System productivity and yield of component crops as affected by intercropping maize and common bean varieties with distinct morphological characteristics

Selection of maize and legumes variety selection in Ethiopia target only sole cropping system without considering the relative performance of varieties of varying morphologies under maize/legume intercropping. The objective of this study was to assess the effects of intercropping maize and common bean varieties with different morphologies on yield and system productivity of maize/common bean intercropping system. The treatments consisted of factorial combinations of three maize (BH543, BH661 and Gibe-2) and three common bean (Anger, Nassier and Haramaya) varieties and sole crops of the six varieties, which were laid out in randomized complete block design with three replications. The experiment was conducted at Bako, western Ethiopia, during the main cropping seasons of 2011 and 2012. Main effects due to variety and cropping system were significant for maize biomass and grain yield in both years. Relative to sole cropping system, intercropping significantly reduced maize and common bean grain yields by 7% and 70%, respectively. Intercropping increased plant height of common bean by 48% relative to sole crop conditions. Among the different intercropping combinations, growing common bean variety, Haramaya with maize hybrid BH661 gave the highest land equivalent ratio of 1.28, highest relative crowding coefficient of 6.75 and highest net benefit of Birr 23,328 ha-1. As a strategy to maximize land productivity and resource use efficiency, intercropping that involves the two compatible varieties of the component crops is recommended for Bako and similar areas of western Ethiopia

The effects of drought stress on assimilate availability and metabolism in the source and sink organs of common bean (Phaseolus vulgaris L) genotypes

Changes in carbohydrate status and metabolism in the source and sink organs determine rate of growth and yield of plants subjected to drought stress. The objective of this study was to assess the effect of lost-flowering drought stress on assimilate synthesis at source level and availability of the assimilates for metabolism in the reproductive sink organs of common bean (Phaseolus vulgaris L.) genotypes differing in degree of drought resistance. A drought-resistant inbred line (SEA 15) and a drought-susceptible cultivar (BrSp) were grown under non-stress and drought stress commenced at early pod-filling stage. Plants were raised in a vegetation hall during the summer of 2005. Drought stress reduced the seed yields of BrSp and SEA 15 by 53 and 30%, respectively. Harvest index of the susceptible genotype decreased by ca. 29%, whereas no effect of drought was found for the partitioning index in the resistant genotype implying marked differences in sink strength at whole plant level between the genotypes. Drought stress did not affect the concentration of sucrose in leaves and seeds of SEA 15 during most part of the stress period. On the contrary, the stress caused 18 to 30 and 29 to 47% reductions in leaf and seed sucrose concentrations of BrSp, respectively. Relative to control treatments, drought stress decreased seed starch ccumulation of BrSp throughout the stress period (by 16 to 18%) whereas the decrease (by 20%) was found only at 20 d stress for SEA 15. The findings revealed that the underlying differences in sink establishment and yield of the bean genotypes differing in degree of drought resistance reside primarily in the capacity of the source to supply assimilates (i.e. source-strength) under drought conditions

Effects of drought stress on seed sink strength and leaf protein patterns of common bean genotypes

Assimilate availability and the capacity to utilise them in the reproductive structures to a large extent determine reproductive sink establishment and yield of crops under drought stress. This study was carried out to investigate the effect of drought stress imposed at early pod-fill stage on seed sink strength of common bean ( Phaseolus vulgaris L.) genotypes differing in drought resistance. Quantitative and qualitative changes in leaf protein patterns was assessed using 2D-gel electrophoresis. A drought-resistant inbred line (SEA 15) and a droughtsusceptible cultivar (BrSp) were grown under non-stress and drought stress conditions in a vegetation hall during the summer of 2004. Drought stress commenced at early pod-filling stage caused 53 and 30% seed yield reductions in BrSp and SEA 15, respectively. The effect of drought on seed yield was primarily due to the significant reduction in number of seeds per plant (48% for BrSp vs. 35% for SEA 15). Whereas seed sucrose concentrations of BrSp decreased by 29 to 47% under drought conditions, the stress resulted in an increase (up to 43%) in concentration of the carbohydrate in SEA 15 seeds. Despite the genotypic difference found for seed sucrose import, seed starch accumulations of the two genotypes decreased under drought stress. For both genotypes, none of the seed sink capacity parameters (numbers and volumes of cotyledonary cells and starch granules per seed) were significantly affected by the stress imposed implying that the drought-induced decrease in seed starch accumulation could be due to limitations in assimilate availability and/or other sink activity factors within the seed. A total of 230 leaf proteins were differentially expressed due to drought out of which 23.5, 15.1, 4.3 and 3.5% were down-regulated, up-regulated, newly appeared and disappeared, respectively. Identification and assigning possible functions in the crop\u2019s response to drought of the stress-induced proteins warrant further study.La disponibilit\ue9 des assimilats et la capacit\ue9 de les utiliser dans des structures reproductrices, d\ue9terminent en grande partie l\u2019\ue9tablissement du \u201csink\u201d reproducteur et les rendements des cultures en conditions de secheresse. Cette \ue9tude avait pour objectif l\u2019\ue9tude de l\u2019effet du stress hydrique impos\ue9 au stade du remplissage des gousses, sur la consistence du \u201csink\u201d de graines de g\ue9notypes du haricot commun ( Phaseolus vulgaris L.) de diff\ue9rente r\ue9sistance \ue0 la secheresse. Des changements quantitatfs et qualitatifs dans les structures de prot\ue9ine des feuilles \ue9taient \ue9valu\ue9s par l\u2019\ue9lectrophor\ue8se 2D-gel.Une souche pure r\ue9sistante \ue0 la s\ue9cheresse (MER 15) et un cultivar non r\ue9sistant \ue0 la s\ue9cheresse (BrSp) \ue9taient cultiv\ue9s \ue0 la fois en conditions de stess et sans stress hydrique dans un hall de vegetation au cours de l\u2019\ue9t\ue9 2004. Le stress hydrique impos\ue9 t\uf4t au stade de remplissage de gousses a entrain\ue9 une r\ue9duction de rendement en grains de 53 \ue0 30% dans BrSp et SEA 15, respectivement. L\u2019effet du stress hydrique sur le rendement en grains \ue9tait principalement d\ufb \ue0 la r\ue9duction significative du nombre de grains par plant (48% pour BrSp contre 35% pour SEA 15). Alors que les concentrations en sucrose dans les grains de BrSp avaient d\ue9cru de 29 \ue0 47% en conditions de s\ue9cheresse, la concentration en hydrates de carbone a augment\ue9 jusqu\u2019\ue0 43% dans les grains de SEA 15. Malgr\ue9 la diff\ue9rence g\ue9notypique trouv\ue9e pour l\u2019importation du sucrose dans la graine, l\u2019accumulation de l\u2019amidon dans la graine de deux genotypes a d\ue9cru en conditions de s\ue9cheresse. Pour les deux genotypes,aucun des param\ue8tres de la capacit\ue9 du sink du grain (nombres et volumes de cellules de cotyledons et granules d\u2019amidon par grain) \ue9taient significativement affect\ue9s par le stess impos\ue9, induisant une r\ue9duction dans l\u2019accumulation de l\u2019amidon dans le grain qui serait due \ue0 la disponibilit\ue9 des assimilats et/ou d\u2019autres facteurs de l\u2019activit\ue9 du sink dans la graine. Au total 230 prot\ue9ines dans les feuilles \ue9taient exprim\ue9es de fa\ue7on diff\ue9rentielle suite \ue0 la s\ue9cheresse en dehors de laquelle 23.5, 15.1, 4.3 et 3.5% \ue9taient respectivement sous r\ue9gul\ue9s, sur-r\ue9gul\ue9s, nouvellement apparus et disparus. L\u2019identification et l\u2019attribution des fonctions possibles des prot\ue9ines sous tress induit en r\ue9ponse de la plante \ue0 la s\ue9cheresse n\ue9cessitent une \ue9tude suppl\ue9mentaire

