*New Perspectives in Grapevine (*Vitis *spp.) Breeding DOI: http://dx.doi.org/10.5772/intechopen.105194*

grown. For this reason, a study was carried out to develop more suitable rootstocks for areas with drought problems. Researchers assessed the drought tolerance of M-rootstocks physiological (gas exchange and stem water potential) and transcriptomic performances (genes involved in ABA synthesis and ABA-mediated responses to drought) were evaluated under well-watered and water-stressed conditions. In the study, drought-resistant genotypes were determined by using novel genotypes (M-rootstocks) developed by the University of Milan [158].

Due to the demand for new grapevine genotypes that are especially resistant to biotic and abiotic stress conditions, grape and rootstock breeding studies have increased in recent years and many studies have been carried out on gene regions that may be associated with these stress conditions, especially with the help of molecular methods. Due to their different advantages as rootstock, the most preferred species are *V. berlandieri, V. riparia* and *V. rupestris*. The rootstocks not only protect the grapevines from phylloxera pests but also provide the water and nutrients needed by the cultivar/genotype in different soil types. It has been reported that different rootstock species show differences in supply the nutritional needs of the grafted cultivars/genotypes. Gautier et al. [159] investigated the extent to which rootstocks with different genetic backgrounds modify the mineral composition of the petioles of the scion. In a study conducted by grafting vines of the Cabernet-Sauvignon cultivar on 13 different rootstock genotypes, it was reported that the mineral content of the petioles of the genotypes containing *Vitis riparia* in their genetic history can vary greatly. This is important proof that rootstocks can greatly affect mineral intake. An example of the effective use of rootstocks against different biotic stress factors is the study of Dalbó and Souza [160]. Researchers used rootstocks for grapevine decline and dieback, which is a big problem especially in Southern Brazil. This disease is characterized a set of symptoms that lead to the weakening and death of affected plants. In soils with insufficient aeration, root rot fungi can seriously damage the roots of vines and even cause death. The development of root rot resistant grape rootstocks is the one of the main goal in grapevine and rootstock breeding programs. In these breeding programs, first of all, resistant cultivars/genotypes should be determined. In one of the studies, some of the *Vitis caribaea* hybrids were resistant to root rot, while at the same time some undesirable characteristics such as overgrowth and absence of winter dormancy were detected. *Vitis palmata* and *Vitis shuttleworthii* species were also reported to have high resistance. But, the performance of the genotypes and their hybrids was very poor in dry soil conditions and further cross-breeding programs would be required to eliminate undesirable characteristics. Selected lines are evaluated for productivity and fruit quality in rootstock trials with different scion cultivars.

Resistance to phylloxera has been investigated for a long time at UC Davis, which has been working on grape rootstocks and breeding for many years. Recent studies here are investigating the evolution of possible phylloxera strains capable of aggressive nodosite feeding against some resistant rootstocks and foliar feeding strains once rare in the region. In these studies, the reproduction of phylloxera strains was investigated and molecular markers were developed for physical maps associated with resistance genes. As a result of the studies, rootstocks resistant to aggressive root knot nematodes have been developed [161].

Different studies are carried out on rootstock breeding, especially in the USA, Brazil, Europe, Australia, Iran, and China. In these studies, crosses are made in order to develop new rootstocks that are tolerant or resistant to different biotic and abiotic stress conditions, and then their compatibility with the varieties grafted on these rootstocks and their effects on fruit quality are examined. Since rootstock breeding

*New Perspectives in Grapevine (*Vitis *spp.) Breeding DOI: http://dx.doi.org/10.5772/intechopen.105194*

studies are much more laborious and time-consuming than other cultivar breeding programs, they are preferred by a limited number of researchers. However, as the mechanisms that cause stress factors become more understandable at the physiological and genetic level, much more successful breeding programs with promising results will become more preferable all over the world. In addition, with interspecies breeding, there is an increasing number of studies in the world that these new interspecies hybrid genotypes can be used directly in growing instead of using rootstock. Because it is reported that new interspecies hybrids will be much more tolerant in terms of different stress conditions and therefore the need for rootstock usage may decrease.

### **3. Conclusion**

Since grapes are among the most traded fruit types in the world, they have a significant impact on the agricultural economies of the countries. In particular, grapes are preferred by many people due to their different consumption patterns and important effects on human health. However, the demands of consumers can vary rapidly. In order to respond to these rapidly changing consumer demands, quality new grape cultivars should be developed through breeding programs. In these breeding programs, while mainly trying to develop new table and wine grape cultivars, rootstock breeding studies have started to increase in recent years. As a result of research studies carried out by many researchers on the grapevine genome, many characters related to gene regions have been determined and it has become possible to reach the targeted results in grapevine breeding studies in a much shorter time. In recent years, the number of new grape cultivars that are more resistant to biotic and abiotic stress conditions has been increasing rapidly in parallel with climate change and consumer preferences. It is predicted that in the coming years, hybrid cultivars between species will have a greater share in the market with their more resistance to different stress conditions and more friendly characteristics in terms of human and environmental health. As a result of the intensive studies carried out by many scientists with the grapevine genome, it is expected that transgenic grapevine plants, which are more accepted by many parts of the society, will take their place in the markets in a short time. With the integration of biotechnology into breeding programs in a way that will address the ethical concerns of consumers, breeding studies will gain momentum and it will be possible to feed the growing world population and make more sustainable viticulture.

### **Funding**

This research did not receive any external funding.

### **Conflicts of interest**

The author declares that there is no conflict of interest in this article.

### **Data availability statement**

Not applicable here.

*Case Studies of Breeding Strategies in Major Plant Species*
