Tolerant Rice Varieties Research Articles

Evaluation of the genetic variability and genetic advance for salt tolerance in rice genotypes

Soil salinity is considered as one of the greatest threats for rice production. Genetic variability analysis of morphological traits related to salt injury is mandatory, which could be helpful in the development of an appropriate breeding program for the selection of salt tolerant rice genotypes from the existing germplasm towards developing new salt tolerant rice varieties. Therefore, the present study has been aimed to evaluate the genetic variability parameters for fourteen morphological traits in thirty local and high yielding rice genotypes using hydroponic culture. Among the rice genotypes under study, Boilam, Nonabokri, Gunshi, Motabamonkhir showed the best performance regarding the morphological traits under different saline conditions (6 dSm -1 and 10 dS m-1). The PCV values were greater than the GCV values for all studied traits indicating the greater environmental influence on the traits. The highest percentage of GCV and PCV were observed in root dry weight, while the lowest were exhibited in main axis diameter. To assist the breeding program, along with variability, estimation of heritability and genetic advance has also been done. High heritability ranging from 80.24% to 94.66% was found among the traits. The genetic advance was highest for survival rate and the lowest was in root dry weight. Eventually, the results indicated the presence of high genetic variability, along with high heritability and genetic advance among genotypes and studied traits, which could provide further insight towards selection of parents for the development of salt tolerant rice varieties.Progressive Agriculture 28 (4): 262-270, 2017

Swamp land optimization in supporting food security and enhancing farmers welfare in South Sumatra Indonesia

Swamp land in Indonesia spread in Sumatra, Kalimantan and West Papua. In Sumatra the largest swamp land area is located in South Sumatera Province. Unfortunately only few of the areas have been utilized due to its fragility, in which farmers could only cultivate rice on it once a year. The purpose of this paper is to develop a feasible farming pattern in swamp land to help farmers and practitioners in optimizing it by managing its water level. Shallow and mid swamp land can be cultivated using rotation model of crops (rice, corn, cassava), horticulture (cucumber, long beans, watermelon etc), fish farming (catfish, snake head fish, tilapia), and duck farming, whereas submergence tolerant rice varieties can be cultivated alternating with fish farming in deep swamp land. This study shows that such swamp land management is financially feasible showing by its positive NPV value, BCR value is above 1.00, and IRR value is greater than the interest rate. Therefore, implementation of this farming pattern is expected to increase farmers’ income and household food supply as well as village food supply.

Coping with flashflood under changing climate in north-eastern haor areas of Bangladesh: potentials of promising crop production practices

Haors are large bowl shaped fl oodplain depressions and one of the most important agro-ecological zones in Bangladesh. However, rice production in this area has been severely impacted by recent events of frequent early fl ashfl oods. Many experts have linked the changes of fl ooding time and duration in haor area to global climate change. Farmers need short duration, relatively tall, lodging tolerance and non-shattering rice varieties to cope with the fl ashfl ood. With this contrast, this study is conducted in Tahirpur and Biswambarpur upazila of Sunamganj district to examine occurrence time and duration of fl ashfl ood; identify fl ashfl ood coping crop production practices; and fi nally investigate relationship between socio-economic characteristics of farmers and their fl ashfl ood coping crop production practices. Hence, this study utilizes a set of approaches viz. structured questionnaire survey, key informants interview with stakeholders and focus group discussions to get primary data and secondary data also collects to conceptualize the problems. Results reveal that short duration, varietal diversifi cation, tall plant type of rice varieties are found popularly used practices in haor area. Although other coping practices like harvesting of rice at 80 percent maturity, early transplanting, aged seedling and rabi crops have substantial impact in coping fl ashfl ood but they are not extensively practiced. Study also reveals that education levels of farmers have highly positive and signifi cant relationship with fl ashfl ood coping crop production practices; high coping practices are observed in educated farmers. In order to increase coping ability of farmers of farm practices, it is utmost important to link between government and development agencies to provide adequate technical support, extension service, education, income generating opportunity and water conservation measures.

