Introduction
Climate change is a major environmental problem, causing concern to various corners of our ecosystem. It is a result of global warming, environmental pollution and inefficient use of our natural resources. Climate change has affected almost all living organisms, including plants, animals, microorganisms and undoubtedly, man. It poses a serious threat to our ecosystem and is listed as a major concern in the Grand Challenges of the U.N. for Millennium Development and Millennium Ecosystem Assessment (Garrett 490). A wide variety of its implications, have made climate change, an important topic for researchers. There has been more awareness among researchers on climate change and its causative diseases, than ever before. Greenhouse gas emissions are one of the prime causes for climate change. Elevated CO2 levels increase risk of infections (Garrett 492). Elevated ozone structures, precipitation, acid rain, high humidity, and extreme temperatures, are all important contributing factors to climate change. Elevated temperatures due to global warming have had a direct bearing on the plant kingdom. Elevated temperatures also cause phenological shifts in plant development (Patel and Franklin 578). They alter plant architecture throughout the year and show different effects in different species of plants. Studies conducted by Staniak (1) have shown that drought stress and soil moisture deficiency significantly reduced yield and food value of forage grasses. Climate change affects agricultural lands in several ways. Elevated temperatures interfere with the ability of the plant to use moisture (Clive 24). They cause reduction in crop yield, with and without carbon fertilization. They also affect water availability for irrigated crops (IFPRI 24). Extreme temperatures can cause plants to increase in size with greater humid surface area, thus attracting more pathogens. Other adverse consequences are wilting, leaf burning and changes in physiological responses such as changes in RNA metabolism, plant growth, protein synthesis and an increased susceptibility to pathogens (Garrett 492). Rapid genetic changes have also been found in plants. These genetic changes have made an abundant species endangered or have increased new species of vectors. Plants also suffer nutrient loss due to extreme conditions like drought stress or winter stress. Research studies by Way et.al (144) have shown that both short-term and long-term stress have led to upregulation of genes which prevent damage to cell membranes due to dehydration. Changes in plants such as stomatal closure, inhibition of leaf growth and changes in leaf architecture have also been noted (Garrett 493). Studies by Chakraborty et al. have revealed that elevated CO2 levels have revealed increased disease severity in plants. These result in low yield of crop production, and the inability to meet increasing food demands with increasing world population.
Erratic weather, untimely rain and snowfall, floods, cyclones and extreme temperatures, all contribute to low yields of crop production. According to a UN report in October 2016, nearly 122 million people could live in extreme poverty by the year 2030 due to climate change consequences (United Nations 2016). The UN reports that around 80% of the world’s hungry live in disaster prone and environmentally degraded areas. Climate change is a major growing threat to food security throughout the world. Impact on agricultural sector is severe and will become ever so harsh in the coming years. The threat will surmount to low crop yields, nutrient loss of crops, increase in crop and pest diseases and outbreaks. Moreover, water intake of crops increase with increased transpiration, elevated temperatures and precipitation changes. Risk to world agriculture is one of the biggest threats of global warming. Developing countries are at a greater risk than developed countries due to difficulty in climatic adaptation. Costs involved in climatic adaptation are manifold, related to investments in child malnutrition, and in increasing productivity. Climate change has led to a lower calorie availability, which is predicted to decline even more by 2050. According to a food policy report by International Food Policy Research Institute (IFPRI) in 2009, there will be a 10% decline in calorie availability in 2050, than it was in 2000, throughout the world (IFPRI 10). The UN Intergovernmental Panel on Climate Change (IPCC) reviewed fossil-fuel emissions in 2001 to about 7 billion tons of carbon (Cline 24). The figures were expected to rise by 16 billion in 2050 and 29 billion in 2100. It was predicted that surface temperature would increase by 50C by the 2080s (Cline 24). Global warming would cause a 16% decline in agricultural productivity without carbon fertilization and a 3% decline if carbon fertilization would benefit. Equatorial countries and highly elevated places will receive the most damage. Extremely adverse outcomes will be seen in Africa, Latin America and South Asia. North America would show a 6% decline in agricultural productivity without carbon fertilization while Europe will have minimal losses. Large losses would be seen in Africa, with a decline of 6-19%. In Asia, the two greatly developing countries, India and China, will each show a marked difference in decline of agricultural productivity. India being closer to the equator would see losses of 30-40% while China’s decline would be a modest 7%. Such alarming rates of decline need to be dealt with efficiently in the future, especially in the developing countries where there is maximum decline of agricultural productivity.
