Unraveling different begomoviruses, DNA satellites and cryptic species of Bemisia tabaci and their endosymbionts in vegetable ecosystem.

Bemisia tabaci species complex contains more than 46 cryptic species. It has emerged as an important pest causing significant yield loss in many cultivated crops. This pest is also a vector for more than 100 species of begomoviruses, that are a major threat for the cultivation of many crops in different regions of the world. The relation between cryptic species of the B. tabaci species complex and associated begomoviruses that infect different crops remains unclear. In the present study, four cryptic species (Asia I, China 3, Asia II 5 and Asia II-1) of B. tabaci and four associated endosymbionts (Arsenophonus, Cardinium, Rickettsia and Wolbachia) were identified in different vegetable crops. The vector-based PCR detection revealed five different begomoviruses such as okra enation leaf curl virus (OELCuV), tomato leaf curl Palampur virus (ToLCPalV), squash leaf curl China virus (SLCCNV), chilli leaf curl virus (ChiLCuV), and tomato leaf curl New Delhi virus (ToLCNDV). Of these begomoviruses, the maximum infection rate was observed (9.1%) for OELCuV, followed by 7.3% for ToLCNDV. The infection rate of the other three viruses (SLCCNV, ChiLCuV, ToLCPalV) ranged from 0.9 to 2.7% in cryptic species of B. tabaci. Further, each cryptic species was infected with multiple virus species and the virus infection rate of Asia I, Asia II-5, China 3 and Asia II-1 was 21.2%, 15.1%, 15.1% and 0.6% respectively. Similarly, in case of betasatellites the highest infection rate was 12% for ToLCBDB, followed by 6% for OLCuB and PaLCB. With regard to alphasatellites, the highest infection rate was 18.2% for AEV and 3% for CLCuMuA. This study demonstrates the distribution of cryptic species of whitefly and their endosymbionts, and associated begomoviruses and DNA satellites in vegetable ecosystem. We believe that the information generated here is useful for evolving an effective pest management strategies for vegetable production.

Comparative transmission of Bhendi yellow vein mosaic virus by two cryptic species of the whitefly, Bemisia tabaci (Hemiptera: Aleyrodidae).

The leaf sample from okra plants showing prominent yellow vein mosaic symptoms and healthy plant without any virus symptoms were collected from farmer's field. The presence of begomovirus in the infected sample was confirmed by polymerase chain reaction (PCR) and the amplicons were cloned and sequenced. The genome analysis showed that the isolate in the present study had 99% nucleotide identity with Bhendi yellow vein mosaic virus (BYVMV) revealing it as BYVMV variant. The genetic species of Bemisia tabaci collected from fields were identified as Asia-1 and MEAM-1 genetic species based on silver leaf assay, sequence characterized amplified region marker, and mtCOI gene sequence. The comparative virus-vector relationship of both genetic species of B. tabaci indicates a minimum of two and three B. tabaci in MEAM-1 and Asia-1 genetic species, respectively, per plant were required to transmit the disease. The minimum acquisition access period and inoculation access period of 15 (MEAM-1) and 20 min (Asia-1) were required to transmit the YVMD; it was further confirmed by nucleic acid hybridization using coat protein gene-specific probe of BYVMV. With respect to the sex, the female B. tabaci were more efficient in transmitting the disease as compared to male ones in both the genetic species of B. tabaci. The MEAM-1 to transmit the BYVMV more efficiently than Asia-1 genetic species of B. tabaci.