Drought-tolerant Lines Research Articles

Identification of Drought Tolerant Mutant Lines of TEF [ERAGROSTIS TEF (ZUCC.) TROTTER


 
 
 Introduction: Tef [Eragrostis tef (Zucc.) Trotter] is the major food crop in Ethiopia where it is annually cultivated on about 30% of the total area allocated to cereals. The productivity of tef is, however, significantly reduced by drought which can occur at either the early or the late developmental stage of the crop.
 Methodology: A total of 10,000 EMS (ethyl methane sulfonate) mutagenized M2 tef populations were screened first for early and second for terminal drought tolerance. The performance of candidate lines was investigated using diverse agronomical and physiological parameters.
 Results and discussion: Several promising lines were obtained for both early and terminal drought tolerance. Among these, genotypes with outstanding performance were found for two drought tolerant tef lines targeting early drought tolerance (dtt2 and dtt13) and three terminal drought tolerant lines targeting terminal drought tolerance (tdt9, tdt15 and tdt19).
 Conclusions: Candidate lines for both early and terminal drought tolerance will play vital roles in deve- loping drought tolerance in tef improvement.
 KEY WORDS: DROUGHT TOLERANCE, ERAGROSTIS TEF, ORPHAN CROP, MOISTURE SCARCITY, TEF
 
 

Drought Tolerance Screening of Maize Inbred Lines at an Early Growth Stage

Drought is one of the major abiotic factors that have a serious effect on the production of cereals crops including maize, which is grown widely in the world. Screening based on drought facilitates selection of inbred lines and an understanding of drought­tolerant traits. The effect of drought stress and rescue after stress on maize inbred lines was investigated in this study. Different plant growth attributes namely plant height, leaf area and weight, stem weight, root length, shoot and root fresh and dry weight, and total leaf chlorophyll content were measured. Six flint inbred lines (FLD 12, FLD 23, FLD 24, FLD 33, FLD 35, and FLD 37) were screened as drought-tolerant lines, whereas another six flint inbred lines (FLD 01, FLD 13, FLD 16, FLD 18, FLD 29, and FLD 31) were screened as drought susceptible lines. Growth attributes under different drought conditions were subjected to a correlation test and analysis of variance and showed highly significant relationships with each other. The drought effect differed with different inbred lines, indicating a wide variability of drought response at the early growth stage of maize plants. The results obtained from this study will be useful for selecting maize inbred lines in future breeding programs for enhancing drought tolerance.

GALUR-GALUR MUTAN PADI PADA KONDISI SAWAH TADAH HUJAN

Evaluation some mutant rice lines on rainfed area. Some mutant rice lines are expected to have good adaptability in the rainfed areas. Evaluation of drought tolerant rice lines in the rainfed land has been conducted in District Jakenan, Pati, Central Java in DS 2014. The Study used a randomized experimental design with 2 replications treatment 38 drought tolerant mutant rice lines and four varieties for the check. Mutant lines were evaluated coming from Co60 gamma-rays against Inpari 13. Varieties for check used is Inpari 13, Inpari 10, Inpari 23, and Situ Bagendit. Seedling age 20 days after sowing of each line and varieties grown as much as 1-3 seeds per hole on a plot measuring 2 m x 5 m with a spacing of 20 cm x 20 cm. Watering depends on rain and pump water from rainwater reservoir. The results showed that the lines tested had noticeable difference to the five agronomic characters were observed, but no real character number of productive tillers. A total of 13 genotypes showed higher yields than all varieties. Two genotypes showed a different result was significantly higher than Inpari 13 are BP17280M-26D-1-SKI-1-IND-1 (3.89 t / ha) and BP17280M-24C-2-1-SKI-1-IND- 1 (3.54 t / ha). While the best varieties Inpari 13 and Situ Bagendit achieve respectively 2.88 t / ha and 3.04 t / ha. The average best genotypes age at 50% flowering is 68-70 DAS and harvest age is HSS 98-104. With this result is expected to give a great chance on the tests subsequent to the development of new varieties of rainfed rice.

