Tolerant Rice Varieties Research Articles

Interéaction of submergence tolerance and drought yield QTLs (Sub1 and qDTYs) enhances morpho‐physiological traits and survival of rice (Oryza sativa L.) under submergence

AbstractClimate change has caused increasing incidences of the extreme flooding around the world, which has impacted rice production, especially in rainfed ecosystems. Breeding for submergence tolerant rice varieties has been conducted to mitigate the adverse effects and help farmers to reduce yield loss. The present study was carried out to introgress the submergence tolerance QTL (Sub1) from IR64‐Sub1 into drought‐tolerant lines; UKM5 and UKM91 possessing the drought yield quantitative trait loci (qDTYs), viz. qDTY12.1 and qDTY3.1, and to evaluate the effects of the combination of these QTLs in improving the morpho‐physiological traits and survival under submergence. UKM5 and UKM91 were selected as the recipient of the Sub1 locus because of the intermediate submergence tolerance they possessed even though they only have qDTY/s. Therefore, the introgression of Sub1 into these lines was hypothesised to enhance survival. Submergence stress was given for 14 days to BC1F4 lines from the two breeding populations. Lines with better survival than the tolerant check, IR64‐Sub1 were selected and evaluated under 18 days of submergence stress. Generally, lines with Sub1 and qDTYs from UKM5*/IR64‐Sub1 and UKM91*/IR64‐Sub1 populations had higher survival rate (SR) of 90–100%, lower shoot elongation percentage (EP) and a smaller percentage of chlorophyll content change (CCC) than IR64‐Sub1. The selected lines also showed a low percentage of non‐structural carbohydrate change (NSCC) which related to the ability to recover after submergence. In both populations, the interaction of qDTY3.1 with Sub1 proved to give the best improvement on EP and CCC. This experiment provides novel findings; that is, the combinations of Sub1 + qDTY12.1 + qDTY3.1 showed high survival rate in the population of UKM5*/IR64‐Sub1, while qDTY3.1 improved SR of the lines from UKM91*/IR64‐Sub1 population to 100%. These results proved that the action of Sub1, qDTY/s and their interaction differ in contrasting population or background. The QTL combinations showed a consistent effect in both submergence experiments and proved the effectiveness of Sub1 and qDTYs combinations in enhancing the morpho‐physiological traits and survival.

Epigenetic Control of Plant Response to Heavy Metal Stress: A New View on Aluminum Tolerance.

High concentrations of heavy metal (HM) ions impact agronomic staple crop production in acid soils (pH ≤ 5) due to their cytotoxic, genotoxic, and mutagenic effects. Among cytotoxic ions, the trivalent aluminum cation (Al3+) formed by solubilization of aluminum (Al) into acid soils, is one of the most abundant and toxic elements under acidic conditions. In recent years, several studies have elucidated the different signal transduction pathways involved in HM responses, identifying complementary genetic mechanisms conferring tolerance to plants. Although epigenetics has become more relevant in abiotic stress studies, epigenetic mechanisms underlying plant responses to HM stress remain poorly understood. This review describes the main epigenetic mechanisms related to crop responses during stress conditions, specifically, the molecular evidence showing how epigenetics is at the core of plant adaptation responses to HM ions. We highlight the epigenetic mechanisms that induce Al tolerance. Likewise, we analyze the pivotal relationship between epigenetic and genetic factors associated with HM tolerance. Finally, using rice as a study case, we performed a general analysis over previously whole-genome bisulfite-seq published data. Specific genes related to Al tolerance, measured in contrasting tolerant and susceptible rice varieties, exhibited differences in DNA methylation frequency. The differential methylation patterns could be associated with epigenetic regulation of rice responses to Al stress, highlighting the major role of epigenetics over specific abiotic stress responses.