Evaluation of Drought Tolerant Rice Varieties under Various Methods of Crop Establishment under Rainfed Condition of Bihar

Evaluation of Drought Tolerant Rice Varieties under Various Methods of Crop Establishment under Rainfed Condition of Bihar

Variation in Expression of <i>Sub</i>1 Gene and Association with Submergence Stress Related Traits in Advance Rice (<i>Oryza sativa</i> L.) Genotypes as a Tool of Climate Change Adaptation

Floods have now become most detrimental natural catastrophe worldwide due to radical climatic fluxes. Therefore, there is a dire necessity to develop a high yielding rice lines to deal with this scenario. For this purpose, a large scale experiment was conducted including one hundred and fifteen (115) rice genotypes having SUB1 gene imported from International Rice Research Institute (IRRI) Philippines, six local cultivars/approved varieties and three high yielding rice varieties i.e. Sabitri, IR6 and NSICRC222 being used as potential varieties in different countries of Asia as susceptible check and IR64-SUB1 as tolerant check. The genotypic screening was performed using two PCR-based DNA markers i.e. ART5 and SC3. Phenotypic screening was conducted in a natural pond to assess the interaction of SUB1 gene in natural stagnant flood water as well as the suitability of introgression of SUB1 gene into approved varieties and elite rice lines. The genotypes were assessed in terms of plant survival percentage, submergence tolerance index, physical condition, stem elongation, number of grains per panicle, thousand grain weight, grain yields and deviations in these traits after submergence stress. The PCR results suggested that both the primers ART5 and SC3 may be used as potential PCR-based markers for molecular screening of rice genotypes for SUB1 QTL. Furthermore, it confirmed the presence of SUB1 gene in all the lines imported from IRRI, while it was absent in all the local cultivars studied. All the genotypes with submergence tolerant gene (SUB1) showed significantly greater tolerance level in submergence stress of 14 days, as compared to other local cultivars/varieties, authenticating the effectiveness of SUB1QTL in conferring submergence tolerance. Significantly different performances of all the SUB1 genotypes in terms of all the studied traits indicate high Genotypic and Genotypic Environment Interaction (GEI) of SUB1QTL. Employment of SUB1 lines such as R105479:149-18, IR64-SUB1 and Rl05469:81-22-3 in breeding programs for developing flood tolerant rice varieties might further upsurge rice yields in flash flood areas. Correlation analysis revealed that plant survival percentage after submergence, reduced stem elongation during submergence and submergence tolerance index are very important traits for developing submergence tolerant lines.

Molecular Diversity Analysis for Zinc Deficiency Tolerance under Aerobic Rice (Oryza sativa L.) Ecosystem

Rice (Oryza sativa L.) is the “Global Grain” because of its use as prime staple food in about 100 countries of the world. Aerobic rice provides for effective use of water as the concept of flooding paddy fields is abandoned in this ecosystem. But due to the transition from flooding of paddy fields to aerobic system of rice cultivation many factors that determine nutrient (Zn) bioavailability changes in addition to water deficit. Achieving higher yields under aerobic conditions requires new varieties of “aerobic rice” combining both the water stress tolerance and nutrient (especially Zn) deficiency tolerance traits. Molecular marker technologies are the effective tools and they are used for the assessment of genetic variability because they are not influenced by the environment. Among the molecular markers, Simple Sequence Repeat (SSR) has proved to be the most powerful tool for variety identification in rice and has much potential in genetic and breeding studies. Among the 16 SSR markers specific to zinc deficiency tolerance used for assessing the genetic diversity, 13 primer pairs (81.25%) were polymorphic. The number of alleles per microsatellite locus ranged from 2 to 5, averaging 2.53 alleles per locus. Polymorphism information content (PIC) values ranged from 0.43 (RM242) to 0.69 (RM1089 and RM3331), with an average of 0.58. The Unweighted Pair Group Method with Arithmetic Mean (UPGMA) dendrogram revealed two major groups with three clusters and the wide range of dissimilarity values (0.68–1.00) which showed a high degree of diversity among the germplasm lines. The results of the genetic diversity will be useful for the selection of the parents for developing zinc deficiency tolerant rice variety under aerobic condition through molecular breeding programme.