Transcriptomic analysis of Eruca vesicaria subs. sativa lines with contrasting tolerance to polyethylene glycol-simulated drought stress

BackgroundEruca vesicaria subsp. sativa is one of the Cruciferae species most tolerant to drought stress. In our previous study some extremely drought-tolerant/sensitive Eruca lines were obtained. However little is known about the mechanism for drought tolerance in Eruca.MethodsIn this study two E. vesicaria subs. sativa lines with contrasting drought tolerance were treated with liquid MS/PEG solution. Total RNA was isolated from 7-day old whole seedlings and then applied to Illumina sequencing platform for high-throughput transcriptional sequencing.ResultsKEGG pathway analysis indicated that differentially expressed genes (DEGs) involved in alpha-Linolenic acid metabolism, Tyrosine metabolism, Phenylalanine, Tyrosine and tryptophan biosynthesis, Galactose metabolism, Isoquinoline alkaloid biosynthesis, Tropane, Piperidine and pyridine alkaloid biosynthesis, Mineral absorption, were all up-regulated specifically in drought-tolerant (DT) Eruca line under drought stress, while DEGs involved in ribosome, ribosome biogenesis, Pyrimidine metabolism, RNA degradation, Glyoxylate and dicarboxylate metabolism, Aminoacyl-tRNA biosynthesis, Citrate cycle, Methane metabolism, Carbon fixation in photosynthetic organisms, were all down-regulated. 51 DEGs were found to be most significantly up-regulated (log2 ratio ≥ 8) specifically in the DT line under PEG treatment, including those for ethylene-responsive transcription factors, WRKY and bHLH transcription factors, calmodulin-binding transcription activator, cysteine-rich receptor-like protein kinase, mitogen-activated protein kinase kinase, WD repeat-containing protein, OPDA reductase, allene oxide cyclase, aquaporin, O-acyltransferase WSD1, C-5 sterol desaturase, sugar transporter ERD6-like 12, trehalose-phosphate phosphatase and galactinol synthase 4. Eight of these 51 DEGs wre enriched in 8 COG and 17 KEGG pathways.ConclusionsDEGs that were found to be most significantly up-regulated specifically in the DT line under PEG treatment, up-regulation of DEGs involved in Arginine and proline metabolism, alpha-linolenic acid metabolism and down-regulation of carbon fixation and protein synthesis might be critical for the drought tolerance in Eruca. These results will be valuable for revealing mechanism of drought tolerance in Eruca and also for genetic engineering to improve drought tolerance in crops.

Parent-offspring regression, correlation and genetic advance of drought and yield traits at early generation in groundnut (Arachis hypogaea L.)

A study was carried out to estimate the parent-offspring regression and correlation and, to determine genetic advance of yield and drought related traits of groundnut at early segregating populations. All the experiments were conducted in the dry season 2015/2016 at the International Crops Research Institute for the Semi-Arid Tropics ICRISAT Samanko, Mali under full irrigation and drought stress conditions. The data were collected on plot basis on both water-stressed and fully irrigated plots in the F1, F2 and F2:3 generations of two populations. Data collected included chlorophyll concentration (SCMR), Specific Leaf Area (SLA) (cm2/g) and Pod Yield (PY)(kg/ha). Results of the parent offspring regression for the two populations evaluated both water regimes were low and revealed importance of non-genetic effects. Consequently, the genetic advances for the two crosses were mostly low to moderate irrespective of the generation and environment under study. Selection at early generation in groundnut could be slow under drought. Based on the findings, selection for drought tolerance would be inefficient to identify high yield and drought tolerant lines at early generation in groundnut. The highest heritability estimates for F1:F2 were 42% for SCMR 60 DAS and at 80 DAS under well-watered conditions, 20% ± 0.20 for SLA at 60 DAS and at 80 DAS under drought stressed conditions. The highest heritability estimates for F2:F3 progenies were observed from SCMR 60 DAS (22% ± 0.09) under well-watered conditions and SLA 60 DAS (22% ± 0.08) under water-stressed conditions. Key words: Groundnut, heritability, drought stress, breeding.