Impact of Climate Change on Paddy Production: Evidence from Nepal

This study assesses the long-run relationship and short-run dynamics between paddy yields and climate variables, particularly maximum and minimum temperature and rainfall, using time-series data from 1971 to 2014 in Nepal. Applying Autoregressive-Distributed Lag Regression or ARDL bounds testing approach for analysis of co-integration between the variables, we confirm that there is a long-run relationship among the variables. Furthermore, we employ Granger non-causality tests for robustness. The findings reveal that rainfall has substantial effects on the rice yield. Specifically, a positive and significant relationship exists between rice yields and rainfall and that this relationship is unidirectional. Rainfall impacts on rice yield and holding all things constant, a 1 mm increase in rainfall increases rice yields by 0.65 percent. Given the effects of temperature on rice crops and increasing climate change vulnerabilities, agricultural scientists should focus on research and development of temperature tolerant rice varieties in the production of rice yields.

Standardizing irrigation and planting schedule of salt tolerant rice (Oryza sativa) and wheat (Triticum aestivum) varieties for higher water productivity and yield in reclaimed sodic soils of Indo-Gangetic plains of India

Rice (Oryza sativa L.)-wheat (Triticum aestivum L.) system (RWS) grown on 10 m ha in the Indo-Gangetic Plains (IGP), is essential for food security of India. In IGP soil sodicity is very common and reclamation with gypsum is very expensive, so adoption of salt tolerant varieties of rice and wheat could be a better option. A field experiment was, therefore conducted for three years (2012-2015) in RWS to evaluate the performance of salt tolerant varieties under different dates of transplanting/sowing and irrigation scheduling. In kharif season, three irrigation scheduling, i.e. complete submergence/farmers practice (CS/FP), 3 days after disappearance of ponded water (DAD), and 5 DAD as horizontal factor and four transplanting dates (21 June, 1 July, 11 July, 21 July) as vertical factor conducted in strip plot design replicated thrice. In rabi season, three irrigation schedules, i.e. IW/CPE = 1.0, 0.8, and 0.6 as horizontal factor and four dates of sowing, i.e. 10 November, 20 November, 30 November, 10 December, as vertical factor and two salt tolerant wheat varieties, viz. KRL 210 and KRL 213 in subplots was conducted in strip split plot design, replicated thrice. Results indicated that salt tolerant rice variety Basmati CSR-30 can be transplanted on 1 July to get better yield attributes, highest grain yield (3.63 t/ha) and water saving (32.5%) by adopting irrigation scheduling of 5 DAD with highest irrigation water productivity (0.522 kg/m3). In rabi season, salt tolerant wheat varieties can be sown on 20 November following irrigation schedule of IW/CPE=1.0 (KRL-210: 6.76 t/ha and KRL-213: 6.88 t/ha) to get highest grain yield.

Whole genome sequence analysis of rice genotypes with contrasting response to salinity stress

Salinity is a major abiotic constraint for rice farming. Abundant natural variability exists in rice germplasm for salt tolerance traits. Since few studies focused on the genome level variation in rice genotypes with contrasting response to salt stress, genomic resequencing in diverse genetic materials is needed to elucidate the molecular basis of salt tolerance mechanisms. The whole genome sequences of two salt tolerant (Pokkali and Nona Bokra) and three salt sensitive (Bengal, Cocodrie, and IR64) rice genotypes were analyzed. A total of 413 million reads were generated with a mean genome coverage of 93% and mean sequencing depth of 18X. Analysis of the DNA polymorphisms revealed that 2347 nonsynonymous SNPs and 51 frameshift mutations could differentiate the salt tolerant from the salt sensitive genotypes. The integration of genome-wide polymorphism information with the QTL mapping and expression profiling data led to identification of 396 differentially expressed genes with large effect variants in the coding regions. These genes were involved in multiple salt tolerance mechanisms, such as ion transport, oxidative stress tolerance, signal transduction, and transcriptional regulation. The genome-wide DNA polymorphisms and the promising candidate genes identified in this study represent a valuable resource for molecular breeding of salt tolerant rice varieties.

