state of Maharashtra. All 20 test isolates exhibited a great cultural variability in mycelial growth, colony colour, growth speed, colony shape and sporulation. Significantly highest mycelial growth was found in isolate AcHl (90.00 mm), followed by AcBl (89.67 mm) and AcAn (88.83 mm). Among morphological variability in respect of mycelial width, conidial dimensions, beak length and number of vertical and horizontal septa eight isolates exhibited large mycelial width (7.05 to 9.80 µm), six isolates with medium sized with mycelium width (5.40 to 6.46 µm) and six with small sized mycelium width (3.25 to 4.86 µm). On the basis of average conidial dimensions (length X breadth), the test isolates were categorized into three groups viz., large, medium and small sized conidia were found in nine isolates of which average length ranged from 36.37 to 50.32 µm and width from 13.06 to 17.19 µm; seven isolates were with medium sized conidia (26.80-35.37 X 9.94-14.73 µm) and rest four isolates with small sized conidial (22.45-25.17 X 7.28-9.27 µm). About eight isolates exhibited long beak length (11.05 to 16.43 µm), seven isolates with medium beak length (8.13 to 11.27 µm) and rest five isolates were of short beak length (6.04 to 7.46 µm). Among the test isolates, horizontal septation on conidia was ranged from 1 to 12 and vertical septation from 0 to 3. All of the 20 isolates of A. carthami exhibited a wide range of pathogenic variability. However, the aggressive isolates (viz., AcHl, AcBl, AcAn, AcJg, etc.) showed least incubation period, highest leaf spot frequency with maximum sized leaf spots.
Keywords: Alternaria carthami, safflower, cultural, morphological, pathogenic variability.