Suppression of chili leaf curl virus (ChLCV) incidence in chili (Capsicum annuum L.) across Bangladesh via manipulated planting date and spacing

Abstract

A 2-year factorial experiment was undertaken in RARS, Jessore in 2019 and 2020 following randomized complete block design with three replicates to evaluate the impact of planting date and spacing on ChLCV disease development and its vector whitefly abundance in chili (Capsicum annuum) modulating chili growth and yield attributes. The field experiments were found consistent between the years improving the reliability and generalizability of the data. The factors planting date and spacing separately produced statistical variation in ChLCV epidemiological parameters along with growth and yield attributing characters. Of the three chili planting dates, early planting (January 1) significantly suppressed ChLCD incidence, severity and its vector whitefly abundance over mid (February 1) and late planting (March 1) dates. Among four spacings, spacious plant spacing (50 × 60 cm) performed significantly better than other spacings in reducing ChLCD incidence and thereby expediting chili growth and yield. No statistical variation was documented between two narrow spacings of 50 × 30 cm and 50 × 40 cm in most of the studied parameters. Regression analyses depicted AUSiPC and AUDPC declined by 13.07 and 12.66 with each unit increase in plant spacing ensuring good fits of the models. A three-variables contour plot illustrated how vector whitefly abundance in chili stimulated ChLCD incidence and reduced chili yield while a 3-D wireframe pointed out that ChLCD incidence accelerated both AUSiPC and AUDPC. PCA analysis identified the major components of the studied parameters impacting disease incidence and chili yield. Cluster analyses well supported the PCA analysis and distinctly branched all the studied parameters into two, one associated with chili yield promoting characters and another with yield constraining ChLCD epidemiological attributes positioned in different nodes with variable similarity matrix. Molecular PCR analysis confirmed the presence of ssDNA (+) ChLCV in sampled plants.