Impact of Climate Change on Paddy Production: Evidence from Nepal

This study assesses the long-run relationship and short-run dynamics between paddy yields and climate variables, particularly maximum and minimum temperature and rainfall, using time-series data from 1971 to 2014 in Nepal. Applying Autoregressive-Distributed Lag Regression or ARDL bounds testing approach for analysis of co-integration between the variables, we confirm that there is a long-run relationship among the variables. Furthermore, we employ Granger non-causality tests for robustness. The findings reveal that rainfall has substantial effects on the rice yield. Specifically, a positive and significant relationship exists between rice yields and rainfall and that this relationship is unidirectional. Rainfall impacts on rice yield and holding all things constant, a 1 mm increase in rainfall increases rice yields by 0.65 percent. Given the effects of temperature on rice crops and increasing climate change vulnerabilities, agricultural scientists should focus on research and development of temperature tolerant rice varieties in the production of rice yields.

Swampy rice lines for iron toxicity tolerance and yield components performance under inland swamp at Sorong, West Papua, Indonesia

Abstract. Maruapey A, Wicaksana N, Karuniawan A, Utami DW, Windarsih G. 2020. Swampy rice lines performance for iron toxicity tolerance and yield components under inland swamp at Sorong, West Papua, Indonesia. Biodiversitas 21: 5394-5402. The extensification of sub-optimal lowland farming strategy is expected to support the increase of rice production. Based on the efforts, the development of tolerant rice varieties to Fe-toxicity to be used in the swampy land area is one of the approaches for increasing rice production. Currently, promising rice lines that are tolerant to Fe-toxicity has been developed using molecular breeding approach for inland swampy area. The objective of this research was to evaluate the performance of 15 promising rice lines that have various genetic backgrounds in inland swamp in Sorong, West Papua. The field experiment was conducted during the second rice planting season (August 2018 to February 2019) to evaluate the performance of the promising rice lines to the morpho-agronomic performance under the lowland swamp conditions. The trial was laid out in a Randomized Complete Block Design (RCBD) consisting of 4 m x 5 m square plots, with 25 cm x 25 cm planting distance and 3 replications. The results revealed that most of the lines had good performances on the Fe-toxicity tolerance, based on bronzing, root length, and biomass characters. The G1 line had the best performance on yield component characters, especially the panicle length. This line also had the highest grain yield (6.15 ton.ha-1) followed by the next promising line of G7 (5.92 ton.ha-1). The genetic performance of these lines showed that they contained IRT (Iron Regulation Transporter) alleles that contributed to partitioning the Fe tolerance mechanism.

Factors Affecting Production of Flood Tolerant Rice Variety in Assam: A Farm Level Study

A field study was conducted in Jorhat district of Assam. The objective of the study is to obtain a better understanding of the factors affecting rice production at the farm level. The data were collected from 80 farmers using multistage random sampling technique. A regression analysis Cobb –Douglas model was used to identify the factors affecting rice production at farm level (Adopters and Non Adopters).The empirical evidence finds that FYM cost (0.074) and fertilizer cost (0.107) were found to be positive and significant indicating that with 1 % increase in both the inputs would increase the rice production and thereby increase the gross return by 7.4 and 10.7 %, respectively. Problems faced by the farmers as collected by primary survey were ranked using the ranking method. Among adopters, the major problem observed was high seed cost according to 33.33 % of total adopters and lack of extension contacts was a serious problem as reported by 26.00 % of non adopters due to which they were lagging knowledge about flood tolerant rice varieties.

Gender focused training and knowledge enhances the adoption of climate resilient seeds

Adoption of any agricultural technology depends upon the way in which farmers are being informed about its benefits. Educational status, caste, gender and other social issues also play a significant role in the adoption process. To evaluate the impact of trainings on quality seed production, access to the climate resilient rice seeds, availability of information about seed sources and use of IRRI super bags, a randomized experimental research was carried out over a period of two years across five different states of India. The baseline and a follow-up survey was conducted to capture the farming practices followed by during wet seasons of 2016 and 2017, respectively. The impact of trainings, seed use, information given and agro-based goods was evaluated by comparing the adoption behaviour of treatment and control farmers. There was an increase (28.8%) in the practice of using salt solution to clean seeds primarily due to the impact of quality seed production (QSP) trainings. Female farmers responded more than the male farmers as number of women adopting the practice was higher than men. The impact of the trainings on farmers' knowledge and adoption of climate resilient/stress tolerant rice varieties (STRV) was also more pronounced on females than on male farmers. Farmers’ access to seeds substantially enhanced the adoption and reusability irrespective of the gender. Similarly, the information delivered to the farmers was quite economical in enhancing the awareness and adoption of climate resilient rice, but the effect was predominantly driven by female farmers. Female farmers performed relatively better with respect to the storing the new seeds in IRRI super bags. Thus, incentivising farmers in general and female farmers in particular can serve as a potential means to adopt agricultural technologies that have potential to boost rural economy and enhance the food security. The results are being supported by a rigorous empirical analysis.

