IDENTIFICATION OF PEDILANTHUS LEAF CURL VIRUS AND A NOVEL BETASATELLITE-INFECTING RADISH (RAPHANUS SATIVUS L.) IN PAKISTAN

Abstract

Single stranded DNA viruses (Genus Begomovirus) are economically important plant pathogens that are responsible for significant yield losses in dicotyledonous plants including radish (Raphanus sativus L.). However, their distribution and diversity in certain regions of Pakistan are still not sufficiently described. During systematic field surveys conducted across six districts of Punjab province (Faisalabad, Okara, Toba Tek Singh, Multan, Lahore, and Layyah), more than 120 radish fields as well as vegetable markets were inspected, but the infected plants were detected only in six localities of Thal desert in district Layyah. The radish plants exhibiting vein thickening, leaf shortening, and enations were observed, suggestive of a geminivirus infection. Total DNA isolated from symptomatic leaves was analyzed by diagnostic PCR. Amplification using coat protein primers targeting the DNA-A component yielded a 771 bp fragment (GenBank Accession No. PV872843), while universal primers for betasatellites amplified a 1361 bp fragment (GenBank Accession No. PV872842). The sequence similarity analysis revealed that DNA-A component shared similarity with Pedilanthus leaf curl virus, whereas the associated betasatellite showed 85% nucleotides identity with radish-infecting betasatellites. According to the betasatellite species criteria established by ICTV which defines distinct species at less than 91% nucleotide sequence identity, this isolate represents a divergent species for which the name Radish leaf curl Layyah betasatellite is proposed. The phylogenetic tree for coat protein suggested its close clustering with Pedilanthus leaf curl virus and Cotton leaf curl Kokhran virus reported from the region. However, betasatellite clustered with papaya infecting betasatellite previously reported from radish crops in India. This study documents, the natural occurrence of Pedilanthus leaf curl virus and a novel Radish leaf curl Layyah betasatellite infecting radish in Pakistan. Our findings underscore the occurrence of begomovirus with new betasatellite complexes in the region and highlight the need for continuous surveillance strategies to safeguard radish cultivation. Keywords: RRadish, geminiviruses, begomoviruses, betasatellites, leaf curl disease