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Quantification of drought tolerance in Ethiopian common bean varieties  [PDF]
Asrat Asfaw, Matthew W. Blair
Agricultural Sciences (AS) , 2014, DOI: 10.4236/as.2014.52016
Abstract:

Understanding the level of drought tolerance of the varieties available in each country is of paramount importance for breeding common bean for drought adaptation. The goal of this study was to evaluate 25 common bean genotypes of which 24 were released/recommended varieties for production by farmers and one was a drought tolerant check. The genotypes were planted at two sites in Ethiopia, Hawasssa and Amaro, using variable sowing dates, one that was early to avoid drought and one that was late to expose the crop to drought. The experiments were repeated over two years in Hawassa and one year in Amaro. This resulted in treatments with high and low total seasonal rainfall and six environments for analysis. The impact of drought stress on the trait expression of the varieties was not uniform across traits assessed and varieties tested. The effect of drought on photosynthate translocation and partitioning traits was much greater than on yield component traits in the varieties studied. This indicating less breeding efforts has been made in improving the varieties ability to mobilize photosynthate to the developing grain as compared to the yield component traits. Drought tolerant varieties like Hawassa Dume maintained better photosynthate translocation and partitioning than the drought sensitive varieties like Brown Speckled bean. Hawassa Dume also showed better yield stability and performed well under both drought stress and nonstress conditions. Our results indicate the relevance of high levels of photosynthate translocation and partitioning as an effective selection objective for improving drought tolerance in common bean. The information generated on the drought tolerance of the available varieties should help in the design of a breeding strategy that incorporates adaptation traits with commercial characteristics preferred by common bean farmers for varieties to be grown in diverse environments.

Behavior of Bread Wheat (Triticum aestivum L.) Male Sterilized with Cytoplasmic-genetic and Chemical Systems and Their Impact in Hybrid Seed Production
Asfaw Adugna
Asian Journal of Plant Sciences , 2005,
Abstract: In this study the two pollination control systems, i.e. Cytoplasmic Male Sterility (CMS) and the use of Chemical Hybridizing Agents (CHA), were compared to discover their efficiency for the sterility reaction and their impacts in hybrid seed production. The result has shown that both systems were equally effective in their sterility performance. However, CHA resulted in reduced out crossing percentage due to female sterility, germination percentage and hundred seed weight of the hybrid seed due to toxicity. Overall the CMS system was better than the CHA system (based on the particular CHA used in this study) for attributes related to hybrid seed production.
Alternate Approaches in Deploying Genes for Disease Resistance in Crop Plants
Asfaw Adugna
Asian Journal of Plant Sciences , 2004,
Abstract: Plant breeders are much concerned about the durability of the resistance gene(s) that they are incorporating into the better performing backgrounds to tolerate biotic stresses. While resistance that is controlled by a single major gene (vertical resistance) is simple to achieve, the one controlled by poly genes (horizontal resistance) is not. There are a number of ways to make the non-durable resistance genes durable. Comprehensively, the exploitation of genes with known durability, the use of quantitative resistance and the use of gene deployment are suggested to be some of them that can lead to the better ways of achieving durability of resistance. There are also various approaches of deploying genes to achieve durability of resistance. Therefore, to realize durability of disease resistance genes in crop plants any one of the approaches that are dealt in this study can be used without compromising their economic feasibility.
Lateral phase separation of confined membranes
Mesfin Asfaw
Physics , 2010, DOI: 10.1142/S0217979211057864
Abstract: We consider membranes interacting via short, intermediate and long stickers. The effects of the intermediate stickers on the lateral phase separation of the membranes are studied via mean-field approximation. The critical potential depth of the stickers increases in the presence of the intermediate sticker. The lateral phase separation of the membrane thus suppressed by the intermediate stickers. Considering membranes interacting with short and long stickers, the effect of confinement on the phase behavior of the membranes is also investigated analytically.
Modeling an efficient Brownian heat engine
Mesfin Asfaw
Physics , 2008, DOI: 10.1140/epjb/e2008-00308-5
Abstract: We discuss the effect of subdividing the ratchet potential on the performance of a tiny Brownian heat engine that is modeled as a Brownian particle hopping in a viscous medium in a sawtooth potential (with or without load) assisted by alternately placed hot and cold heat baths along its path. We show that the velocity, the efficiency and the coefficient of performance of the refrigerator maximize when the sawtooth potential is subdivided into series of smaller connected barrier series. When the engine operates quasistatically, we analytically show that the efficiency of the engine can not approach the Carnot efficiency and, the coefficient of performance of the refrigerator is always less than the Carnot refrigerator due to the irreversible heat flow via the kinetic energy.
Thermally activated barrier crossing and stochastic resonance of a flexible polymer chain in a piecewise linear bistable potential
Mesfin Asfaw
Physics , 2010, DOI: 10.1103/PhysRevE.82.021111
Abstract: We study the stochastic resonance (SR) of a flexible polymer chain crossing over a piecewise linear bistable potential. The dependence of signal to noise ratio $SNR$ on noise intensity $D$, coupling constant $k$ and polymer length $N$ is studied via two state approximation. We find that the response of signal to the background noise strength is significant at optimum values of $D_{opt}$, $k_{opt}$ and $N_{opt}$ which suggests novel means of manipulating proteins or vesicles. Furthermore, the thermally activated barrier crossing rate $r_{k}$ for the flexible polymer chain is studied. We find that the crossing rate $r_{k}$ exhibits an optimal value at an optimal coupling constant $k_{opt}$; $k_{opt}$ decreases with $N$. As the chain length $N$ increases, the escape rate for the center of mass $r_{k}$ monotonously decreases. On the other hand, the crossing rate for the portion of polymer segment $r_s$ increases and saturates to a constant rate as $N$ steps up.