Early Maturing Drought Tolerant Rice Variety BRRI dhan71 Suitable for Drought Prone Environment in Bangladesh

Drought is the second most treacherous climate-related risk for rice production in rainfed lowland areas. To counter this climate vulnerability, a new rice variety with enhanced drought tolerance was developed. The promising line IR82589-B-B-84-3 was subjected to advanced yield trials to evaluate specific and general adaptability with standard check in on-station as well as on-farm conditions of Bangladesh following randomized complete block (RCB) design with three replications in wet (T. Aman) season. IR82589-B-B-84-3 was developed as a drought-tolerant rice variety BRRI dhan71, which plant height 108 cm and growth duration 115 days after proper evaluation by National Seed Board (NSB) Bangladesh. It was found that this variety is the higher drought tolerance (up to 28 days) during reproductive stage. It can produce 5.5 t/ha grain yield in standard condition and 4.0 t/ha grain yield in medium drought condition but 3.0-3.5 t/ha grain yield in severe drought condition. Grain yield is also not affected by water scarcity during reproductive stage where parch water table depth is more than 70-80 cm from the surface and reduced soil moisture (<20%). Thousand grain weight of the variety is 24 gm, amylose content is 24%. It has long, erect and deep green colored flag leaf. The results indicated that farmers can maximize net profit by cultivating BRRI dhan71 because it required less input, early maturing than existing varieties, drought tolerant and they also get opportunity to cultivate Mustard, Barley, Potato and vegetables after harvesting it. Thus total productivity will be augmented and food security can also be sustained by the cultivation of BRRI dhan71.

Performance of Drought Tolerant Rice Varieties in Malkangiri District of South Eastern Ghat Zone of Odisha

Drought is the major problem in India and occurrence at the time of critical growth stages, reduce crop yield significantly. The National Rice Research Institute, Cuttak, Odisha has developed so many drought tolerance rice varieties to reduce the economic loss due to drought. Krishi Vigyan Kendra, Malkangiri introduced NRRI released two rice varieties i.e. Sahbhagi Dhan and Satyabhama at framers' field to evaluate the performance of these drought tolerant varieties in South Eastern Ghat Zone of Odisha. The highest plant height was observed with the rice variety Satyabhama (104.1 cm). But, overall performance of Sahbhagi Dhan was better as compare to Satyabhama and local check verity (Khandagiri). Sahbhagi Dhan gave highest yield of 36.5 q/ha, which was statistically differed from others. Correlations study for Sahbhagi Dhan was assessed and observed the positive correlation for grain yield with all studied characters except plant height. For economic point of view, Sahbhagi Dhan recorded highest net return of Rs.19, 925/- per ha along with B:C ratio of 1.6 as compared to the rest two varieties.

Evaluation of Short Duration Drought Tolerant Rice Varieties in Drought Prone Areas of Subarnapur District of Odisha

A study was conducted in farmer’s field through technology demonstrations during Kharif season of 2018 and 2019 in Subarnapur district of Odisha to recommend the most suited short duration drought tolerant upland rice variety particular to the locality. Six different varieties like Sahabhagi dhan, Mandakini, Jogesh, DRR-44, and DRR-42 & Khandagiri were taken with four replications in Randomized Block Design in both years. Technology demonstration included not only the improved short duration varieties, but also a package of good agronomic practices viz. line sowing, seed treatment with Bavistin, proper fertilization with dose @ 80:40:40 NPK/ha, pre emergence herbicide application with pretilachlor, needful manual weeding and need based plant protection chemicals. The results of demonstration showed that farmers could increase rice productivity notably by adopting improved variety Sahabhagi dhan and DRR-44. These varieties recorded higher grain yields of 64% and 46%, respectively, and fetched a sum return of Rs 25620 and Rs 25275 over farmers’ local variety Khandagiri.

