**4. Hybrid rice production under abiotic stress**

Adverse environmental conditions like abiotic factors, triggering abiotic stresses, run a key role in determining the productivity of rice yields. Biologically, abiotic stress is considered as a substantial deviation from the model environments in which plants are grown, inhibiting them from expressing their complete genetic potential regarding growth, development and reproduction [120]. Agriculture production in Bangladesh is dwindled mainly due to biotic and abiotic stresses. Abiotic stress ubiquitously affects the crop growth and development process worldwide. Hence, these are one of major areas of concern to fulfill the required food demand [121, 122]. The major abiotic stresses, drought, flooding, salinity are making the risks to food and nutritional security from tropics to temperate regions worldwide. Drought affects plants in numerous ways like it affects plant growth, yield, membrane integrity, pigment content, osmotic adjustments, water relations and photosynthetic activity [123]. Over the last three decades, the temperature of the country has increased significantly. It is estimated that by 2030, 2050 and 2100, the temperature may increase around 1, 1.4 and 2.4°C, respectively [124]. This is significant as an increased temperature reduces the yield of rice. Therefore, the country is in a risky situation in meeting future challenges concerning food security.

Bangladesh is facing salinity intrusion into the arable agricultural lands. The decline in rice yield under judiciously salt-affected soils is anticipated to be 68 percent [126]. Due to global warming, the rise in sea levels, surplus irrigation without appropriate drainage in the inland area under salt stress is growing. Flash flood and cold injury also cause rice production loss almost every year in Bangladesh. Rainfed conditions in Bangladesh are quite complex, where multiple stresses frequently prevail and even follow in quick succession within a single cropping season. Two or more abiotic stresses often coexist in many rainfed lowland and saline areas of Bangladesh. Most of the rainfed areas in Bangladesh are often occurred by multiple abiotic stresses such as flooding, drought and salinity even within the same cropping season near the coastal areas. Therefore, we need to breed new hybrid rice varieties that could tolerate more than one abiotic stress and yield high under normal favorable rainfed conditions as well.

Northern districts of Bangladesh are cold prone areas of the country. Usually, Boro (winter) rice is seriously affected by cold during the seedling and flowering stage. Seedling mortality sometimes goes up to 90%, especially in the northern part of the country. In recent years, more than 2.0 million hectares of rice crops in the cold prune area of Bangladesh have been seriously affected by extreme cold stress,


**149**

*Nitrogen Use Efficiency in Rice under Abiotic Stress: Plant Breeding Approach*

increase the production capacity of rice under saline conditions.

rice is the demand of the time to sustain food security.

**5. Future outlook and conclusions**

Climate change has affected Bangladeshi agriculture a lot. The most pronounced

Among the essential nutrient elements, nitrogen has a paramount importance for rice growth and development in natural ecosystems. To promote optimum N nutrition for the higher rice yield, it is important to explore the possible variability in NUE in rice genotypes. Understanding the molecular mechanisms of variable NUE in rice genotypes would help to develop NUE in the elite rice variety under abiotic stressful conditions using traditional and molecular plant breeding methods, including genome editing. Global climate change plunges world rice production toward various abiotic stress. Flooding, drought and salinity are correlated to cause problems in rice production. If rice seedlings experience flooding during the vegetative stage, they may suffer from terminal drought during the reproductive stage, depending on the ecosystems. Likewise, periodic drought conditions may upregulate