Phenotypic screening of rice varieties for tolerant to salt stress at seed germination, seedling and maturity stages

Salinity affects all growth stages of rice in varying degrees starting from germination up to maturation. The present study was conducted to screen the commonly cultivated rice varieties in salinity affected areas in Sri Lanka against salt stress. Screening of 21 improved rice varieties and check variety Pokkali was performed at seed germination, seedling and maturity stages in petri dishes, in a hydroponic system and in soil filled pots, respectively. Rice varieties were tested for ability to sustain seed viability, growth performance of seedling and plant survival, growth performance and grain yield reduction at maturity under salt stress. At germination stage, Bg 406 and Pokkali were identified as highly tolerant rice varieties whereas, At 402 showed the highest tolerance level followed by Pokkali, Bg 369 and At 354 at seedling stage. Based on the mean separation on survival of plants per pot at 12 dS/m and 8 dS/m, three groups (highly tolerant, tolerant and susceptible) could be identified. Percentage reduction increased with increasing salt levels for most of the parameters tested (PH, PL, RDW, SDW, PWT, PNO and YLD). Based on the phenotypic observations Pokkali was identified as high salinity tolerant variety whereas Bg 369, At 354, At 402 were identified as salinity tolerant varieties at maturity stage.

DNA sequence polymorphism of Pup1 linked K20-1 STS region can be effectively used in molecular breeding of rice for phosphorus deficiency tolerance

Pup1 is the major quantitative trait locus (QTL) for phosphorus deficiency (PD) tolerance in rice. The molecular markers linked to Pup1 are available for numerous rice genotypes. However, novel haplotypes of Pup1 could be detected if specific landraces are subjected to genetic analyses. A set of 30 local rice genotypes were assessed for PD tolerance and in the present study, they were characterised by sequencing K20-1 , a co-dominant locus within the Pup1 locus. The DNA polymorphism was also checked for the association with PD tolerance. A total of 10 SNPs and one INDEL were discovered among the 32 genotypes including Kasalath and Nipponbare as PD tolerant and sensitive reference rice varieties, respectively. Four unique SNPs were discovered in the studied germplasm that are not present in either Kasalath or Nipponbare . The SNP located at the 209th position was very important as it is unique to highly PD tolerant landraces Murungakayan and Suduheenati , and varieties H-4, H-7 and H-10. These five genotypes lack the INDEL region present in Kasalath highlighting the presence of novel Pup1 haplotypes in country specific rice varieties/ landraces, and they can be used as parental genotypes to introduce PD tolerance into new varieties in rice breeding programmes in Sri Lanka.

Effect Of Planting Geometry On Growth Of Rice Varieties

A field experiment was conducted under humid subtropical agro-climatic condition of Nepal during rainy season of 2014. The experiment was laid out in to two factor Randomized Complete Block Design with three replications consisting three drought tolerant rice varieties (Sukhadhan-4, Sukhadhan-5 and Radha-4) and four planting geometry (15 cm × 10 cm, 15 cm × 15 cm, 20 cm × 15 cm and 20 cm × 20 cm). The results revealed that the highest plant height and maximum leaf area index was recorded in planting geometry 15 cm × 10 cm in all growth stages. Whereas, planting geometry 20 cm × 15 cm produced the maximum number of tiller m-2 in all growth stage. While planting geometry 20 cm × 15 cm and 20 cm × 20 cm produced statistically similar crop growth rate and dry matter accumulation in all stage of growth. Regarding the varieties, Sukhadhan- 4 showed highest plant height up to 75 DAT and plant height was statistically similar to Radha - 4 in 60 and 75 DAT. But maximum number of tiller m-2, leaf area index, crop growth rate and dry matter accumulation were recorded in Sukhadhan – 5 varieties. Int. J. Appl. Sci. Biotechnol. Vol 5(4): 423-429

Heat stress-responsive transcriptome analysis in heat susceptible and tolerant rice by high-throughput sequencing

