Rice is the world’s major staple cereal crop and feeds over half of the world’s population. It is also an essential security food crop, covering 60% of World food consumption. Climate change affects crop production through exposure to different biotic and abiotic stresses. Approximately 70% of crop yield is lost due to these stresses
(Sahoo et al., 2014). Farmers of India produce an average of 5 tonnes/ha of rice, whereas the normal yield potential is 10 tonnes/ha. This difference in yield is due to different stresses. Many countries have developed and adopted stress-tolerant rice varieties to reduce production losses
(Bairagi et al., 2021). The production rate of rice, a major food for millions of people worldwide, is hindered by environmental stresses, resulting in a potential yield reduction of 10-15%. The abiotic stresses that affect rice crops include a range of factors such as salinity, drought, Flooding, harmful radiation, heavy metals and high temperatures. These factors lead to physiological, biochemical and morphological changes in the rice crops, ultimately reducing rice productivity worldwide (Table 1). In addition, biotic stresses like (GM) gall midge, (BPH) blast, brown plant hopper and (BLB) bacterial blight also play an important role in decreasing the quality and productivity of rice grains (Table 2). Addressing these stress factors is critical to ensure sustainable rice production and meet global food demands (Fig 1). The frequencies of both droughts and floods are likely to increase due to increased irregular rainfall patterns and harsh weather occurrences. Additionally, high temperatures can damage rice production by affecting growth and development, particularly during pollination. High temperatures can impact rice growth and development at any stage, especially during pollination. These harmful consequences can be efficiently addressed by plant breeding. Over the past few decades; rice breeding has achieved remarkable success, especially in regions conducive to crop growth. In 1970, modern high-yielding (HYVs) varieties gained rapid acceptance in irrigated and lowland areas with suitable rainfall. These kinds were less effective in regions with inadequate water management and adverse soil conditions, leading to low production and forcing farmers to continue farming low-yielding crops. During this time, breeding for abiotic stress resistance proliferated. Despite the wide adoption of HYVs (high-yielding varieties) in irrigated and rainfed areas and their widespread coverage in most tropical Asian production areas, the existing rice varieties remain insensitive to substantial abiotic stressors, further intensified by climate change. Among these challenges include salinity, submergence and drought, which are the most prevalent, reducing yields across millions of hectares in rice production areas. The limited impact of modern high-yielding rice varieties in unfavourable rainfed environments has led to the development of rice types that resist abiotic stressors like high temperature, salinity, drought and flood. These varieties will defend against the negative of climate change. The article emphasizes advancements in rice genetics and breeding for stress tolerance, focusing on varieties appropriate for coastal locations where floods and salt are issues and where rising sea levels will limit future rice production.
Abiotic stresses and their action
Drought
Drought is a significant disruptive and hazardous abiotic stress in the current climate change scenario, impacting millions worldwide annually. Drought is determined by rainfall intensity and pattern, lasting from a few days to months or even years. Plants are generally affected by three common drought types: (f) early-season drought, which is responsible for late transplanting and mild intermittent stress. This condition affects the plant’s health and is responsible for late-maturing genotypes. Developing drought-resistant rice cultivars is difficult because of the complicated quantitative nature of the variables involved
(Ndikuryayo et al., 2023). Healthy plant growth and yielding low water affected the deep root system, with high root length density at depth can help water extraction in highland conditions
(Zia et al., 2021). Water deficit in drought also inhibits cell expansion, early vegetative stage, internode elongation and decreased plant height, causing a reduction in leaf area. Drought reduces the photosynthetic activity and growth of plants in developmental stages. Severe dryness denatures the photosynthetic proteins
(Yang et al., 2022). Eastern India developed drought-tolerance rice varieties such as CR dhan, Anjali, Vandana, Indira Barani dhan, Sahbhagi Dhan, Abhishek, Shushk Sanrat, NDR 97 and Susk Samrat
(Arora et al., 2018). The (IRRI)International Rice Research Institute released and developed several drought-tolerant rice varieties like DRR and Sahbhagi dhan, which are 44, 43 and 42 in India under drought conditions
(Kumar et al., 2021).
