Factors affecting in vitro cultivation of grape (Vitis vinifera L.): a review

Grape (Vitis vinifera L.) is globally cultivated as commercial fruit crop usually used for fruit purpose or industrial product. The objective of the current review is to review and identify the research gap on the effect of different growth media and vitrification on shooting and rooting performance of grape. Factors affecting rooting of grape cuttings can be internal or external factors. Currently, grapevines are very sensitive to disease in the conventional method of propagation. Even if tissue culture is recommended for healthy propagation of the grape varieties, still factors affecting the growth of the plant verifications were reported. This, review paper progressively revised for the existing factors and possible solutions during in vitro propagation of grapevines.


Introduction
Grape (Vitis vinifera L.) is globally cultivated as commercial fruit crop usually used for fruit purpose or industrial product (Orhan et al., 2009). It also used in folk medicine for its biological activities since ancient times. From commercial viticulture perspective, nearly all grape varieties are propagated through stem cutting, layering and grafting in most parts of the world. However, this increases the susceptibility of cultivated varieties to disease causing agents (microbes, mites, insects, nematodes, fungi, bacteria, viruses and more importantly Phylloxera) (Alizadeh et al., 2010). Factors like slow and seasonal multiplication and infection with pathogens have constrained the use of conventional plant propagation methods, thus lead to development of new and novel methods of propagation like in vitro multiplication, which ensures the production of virus and disease free elite planting material in large numbers. Even, in vitro micro propagation of grape cultivars challenged by different factors: media types, concentration of hormones, vitrification and growing mechanisms. Study conducted on shoot multiplication in grape cv. perlette clearly described, the role of cultivation media (Jamwal et al., 2013). Thus, the combination of various growth regulators and their concentrations significantly influences shoot length due to their effect on cell division and cell expansion (Khan et al., 2015). Virtification is another factor (bottleneck) for the establishment of grape tissue culture (Bi et al., 2017). Though it is known that, grapevine (Vitis vinifera L.) is one of the most widely distributed fruit crop of the world, today the need for grapevine fruit is increasing (Richard et al., 2010). This happened because of increase in the number of wine industries and more demand for fresh and dried fruits (Fayek et al., 2009). Therefore, to fit the demand for grape a healthy micro-propagation is too much needed (Patrice et al., 2006). The aim of this work was to assess the factors affecting tissue culture of grapes.
Objectives  To review the factors of different growth regulators on in vitro growth performance of grape  To identify research gap on the investigated results and forwarding recommendations.
Literature reviews on factors affecting in vitro cultivation of grape

Review on hyperhydricity (vitrification) and controlling mechanism
Hyperhydricity of micro propagated shoots also known as Vitrification is unconditionally results from growth and culture condition, which affects Int. J. Agril. Res. Innov. Tech. 10(1): 1-5, June 2020 the survival and quality of micro-propagated grape cultivars (Gemechu and Feyissa, 2016). Vitrification affects the survival and quality of micro propagated plants. It highly affects the shoots and leaf parts of the plants. To get healthy propagules, it is necessary to look the cause and in vitro controlling of Vitrification (Rasco and Pateña, 1997).
Liquid and low agar media is also one causing agent of Vitrification as it induced cellulose formation along with induced and disoriented cellulose biosynthesis, which is manifested in non-functional guard cells. Mal-functioning stomata in addition affect the cuticle contributed to increased transpiration and desiccation of in vitro formed leaves. Thus, agar should not be considered simply as a means of solidifying culture media: In general, the concentrations of agar affect the chemical and physical characteristics of a culture medium (Ziv, 1991). The problem of Vitrification on micro propagation of the grapevine has been reported (Alizadeh et al., 2010;Kinfe, 2010) but there are few reports which mention decreases of Vitrification.
As, Vitrification of shoots appear during the multiplication stages, reductions of Vitrification in vitro result in increment of shoot numbers (Kumsa, 2016). There are a number of mechanisms used to reduce Vitrification: can be reduced by aeration of culture volume and changing of the concentration of growth regulators (Sharma and Mohan, 2006). In another way, an effective procedure for obtaining healthy shoots from in vitro culture of propagates was ventilating the culture vessels (Laia et al., 2005).
Adjusted Agar and BAP concentrations to produce non-vitrified shoots of grapevine Study conducted on two grape varieties (Canonannon and Chenin blanc) confirmed that 0.5 mg L -1 BAP and 7.5 g L -1 agar concentrations were contributed in production of maximum number of normal shoots/explant (Table 1).  Source: (Gemechu and Feyissa, 2016).

Effect of time intervals on number of normal and vitrified shoots/explant
At the day, intervals after culture were 0 to 20; numbers of vitrified shoots were low. But, when the days after culture were increased to 20 to 40, normally produced shoots were changed to vitrified shoots in both varieties (Fig. 1). Source: (Kumsa, 2011).

Summary and Conclusion
Currently, grapevines are very sensitive to disease in the conventional method of propagation. Even if tissue culture is recommended for healthy propagation of the grape varieties, still factors affecting the growth of the plant verifications were reported. This, review paper progressively revised for the existing factors and possible solutions during in vitro propagation of grapevines.