First Report of the Association of Zygocactus Virus X with Dragon Fruit (Hylocereus spp.) Plants from Telangana, India

Abstract

Dragon fruit (Hylocereus spp.) a member of the family Cactaceae, is widely cultivated throughout the world, includingspan style="font-family:'Times New Roman'; letter-spacing:0.05pt; color:#333333"> India. During 2020-2021 crop growing season, mosaic symptoms were observed on the cladodes of dragon fruit plants (Purple Pink cultivar: 1-2% disease incidence) grown at a farmer’s field of Telangana, India (Fig. S1 a). The symptomatic cladodes (n= 4), observed under leaf-dip electron microscopy (Zuchmaan and Zellnig, 2009) at Indian Agricultural Research Institute, New Delhi, revealed the presence of flexuous rod- shaped virus-like particles (Fig S1 b). Virus particles were of 580 x 13 nm size, corresponding to the genus Potexvirus. For further confirmation, the total RNA isolated from symptomatic cladodes using a NucleoSpin RNA Plant Mini kit (Macherey-Nagel). Subsequently, a reverse transcription polymerase chain reaction (RT-PCR) was performed using the PrimeScript 1st strand cDNA Synthesis Kit (Takara Bio). The cDNA was further amplified with the primers specific to coat protein (CP) gene of four different species of the genus Potexvirus known to infect members of Cactaceae family. Four sets of primers were used for detection, viz., Cactus virus X (CVX) (F, 5′-ATGTCTACTACTGGAGTCCA-3′; R, 5′-CTACTCAGGGCCTGGGAGAA-3′); Pitaya virus X (PiVX) (F, 5′-ATGGCTACTCAAACAGCACAA-3′; R, 5′-CTACTCTGGGGAGGGAAG-3′); Schlumbergera virus X (SchVX) (F, 5′-ATGTCGACCACTCCATCTTC-3′; R, 5′-TTATTCAGGGGATGGTAGTA-3′) and Zygocactus virus X (ZyVX) (F, 5′-ATGTCTAACACTGCAGGAGT-3′; R, TCATTC GGGACCCGGTAGGA-3′) (Duarte et al., 2008; Janssen et al., 2021; Parameswari et al., 2021), by following the PCR profile (Park et al., 2018). The species-specific primers of CVX, PiVX and SchVX did not amplify any amplicon, whereas the primers specific to ZyVX at nucleotide position 5841-6521 from complete CP gene have resulted in amplification of expected size (~680 base pairs) from all the samples. The gel-purified RT-PCR products were cloned into a pDrive cloning vector (Qiagen, Germany) and sequenced bi-directionally using Sanger sequencing. The resultant sequences (681 nt) of the CP gene showed 98% (nucleotide) and 100% (amino acid) sequence similarity with the CP gene sequence (Accession No: KY581590) of ZyVX. Hence, one representative sequence was deposited to the NCBI GenBank database as ZyVX-DPC isolate (Accession number- OK415019). The Neighbour Joining Phylogenetic Tree constructed using MEGA6 software (Tamura et al. 2013) showed grouping of Indian ZyVX-DPC isolate with the previously reported ZyVX isolates from Korea, Taiwan, China and Germany (Fig. S1c). These results confirmed the association of ZyVX with the symptomatic cladodes of dragon fruit plants collected from Telangana, India. Earlier studies revealed that ZyVX is a member of the genus Potexvirus known to infect dragon fruit plants from Brazil and China (Duarte et al., 2008). In India until now, anthracnose disease (Colletotrichum siamense) and CVX from Hylocereus spp. were reported (Abirami et al., 2019; Parameswari et al., 2021). To the best of our knowledge, this is the first report of ZyVX infection on dragon fruit in India. The draon fruit, being vegetatively propagated and with increasing cultivable area in India (Abirami et al, 2019), the present study gains significance. Further studies on mode of virus transmission, estimation of crop yield losses, host range studies and finding out source of resistance are essential.