Salinity
Soil salinization is another critical issue that the globe is now confronting. Sodium-induced soil salinity, widely distributed globally, is a leading cause of reduced the production of rice. Salt-affected land area in India amounts for 6.73 million hectares (mha), which is expected to expand to 16.2 million hectares by 2050
(Kundu et al., 2022). Among various approaches, marker-assisted breeding has successfully created new, improved and high-yielding rice varieties with enhanced salt tolerance
(Rasheed et al., 2022). Salt tolerance is a complicated phenomenon that necessitates various independent and interconnected systems. In recent years, developed six salt-tolerance rice lines: CSR56, CSR52, CSR49, CSR76 and CSR60.CSR56, CSR46, CSR76 and CSR60 are long, slender grains tolerant of salinity of EC ~ 8.00 dS/m and sodicity pH of 9.9
(Krishnamurthy et al., 2022). Previously, in India, various research was done to get the salt tolerance rice and develop high-yielding indica rice, including IR64, BR11 and BRRI Dhan 28 at the seedling stage
(Mare et al., 2023). Recent crop research has successfully progressed to using molecular genomics to discover and clone salt-tolerance genes in plant responses to salinity stress
(Das et al., 2023).
High and low temperature
The earth’s surface temperature has increased significantly in recent decades due to global climate changes and rising greenhouse gas emissions. Temperatures are anticipated to climb from 2 to 4 degrees Celsius by 2050
(Xu et al., 2021). High-temperature periods last for exceeding eight days, 5-7 days and 3-5 days. They are generally classified as heat injury, moderate and mild. The low temperatures ranging from <0°C and 0 to 15°C are accordingly classed as cold or freezing stress
(Yamamoto et al., 2012). In the last ten years, Extensive attempts have been undertaken. To identify genes/QTLs that improve cold tolerance in rice and heat are complex traits
(Pan et al., 2023).
Submergence
One of the most significant obstacles to successful rice production is submergence, which limits the crop’s growth and productivity. Notably, over 16% of the global rice-growing regions are susceptible to Flooding. A previous report revealed that Africa and Asia are the most affected continents by flood, which threatens rice cultivation and yield
(Koppa et al., 2021). Flash floods are a recurrent challenge to rice farming in Southeast Asia’s and the South’s rainfed lowlands. These floods can result in plants remaining wholly submerged in water for approximately two weeks, negatively impacting rice crop adaptability. However, rice plants can develop anatomic and metabolic traits that enable them to cope with submergence or waterlogging. Aerobic crops cannot withstand waterlogging, whereas paddy may thrive in shallow standing water. The complete submergence of plants caused by impeding growth processes and flash flooding hinders gaseous exchange. This ultimately results in plant mortality and decay
(Dar et al., 2021). The extent of damage caused by submergence is contingent upon the depth and duration of flood, the topography of the land and floodwater conditions. In 1970, the International Rice Research Institute (IRRI) pioneered identifying submergence- tolerant rice varieties, collecting over 100,000 rice germplasms, including 1,000 submergence-resistant varieties from flood areas.
Heat
Heat stress is a significant abiotic limitation for rice cultivation, following only drought and salinity. High temperatures are prevalent and pose a challenge to rice production. The rise in greenhouse gasses in the atmosphere, resulting in global warming, significantly contributes to the increase in atmospheric temperature. This phenomenon is a significant source of heat stress and negatively impacts rice production
(Yang et al., 2021). Therefore, identifying heat-tolerant varieties is of utmost importance to ensure stable yields. In this regard, previous research has identified several rice cultivars that exhibit high heat tolerance, including Indica rice varieties IR36 and IR24, Japonica cultivars such as Koshihikari and Akita Komachi and an aus landrace known as (N22) Nagina 22. Of these, N22 has been found as the highest heat-stress resistant type. Its ability to identify specific chromosomal segments during the reproductive.