Abstract As one of the most vital major food crops feeding almost half the earth's population, rice often suffers from heat stress in tropical and subtropical regions. To study rice heat stress tolerance mechanism is critical for breeding new heat tolerant rice varieties. We performed RNA-Seq analysis to check rice transcriptomic differences responsive to heat stress in both heat-tolerant (HT, HT54) and heat-sensitive (HS, HT13) lines. A sum of 0.603 billion reads were acquired on behalf of 32,391 unique genes. Compared with 0 h, a sum of 2275 genes showed enhanced regulation while 2270 genes showed inhibited regulation in the HS line at 12 h, contrarily 2603 genes showed enhanced regulation and 2900 genes showed inhibited regulation in the HT line. A sum of 1438 genes showed enhanced regulation and 1237 genes showed inhibited regulation in the HS line at 24 h, contrarily 1599 genes showed enhanced regulation and 1754 genes showed inhibited regulation in the HT line. About 22,490 genes were assigned to gene ontology (GO) term in terms of biological process, cellular component and molecular function categories. Compared with 0 h, a sum of 8 and 4 genes showed different expression (RFC ≥ 2.0) between the HT and HS rice lines at 12 and 24 h, respectively. This work most probably set a solid foundation for elucidating the heat stress tolerance mechanisms and crop genetic improvement in rice.

Phenotypic Screening and Molecular Characterization of 10 Rice (Oryza sativa) Landraces for Cold Tolerance

Phenotypic screening of existing 10 familiar landraces performed at germination and seedling stages and their molecular characterization were conducted at Bangladesh Institute of Nuclear Agricultural (BINA) during the period of December 2014 to May 2015 to screen out better cold tolerant genotypes among 10 landraces where one susceptible, two moderately tolerant and two tolerant BRRI released varieties were used as check genotypes. The present study evaluated several parameters at the germination stage after 7 days of germination and at the seedling stage after 28 days of seedling growth for phenotypic screening. Modified hydroponic method was used at the seedling stage and the temperature treatments were maintained artificially at 15°C and 25°C respectively. Polymorphic microsatellite or SSR markers were selected for molecular characterization showing that attributes were positively regulated due to cold stress in BRRIdhan 36, LR 114- Badiabona and LR 54- Tor Balam. The findings of genetic diversity analysis for landraces LR 114- Badiabona and LR 54- Tor Balam appeared to resemble to that of tolerant genotype BRRIdhan 36. Based on phenotypic screening and UPGMA dendrogram study, landraces LR 114- Badiabona and LR 54- Tor Balam appeared superior as genetic material. Better cold tolerant rice variety may be developed from further breeding process.J. Environ. Sci. & Natural Resources, 10(1): 85-91 2017

Towards Developing Salinity Tolerant Rice Adaptable for Coastal Regions in Indonesia

Lowland rice areas along the coastal regions are a major contributor for rice production in Indonesia. Sustainability of rice production in those areas is challenged by the increase of soil salinity as the result of sea water inundation. The problem is exacerbated by the increase of sea water level as the impact of global climate change. High concentration of salt ion in the soil could significantly reduce rice growth and yield. Development of salinity tolerant rice varieties is therefore important to maintain sustainability of rice production in the coastal regions. Breeding programs to improve salinity tolerance of Indonesian rice has been established in Indonesian Centre for Rice Research. Through intensive salt tolerant screening program genetic variations in salinity tolerance have been identified within rice germplasm allowing the improvement of salinity tolerant of existing rice varieties. Different genetic resources have been used for salinity tolerant improvement including landraces, improved varieties and introduction lines. A number of promising salt tolerant rice breeding lines have been developed and showed adaptability to salt affected areas in the lowland coastal areas. Two new salt tolerant rice varieties have been released recently which are adaptable to salt affected areas. This paper will describe the progress in the breeding programs to develop salt tolerant rice for lowland rice areas in the coastal regions. Strategy to accelerate the improvement of the salinity tolerant of Indonesian rice varieties in the future will be also discussed.Keywords: rice, breeding, salinity tolerance, coastal regions.

