Studies on Effect of A. niger on Physiological Weight Loss and Biochemical Changes in Black Mould Rot Diseased Onion
*Corresponding author: Prajapati BK, Department of Plant Pathology, B. A. College of Agriculture, Anand Agricultural University, Anand, Gujarat, India, E-mail: email@example.com
Black mould rot of onion is an important post-harvest diseases of onion which effects on the quality deterioration of onion bulbs by utilizing its nutrient contents. Here, present research was carried out to study the losses of different nutrients from onion bulbs after the infection of A. niger in three different varieties. Onion bulbs inoculated with A. niger showed loss in weight as compared to uninoculated bulbs at 30, 60 and 90 days after inoculation. Highest per cent physiological weight loss was recorded in Gujarat Anand white onion-3 variety (10.48 g and 16.70%) followed by Nasik yellow (11.54 g and 14.45%) and Nasik red (11.73 g and 10.59%) after 90 DAI. Total soluble sugar content in onion bulbs inoculated with A. niger progressively decreased as the incubation period was increased over control in all three varieties. Least TSS (10.90, 6.39 and 6.09%) and reducing sugar content (1.81, 1.13 and 1.09%) was recorded in onion bulbs after 90 DAI over control (18.21, 17.25 and 14.11%), (6.91, 5.48 and 5.23%) in Nasik red, yellow and Gujarat Anand white onion-3 varieties, respectively. There was appreciable decrease in phenol content in onion bulbs inoculated with A. niger up to 60 DAI due to utilization by fungi and then there was increase in total phenol content in onion bulbs up to 90 DAI when inoculated with A. niger. Total phenol content of healthy Nasik red, yellow and Gujarat Anand white onion-3 varieties were 51.23, 46.07 and 38.78 per cent, which showed maximum reduction after 60 DAI (30.69, 27.36 and 20.24%) and found increased after 90 DAI (33.72, 29.60 and 26.22%). Significantly lowest amount of ascorbic acid content was recorded at 90 DAI (0.03, 0.014 and 0.014 mg/100g) over control (0.14, 0.14 and 0.13 mg/100g), least pyruvic acid content was found at 90 DAI (257.82, 217.11 and 158.65 mg/100 g) over control (755.48, 589.77 and 512.78 mg/100 g), least acidity content was found at 90 DAI (2.05, 2.81 and 1.28%) over control (6.40, 5.76 and 3.84%) in Nasik red, Nasik yellow and Gujarat Anand white onion-3 varieties, respectively.
Onion, Aspergillus niger, Total sugar, Reducing sugar, Phenol, Ascorbic acid, Pyruvic acid, Acidity content.