Department of Plant Pathology, Punjab Agricultural University, Ludhiana-141004
National Symposium on “Plant Pathology in the Changing Global Scenario” held at National Bureau of Plant Genetic Resources, New Delhi on February 27–28, 2009
Early blight of tomato caused by Alternaria solani (Ell. and Mart.) Jones and Grout is a serious disease threatening tomato cultivation in the Punjab state. The disease affects all the above ground plant parts and assumes serious proportions under favourable weather conditions causing losses to the tune of 46 per cent. The present investigations were under taken to ascertain the effect of leaf wetness durations and plant age on the severity of disease. The studies revealed that a minimum of 8 hr leaf wetness was required to cause infection and produce disease on tomato plants. The disease severity increased with increase in duration of wetness period. No significant increase in disease severity was observed as the wetness duration increased from 24 hr to 48 hr. A positive correlation was observed between leaf wetness duration and disease severity and leaf wetness and lesion area. Similarly, there was a significant positive correlation of r=0.96 and r= 0.99 between plant age and lesion size and between plant age and disease severity, respectively. The disease severity was lowest (19%) on 30 days old plants while it was highest (75%) on 105 days old plants. Likewise, lesion size increased linearly with the age of the plant and it was lowest (5x4 mm) in 30 days old plants while it was highest (18x12 mm) in 105 days old plants. However, incubation period decreased with the age of the plant with a significant negative correlation of r = -0.83.