Yield and Response of Bean Breeding Lines for Drought Tolerance to Field Diseases

Climate change has resulted in an increase in the intensity of droughts and rains, and higher temperatures which are adversely affecting crop production in Africa. It has also influenced the distribution and increased the occurrence of disease and pest epidemics. Common bean (Phaseolus vulgaris L.) is especially sensitive to these changes. Most released varieties are not well adapted to environmental extremes and extended periods of drought in particular has become a major constraint. In this study, 462 advanced breeding lines developed for drought tolerance were evaluated for yield, agronomic traits and disease response in two contrasting agro-ecologies, Kawanda in the Lake Victoria crescent and Kachwekano in the southwestern highlands. Analysis of variance indicated significant differences (P < 0.05) among lines for most variables and environments (P < 0.001). Performance was better at Kachwekano than Kawanda with mean yields ranging from 928 to 2251 kg ha-1, and 698 to 2036 kg ha-1 respectively. Angular leafspot, common bacterial blight and rust diseases varied between locations, and among lines with no visible to sever symptoms. Based on Wricke’s ecovalence estimates for stability, SCN20, SCN13, SEN114, SEC40 and SEC35 expressed yield stability and superiority. Of the 462 lines, 6.3 % maintained >1500 kg ha-1, the minimum anticipated commercial yield of new varieties, in all the trials, both seasons and in each year; 5.0 % also maintained above average yields. The most outstanding (1629-3944 kg ha-1) were; DAB299, DAB291, DAB234, DAD34, DAB478, DAB487, DAB543, DAB231, SCN20, SCR66, SCR60, and SER335. These are recommended for development of new varieties.

Comparative proteome analysis of drought-sensitive and drought-tolerant maize leaves under osmotic stress

Drought is a major yield-limiting factor in maize production. Osmotic stress was applied to two maize inbred lines with polyethylene glycol 6000 treatments. Proteins from the leaves were analyzed by two-dimensional gel electrophoresis and peptide mass fingerprinting at two time points, 24 and 48 h after osmotic stress. Thirty-five proteins were differentially expressed between control and treatment groups in the two maize inbred lines. In ‘Qi319’, a drought-tolerant inbred line, there were five up-regulated proteins at 24 h and 13 up-regulated and one down-regulated protein at 48 h. In drought-sensitive line ‘Zheng58’, 10 proteins were up-regulated at 24 h, while six proteins were up-regulated at 48 h. The 35 proteins were subjected to mass spectrometry and 17 proteins were successfully identified. These proteins were classified into six categories: photosynthesis-related, energy and metabolism, signaling pathways, protein synthesis, defense-related, and unclassified.

Study of broad sense heritability and genetic advance for grain yield and yield components of drought tolerant tef [Eragrostis tef (Zucc.) Trotter] genotypes

Genetic variability is a pre-requisite to crop improvement. The objective of the present study was to assess and quantify the genetic variability, estimate heritability and genetic advance for yield and yield contributing characters of drought tolerant tef genotypes based on agro-morphological traits. A total of 49 tef materials [(42 drought tolerant tef advanced lines, the parents of the advanced lines (Dtt2, Dtt13, Quncho and the cultivar Kaye Murri), two varieties (Tsedey and Simada) released for low moisture area and a local check cultivar from each location)] were planted in 7 x 7 simple lattice design at Melkassa and Alemtena in the Central Rift Valley of Ethiopia. Important agronomic data were collected and subjected to analysis using statistical analysis software (SAS). The combined analysis of variance (ANOVA) over locations showed significant location and genotype main effects (P≤0.01) for most of the traits. The genotype x location interaction effect was not significant (P> 0.05) for all traits evaluated, except for days to physiological maturity and number of primary panicle branches per main shoot. Phenotypic coefficients of variation (PCV) and genotypic coefficient of variation (GCV) for the characters such as days to physiological maturity, number of fertile tillers per plant and days to seedling emergence showed very small difference demonstrating that the observed variations for these traits were mostly due to genetic factors with little impact of environment. High heritability and genetic advance were noted for panicle length and days to heading signifying the ease of phenotype-based selection for the improvement of those traits.

