Utilization of Carbon, Nitrogen and Sulphur Compounds by Kabatiella zeae Narita et Hiratsuka

Abstract Morphogenesis of two K. zeae isolates (V7486 and ZP24986) on carbon, nitrogen and sulphur solid nutritive media after 2, 10, 18 and 28 days of incubation were studied. Highly significant differences were found between the isolates in regard to the use of compounds containing these elements. On carbon sources the fungus generally developed smaller colonies of branchy, loose, creamy-brown appearance, with abundant sporulation and abnormal conidia. Sucrose and D-glucose were the best carbon sources for K. zeae because both isolates had the maximum growth, abundant to medium abundant sporulation and mostly typical conidia. K. zeae colonies on organic and inorganic nitrogen and on sulphur sources too were leathery, creased, predominantly pink. Organic nitrogen sources lead to maximum growth and abundant sporulation, whereas ammonium and nitrate compounds caused intermediary growth and medium to very poor fungus sporulation. Addition of different sulphur sources, except sodium thiosulphate and thiocarbamide, did not affect the growth and sporulation of V7486. The growth of ZP 24986 depended on potassium and ammonium sulphate and sodium bisulphate.     

Morphology of a New Pathotype of Bipolaris zeicola (Stout) Shoemaker

Conidia of a new pathotype of Bipolaris zeicola (Stout) Shoemaker, which causes Helminthosporium corn leaf spot (HCLS) on inbreds derived from B73, are morphologically atypical on potato dextrose agar (PDA). The average conidial length on PDA (31.9 μm) is half that on naturally infected leaf (65.2 μm). Conidiogenuous cells terminally and subterminally located on short conidiophores produce new conidia which behave as initial conidia, i.e. they immediately elongate or germinate. Sometimes, they appear in chains. Based on conidial morphology on leaf materials and on wheat straw agar (WSA), the investigated fungus was identified as B. zeicola.