Role of rootstocks to mitigate biotic and abiotic stresses in tropical and subtropical fruit crops: A review

Abstract

Fruit cultivation not only plays a crucial role in nutritional security but also offers employment opportunities, higher income and productivity to the farming community. Biotic and abiotic stresses are the most ominous factors in fruit production, which reduces the growth and productivity thereby resulting in an impact on global fruit production and availability. Biotic and abiotic stresses, including drought, extremes of temperature, various pest and diseases, salinity in soil and water are problems which are becoming acute. There is an urgent need to improve biotic and abiotic stress tolerance in fruit crops by using traditional breeding and biotechnology approaches like gene silencing and transgrafting. Nowadays, the virus resistance transgenic rootstocks are developed by using small interfering RNA s (silencing RNA) method. Rootstock breeding in fruit crops is a great challenge due to difficulty in identification of tolerant or resistance rootstock for various purposes. In this paper, we have discussed the various biotic and abiotic stresses, resistance mechanisms, and available resistant rootstocks so far as well as challenges in rootstock breeding which can be helpful to manage stress conditions in fruit cultivation. Further research is needed to develop the resistance rootstocks by using modern rootstock breeding methods with various biotechnological approaches. Introduction During recent decades, climate change, various biotic and abiotic stresses are the serious challenges being faced worldwide which influences the performance of fruit crops and showed a negative impact on global fruit production and availability. The reduction of yield due to poor utilization of land areas, poor adaptability under adverse biotic and abiotic stress condition, lack of awareness about the adoption of improved hi-tech horticultural practices, continuing reduction in the availability of cultivable area, low yielding varieties and inadequate technological up-gradation (Tsering dolkar et al., 2018) [97]. The stresses like biotic and abiotic play crucial roles in the growth, survival, adaptability, productivity and yield of fruit crops (Redondo-Gomez, 2013) [83]. Biotic and abiotic stresses, including drought, extremes of temperature, various pest and diseases, salinity in soil and water are problems which are becoming acute (Flowers, 2004) [37]. Due to the limited availability of cultivable area and even that is not suitable for cultivation, fruits are cultivated under unfavourable soil and stress condition to meet the huge market demand for fruits. The rootstocks play a major role in fruit cultivation by influencing canopy architecture, adaptability to adverse climatic condition, nutritional uptake, flowering, yield and fruit quality. Besides, rootstocks can also be used for high-density planting (HDP) and build up resistance to biotic and abiotic stresses such as pest and diseases incidence, drought, salinity, nematode infections, thermal stress and nutritional stress (Reddy et al., 2003) [82]. Among the abiotic stresses, salinity is one of the major ones that affect growth and yield of plants in arid and semi-arid areas throughout the world (Chelli i-Chaabouni et al., 2010) [22]. Most of the plants produce osmoprotectant metabolites such as proline, glycine-betaine and soluble sugars to protect the cells against the damaging effects from salt stress. Halophytes plants which can survive and reproduce even under high salt concentration with 200 mM NaCl, Galophytes plants are cannot survive in salinity condition and eventually die.