Provision of food security in the world is a daunting task. Estimates by the Food Agricultural Organization in the years 1998-2000 show that there were 840 million undernourished people in the world, out of which 799 million live in developing countries. 6 million children die every year due to hunger and malnutrition (FAO 4). Though there has been a decrease of 2.5 million per year, the pace at which the program progresses is really slow and unacceptable. Several anti hunger programs have been started since then and are providing adequate diet for anyone. But the task is still far from being achieved. High food costs have made it unfeasible for poor people to buy food. Sustainable development of our resources is another way of providing more to each one of us. Concentration of sustainable agricultural development in developing countries where there are the majority of hungry people in the world, can lead to increased crop productivity, thus providing food and relief to the underprivileged (FAO 5). Use of chemical fertilizers to promote high crop productivity have led to an ecological imbalance due to toxic absorption by soil or inducing such chemicals into water bodies during disposal and contaminating water bodies. Fertilizers and pesticides, also have adverse effects on human health. They remain on crops while being consumed thus harming human health (Russo et al 57). Plants species cultivated by modern methods are also more prone to diseases. Considering the increased disadvantages of fertilizer usage, fungal endophytes are a big boon for the agricultural industry. Less availability of arable land, depleted water resources and an unfavorable climatic condition, all add to abiotic stress factors to which a plant is subjected. Abiotic stress in plants leads to physiological, morphological, biochemical and molecular changes which affect growth and productivity of plants. (Singh et al. 175). Corrective measures to such stress would involve techniques which are tolerant to such stress, thus promoting high crop yields. Fungal endophytes are the perfect answers to such problems. Fungal endophytes are types of fungal symbionts which live within the plant tissue of the host plant. Class I endophytes are transmitted through seeds whereas Class II endophytes are transmitted from plants to plants and are found in huge number in the ecosystem (Singh et al. 180). They help the host plant by conferring stress tolerance to high-stress environments such as one caused by climate change. They include drought tolerance, growth rate, and help in osmoregulation and stomatal regulation and in elongating roots to aid in nutrient absorption. They also offer resistance to salinity. Fungal endophytes act as stress tolerants in the following two ways: 1) activation of host stress response system when the host is exposed to stress, and 2) biosynthesis of anti-stress chemicals. Endophytes also protect the host plant from attack by pathogens. The tomato plant is a major crop in the world but its productions have reduced drastically due to abiotic stress. Studies undertaken by Cortina and Culianez-Macia (75) have shown the effects of endophytes on its growth promotion and resistance to abiotic stress. An endophytic bacterium like Agrobacterium tumefaciens was used to induce a yeast namely trehalose-6-phosphate synthase (TPSI) into the tomato genome. Results were compared to a wild-type tomato plant under different abiotic stress conditions. Both plants were subjected to a 15-day water stress. The wild-type tomato plant showed wilting and rolling of leaves due to water stress. It was interesting to note that the transgenic tomato plant remained unaffected and showed normal plant growth. Both plants were then tested for salt tolerance by treatment with lithium chloride (LiCl). The wild-type tomato plant showed lesions on leaf margins and toxic lithium was detected on the surface of leaves. But the transgenic sample seemed to be barely affected by the LiCl and there were no traces of toxic lithium on its leaf surface. When both plants were treated with H2O2, there was inhibited root growth in the wild-type where as the transgenic sample contained long, thick roots. Thus, it can be clearly seen that the TPSI gene has altered biological pathways of the tomato plant metabolism and endophytes promote plant growth, health and yield. These results can go a long way in the exploration of endophytes which combat abiotic stress of plants. Thus plants can be grown by altered biological pathways caused by endophytes. It is a vital way of combating climate change, and increasing crop production under abiotic stress. Owing to their popularity and wide usage in several forms, several tomato hybrids are available today. A research study undertaken by Abbamondi et.al showed that around 11 rhizopheric strains and 12 root endophytes were isolated from tomato roots from different tomato cultivars (1). Tomato samples were tested for various characteristics. A statistical analysis between inoculated and non-inoculated plants showed greater root length; inclusive in surface area root hair initiation and elongation were noted. Several such studies have been performed which highlight the significance of endophytic behavior. Replacements of chemical fertilizers by endophytes promote food safety and maintenance of environmental equilibrium.
Fungal endophytes function according to a special habitat. C. protuberate found in the yellow stone National Park, WY, is a type of fungal endophyte which survives only along with its host plant. When exposed to temperatures greater than 380C, both the host plant and the fungal endophyte cannot survive alone. Fusarium culmorum is another fungal endophyte functions specific to its habitat. It offers salt tolerance to its non-coastal host plant (Singh et al. 178). Fungal endophytes are beneficial to plants in several ways. They help in speeding up photosynthesis, helped in enhanced and efficient absorption of nutrients and water. They are tolerant to both biotic and abiotic stress, thus helping the host plant to adapt to its stressful environment. Several research studies have been performed, taking into consideration various biotic and abiotic stress factors on plant architecture. One such study was conducted by Murphy et.al (2) showed effects of several abiotic stresses such as heat, drought; pathogen and nutrient stress on wild barely species, Hordeum murinum which is an annual grass. Samples were subjected to multiple stresses and results were analyzed to show that all the plants which were inoculated with endophytes, survives, where as only 13% of control plants survived. Greater root and short weight and the mean plant were all found to be significantly great in endophyte-inoculated plants. The study highlighted the significance of endophytes in multiple stress conditions. This is a promising study as it opens new avenues for the planning of new agricultural techniques, promoting high yield outputs.
Crop engineering has reached a new high ever since technology has been at its best. High agricultural output, high nutrient food crops and food security have been a major concern to all food related industries. Not only were hybrid crops expensive ever so long, but the cost of agriculture has also been at an all-time high. . Endophytes are a boon for agriculturists and consumers alike. It aims to replace chemical fertilizers and other biological enhancing agents which have their own adverse effects on human health. The most advantageous characteristic feature of endophytes is their ability to tolerate biotic and abiotic stress. In addition to tolerance, they also impart this tolerance to the host plant. This era has noticed the most adverse climate changes throughout the world. Climate change has affected all countries, irrespective of their development and technology. Its adverse implications have been felt all around the world in the form of precipitation, acid rain, floods, untimely rain and snowfall etc. All these have affected plant architecture tremendously. The advent of endophytes into the plant world has been very promising. Its ability to handle elevated temperatures and nutrient loss has been tremendous. Research studies have shown their authenticity in positive outcomes. Their ability to overcome extreme temperatures, yet maintaining output and nutrition is very promising to the world. Its low cost and easy mode of application are other added advantages. The positive effects of endophytes can be applied to research more broadly in order to derive its full benefits. Its positive results can be applied to new food programs which aim, not only on increased yield output, but on nutritional value as well.
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