Pathogenic and non-pathogenic mycoflora in the air and phylloplane ofTriticum aestivum L.

Aerobiological investigations were carried out over wheat (Triticum aestivum L.) fields near Barrackpore, West Bengal, India for two consecutive crop seasons. In 1990–91, except for the very seedling stage there was a more or less uniform spore count up to the maximum vegetative growth state and from flowering onwards, a gradual increase in total cfus was observed with the peak (331 CFUs) during the harvesting stage. In the second season, similar results were recorded where peak spore load (2064 CFUs) in the air was during harvesting operation followed by a sudden decline in the empty field.Cladosporium spp. dominated both the seasons mainly up to February.Penicillium, Curvularia, Aspergillus andCephalosporium were the most frequent non-pathogenic fungal types. Among the pathogenic fungi,Alternaria andDrechslera were recorded to be the most virulent to wheat crop, after inflorescence to later stages in both the seasons causing heavy leaf damage producing necrotic spots during which peak cfus were found.Fusarium was frequently found showing the peak during vegetative growth period.Sclerotium was more common in the second season than in the first season. High occurrence ofnigrospora was recorded in the earlier stages. Sterile forms' were found regularly. The phylloplane studies revealed thatCladosporium was the most dominant flora contributing 40–66% up to February in winter; gradually disappeared from the leaf surface with the onset of summer.Aspergillus andPenicillium showed the reverse picture. WhileCurvularia was isolated in high amount during later stages;Nigrospora mainly during the vegetative growth stages.Alternaria (caused Alternaria blight) andDrechslera were significantly isolated during harvesting (28.08%)and at late ‘grain maturation’ stage (80.10%), respectively.Sclerotium and ‘Sterile forms’ were recorded regularly unlikeFusarium andHelminthosporium.