Abstract
The cultivation of dolichos bean [Lablab purpureus (L.) Sweet] has been severely affected by dolichos yellow mosaic virus (DoYMV, Begomovirus) transmitted by whitefly, Bemisia tabaci (Hemiptera: Aleyrodidae). We tested the transovarial transmission of DoYMV in next-generation B. tabaci by PCR, real-time PCR, Southern blot hybridization, and biological transmission. The eggs, laid by DoYMV-exposed B. tabaci, carry the virus in a unique pattern. Only the eggs laid in between 3 and 6 days post virus acquisition by a parent B. tabaci were DoYMV positive. When tested individually in real-time PCR, around 31–53% of the eggs carried the virus. The presence of DoYMV in ovaries and F1 eggs was further substantiated by the hybridization of a Cy3-conjugated nucleic acid probe complementary to the viral strand of DoYMV. Viral DNA was also detected in F1 adults and F2 eggs. B. tabaci progenies carried not only the DoYMV DNA but were also infective. The F1 adults transmitted DoYMV to all tested plants and produced strong yellow mosaic symptoms. An increase in viral copies from egg to nymphal stage indicated propagation of DoYMV in B. tabaci. However, the increase was for a short period and decreased thereafter. The present study provides the first evidence of transovarial transmission and propagation of a bipartite begomovirus in its vector, B. tabaci Asia II 1. The transovarial transmission and replication of DoYMV in B. tabaci have great epidemiological relevance as B. tabaci can serve as a major host of the virus to bridge the gap between the cropping seasons.
Highlights
Begomovirus is the largest known genus of plant viruses, which contains more than 445 virus species (ICTV, 2020)
We report here the transovarial transmission of a bipartite begomovirus, Dolichos yellow mosaic virus (DoYMV), by B. tabaci Asia II 1
The present study provides the first evidence of propagation and transovarial transmission of DoYMV infection by B. tabaci Asia II 1
Summary
Begomovirus (family Geminiviridae, order Geplafuvirales) is the largest known genus of plant viruses, which contains more than 445 virus species (ICTV, 2020). B. tabaci transmits begomoviruses in a persistent-circulative manner and the virions pass along the food canal after ingestion and reach the digestive tract. They are bound by the receptors located at midgut of B. tabaci. Begomoviruses are not reported to multiply in their vectors except in the case of tomato yellow leaf curl virus (TYLCV). To date, there are at least two exceptions: monopartite begomoviruses TYLCV and tomato yellow leaf curl Sardinia virus (TYLCSV). TYLCV and TYLCSV have been reported to be transovarially transmitted by B. tabaci MEAM1 and MED (Ghanim et al, 1998; Bosco et al, 2004). We report here the transovarial transmission of a bipartite begomovirus, Dolichos yellow mosaic virus (DoYMV), by B. tabaci Asia II 1. The initial observations instigated us to investigate the transovarial transmission of DoYMV by its vector, B. tabaci
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