Malays. Appl. Biol. (1997) 26(1): 87-92
PATHOGENICITY STUDIES ON THE SEED-BORNE PHASES OF ALTERNARIA SPP. ON CAULIFLOWER AND CABBAGE
MOHD. IMRAN KHAN1*, AZIZAH HASHIM, M.1, ABUL-FAZAL2, and MUNAWAR FAZAL2
1Department of Soil Science, Faculty of Agriculture, Universiti Putra Malaysia, 43400 UPM, Serdang, Selangor, Malaysia
2 Department of Botany, Aligarh Muslim University, Aligarh-202002, India
ABSTRACT
Species of Alternaria were found frequently associated with samples of Brassica oleracea L. (cabbage and cauliflower). Three species of Alternaria viz., A. altemata, A. brassicae and A. brassicicola found pathogenic on different plant parts were evaluated for seed-borne phases in incubation trials and their pathogenicity tested in both laboratory and pot trials under greenhouse conditions. Under incubation, the frequency of isolation from respective blotter and agar plate methods were as follows: A. altemata: 1.7 - 16.0% and 2.7 - 10.7%; A. brassicae: 1.7 - 6.7% and 1.7 - 9.0% and A. brassicicola: 5.0 - 20.0% and 3.3 - 18.7%. Pretreatment of seeds with sodium hypochlorite reduced the frequency of these fungi but did not eliminate them from the seeds. This indicated that these fungi were probably seated deep in the seed tissues. The pathogenicity studies in the laboratory indicated that all three Alternaria species were responsible for reduction in seed germination and pre- and post-emergence damping-off of seedlings. Results from greenhouse trials revealed that A. brassicae and A. brassicicola caused more damage through blighting of leaf and/or seedlings whereas, A. altemata showed no apparent symptom except for germination loss. A. brassicicola appeared to be more pathogenic than the other two species.
ABSTRAK
Spesies-spesies Alternaria selalu terdapat bergabung dengan sampel-sampel Brassica oleracea L. (kobis dan bunga kobis). Tiga spesies Alternaria iaitu, A. altemata, A. brassicae dan A. brassicicola yang didapati patogenik pada bahagian-bahagian tanaman yang berbeza telah dinilai untuk fasa-fasa pembawa biji benih dalam ujikaji pengeraman dan kepatogenan di kedua-dua makmal dan ujian pasu dalam rumah hijau. Di bawah pengeraman, kekerapan pemencilan dari kaedah blotter dan piring agar masing-masing adalah seperti berikut: A. altemata: 1.7 - 16.0% dan 2.7 - 10.7; A. brassicae: 1.7 - 6.7% dan 1.7 - 9.0% dan A. brassicicola: 5.0 - 20.0 dan 3.3 - 18.7%. Pra-rawatan biji benih dengan sodium hipokloril menurunkan kekerapan kulat ini tetapi tidak melenyapkannya daripada biji benih. Kajian kepatogenan di dalam makmal menunjukkan bahawa A. brassicae dan A. brassicicola menyebabkan banyak kerosakan melalui penghawaran daun dany atau anak benih manakala A. altemata tidak menunjukkan simptom kecuali kehilangan percambahan. A. brassicicola didapati lebih patogen berbanding dua spesies lain.
Key words: Alternaria spp., Brassica oleracea, frequency, pathogenicity
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