Thermally activated barrier crossing rate for a coupled system moving in a ratchet potential
Mesfin Asfaw
Physics , 2014,
Abstract: We explore the dependence of the thermally activated barrier crossing rate on various model parameters for a dimer that undergoes a Brownian motion on a piecewise linear bistable potential employing the method of adiabatic elimination of fast variable. By introducing a different model system and approaches than the previous works \cite{c4,c5}, not only we recapture the previous results but we further show that systematic elimination of the fast changing variable leads to an effective Kramers type potential. It is shown that for rigid dimer, the escape rate $R$ monotonously decreases with $k$. On the other hand, in the presence of time varying force, the signal to noise ratio (SNR) attains a pronounced peak at particular barrier height $U_{0}$.
Unbinding transitions of multicomponent membranes and strings
Mesfin Asfaw
Physics , 2007,
Abstract: We present a theory of unbinding transitions for membranes that interact via short and long receptor/ligand bonds. The detail of unbinding behavior of the membranes is governed by the binding energies and concentrations of receptors and ligands. We investigate the unbinding behavior of these membranes with Monte Carlo simulations and via a comparison with strings. We derive the scaling laws for strings analytically. The exact analytic results provide scaling estimate for membranes in the vicinity of the critical point.
Effects of Salinity on Seedling Biomass Production and Relative Water Content of Twenty Sorghum (Sorghum biolor L. Moench) Accessions
Kinfemichael Geressu Asfaw
Research Journal of Agronomy , 2012, DOI: 10.3923/rjagr.2010.24.30
Abstract: Salinity is a continuing problem in the arid and semi-arid tracts of the world. It could be alleviated using irrigation management and/or crop management. However, the former approach is outdated and very expensive. Nevertheless, the latter is economical as well as efficient and it enables to produce salt tolerant crop lines. But prior to that there is a need to confirm the presence of genetically based variation for salt tolerance among different species or varieties of a particular crop at different growth stages. Thus, twenty lowland sorghum (Sorghum bicolor L. Moench.) accessions were tested during early seedling biomass production at 2, 4, 8 and 16 dS m-1 salinity levels. Distilled water (0 dS m-1) was used as a control. Data analysis was carried out using jmp5 statistical software (version 5.0). Seedling Shoot Fresh Weight (SFW), seedling Shoot Dry Weight (SDW), seedling Root Fresh Weight (RFW) and seedling Root Dry Weight (RDW) were measured. The two ways ANOVA for accessions found statistically insignificant with respect to most parameters recorded (p>0.05) but it was significant with respect to RFW (p<0.001). On the other hand, the two ways ANOVA for treatments displayed statistical significance for all parameters at p<0.0001 except at p<0.01 for RFW. However, it was insignificant for accession*treatment interaction (p>0.05). Accessions such as 235461, 69239, 223550, 69029 and 23403 were found to be salt tolerant during seedling biomass production and in Relative Water Content (RWC). On the other hand, accessions 22885, 233247, 237264, 237265 and 237267 were found to be salt sensitive during seedling biomass production and in RWC. The rest sorghum accessions were intermediate in their salt tolerance. The study affirmed the presence of broad intraspecific genetic variation in sorghum accessions for salt stress with respect to their early biomass production and Relative Water Content (RWC).
Effects of Salinity on Seedling Biomass Production and Relative Water Content of Some Haricot Bean (Phaseolus vulgaris) Varieties
Kinfemichael Geressu Asfaw
Research Journal of Agronomy , 2012, DOI: 10.3923/rjagr.2010.63.69
Abstract: The aim of this research was to study the effects of salinity on 14 haricot bean (Phaseolus vulgaris) varieties at 0, 2, 4, 8 and 16 dS m-1. Data analysis was carried out using jmp 5 (version 5.0) and SPSS (version 12) statistical softwares. Seedling Shoot Fresh Weight (SSFW), Seedling Shoot Dry Weight (SSDW), Seedling Root Fresh Weight (SRFW) and Seedling Root Dry Weight (SRDW) were measured and seedling Shoot Relative Water Content (SRWC) and seedling Root Relative Water Content (RRWC) were calculated. The two ways ANOVA for varieties found statistically insignificant with respect to Seedling Root Fresh Weight (SRFW), seedling Shoot Relative Water Content (SRWC) and seedling Root Relative Water Content (RRWC) (p>0.05) but it was significant with respect to Seedling Shoot Fresh Weight (SSFW), Seedling Shoot Dry Weight (SSDW) and Seedling Root Dry Weight (SRDW) (p<0.05). On the other hand, the two ways ANOVA for treatments displayed statistical significance for all the above parameters at (p<0.0001). However, it was insignificant for variety treatment interaction (p>0.05) with respect to the entire parameters. Varieties such as Awash-1, Argene, Chore, Mexican 142 and Awash Melka were found to be salt tolerant during seedling biomass production and in Relative Water Content (RWC). On the other hand, varieties Red Kidney (DRK), Dimtu, Gofta, Cranscope and Sinkinesh were found to be salt sensitive during seedling biomass production and in RWC. The rest haricot bean varieties were intermediate in their salt tolerance. The study affirmed the presence of broad intraspecific genetic variation in haricot bean varieties for salt stress with respect to their early biomass production and Relative Water Content (RWC).
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