Marker assisted introgression of bacterial blight resistant gene into submergence tolerance rice variety BRRI dhan52

BRRI dhan52 is a uniquire submergence tolerant rice variety containing prominant genetic background of BR11, a mega rainfed lowland rice (RLR) variety of Bangladesh, but is susceptible to bacterial blight (BB) caused by Xanthomonas oryzae pv. oryzae (Xoo). The variety is considerably popular in the southern part of Bangladesh due to its high yield in flash flood condition and comparatvely medium slender grain. Molecular markers linked to BB resistance genes (Xa genes) and submergence QTL (SUB1) were utilized in a marker-aided selection program to develop elite breeding lines with broad-spectrum resistance to bacterial blight. Sequence tagged site (STS) and simple sequence repeat (SSR) markers were essentially used to detect the genes for BB and submergence as well. In backcross generation, markers closely linked to Xa21 and SUB1 QTL were used to select desirable plants possessing these resistance genes (foreground selection) and microsatellite markers polymorphic between donor and recurrent parent were also used to select plants that have maximum contribution from the recurrent parent genome (background selection). In BC1F1 generation, three best plants consiquently were selected from previously selected ten double heterozygous (Xa21 and SUB1 QTL) plants. The percentage of recipient genome recovery in the best plant 1, 2 and 3 were 78.7%, 75.83% and 75.4%, respectively. Eventually this work illustrates the successful application of marker-assisted breeding for introgression of bacterial blight resistant gene into a rice variety of Bangladesh.Bangladesh J. Agril. Res. 42(3): 403-411, September 2017

Climate resilient technological interventions to ensure food security in flood affected area – An experience from NICRA village, Dhubri, Assam

The study was conducted in villages of Dhubri district in Assam under National Innovation on Climate Resilient Agriculture (NICRA) project implemented by Krishi Vigyan Kendra, Dhubri during 2013 to 2015. The villages are situated under Bilasipara sub-division in the district ‘Dhubri’ of Assam, India on 26° 15. 425´ to 26° 16.570´ N latitude and 90° 14.034´ to 90° 18.040´ E longitude at an elevation of 128 ft from mean sea level. Recurrent floods has been the principal constraints in food production in these villages affecting mainly winter ( Kharif ) rice during the growing season as well as summer rice ( Boro and Ahu ) at the time of maturity. The prevailing weather patterns of the area were observed to have a strong bearing on the occurrence, intensity and magnitude of floods. About 71 per cent of total rainfall occurs during monsoon period (June to September), the winter being virtually dry leaving little scope for growing any Rabi crop. To ensure rice production to climatic variability leading to flood, site specific climate resilient technologies such as staggered planting rice variety ‘Gitesh’, flood escaping, short duration HYV rice ‘Luit’ for post and pre-flood situation, submergence tolerant rice variety ‘Swarna Sub 1’ and mid duration HYV of rice ‘Joymati’ during preflood situation were tested and demonstrated in the project villages. It was necessary to observe the performance of these varieties to the climatic vulnerability as well as farmer’s acceptability. The average yield of the rice variety ‘Gitesh’ (45 days aged seedlings), ‘Luit’ (post flood situation), ‘Luit’ (pre-flood situation), ‘Swarna Sub 1’ and ‘Jomati’ were found to be 40 to 42, 26.3 to 36, 23.35 to 31.39, 33 to 45 and 42.37 to 50.76 q per hectare, respectively. As a result of the study and demonstration to endure recurrent flood and climatic variability, the newly introduced winter rice varieties, Gitesh has spread over the highest area in the project villages (90.00%) followed by ‘Swarna Sub 1’ (75.00 %) and ‘Luit’ (66.67 %) due to flexibility in seedling age facilitating delayed transplanting, submergence tolerance upto 14 days and allowance for transplanting after recession of flood, respectively.

