EFFECT OF DIFFERENT SOWING TIME ON VIRAL DISEASE INCIDENCE AND SEVERITY OF PUMPKIN COLLECTED FROM DIFFERENT SOURCES OF BANGLADESH

Abstract

A field experiment was conducted at the experimental farm of Sher-e-Bangla Agricultural University (SAU), Dhaka, during the period from November‘ 2016 to March‘ 2017. The study was done to evaluate the effect of sowing dates on pumpkin viral diseases and to detect different viruses of selected sources. In total of four type‘s pumpkin seeds were used in the experiment which are collected from four sources of Bangladesh, they are Narayanganj (S 1 ), Narshingdi (S 2 ), Dhaka (S 3 ), and Gazipur (S ). These sources were tested in two sowing date that were 25 th 4 October‘2016 and 5 th November‘2016 respectively. The experiment was laid out in a RCBD with three replications. At early sowing, the highest disease incidence and severity were found (92.41% and 97.33%, respectively) in S (Narshingdi) and the lowest disease incidence and severity were found (63.33% and 81.61%, respectively) in S 2 (Narayanganj). Similarly in late sowing, the highest disease incidence and severity were found (94.14% and 97.32%, respectively) in S (Narshingdi) and the lowest disease incidence and severity were found (57.49% and 82.26%, respectively) in S 1 2 (Narayanganj). Significant variations were found in both growth and yield contributing parameters. In both sowing times, the highest aphid population was found in month of February and the lowest in March. There were a positive correlation exists between disease incidence (%) and disease severity with aphid population both in early and late sowing. It revealed that disease incidence and severity increased with the increase of aphid population. During experiment, four different categories of symptoms were identified as viral symptoms in field such as fern leaf, mosaic, chlorosis and yellowing, and leaf distortion by visual observation. In Serological test, among

1 four types of symptoms mosaic, chlorosis and yellowing confirmed as Cucumber mosaic virus (CMV) by using CMV antiserum through DAS-ELISA.