effects of climate change are the heat stress, periodic drought conditions, and salinity intrusion in coastal belts due to sudden flood and flash flood in major ricegrowing areas of Bangladesh. In the last couple of decades, the salinity affected area increased drastically in Bangladesh (**Table 3**). Due to periodic drought and saline water intrusion in the coastal belt, the already existing problem of high amounts of salts in the upper surface soil has intensified. In the future, efforts should be directed to develop climate-smart hybrid rice, which can perform stably under diverse environmental conditions. Nonetheless, China is now feeding 20 percent of the world's population from only 10 percent of the world's arable land where hybrid rice covers around 57 percent of the total cultivated rice area [125]. They have achieved this success by adopting research on region-based and stress-tolerant hybrid rice development. Their way of success was not so smooth, but eventually, they overcome all the obstacles. On the other hand, rice is called "the life of the people of Bangladesh." No obvious alternative crop can replace rice presently. Initially, after the introduction of hybrid rice in Bangladesh in 1998, the area under hybrid rice cultivation significantly increased, but not up to the mark. Currently, only 7.48 percent of the total rice area is under hybrid rice cultivation in Bangladesh [126]. We have released hybrid rice for a favorable environment. It is now worldwide accepted that hybrid rice can give 15-20% more yield compared to inbred high yielding rice cultivars. Therefore, the development of abiotic stress tolerant hybrid

causing partial to total yield loss, especially in the northern part of the country. In the haor areas of Bangladesh, early planted Boro rice has to face cold stress at the reproductive stages (Panicle initiation to flowering). If the mean temperature goes down below 20°C for more than 5-6 days during the reproductive stage of the hybrid rice plant associated with spikelet sterility, cause serious yield damage. In particular, abiotic stresses significantly constrain rice production in Bangladesh and the frequency of these stresses is, unfortunately, likely to increase with climate change. Hybrid rice breeding programs around the world have preemptively responded by breeding stress-tolerant rice varieties. By manipulating the heritable variation present in the germplasm, we can develop abiotic stress-tolerant cultivars through breeding techniques, but it is a cumbersome and time-consuming process. The slow progress is due to the complexity of the problem involving environmental conditions and the genetic system. The development of stress-tolerant hybrid rice varieties has gained momentum among the breeders in the recent past. The development of hybrid rice with inbuilt stress tolerance is most desirable to

*DOI: http://dx.doi.org/10.5772/intechopen.94038*

#### **Table 3.**

*Extent of soil salinity during the last four decades (1973–2009) in coastal areas of Bangladesh.*

#### *Nitrogen Use Efficiency in Rice under Abiotic Stress: Plant Breeding Approach DOI: http://dx.doi.org/10.5772/intechopen.94038*

*Recent Advances in Rice Research*

**4. Hybrid rice production under abiotic stress**

QTLs/genes needed for multiple abiotic stress tolerance, NUE and associated novel traits in rice could be discovered through a holistic breeding approach (**Figure 2**).

Adverse environmental conditions like abiotic factors, triggering abiotic stresses, run a key role in determining the productivity of rice yields. Biologically, abiotic stress is considered as a substantial deviation from the model environments in which plants are grown, inhibiting them from expressing their complete genetic potential regarding growth, development and reproduction [120]. Agriculture production in Bangladesh is dwindled mainly due to biotic and abiotic stresses. Abiotic stress ubiquitously affects the crop growth and development process worldwide. Hence, these are one of major areas of concern to fulfill the required food demand [121, 122]. The major abiotic stresses, drought, flooding, salinity are making the risks to food and nutritional security from tropics to temperate regions worldwide. Drought affects plants in numerous ways like it affects plant growth, yield, membrane integrity, pigment content, osmotic adjustments, water relations and photosynthetic activity [123]. Over the last three decades, the temperature of the country has increased significantly. It is estimated that by 2030, 2050 and 2100, the temperature may increase around 1, 1.4 and 2.4°C, respectively [124]. This is significant as an increased temperature reduces the yield of rice. Therefore, the country is in a

risky situation in meeting future challenges concerning food security.

and yield high under normal favorable rainfed conditions as well.