Mahalanobis D2 and principle component based genetic divergence, selection criteria and genetic variability studies in cold tolerant rice (Oryza sativa) genotypes

The present investigation was carried to assess the genetic variability, trait relationship, path analysis, D2 analysis and principal component analysis in thirty eight genotypes. All the traits under this study shown the significant difference for ANOVA and high GCV and PCV is observed for Panicle exertion and seed yield per plant. High heritability coupled with high genetic advance as per cent mean was observed for seed yield per plant and tillers per plant. All the characters except test weight showed the positive and significant correlation with seed yield at phenotypic level. Path analysis revealed that filled grains per panicle and spikelet fertility showed positive direct effect on seed yield. Diversity studies indicated that inter cluster distance was maximum between cluster II and VII followed by cluster II and VI & cluster I and VII. Principle component analysis indicated that first five principal components contributed to 85.81% of the total diversity is contributed by plant height, seed yield per plant, spikelet fertility, panicle exertion, panicle length, filled grains per panicle and tillers per plant. Selection based on the results of the present study could be exploited in designing future plant breeding programmes for development of high yielding cold tolerant rice varieties.

Evaluation of yield performance and establishment methods of drought tolerant rice genotypes under rainfed condition in drought prone areas of Bangladesh

Two field experiments were carried out at farmer’s field of Rajshahi and Chapainawabgonj under the Department of Agronomy, BINA during aman season of 2017 and 2018 consecutively to evaluate the drought tolerant rice varieties under different establishment methods in rain fed condition. First experiment (E1) was conducted to find out the performance of varieties and second experiment (E2) was to find out the suitability of method of transplanting/sowing in combination with short duration aman varieties. Different methods were as direct seeding, puddled and un-puddled transplanting and cultivars were used to cultivate BRRI dhan56, Binadhan-7, Binadhan-17 (except in second experiment) and Huttra (local cultivar). The experiment was laid out in a randomized complete block design with three replications. The recommended fertilizer doses applied for the experiment were 80 kg N ha-1, 15 kg P ha-1, 50 kg K ha-1, 20 kg S ha-1 and 2 kg Zn ha-1. Nitrogen, phosphorus, potassium, sulphur and zinc were supplied from urea, TSP, MoP, gypsum and zinc sulphate monohydrate respectively while urea was applied in three equal splits. Among the cultivar Binadhan-17 produced statistically higher grain yield (5.62 t ha-1) at Chapainawabgonj. Among methods Binadhan-7 statistically higher grain yield 5.32 t ha-1 and 5.21 t ha-1, respectively) in puddle transplanting method both Chapainawabgonj and Rajshahi region during 2017. Among the cultivar Huttra (local) produced statistically higher grain yield (5.43 t ha-1) at Chapainawabgonj. Among methods, BRRI dhan56 statistically higher grain yield 6.37 t ha-1 and 6.19 t ha-1, respectively) in puddle transplanting method bothat Rajshahi and Chapainawabgonj during 2018. Overall results indicates that BRRI dhan56, Binadhan-7, Binadhan-17 performed better in puddled transplanting, Huttra (local) in direct seeding method in drought prone region of Bangladesh.