Regeneration of rice somaclons tolerant to high level of abscisic acid and their characterization via RAPD markers

BackgroundThe main objectives of this study were to compare two in vitro selection procedures for developing drought-tolerant cell lines from rice cultivars, regenerate plants from the selected cells, and use the random amplified polymorphic DNA (RAPD) method for genetic characterization of somaclons. Callus was derived from mature embryo cultures of tow Egyptian rice cultivars, Sakha 102 and Giza 178.ResultsThe direct in vitro selection method indicated that the callus weight of the two cultivars was significantly decreased in response to increasing ABA concentrations. The shoot formation revealed significant differences among ABA concentrations and highly significant for interaction between rice cultivars and ABA concentrations. The percentage of shoot formation either increased or decreased with increasing ABA levels in rice cultivars. However, Giza 178 cultivar was slightly stable for shoot formation than the cultivar Sakha 102. The obtained results for stepwise selection method indicated also that the shoot formation was obtained till 6 mg/L ABA. The results of the RAPD analysis indicated that the rice cultivars and their somaclons were classified into tow clusters. The polymorphic information content (PIC) per primer ranged from 0.715 to 0.906 with an average of 0.860. The results of UPGMA clustering were consistent with those of the PCoA.ConclusionsThe percentage for Sakha 102 was 10.8, 7.7, and 2.2% on 2, 4, and 6 mg/L ABA, respectively, and was 16.4, 10.0, and 3.4% for Giza 178 cultivar, at the ABA concentrations of 2, 4, and 6 mg/L, respectively. The genetic similarity among the fifteen genotypes ranged from 0.30 to 0.82. Rice cultivars and their somaclons were classified into five clusters.

Drought Yield QTL (qDTY) with Consistent Effects on Morphological and Agronomical Traits of Two Populations of New Rice (Oryza sativa) Lines.

Drought has been a major limiting factor for rice production. Drought yield QTLs (qDTYs; QTLs = quantitative trait loci) were pyramided into MRQ74 and MR219 to produce drought tolerant lines. In this study, new drought tolerant MRQ74 and MR219 pyramided lines (PLs) were evaluated under drought stress (RS) and non-stress (NS) conditions to evaluate the effects of different qDTYs combinations on morphological and agronomical traits. MRQ74 PLs having qDTY12.1 possessed the best root length (RL) under both RS and NS but the effect was only significant for MR219 PLs under RS. Some qDTYs combinations also found to have consistent effect on the same trait of both populations. PLs with only qDTY12.1 showed the highest grain yield (GY) under RS in both populations which means qDTY12.1 controlled RL and caused higher GY under drought condition. The interaction of major-effect qDTY12.1 with qDTY2.2 also shows significant effect on leaf rolling (LR) of both PL populations. These qDTYs proved to be beneficial in improving traits related to drought tolerance. Selected PLs with qDTY12.1 combinations also found to have better RL and root weight (RW) under RS. Improvement of morphological and agronomical traits led to higher GY of PLs. Therefore, qDTY12.1 either is present singly or in combination with other qDTYs was the best qDTY due to its consistent effect on morphological and agronomical traits and GY across populations under RS and NS.

Genetic characterization and population structure of maize populations using SSR markers

Maize is a major staple food in sub-Saharan Africa. However, due to the threats posed by biotic and abiotic constraints to its production, it is a prerequisite to conserve germplasm with diverse genetic background and to seek for favourable genotypes with such background for improvement of superior genotypes. This study assessed the diversity of 70 white maize populations developed at CSIR-Savanna Agricultural Research Institute with resistance/tolerance to drought and low soil nitrogen (Low-N) using 31 SSR markers. A total of 288 alleles were detected among the germplasm used with a range of 4 to 17 alleles per locus and an average allele number of 9.60 alleles per locus. Polymorphic Information Content values for the SSR markers ranged from 0.32 to 0.85 with a mean value of 0.68. The average heterozygosity obtained from the markers was 0.54 and gene diversity ranged from 0.35 to 0.87 with a mean gene diversity value of 0.71 indicating a high level of polymorphism among the populations. Clustering based on Jaccard's similarity coefficient and an Unweighted Pair Group Method with Arithmetic Mean (UPGMA) revealed 5 clusters for the 70 populations. Evanno method for population structure clustering further revealed two sub-populations. Sub-population 1 was more genetically diverse with an Fst value of 0.18 than sub-population 2 which recorded an Fst value of 0.013. These results indicated that the SSR used were very polymorphic for diversity studies. Also, the studied maize populations are diverse and heterozygous, making them ideal source populations for extraction of drought and low-N tolerant inbred lines.