Grain Yield, Dry Weight and Phosphorus Accumulation and Translocation in Two Rice (Oryza sativa L.) Varieties as Affected by Salt-Alkali and Phosphorus

Salt-alkali is the main threat to global crop production. The functioning of phosphorus (P) in alleviating damage to crops from saline-alkaline stress may be dependent on the variety of crop but there is little published research on the topic. This pot experiment was conducted to study if P has any effect on rice (Oryza sativa L.) yield, dry matter and P accumulation and translocation in salt-alkaline soils. Plant dry weight and P content at heading and harvest stages of two contrasting saline-alkaline tolerant (Dongdao-4) and sensitive (Tongyu-315) rice varieties were examined under two saline-alkaline (light versus severe) soils and five P supplements (P0, P50, P100, P150 and P200 kg ha−1). The results were: in light saline-alkaline soil, the optimal P levels were found for P150 for Dongdao-4 and for P100 for Tongyu-315 with the greatest grain dry weight and P content. Two rice varieties obtained relatively higher dry weight and P accumulation and translocation in P0. In severe saline-alkaline soil, however, dry weight and P accumulation and translocation, 1000-grain weight, seed-setting rate and grain yield significantly decreased, but effectively increased with P application for Dongdao-4. Tongyu-315 showed lower sensitivity to P nutrition. Thus, a more tolerant variety could have a stronger capacity to absorb and translocate P for grain filling, especially in severe salt-alkaline soils. This should be helpful for consideration in rice breeding and deciding a reasonable P application in saline-alkaline soil.

Simultaneous Improvement and Genetic Dissection of Salt Tolerance of Rice (Oryza sativa L.) by Designed QTL Pyramiding.

Breeding of multi-stress tolerant rice varieties with higher grain yields is the best option to enhance the rice productivity of abiotic stresses prone areas. It also poses the greatest challenge to plant breeders to breed rice varieties for such stress prone conditions. Here, we carried out a designed QTL pyramiding experiment to develop high yielding “Green Super Rice” varieties with significantly improved tolerance to salt stress and grain yield. Using the F4 population derived from a cross between two selected introgression lines, we were able to develop six mostly homozygous promising high yielding lines with significantly improved salt tolerance and grain yield under optimal and/or saline conditions in 3 years. Simultaneous mapping using the same breeding population and tunable genotyping-by-sequencing technology, we identified three QTL affecting salt injury score and leaf chlorophyll content. By analyzing 32M SNP data of the grandparents and graphical genotypes of the parents, we discovered 87 positional candidate genes for salt tolerant QTL. According to their functional annotation, we inferred the most likely candidate genes. We demonstrated that designed QTL pyramiding is a powerful strategy for simultaneous improvement and genetic dissection of complex traits in rice.

Variability of upland rice genotypes response to low light intensity

Hairmansis A, Yullianida, Supartopo, Jamil A, Suwarno. 2017. Variability of upland rice genotypes response to low light intensity. Biodiversitas 18: 1122-1129. Plantation areas have a great potential to be utilized for upland rice production through intercropping. One of major constraints in the cultivation of upland rice as intercropping is low light intensity caused by shading. Improvement of rice varieties for shading tolerance is therefore important to increase rice production in upland areas. The objective of this study was to investigate the variability of upland rice genotypes responses to shading and identify the best genotypes for intercropping rice cultivation. Thirty-eight upland rice breeding lines, the shading tolerant rice variety Jatiluhur, and the shading susceptible rice variety IR64 were evaluated for their response to low light intensity in the greenhouse and the field. Greenhouse screening was conducted to determine their shading tolerance in vegetative stage while evaluation in the field was performed to evaluate their agronomic performance under 55% shading and normal conditions. Variation in upland rice genotypes on low light stress was revealed both in greenhouse and field trials. In the greenhouse trial, 12 genotypes showed higher survival rate compared to tolerant rice variety Jatiluhur. Field evaluation demonstrated that 55% shading increased plant height, reduced productive tiller number, delayed flowering time, increased spikelet sterility and reduced grain yield. Upland rice breeding line B11908F-TB-3-WN-1 showed high yield relative in shading condition compared to normal condition and had high-stress tolerance index (STI) which indicated the genotype was tolerant to shading.

