Transmission dynamics and localization of tomato leaf curl New Delhi virus in cucurbits via sweet potato whitefly, Bemisia tabaci (Gennadius).

Abstract

Background: Bitter gourd (Momordica charantia), ridge gourd (Luffa acutangula), and pumpkin (Cucurbita pepo) are major vegetables of the Cucurbitaceae family cultivated extensively in India. However, their production is severely affected by begomoviruses, which inflict significant global damage to cucurbits. Among these, tomato leaf curl New Delhi virus (ToLCNDV), a whitefly-transmitted, persistent, circulative, and non-propagative begomovirus, seriously threatens cucurbit cultivation, often leading to substantial yield losses.

Methods and results: Understanding the interactions between vectors and viruses is therefore critical. This study explored the transmission dynamics, localization, and titre of ToLCNDV in bitter gourd, ridge gourd, and pumpkin. A maximum transmission rate of 80% was achieved when 15 whiteflies (Asia I cryptic species) were given an acquisition access period (AAP) and an inoculation access period (IAP) of 24 h. However, transmission was observed even after 1 h of AAP and IAP respectively. Immunofluorescent assays showed that ToLCNDV accumulated as vesicle-like structures in the midgut and salivary glands of B. tabaci. Using conventional PCR, ToLCNDV yielded an expected amplicon size of 1500 bp in the midgut and salivary gland DNAs of B. tabaci. The maximum viral titre of 7.2 × 10⁷, 3.4 × 10⁶ and 1.3 × 10⁶ copies per µl at 24 h of IAP were observed in 20-day post-inoculation symptomatic leaves of bitter gourd, ridge gourd and pumpkin, respectively.

Conclusions: Bemisia tabaci (Asia I) efficiently transmitted ToLCNDV in bitter gourd, ridge gourd, and pumpkin. Localization studies confirmed the presence of virus particles in the midgut and salivary glands of viruliferous whiteflies. qPCR assays quantified viral titres in infected cucurbit crops. These findings enhance the understanding of virus-vector interactions and provide valuable insights for developing effective management strategies to combat leaf curl disease in cucurbits.