Evaluation of Drought Tolerance in Arkansas Cowpea Lines at Seedling Stage

Cowpea [Vigna unguiculate (L.) Walp.] is not only a healthy, nutritious, and versatile leguminous crop; it also has a relatively high adaptation to drought. Research has shown that cowpea lines have a high tolerance to drought, and many of them can survive more than 40 days under scorching and dry conditions. The cowpea (Southern pea) breeding program at the University of Arkansas has been active for more than 50 years and has produced more than 1000 advanced breeding lines. The purpose of this study was to evaluate the drought-tolerant ability in Arkansas cowpea lines and use the drought-tolerant lines in cowpea production or as parents in cowpea breeding. A total of 36 University of Arkansas breeding lines were used to screen drought tolerance at the seedling stage in this study. The experiment was conducted in the greenhouse using a randomized complete block design (RCBD) with two replicates, organized in a split-plot manner, where the drought treatment (drought and nondrought stress) as the main plot and the cowpea genotypes as the subplot. Drought stress was applied for 4 weeks, and three drought-tolerant–related traits were collected and analyzed. Results showed that cowpea breeding lines: ‘17-61’, ‘17-86’, ‘Early Scarlet’, and ‘ARBlackeye #1’ were found to be drought tolerant.

Molecular profiling in relation to drought tolerance in advance breeding lines of rice using microsatellite markers

Using agro-morphological characters and microsatellite markers, advance breeding lines of rice were discriminated for their ability to tolerate drought stress at reproductive stage. Experimental materials consisting of 17 advance breeding lines and a check were evaluated in randomized block design with three replications under irrigated condition and drought condition created under rainout shelter during three consecutive years. An analysis of variance revealed significant differences among the genotypes for all the ten agro-morphological characters evaluated under both the conditions across the years. Principal component analysis showed the relative importance of root length, number of tillers per plant, number of grains per panicle, harvest index and grain yield per plant among agro-morphological characters and stress tolerance level, stress susceptibility index, stress tolerance index and drought tolerance efficiency among drought tolerance indices as the important classification variables. Relative mean performance in respect of grain yield as well as drought tolerance indices reflected remarkably greater degree of drought tolerance in 11 advance breeding lines and the check, discriminating them from remaining entries under evaluation. Utilizing a panel of 32 microsatellite primers, selective amplification of targeted genomic regions revealed that the primers RM 72, RM 163, RM 212, RM 225, RM 231, RM 302, RM 327, RM 518, RM 521, RM 555, RM 1349, RM 3549 and RM 5443 were highly informative with greater gene diversity and discrimination ability. Hierarchical cluster analysis based on molecular profiles discriminated the entries into five genotypic groups and drought tolerant entries were accommodated into three distinct groups with remarkably greater efficiency (85.7%). Principal coordinate analysis based two dimensional plots of microsatellites dependent genetic profiles displayed a very close correspondence with the genotypic clustering pattern revealed from a perusal of dendrogram. Sequential exclusion of primers in cluster analysis led to identification of RM 212, RM 231, RM 324, RM 431, RM 521, RM 3549 and RM 6374 as the most useful primers for discrimination of drought tolerant and susceptible lines of rice. Molecular profiling based on these markers can be utilized as efficient tools for discrimination and identification of drought tolerant lines.

Drought Stress Tolerance Screening of Elite American Breeding Rice Genotypes Using Low-Cost Pre-Fabricated Mini-Hoop Modules