Cold
Rice is a cold-sensitive crop subject to abiotic stressors, with low temperatures being the critical limiting factor in its production in temperate and high-elevation regions. The increasing frequency of extreme low-temperature events in recent decades, a consequence of ongoing climate change, has further exacerbated this challenge. As a result, there is a pressing need to develop effective measures to protect rice crops from the harmful effects of these environmental stressors. Such measures could enhance rice production’s resilience in the face of climate change, contributing to food security and sustainable development (
Yaduvanshi et al., 2021). Cold stress is a significant problem that adversely impact on the development and growth of different stages of rice plants including vegetative, reproductive and germination stages, resulting in a considerable decline in yield. At the cold stress, the germination stage negatively impacts the germination speed and the percentage. Various populations have seen numerous quantitative trait loci (QTLs) associated with germinability with low temperatures. reported identifying 11 putative QTLs spread across chromosomes 3, 4, 5, 7, 9, 10 and 11 that regulate low-temperature germinability. However, it is noteworthy that few QTLs were discovered cold tolerance during the bud stages of plant compared to the germination stage of rice
(Xu et al., 2020).
Types and mechanisms of biotic stresses
Bacterial blight
Bacterial blight (BLB) caused by
Oryzae (Xoo)
Xanthomonas oryzae pv. Significantly threatens rice crops. Production losses up to 80-100% in high infection stages have been reported, with moderate infections leading to a loss of 20-30%
(Yang et al., 2022). These losses are attributed to some part of seed grain filling those results from very low photosynthetic action. Only 11 of the 45 resistant (R) genes found by BLB were fine-mapped and cloned for use in contemporary biotechnology. A marker-assisted pyramiding strategy combined four BLB-resistant genes (Xa5, Xa21, xa4 and xa13) of high-yielding rice varieties, resulting in broader and more permanent resistance. This approach has resulted in the most stable combination of BB genes, displaying resistance to most pathogen isolates
(Kumar et al., 2023). BB R genes identified as wild, domesticated species landraces and mutants that are resistant against different Xoo strains.
Blast
The fungus
Pyricularia oryzae is a potent threat to rice production, a staple crop that sustains millions worldwide. Rice blast, caused by this fungus, presents significant challenges to rice cultivation. This disease poses a substantial risk to global food security and has the potential to cause significant economic damage
(Devanna et al., 2022). As such, it is critical to develop strategies to mitigate the impact of
Pyricularia oryzae and prevent its spread over a hundred blast-resistant genes have been discovered, with barely thirty cloned and functionally described.
Brown plant hopper
The brown plant hopper (BPH), scientifically known as
Nilaparvata lugens, is a well-known and highly destructive insect pest that inflicts significant damage on rice crops across Asia. The impact of BPH infestations on rice crops is profound, causing losses of up to 60% of the total yield. This insect pest has become a significant concern for farmers and agricultural researchers, continuously seeking effective strategies to mitigate its impact on rice production. Identifying and functionalizing genes that confer resistance to brown planthoppers (BPH) provides a unique chance to use genes in marker-assisted gene introgression programs efficiently.
Around 40 BPH resistance genes have been found, of which 17 have been extracted and cloned using a map-based method. Recently, genes known to confer 70 BPH resistance identified. Of the 50 genes and 20 QTLs, identified genes and quantitative trait loci (QTLs) were found to be equally derived from wild rice, while only 35 resistance genes/QTLs were sourced from
Oryza sativa. This knowledge is crucial for comprehending their evolution and, ultimately, for developing efficacious strategies for their management and control
(Ishwarya et al., 2022).
Gall midge
The Asian rice (
Orseolia oryzae) gall midge is an insect pest rice that is commonly found in Southeast Asia, China and India during the wet season. The goal was to improve the resistance of these cultivars to the gall midge bug, a significant pest in rice production. This was achieved through the use of marker-assisted introgression/pyramiding techniques. The study results indicate that incorporating these genes significantly improved the resistance of the cultivars to the gall midge insect. This approach presents a viable and promising strategy for developing rice cultivars with improved pest resistance, which is critical for ensuring the sustainability of rice production. Through this approach, advancements in rice breeding can be made towards creating cultivars with improved resistance to pests, thereby reducing the need for chemical pesticides and ultimately leading to healthier and more sustainable rice crops. The successful integration of these genes will contribute towards developing disease-resistant rice cultivars and provide a sustainable solution to the problem of gall midge infestation in rice production.
