PRODUCTION OF INDIAN CITRUS RINGSPOT VIRUS FREE PLANTS OF KINNOW EMPLOYING CHEMOTHERAPY COUPLED WITH SHOOT TIP GRAFTING

Indian citrus ringspot virus (ICRSV) is known to cause serious problem in Kinnow (Citrus nobilis Lour × C. deliciosa Tenora). This paper reports the elimination of ICRSV from Kinnow by chemotherapy coupled with shoot tip grafting under in vitro conditions. Nodal segments from infected mother plant (indexed by indirect ELISA and RT-PCR) were cultured on MS medium containing 2-iP (1mg/l) and malt extract (800 mg/l) along with different concentrations of five antiviral chemicals acycloguanosine, azidothymidine, 2,4-dioxohexahydro-1, 2,5-triazine (DHT), ribavirin and 2- thiouracil. Shoot tips of size 0.7 mm were excised from the sprouts of these nodal segments and grafted on to rough lemon (Citrus jambhiri) under aseptic conditions. The plantlets obtained from chemotherapy coupled with in vitro micrografting were indexed by indirect ELISA and RT-PCR after acclimatization. Maximum effect (37% virus elimination) was seen for ribavirin at 25 mg/l followed by 2-thiouracil at 25 mg/l (21.4%) and acyclguanosine at 25 mg/l (20.8%). Azidothymidine and DHT at the tested doses could not eliminate ICRSV. In the present study only those plants/plantlets were considered virus free, which showed negative reaction both with indirect ELISA and RT-PCR

Production of Indian citrus ringspot virus free plants of kinnow employing chemotherapy coupled with shoot tip grafting

ABSTRACT Indian citrus ringspot virus (ICRSV) is known to cause serious problem in Kinnow (Citrus nobilis Lour × C. deliciosa Tenora). This paper reports the elimination of ICRSV from Kinnow by chemotherapy coupled with shoot tip grafting under in vitro conditions. Nodal segments from infected mother plant (indexed by indirect ELISA and RT-PCR) were cultured on MS medium containing 2-iP (1mg/l) and malt extract (800 mg/l) along with different concentrations of five antiviral chemicals acycloguanosine, azidothymidine, 2,4-dioxohexahydro-1, 2,5-triazine (DHT), ribavirin and 2-thiouracil. Shoot tips of size 0.7 mm were excised from the sprouts of these nodal segments and grafted on to rough lemon (Citrus jambhiri) under aseptic conditions. The plantlets obtained from chemotherapy coupled with in vitro micrografting were indexed by indirect ELISA and RT-PCR after acclimatization. Maximum effect (37% virus elimination) was seen for ribavirin at 25 mg/l followed by 2-thiouracil at 25 mg/l (21.4%) and acyclguanosine at 25 mg/l (20.8%). Azidothymidine and DHT at the tested doses could not eliminate ICRSV. In the present study only those plants/plantlets were considered virus free, which showed negative reaction both with indirect ELISA and RT-PCR

<i>Apple scar skin viroid</i> naked RNA is actively transmitted by the whitefly <i>Trialeurodes vaporariorum</i>

<p>Nucleic acid transfer between plants is a phenomenon which is likely to occur in many ways in nature. We report here the active transmission of <i>Apple scar skin viroid</i> (ASSVd) naked ssRNA species by the whitefly <i>Trialeurodes vaporariorum</i> (<i>Tv</i>). Not only the viroid RNA, its DNA form was also identified from the insect. The viroid transfer efficiency was enhanced with the help of <i>Cucumis sativus</i> Phloem protein 2 (CsPP2), a plant protein known to translocate viroid RNAs. This PP2/ASSVd complex is stably present in the viroid infected cucumber plants, as was identified with the help of immunological reaction. As viroid-like secondary structures are found in some plant RNAs, and PP2 is known to bind and translocate several RNAs, the results have huge implications in transfer of these RNA species between plants visited by the whitefly.</p