A Comparative Study of Different Moisture Stress Tolerant Rice Varieties in Kalahandi District of Odisha

Plant growth and productivity of rice is adversely affected by various biotic and abiotic stress factors. Water deficit is one of the major abiotic stresses, which affects crop growth and yield. Majority of rice cultivated areas in south Asia is under rainfed, where water stress at any stages of growth causes sharp decline in yield. The present study was carried out through front line demonstration under a ‘National Innovation in Climate Resilient Agriculture’ (NICRA) project during kharif seasons of 2018 and 2019 in two villages namely Pipalpada and Kinipadar of Kalahandi district of Odisha with an objective to evaluate the performance of short duration rice varieties viz. Swarna Shreya, Sahabhagidhan, DRR-42 and Naveen as compared to the farmers variety (MTU-1010). Swarna Shreya matured in 115 days and recorded higher plant height (126.83 cm), effective tillers/hill (19.33), length of panicle (28.50 cm), number of panicle/m2 (305.0), filled grains/panicle (128.72) and 1000 grain weight (25.51 g) over other varieties. This variety also produced the highest grain yield of 4.16 t ha-1 with harvest index of 0.56 and total dry matter of 538.10 /m2. The Swarn Shreya produced higher net return of Rs. 41,975/ha with a benefit-cost ratio of 1.20 and additional net return of Rs. 9735/ha as compared to farmers’ variety. The growth and yield performance of Swarna Shreya was found to be satisfactory in spite of occurrence of frequent dry spells during different crop growth stages. Thus, the existing variety, MTU-1010, may be replaced with Swarna Shreya for more productivity, income tolerant during moisture stress conditions.

Effect of Water-Deficit Stress on the Selected Landraces and Improved Varieties of Rice (Oryza sativa L.) in Nepal

Water stress is one of the adverse factors affecting growth, development and productivity of rice. It is crucial to explore the drought tolerant rice varieties and improve their quality for sustainable production for droughtprone environments. The aim of this study was to know the ability of selected landraces (Aapjhutta, Kartika, Aanadi and Jhapamansuli) and improved varieties (Khumal-8, Khumal-10, Khumal-11 and Chainung-242) of rice to tolerate water-deficit stress in Nepal. The rice plants were grown in polyethylene pots. The pots were watered for the first two days of seedling transplantation and then watering was stopped. Survival and survival probability of seedlings were calculated. In addition, the concentration of an osmolyte (proline) was estimated after complete death of the plants in each variety. Two rice varieties, Jhapamansuli and Aapjhutta showed the highest seedling survival under water-deficit stress than the improved and other rice varieties. Results indicated that these two varieties have the ability to survive better than others under the stress by accumulating a high amount of proline as a compatible solute. Thus, these varieties can be preserved and utilized for breeding activities to develop drought tolerant and high yielding varieties.

Polymorphic Identification of Simple Sequence Repeat (SSR) Marker for Developing Aluminum-Tolerance Upland Rice

SSR marker is one of the genetic markers widely applied in plant breeding programs. The application of molecular markers in plant breeding is meant to accelerate the selection of cross-progeny. The research aimed to identify the SSR primers polymorphism between the parent and control that linked to Al tolerance and verify the cross-progeny of five crosses. The result gained from 37 SSR primers used in this study showed that only nine primers are polymorphic. These nine polymorphic primers are RM257, RM214, RM247, RM205, RM490, RM262, RM569, RM271, and RM19. The application of polymorphic markers on five cross-progeny which have shown the same band pattern as the parents and tolerant control on the use of 9 SSR primers recorded as follows: RM257 2 lines, RM214 5 lines, RM247 5 lines, RM205 lines, RM490 13 lines, RM262 5 lines, RM569 7 lines, RM271 4 lines, and RM19 6 lines. The selected SSR primers linked to Al tolerance in this research can be used as a reference for molecular breeding strategies to develop new Al tolerance rice varieties in dryland conditions.

UV-B priming enhances specific secondary metabolites in Oryza sativa (L.) empowering to encounter diverse abiotic stresses

