Micrografting and Heat Treatment Combination for Eliminating Virus of CTV-infected Citrus

Abstract

This study was conducted to eliminate viruses from citrus-infected plants using micrografting and thermotherapy. Six citrus cultivars including a 'Setoka' hybrid were used as plant sources. The TAS-ELISA technique demonstrated that several plants were CTV positive. However, no CTV symptoms were detected in plants obtained from shoots and treated at a high temperature of 40°C during the day and night and micrografted for two weeks with old trifoliate orange rootstock in vitro.Indexing of CTV, SDV, and CTLV for RT-PCR analysis of the eleven citrus seedlings, including 'Setoka', 'Samdajosang', 'Pungkwang', 'Shiranuhi', and 'Ehimekashi dai28go' was virus free following the micrografting and thermal therapy.

In vitro thermotherapy-based methods for plant virus eradication

“…There have been only a few studies using thermotherapy followed by micrografting for virus eradication [ 40 – 42 ]. Several studies that used in vivo system were not included in the present study [ 43 – 46 ].…”

“…Applying thermotherapy (40 °C, 1 week) followed by micrografting, Chae et al [ 42 ] completely eradicated citrus tristeza virus (CTV), satsuma dwarf virus (SDV) and citrus tatter leaf virus (CTLV) for six citrus cultivars.…”

“…Chemotherapy followed by thermotherapy at 36 °C produced higher frequencies of plants free of ACLSV, ASPV and ASGV than 34 °C [ 36 ]. Similar results were repeatedly found in combining chemotherapy with thermotherapy in potato [ 54 ], garlic [ 55 ] and lily [ 56 ], in thermotherapy followed by shoot tip culture in garlic [ 57 ], horseradish [ 53 ], cassava [ 54 , 55 ], nectarine [ 56 ], plum [ 57 ] and pear [ 58 ], in combining thermotherapy with shoot tip cryotherapy in raspberry [ 26 ] and apple [ 27 ], and in thermotherapy followed by micrografting in Citrus [ 41 , 42 ].…”

“…Methods of virus detection and durations after virus eradication treatments determine virus eradication frequencies in a given method. In many of the previous studies, ELISA-based methods were used to screen the virus status, followed by PCR-based methods to confirm the virus status in plants following virus eradication treatments [ 17 , 34 , 42 , 116 ]. In some cases, only ELISA-based methods were used to confirm the virus status in the plants following virus eradication [ 29 , 30 , 55 , 61 , 65 , 71 , 78 ].…”

Adjusting the Minigrafting Technique Applied to Citrus by Using Rootstocks Grown in vitro

“…When this technique is compared to micrografting, it presents higher adherence and great healing rates, fact that makes it easier to graft and generate seedlings in a shorter period of time (Wendling & Hoffmann, 2005). Micrografting is a technique mainly accessed to eliminate viruses in citric species (Ohta et al, 2011;Chae et al, 2013;Sanabam et al, 2015); however, few studies in the literature have assessed the minigrafting technique applied to citric species.…”