Drought is a major abiotic stress factor affecting the growth and development of plants at all stages. Developing a screening tool for identifying drought stress tolerance during seedling establishment is important in the deployment of rice varieties suited to water-limited growing environments. An experiment was conducted to evaluate 100 rice genotypes, mostly belonging to the tropical japonica subspecies, for drought stress tolerance using low-cost, pre-fabricated mini-hoop structures. The rice seedlings were subjected to two different soil moisture regimes- control pots managed at 100% and drought pots at 50% field capacity, from 12 to 30 days after sowing (DAS). Several morpho-physiological parameters including root traits were measured to assess the response of genotypes to drought stress. Significant moisture stress × genotype interactions were found for most of the parameters measured. A cumulative drought stress response index (CDSRI) was developed by adding the individual response indices of all cultivars. Based on CDSRI and standard deviation values, 5 and 28 genotypes were identified as highly sensitive and sensitive to drought, respectively, and 45 as moderately sensitive. On the other hand, 16 and 6 genotypes were classified as tolerant and highly tolerant to drought, respectively. Cheniere, a released cultivar, and RU1402174, an experimental breeding line, were identified as the least and most tolerant to drought among the 100 genotypes tested. Significant linear correlation coefficients were obtained between CDSRI and root growth parameters (R2 = 0.91, n = 100) and CDSRI with shoot growth parameters (R2 = 0.48, n = 100), revealing the importance of root traits in studying and identifying drought tolerant lines during the seedling establishment stages in rice. The tolerant rice genotypes identified will be valuable for rice scientists in studying the mechanism for early season drought as well as for rice breeders for developing new genotypes best suited under growing environments prone to early-season drought.

Making Crops Climate Ready

Making Crops Climate Ready

Identification of Drought Tolerant Mutant Lines of Tef [Eragrostis Tef (Zucc.) Trotter

Introduction: Tef [Eragrostis tef (Zucc.) Trotter] is the major food crop in Ethiopia where it is annually cultivated on about 30% of the total area allocated to cereals. The productivity of tef is, however, significantly reduced by drought which can occur at either the early or the late developmental stage of the crop. Methodology: A total of 10,000 EMS (ethyl methane sulfonate) mutagenized M2 tef populations were screened first for early and second for terminal drought tolerance. The performance of candidate lines was investigated using diverse agronomical and physiological parameters. Results and discussion: Several promising lines were obtained for both early and terminal drought tolerance. Among these, genotypes with outstanding performance were found for two drought tolerant tef lines targeting early drought tolerance (dtt2 and dtt13) and three terminal drought tolerant lines targeting terminal drought tolerance (tdt9, tdt15 and tdt19). Conclusions: Candidate lines for both early and terminal drought tolerance will play vital roles in developing drought tolerance in tef improvement.

English

The use of multiple traits for drought study affirms the complexity of drought tolerance in cowpea. Despite the availability of several traits for drought tolerance evaluation, the rapid screening technique used by many scientists for seedling drought in wooden boxes is the simplest method for screening large populations. The objective of this study was to select drought tolerant cowpea recombinant lines developed from a drought tolerant and susceptible parent using the wooden box screening technique. Two hundred Recombinant Inbred Lines (RILS) an F2:6 generation were used for the study. The parents were drought tolerant line crossed with susceptible line. Screening was done in wooden boxes and plants stressed for 4 weeks and in two sessions. Leaf wilting, relative water content, chlorophyll content during stress, and recovery from drought data were taken. Results from this study showed significant differences (p < 0.05) for relative chlorophyll content for the 4 weeks of water stress and relative water content taken on the second week of water stress for all 200 inbred lines, but no significant differences were observed for the parental checks. Relative water contents taken for RILS during water-stress ranged between 70-20% for drought tolerant and drought susceptible lines respectively. The parental lines used as checks both had relative water contents of 60%. Relative water content for the second experiment ranged between 74-22% for tolerant and susceptible RILS respectively. About 12 inbred lines consistently performed well for recovery, 13 RILS were susceptible. RILS that maintained a higher relative water and chlorophyll contents, with high proportion of survived seedlings were 11. Potential seedling drought tolerant RILS have been identified. Key words:  Cowpea, leaf wilting, chlorophyll, recombinant inbred lines, drought tolerance, relative water content. &nbsp

Genome-wide identification of the glutathione transferase superfamily in the model organism Brachypodium distachyon.

