Occurrence of Banana bract mosaic virus on cardamom

Abstract

During a survey for mosaic disease caused by Cardamom mosaic virus (CdMV) in cardamom plantations, a new kind of viral disease showing chlorotic streak on veins was observed in some plantations. Based on the type of symptom, the disease was named 'chlorotic streak'. In a survey of 77 cardamom plantations at 49 locations in the states of Kerala, Karnataka and Tamil Nadu in India, incidence of the disease ranged from zero to 15%. The plants infected with chlorotic streak tested negative in reverse transcription polymerase chain reaction (RT-PCR) for CdMV. Leaf dip electron microscopy of these samples showed the presence of flexuous virions resembling Potyvirus. Total RNA extracted from these plants when subjected to RT-PCR using primers targeted to conserved region in Potyvirus resulted in an amplicon size of~700 bp. Sequencing and BLAST analysis of this amplicon showed Banana bract mosaic virus (BBrMV) as the closest virus. Using primers specific for BBrMV, the coat protein gene from five different geographical isolates of the virus was cloned and sequenced. Sequence analysis of the coat protein gene showed an identity of >94% with BBrMV isolates while identity with other distinct potyvirus species was <60%, indicating that the causal virus is a strain of BBrMV. Multiple sequence alignment and phylogenetic analyses showed high sequence conservation and close clustering of cardamom isolates along with a few banana isolates from India. This is the first report of the occurrence of BBrMV in cardamom. A reliable RT-PCR-based method was also developed for detection of the virus in cardamom plants.

Population structure of Banana bract mosaic virus reveals recombination and negative selection in the helper component protease (HC-Pro) gene

“…Pentalonia nigronervosa, Rhopalosiphum maidis, and Aphis gossypii [11]. The main host of BBrMV is Musa and recently, BBrMV is reported in small cardamom (Elettaria cardamomum) in India [20] and also infects flowering ginger, Alpinia purpurata (Vieill.) K. Schum in Hawaii [25].…”

Detection of Cardamom mosaic virus and Banana bract mosaic virus in cardamom using SYBR Green based reverse transcription-quantitative PCR

“…It is native of evergreen forests of Western Ghats of South India [6]. Mosaic/katte disease caused by Cardamom mosaic virus (CdMV) (genus: Macluravirus) and chlorotic streak disease caused by Banana bract mosaic virus (BBrMV) (genus: Potyvirus) are the major viral diseases affecting the crop [3,10]. The mosaic disease is characterized by interveinal prominent discontinuous yellowish stripes running out from midrib to the margin of leaves [12].…”

“…Crop losses of 10-60, 26-91 and 82-92 % were reported in first, second and third years of production, respectively [14]. The chlorotic streak disease is characterized by continuous or discontinuous intraveinal chlorotic streak with an incidence ranging from 0 to 15 % in the plantations where either banana was grown nearby or banana was the previous crop [10]. Coat protein gene sequence studies of different isolates revealed that CdMV as variable (identity ranging from 74.8 to 99.3 %) [4,11] while BBrMV was highly conserved (97-99 %) [10].…”

“…The chlorotic streak disease is characterized by continuous or discontinuous intraveinal chlorotic streak with an incidence ranging from 0 to 15 % in the plantations where either banana was grown nearby or banana was the previous crop [10]. Coat protein gene sequence studies of different isolates revealed that CdMV as variable (identity ranging from 74.8 to 99.3 %) [4,11] while BBrMV was highly conserved (97-99 %) [10].Detection of virus is an important component in effective management. As cardamom is mainly propagated vegetatively through tillers, identification of virus-free plants is crucial in selecting mother plants to be used for further propagation.…”

“…Hence sensitive assays are needed for selecting virus-free mother plants. So far, ELISA and RT-PCR based assays were reported for the detection of CdMV and BBrMV infecting cardamom [1,8,10]. The sensitivity of real-time quantitative PCR (qPCR) and real-time reverse transcription (RT) qPCR have been explored by many workers in developing detection assays for several viruses [5].…”