Development of Flood Tolerant Rice Variety: An Enhancement to Food Security in Nigeria

High yielding rain-fed lowland rice cultivars are sensitive to complete submergence stress of more than four days. In Nigeria, rice farms on about 3.6 million ha of rain-fed lowland areas are adversely affected by submergence stress. Consequently, farmers in the major rice producing states of the country lose their entire crop to flooding each year. The identification of a major quantitative traits locus (QTL) on chromosome 9, designated as sub1, has provided the opportunity to apply marker assisted selection to develop submergence tolerant varieties. This study was undertaken to introgress sub 1 into the genetic background of Nigerian lowland rice mega variety (WITA 4) and assess the ability of WITA 4 with sub 1 to withstand submergence stress. Swarna Sub1, one of the FR13A-derived submergence tolerant varieties developed by IRRI, was crossed to WITA 4, a submergence intolerant Nigerian mega variety to produce F1 hybrid. The derived BC1F2 progenies were genotyped and BC1F3 phenotyped. The results of genotyping, using two markers, namely ART5 and SC3, revealed that 18 BC1F3 plants were found carrying Swarna Sub 1 allele of ART5 while 41 BC1F3 carried WITA 4 allele of ART5. Twenty progenies were found carrying Swarna Sub 1 allele of SC3 while 37 plants carried WITA 4 allele. Two plants carried both alleles (H). Seventeen plants were observed to carry Swarna Sub 1 alleles at both markers loci while a total of 36 progenies were observed to carry WITA 4 alleles at both markers loci. The results of the phenotypic screening showed that 12 plants recorded percentage survival above 60%. The two markers showed high selection accuracies, and selection based on the markers could satisfactorily meet the needs of breeding for submergence.

Determinants and implications of crop production loss: An empirical exploration using ordered probit analysis

This study investigates farmers’ perception about the severity of loss for three rice crops, identifies their determinants and explores policy implications based on findings. This research employs an ordered probit model to data collected from 1800 farm households from drought-prone and groundwater depleted areas of Bangladesh. This is the first study of its kind.Severity of rice production loss, while differing across all three rice crops, was higher for rain-fed crops. This was broadly consistent with available independent evidence. Geophysical factors, household characteristics, institutional and market accessibility, and household adaptation strategy were key determinants of crop loss. The impact of these factors was specific to the crop and severity of loss.This study has several policy implications involving market, R & D and institutional support based options. Strengthening support systems for institutional and market accessibility, and science driven climate change adaptation strategy including generation and wider dissemination of drought tolerant rice varieties, and enhancing farmers’ capacity to change rice varieties on a regular basis, constitute key areas for policy intervention.

Characterization of Salt-Induced Epigenetic Segregation by Genome-Wide Loss of Heterozygosity and its Association with Salt Tolerance in Rice (Oryza sativa L.).

In a breeding effort to develop salt tolerant (ST) rice varieties by designed QTL pyramiding, large numbers of progenies derived from four crosses between salt- or drought- tolerant BC2F5 IR64 introgression lines, were subjected to severe salt stress, resulting in 422 ST plants. The progeny testing of the selected F3 lines under more severe salt stress resulted in identification of 16 promising homozygous lines with high levels of ST. Genetic characterization of the 422 ST F3 progeny and 318 random F2 plants from the same four crosses using 105 segregating SSR markers lead to three interesting discoveries: (1) salt stress can induce genome-wide epigenetic segregation (ES) characterized by complete loss of heterozygosity (LOH) and nearly complete loss of an allele (LOA) in the F3 progenies of four rice populations in a single generation; (2) ∼25% of the stress-induced ES loci were transgenerational and inherited from their salt- and drought- selected parents; and (3) the salt-induced LOH and LOA loci (regions) appeared to contain genes/alleles associated with ST and/or drought tolerance. 32 genomic regions that showed one or more types of salt-induced ES in the random and salt-selected progenies from these crosses. The same or different types of ES were detected with two large genomic regions on chromosomes 1 and 6 where more and the strongest ES were found across different populations. 14 genomic regions were found where the salt-induced ES regions were overlapping with QTL affecting ST related traits. The discovery of the three types of salt-induced ES showed several interesting characteristics and had important implications in evolution and future breeding for developing stress-resilient rice and crops.