Seasonal dynamics and prevalence of alfalfa fungal pathogens in Zanjan province, Iran

Document Type: Research Paper

Authors

1 Department of Plant Protection, Agricultural Research Institute, P.O. Box 45195474, Zanjan, Iran.

2 Department of Plant Protection, Faculty of Agriculture, Zanjan University, Zanjan, Iran.

Abstract

During 2000 and 2001, the prevalence of fungal diseases of alfalfa was surveyed under
environmental conditions in Zanjan province, Iran. In total, 15 genera of fungal pathogens were
isolated from plants sampled from the fields. All of these disease interactions had not been previously
recorded in Zanjan and Colletotrichum truncatum, Leptotrochila medicaginis, Phoma medicaginis,
Rhizoctonia crocorum on alfalfa were new disease reports for Iran. In 2000, the mean disease
incidence of fungal pathogens of alfalfa varied by sampling time and field location. Decreases in the
incidence of diseases occurred after cuttings. The incidence of diseases detected in 2000 was
correlated negatively with mean monthly temperature and positively with monthly total rainfall,
indicating that reductions in diseases were associated with higher temperature and less humidity,
irrespective of fungal species. In 2001, Ph. medicaginis was the predominant fungus infected 42.8%
of plants in the alfalfa fields followed by Pseudopeziza medicaginis (39.1%), Uromyces striatus
(33.3%), Peronospora trifoliorum (29.8%), Sporonema phacidioides (17.7%), and Leveillula taurica
(10.1%), irrespective of sampling time and field location. There was no significant correlation
between weather variables and disease incidence for Ph. medicaginis or L. taurica. However, the
incidence of common leaf spot and downy mildew were significantly correlated with both monthly
mean temperature and total rainfall. The incidence of rust was positively correlated with mean
monthly temperature, whereas the incidence of yellow leaf blotch was negatively correlated with
monthly total rainfall. This improved knowledge of diseases of alfalfa in Zanjan will assist in the
future selection of management strategies and breeding of suitable cultivars for use in regions with
similar climatic conditions.

Keywords