**5. Biotechnological challenges to improving tropical plants**

The flora of tropical areas suffers from biotic and abiotic stresses. In the past few years, the effects of climatic changes are significant on tropical plants. It has been reported by the Intergovernmental Panel on Climate Change (IPCC) that the climatic conditions are a precursor to various stresses on plants and are considered the most important influencing factor in the decline of agricultural production in developing countries. Global warming negatively influences tropical and sub-tropical plants due

to rapid alterations in the ecosystem, drought, rainfall patterns, floods, and biological outbreaks [58]. The balanced environment and lack of nutrients are the major constraints that enhance the losses of biological stresses. The losses due to abiotic stresses could be around 50 percent in tropical areas possibly due to a decline in plant metabolism [59].

The tropical plants of agricultural importance are suffering from viruses, bacteria, and insect attacks. Although there has been a substantial increase in food production in developing countries due to advances in breeding practices, the challenges of food security have never been met. The use of biotechnological approaches enables the genome alterations in plants to withstand abiotic and biotic stresses (**Figure 2**), which are usually difficult to achieve by conventional approaches. Advanced genome editing tools such as RNA-induced gene silencing, CRISPR-Cas, genome mapping, and next-generation sequencing have paved the way toward desirable genetic alterations in plants. However, the available biotechnological applications to agriculture in conventional crop species are the use of selective breeding approaches to bring improvement in genetic materials [66]. Some of the conventional crops of the tropical areas include maize, tomato, sweet potato, beans, pulses, nuts, cassava, sorghum, etc. These crops are present in the wet climate in tropical areas. On the other hand, the important crops of dry tropical climates are coffee, rubber, cotton, tobacco, tea, and sugarcane. The ornamental plants have their range such as hibiscus, plumeria, palms, ebony, teak, gardenia, fire brush.

Biotechnology has contributed to the solution of food security challenges by making robust genetic mutations. According to ISAAA infographics, more than 17 million farmers are benefiting from the cultivation of biotechnology crops. More

#### **Figure 2.**

*(A) Coffee berry borer (modified from Benavides et al. [60]), (B & E) Coccinia grandis (modified from; Goebel et al. [61]), (C) coffee leaf rust (modified from Nelson, [62]; Gichuru et al. [63]), (D) stem borer larval caterpillar on sugarcane stalk (modified from Cilas et al. [64]), and (F) cacao swollen shoot virus (modified from; Kouakou et al. [65]).*

#### *Emerging Trends to Improve Tropical Plants: Biotechnological Interventions DOI: http://dx.doi.org/10.5772/intechopen.108532*

than 28 countries are growing 14 biotechnology crops precisely, and major contributors are tropical countries such as Brazil, India, Argentina, China, Indonesia, and Paraguay. The area under biotech crops is 2.7 billion hectares, and 17 million farmers' earnings are associated with it [67]. The genetic alteration strategies are designed to increase crop production, improve quality, and develop resistance against biological agents such as pests, herbs, and bacterial and viral diseases. With the advancement of technology, biotechnological approaches have become robust, accurate, and more reliable, but there are some ethical and environmental concerns about their agricultural applications.

The first contribution of biotechnology to crop improvement came with the development of crops resistance to a broad range of selective herbicides. The biotechnological techniques proved valuable on a socioeconomic as well as on an ecological scale because they reduced the consumption of questionable herbicides. However, due to unorganized applications of herbicides over growing seasons, the resistance to herbicides is emerging that could overcome the advantage of selective tolerance. The scientific challenge to address this issue is diversification of herbicide consumption along with crop rotation. There is the need to make continuous improvements in resistance technologies and the identification of new biochemical pathways in plants to find new targets. A similar challenge resides in another trait of resistance to insect pests, which is also commercially exploited. Many commercially important crops in tropical climate regions are threatened by different insect pests such as coffee rust, Lepidopteran stem borers, Helicoverpa, coffee berry borers [64].

