Validation of micrografting to identify incompatible interactions of rootstocks with virus‐infected scions of Cabernet Franc

Abstract

Background and Aims Grafted grapevines are a key component of modern viticulture. Grafting provides not only resistance to soil‐borne pests, but can also improve adaptability to the environment and can improve fruit yield and quality. Graft incompatibility induced by grapevine viruses causes damage to vineyards worldwide. The aim of the present study was to create a rapid and reliable means of evaluating graft incompatibility resulting from grafting virus‐infected scions onto healthy grape rootstocks. Methods and Results Scions of Control (healthy Cabernet Franc), LR131 (Cabernet Franc infected with GLRaV‐1) and LR132 (Cabernet Franc infected with GLRaV‐1 and GVA) were grafted onto different rootstocks by micrografting, green grafting and bench grafting methods. All the micrografts infected with LR132 failed, while LR131 and Control micrografts had similar survival rates. The impact of LR132 was less severe on green grafted plants, followed by bench grafts. Analysis of variance showed an interaction of grafting method × virus variety × rootstock, affecting grafting survival. When grafted onto Freedom and 101‐14, LR131 inhibited the growth of both scion and rootstock, but no significant impact was seen when LR131 was grafted onto St. George and AXR1. Well‐established callus was visible between the surfaces of LR131 and the rootstocks. The virus GLRaV‐1 was detected moving from the LR131 scion source to rootstocks 7 days after micrografting. Callus formation was delayed by LR132 between scion and rootstock surfaces, and a scion‐rootstock vascular connection did not establish, resulting in the death of all micrografts. Conclusions Micrografting is a reliable and sensitive method to screen for virus tolerant graft combinations compared with green and bench grafting. Significance of the Study The results of the present study validate micrografting as a means of producing credible information for selection of virus tolerant rootstocks, and ultimately vineyards with higher rates of compatible grafts.

Occurrence of Grapevine Leafroll-Associated Virus-3 (GLRaV-3), Complete Nucleotide Sequence and Cultivar Susceptibility to a GLRaV-3 Isolate from Shaanxi Province of China

“…A previous micrografting study with GLRaV-1 and GVA found that 'George' and 'AXR1' were less susceptible to infection by GLRaV-1 and GVA than 'Freedom' and '101-14' when used as rootstocks, suggesting that the reduced susceptibility may be a result of their Vitis. rupestris parentage [49]. Our results showed 'Hunan-1' had reduced susceptibility to GLRaV-3.…”

In Vitro Micrografting of Horticultural Plants: Method Development and the Use for Micropropagation

“…Following the advent of in vitro plant tissue culturing in the early 1900s [7], a grafting system using tissue culture (micrografting) was first demonstrated by Doorenbos [8] in ivy and then Holmes [9] in chrysanthemum in the 1950s, and was later developed and standardized for virus eradication from citrus species by Murashige et al [10] and Navarro et al [11]. To date, in vitro micrografting (IVM) has been widely applied (1) in pathogen management to facilitate the eradication, indexing and transmission of pathogens, as well as the assessments of graft incompatibility induced by pathogen infection [11][12][13][14][15]; (2) to facilitate in vitro rooting [16][17][18][19], to invigorate regenerating plant tissue cultures during micropropagation [19][20][21][22], and for the rapid assessment of graft compatibility [23][24][25][26]; and (3) in studies focusing on the molecular mechanism of graft compatibility, as well as the exchange and trafficking of macromolecules between scions and rootstocks [27][28][29][30].…”

“…Several devices have been used to enable fast and effective union between the rootstock and scion, such as the elastic electric-wire tube [44], aluminum foil [66,76], Parafilm ® strip [42], silicon tube [13,79,80], paper bridge [59], silicone chip [30], plastic clamps [50] or alginate gel beads [44,75,81]. These grafting devices are used to support the graft and hold the scion and rootstock together during graft healing, particularly for the top-slit and top-wedge methods.…”

“…In almond, micrografted plants were cultured on rooting medium and incubated in the dark for 7 days, then transferred to the light of 35-40 µmol m −2 s −1 for two weeks, and finally to 60 µmol m −2 s −1 for one week before in vivo acclimatization [65]. Several studies have reported successful micrografts without a dark incubation period following the grafting procedure [13,24,72,82,86].…”

In vitro biological indexing of grapevine leafroll‐associated virus 3 in red‐ and white‐berried grapevines ( Vitis vinifera )

“…Several in vitro biological methods have been described for indexing of GLRaV‐3 (Tanne et al 1996, Pathirana and McKenzie 2005a,b, Constable et al 2013, Cui et al 2015, 2017, 2019, Hao et al 2017). Compared with field studies (Cirami et al 1988, Walter et al 1990, Pathirana and McKenzie 2005a, Constable et al 2013), in vitro culture can avoid the interference of environmental factors, such as temperature, light and nutrition, and other pathogens, thus ensuring reliability of the results, in addition to its time efficiency (Tanne et al 1993, 1996, Pathirana and McKenzie 2005b, Cui et al 2015, 2016, 2017, 2019, Hao et al 2017). Grapevine plants infected with GLRD express symptoms earlier, and the symptoms are intensified in vineyards under drought stress in the autumn (Tanne et al 1996, Maree et al 2013).…”