The detoxification of harmful metabolites can determine the effectiveness of plant stress responses. Scavenging some of these toxic stress by-products through the reduced form of glutathione is catalysed by members of the glutathione transferase (GST) enzyme superfamily. The involvement of these enzymes was studied in the model organism Brachypodium distachyon (L.)P.Beauv. Bd21 and in its derivative Bd21-3, a more drought tolerant line. Osmotic stress treatment resulted in a decrease in the water potential of both Brachypodium genotypes, the difference between the control and treated plant's ψw decreased by the last sampling day in Bd21-3, suggesting some degree of adaptation to the applied osmotic stress. Increased GST activity revealed a severe defence reaction against the harmful imbalance of the redox environment. Screening for the gene sequences led to the identification of 91 full-length or partial GST sequences. Although purple false brome has a relatively small genome, the number of identified GST genes was almost as high as the number predicted in wheat. The estimation of GST expression showed stress-induced differences: higher expression levels or the fast induction of BdGSTF8, BdGSTU35 and BdGSTU42 gene products presumably indicate a strong detoxification under osmotic stress.

Evaluation of rice genotypes for seedling and reproductive stage drought tolerance

The present investigation was undertaken to evaluate 25 drought tolerant genotypes for seedling stage and reproductive stage drought tolerance. The genotypes were evaluated under gravimetric method at three moisture levels viz., i) control at 100% field capacity (FC) ii) water-deficit stress at 80% Field capacity (80% FC) and iii) water-deficit stress at 60% Field capacity (60% FC) for seedling stage drought tolerance. Observations were recorded on six morphological traits viz., seedling height, root length, shoot length, dry weight, leaf rolling and leaf drying and three physiological traits viz., chlorophyll stability index, proline content and nitrate reductase activity. The variety, APO and landraces viz., Kuliyadichan, Kattanur and Sivappuchithiraikar were identified with all desirable drought tolerant seedling traits and these genotypes also had high stress tolerance index (STI) for all the morphological traits. For reproductive stage drought tolerance, the moisture stress was imposed under field condition. Yield characters viz., number of days to maturity, panicle length, spikelet fertility and single plant yield and three physiological traits viz., chlorophyll stability index, proline content and nitrate reductase activity were recorded. Based on stress tolerance index (STI) and high mean performance, varieties viz., Anna (R) 4 and APO and landraces viz., Kattanur, Kuliyadichan and Sivappuchithiraikar were identified as drought tolerant lines for reproductive stage drought tolerance. From this study, APO, Kattanur, Kuliyadichan and Sivappuchithiraikar were identified as drought tolerant lines for seedling stage as well as reproductive stage. Therefore, these genotypes can be used as potential donors in the development of new drought tolerant varieties in rice.

Effect of intermittent drought on phenotypic traits of F5 RIL Andean intra-gene cross population (BRB 191 X SEQ 1027) of common bean

Drought is a major constraint to common bean ( Phaseolus vulgaris L.) production in East Africa, where irrigation for the crop is very uncommon. The objective of this study was to identify drought tolerant lines and phenotypic traits underlying drought tolerance among 128 F5 recombinant inbred lines (RILs), derived from intra gene pool population, between drought tolerant BRB 191 (source of bc-3) and SEQ 1027. The population was evaluated with eight experimental checks that included BAT 477, CAL 96, DAB 441, DAB 494, and Diacol Calima, NABE 4, SCR 9 and SEQ 1003. A total of 20 phenological, morphological and physiological shoot traits were evaluated, under drought and non-stress conditions, in the field for 2 years (2014 and 2015) at Kawanda in Uganda. New sources of drought tolerance, and previously identified sources of drought tolerance in common bean (BAT 477, DAB 441 and DAB 494), were confirmed based on their superior geometric means and low drought susceptibility. Drought stress in the field significantly affected all measured traits, except harvest index and stem dry weight reduction (P<0.001). Drought significantly reduced yield, yield components and pod harvest index (P<0.01). However, chlorophyll content, canopy temperature, stem dry mass reduction, and 100 seed weight remained stable under season by genotype by water regime treatment interactions (S x G x T). The stability of these traits highlighted their usefulness in selecting for drought tolerance across different environments. Furthermore, pod partitioning index (PPI), harvest index (HI), chlorophyll content and stem dry weight reduction also remained stable under G x T effects. Significant correlations (P<0.001) were maintained between HI and PPI with seed yield under drought stress in field conditions, indicating that photosynthate remobilisation increases yield under drought stress conditions. Key words: Phaseolus vulgaris , photosynthate remobilisation