The most important biological challenges are plant viruses because of their complexity in their life cycle, replication, movement, diversity, and unique capability of developing mutations against resistance. Identification of a causative virus and its pathogen vector is crucial for estimating the epidemiology and economic losses that are essential for the development of management strategy. Viruses can only be detected by using molecular diagnostic techniques. Some potential virus threats of tropical crops are cacao swollen shoot virus, banana bunchy top virus, cassava mosaic virus, plum pox virus, potato virus X, cucumber mosaic virus, African oil palm ring spot virus, rice yellow stunt virus, etc. [68].

Since after their inception, biotechnological approaches have established a reputation as a potential way to overcome food shortages. The choice of biotechnological approaches depends on the targeted pathogen or abiotic stress [69]. For example, the short RNA-based RNAi approaches are efficient against RNA viruses because the viral genome can be targeted before replication and formation of proteins, but to target the DNA genome, CRISPR-Cas is a superior technology. Violation of biosafety measures could cause unwanted gene flow to the other plant or pathogen species.

Although biotech crops are becoming an important hope in the tropical region, some challenges also emerged with the increase in production of biotech crops. For example, with the continuous application of broad-spectrum herbicide on the GM crop plants, resistance also emerges in the weeds, which lose the selective advantage in genetically modified plants. Another area that has been addressed more by biotechnological approaches is the use of bacterial toxins to develop transgenic plants for durable resistance to insect pests. So far, the toxins from *Bacillus thuringiensis* are mostly applied for pest tolerance.

Plant biology is facing an additional level of complexity as compared to mammals because plants are sessile and grow in varied environmental conditions that are far from optimal climate conditions. There is evidence that changes in the ecosystem alter the pathogenicity of viruses and plant pests. In the past few years, various

unpredictable changes have been reported in the tropical ecosystem, which need continuous investigation of the genome characterization of viruses, pests, and the response of host plants. Changes in humidity, temperature, and atmospheric pressure affect the growth of insect pathogens. The development of the post-transcriptional gene silencing strategy needs a very comprehensive study of the host, environment, and pathogen; otherwise, there are chances of horizontal gene transfer to other species [70]. Climate changes lead to ecosystem disturbances at different levels, which affect the efficiency of biotechnology techniques. The climatic changes affect the interaction of the ecological and biological communities including soil, natural habitats, plants, and biodiversity. For example, the plant susceptibility to disease increases due to high temperature and humidity [71]. However, these challenges can be overcome by combining conventional and biotechnological approaches to address biotic and abiotic stresses.

#### **6. Future prospects**

Tropical plants comprise two-thirds of the terrestrial plant species and have great importance in plant biodiversity. Due to increasing population, there is an urgency to double the food production globally. Thus, a series of biotechnological interventions can be made to conserve plant biodiversity (Van Montagu, 2020) and improve crop plants in tropical areas. Medicinal and fruit plants also need attention with regard to biotechnology-assisted breeding to combat biotic and abiotic stresses. Tropical forests can make an important contribution to the global demand for fruits, timber, and biomass. Biotechnological tools should be used to identify the potential of plants as new crops to mitigate malnutrition in tropical regions. Some important crops in tropical regions such as cassava, cowpea, sweet potatoes can be improved as cash crops by biotechnological efforts. Moreover, the nutritional contents of plants can be improved. For example, lathyrus is a leguminous protein-rich crop that is used after overnight soaking to remove the toxins on its split seeds. Engineering lathyrus genome could help in this regard. There are also gaps in the study of marker-assisted breeding on tropical plants, which can become an important tool in crop improvement. The tropical region has a range of medically important plants, and their properties can be broadened to increase diversity. Latest molecular biotechnology tools such as CRISP/ Cas 9 have promising applications in gene activation, repression, gene mutation, and epigenetics. It has been effectively applied to citrus, apple, petunia, and various other plants. Similar research models can be applied to economically important tropical plants.

#### **7. Conclusion**

The sustainability of the food supply chain depends on tropical plants, which are also vital sources of medicine, fiber, wood, and energy. Tropical plants are present in more than 60% of all terrestrial plant species worldwide. In addition to domestication, attempts have been made to enhance these plants using both conventional and cutting-edge scientific interventions. Parthenocarpy, polyembryony, polyploidy, protracted juvenile phase, heterozygosity, and generation cycle problems have been helped by genomic techniques. Innovations in cell and tissue culture have enabled micro-propagation and the commercial plantation of various plants, in addition to