**S2 (4.1.0–8.0 dS/m)**

*Extent of soil salinity during the last four decades (1973–2009) in coastal areas of Bangladesh.*

**dS/m)**

*Source: Soil Resources Development Institute (2010).*

Bangladesh is facing salinity intrusion into the arable agricultural lands. The decline in rice yield under judiciously salt-affected soils is anticipated to be 68 percent [126]. Due to global warming, the rise in sea levels, surplus irrigation without appropriate drainage in the inland area under salt stress is growing. Flash flood and cold injury also cause rice production loss almost every year in Bangladesh. Rainfed conditions in Bangladesh are quite complex, where multiple stresses frequently prevail and even follow in quick succession within a single cropping season. Two or more abiotic stresses often coexist in many rainfed lowland and saline areas of Bangladesh. Most of the rainfed areas in Bangladesh are often occurred by multiple abiotic stresses such as flooding, drought and salinity even within the same cropping season near the coastal areas. Therefore, we need to breed new hybrid rice varieties that could tolerate more than one abiotic stress

Northern districts of Bangladesh are cold prone areas of the country. Usually, Boro (winter) rice is seriously affected by cold during the seedling and flowering stage. Seedling mortality sometimes goes up to 90%, especially in the northern part of the country. In recent years, more than 2.0 million hectares of rice crops in the cold prune area of Bangladesh have been seriously affected by extreme cold stress,

**Years Salinity class and salt affected area (000'ha) Total** 

1973 287.37 426.43 79.75 39.9 833.45 2000 289.76 307.20 336.58 87.14 1020.75 2009 328.43 274.22 351.69 101.92 1056.26

**(000'ha) S1 (2.0–4.0** 

**S3 + S4 (8.1–16.0 dS/m)**

**S5 (>16.0 dS/m)**

**148**

**Table 3.**

causing partial to total yield loss, especially in the northern part of the country. In the haor areas of Bangladesh, early planted Boro rice has to face cold stress at the reproductive stages (Panicle initiation to flowering). If the mean temperature goes down below 20°C for more than 5-6 days during the reproductive stage of the hybrid rice plant associated with spikelet sterility, cause serious yield damage.

In particular, abiotic stresses significantly constrain rice production in Bangladesh and the frequency of these stresses is, unfortunately, likely to increase with climate change. Hybrid rice breeding programs around the world have preemptively responded by breeding stress-tolerant rice varieties. By manipulating the heritable variation present in the germplasm, we can develop abiotic stress-tolerant cultivars through breeding techniques, but it is a cumbersome and time-consuming process. The slow progress is due to the complexity of the problem involving environmental conditions and the genetic system. The development of stress-tolerant hybrid rice varieties has gained momentum among the breeders in the recent past. The development of hybrid rice with inbuilt stress tolerance is most desirable to increase the production capacity of rice under saline conditions.

Climate change has affected Bangladeshi agriculture a lot. The most pronounced effects of climate change are the heat stress, periodic drought conditions, and salinity intrusion in coastal belts due to sudden flood and flash flood in major ricegrowing areas of Bangladesh. In the last couple of decades, the salinity affected area increased drastically in Bangladesh (**Table 3**). Due to periodic drought and saline water intrusion in the coastal belt, the already existing problem of high amounts of salts in the upper surface soil has intensified. In the future, efforts should be directed to develop climate-smart hybrid rice, which can perform stably under diverse environmental conditions. Nonetheless, China is now feeding 20 percent of the world's population from only 10 percent of the world's arable land where hybrid rice covers around 57 percent of the total cultivated rice area [125]. They have achieved this success by adopting research on region-based and stress-tolerant hybrid rice development. Their way of success was not so smooth, but eventually, they overcome all the obstacles. On the other hand, rice is called "the life of the people of Bangladesh." No obvious alternative crop can replace rice presently. Initially, after the introduction of hybrid rice in Bangladesh in 1998, the area under hybrid rice cultivation significantly increased, but not up to the mark. Currently, only 7.48 percent of the total rice area is under hybrid rice cultivation in Bangladesh [126]. We have released hybrid rice for a favorable environment. It is now worldwide accepted that hybrid rice can give 15-20% more yield compared to inbred high yielding rice cultivars. Therefore, the development of abiotic stress tolerant hybrid rice is the demand of the time to sustain food security.