Plants are exposed to various abiotic stresses and there exists sophisticated mechanisms within them for tolerating these stresses. The present study clearly revealed the efficacy of UV-B priming at both seed and seedling stage in tolerant (Kanchana) and sensitive (Aiswarya) rice varieties, to tolerate UV-B stress, polyethylene glycol-6000 (PEG) and NaCl stresses. Increase in UV stress specific characters such as accumulation of UV absorbing compounds [flavonoids (242–368%) and anthocyanin (367–386%) content],increased activity of phenylalanine ammonia lyase (116–210%) and increased leaf cuticular wax content (382–403%) was observed in UV-B primed seedlings of rice subjected to UV-B, NaCl and PEG stresses. The increase in the levels shown as percent increase were highest in seedlings subjected to UV-B stress followed by NaCl and PEG stresses. The influence of priming imprints was more effective in seeds and seedlings of the tolerant rice variety (Kanchana) than the sensitive variety (Aiswarya). Functional groups variation in wax content was more prominent in PEG stress conditions than UV-B and NaCl stresses and it was mainly observed in Aiswarya than in Kanchana. Additionally our results suggests the UV-priming mediated enhancement of the stress tolerance potential of a tolerant variety seems to be more successful than the sensitive variety.

Improvement of Rice Breeding for Salinity Tolerance

Rice is one of the most significant food crop of the world. The production of rice is the second-highest in the world. Salinity is a serious constraint to increase rice production worldwide. Review of recent efforts achieved towards rice breeding for salinity tolerance has a paramount importance beside for rice production improvement in Ethiopia. Rice is a relatively new crop to Ethiopia; however, the crop is relatively well adapted to different parts of the country. Salinity is a problem of many irrigated, arid and semi-arid areas of the world where rain fall is insufficient to leach out salts from the root zone. Typical symptoms of salt injury in rice are stunted growth, leaf rolling, white leaf tip, white blotches in the leaf blade, drying of the older leaves and poor root growth. The main mechanisms of salt tolerance are control of salt uptake, reducing damage under excessive ion uptake and osmotic adjustment. The three major breeding approaches for salinity tolerant varietal development are conventional breeding, marker assisted selection and genetic engineering. Conventional rice breeding approaches exercised for thousands of years. But, the progress is slow, due to the time consuming process, the quantitative nature of most agronomic traits make difficulties in genotypes selection. However, modern breeding is more precise and efficient and easily identify undesirable genes that can be eliminated in future generations. In rice, markers like RAPDs, AFLPs, ISSRs and SSRs have been used. Among these DNA markers, SSRs is highly preferable for gene tagging and mapping efforts. The development of salt-tolerant variety by transgenic way needs more investigation. To date, transgenic salt tolerant variety has not yet reached at farmers’ field. In Ethiopia a little beat was done to identify rice genotypes adaptable to adverse saline soil conditions. From here on, more research findings highly crucial for the development of salinity tolerant rice varieties in the country. Therefore, it is a good opportunity for rice breeders to develop salt tolerant high yielding varieties in Ethiopia. Keywords : Conventional breeding, Genetic engineering, Marker-assisted selection, Rice, Salt tolerance DOI: 10.7176/JEES/10-5-02 Publication date: May 31 st 2020

Yield gap, profitability and inefficiency of Aman rice in coastal areas of Bangladesh

Despite of being an extremely overpopulated country with a limited land resource, Bangladesh has managed to increase its food production to a viable level. Yet it is necessary to increase production of food crop in order to cope with the growing population in a sustainable way. Closing yield gap is a means of attaining sustainability of agricultural intensification to keep pace with the growing crop demand. The objective of the present study is to assess the inefficiency and the yield gap of Aman rice production in climate vulnerable areas in Bangladesh. The study was conducted in Shaymnagar and Kaliganj Upazilas of Satkhira district in Bangladesh and data were collected using a stratified random sampling technique from 110 Aman cultivating farmers. Descriptive statistical techniques as well as Stochastic Frontier model were used to achieve the objectives of the study. The study revealed that, Aman rice cultivation was profitable in the study area. We estimated the model based yield gap, highest recorded yield gap and experimental yield gap. The mean efficiency analysis revealed that farmers could increase their production with optimal use of inputs and proper management systems. Absence of proper knowledge about the optimum input use and lack of institutional training as well as inadequate extension services were responsible for the reduced yield in most farmers’ fields. Salinity has reduced the overall productivity of the region, but it is believed that by popularizing the practice of saline tolerant rice variety and addressing the above mentioned issues the potential production can be achieved in the coastal region.
 Progressive Agriculture 30 (4): 395-404, 2019