Alternate furrow irrigation of four fresh-market tomato cultivars under semi-arid condition of Ethiopia – Part I: Effect on fruit yield and quality

Scarcity of freshwater due to recurrent drought threatens the sustainable crop production in semi-arid regions of Ethiopia. Deficit irrigation is thought to be one of the promising strategies to increase water use efficiency (WUE) under scarce water resources. A study was carried out to investigate the effect of alternate furrow irrigation (AFI), deficit irrigation (DI) and full irrigation (FI) on marketable fruit yield, WUE and physio-chemical quality of four fresh-market tomato cultivars (Fetan, Chali, Cochoro and ARP Tomato d2) in 2013 and 2014. The results showed that marketable yield, numbers of fruits per plant and fruit size were not significantly affected by AFI and DI irrigations. WUE under AFI and DI increased by 36.7% and 26.1%, respectively with close to 30% irrigation water savings achieved. A different response of cultivars to irrigation treatments was found for marketable yield, number of fruits and fruit size, WUE, total soluble solids (TSS) of the fruit juice, titratable acids (TA) and skin thickness. Cochoro and Fetan performed well under both deficit irrigation treatments exhibited by bigger fruit size which led to higher WUE. ARP Tomato d2 showed good yields under well-watered conditions. Chali had consistently lower marketable fruit yield and WUE. TSS and TA tended to increase under deficit irrigation; however, the overall variations were more explained by irrigation treatments than by cultivars. It was shown that AFI is a suitable deficit irrigation practice to increase fresh yield, WUE and quality of tomato in areas with low water availability. However, AFI requires suitable cultivars in order to exploit its water saving potential

Genetic variation for drought resistance in small red seeded common bean genotypes

Common bean ( Phaseolus vulgaris L.) productivity is low in major growing regions of Ethiopia mainly due to drought, caused by low and erratic rainfall. A field experiment was carried out at Gofa in Southern Ethiopia, to assess genetic variability for drought resistance in forty-nine small red seeded common bean genotypes of both local and foreign origin. The genotypes were evaluated under two soil moisture regimes, non-stress (NS) and drought stress (DS). Drought stress was initiated at flowering by withholding application of irrigation water. The average linkage method of clustering grouped the forty-nine genotypes grown under drought stress condition in five clusters. The maximum distance was found between Cluster I and Cluster III. Pattern of variation examined through principal component analysis (PCA) involving morpho-physiological traits showed that the first four PCs accounted for more than 74% of the total variation, of which 59.9% was contributed by the first two PCs. The first principal component alone explained 49.9% and was highly correlated with seed yield, harvest index and geometric mean. The second PC explained 9.7% of the total variation and was highly correlated with days to maturity and drought susceptibility index. Both PCs had higher relative contributions to the total diversity and were the ones that most differentiated the genotypes.La productivit\ue9 du haricot commun ( Phaseolus vulgaris L.) est basse dans beaucoup de r\ue9gions productrices ethiopiennes principalement due \ue0 la s\ue9cheresse et aux pluies irr\ue9guli\ue8res. Un essai sur terrain \ue9tait men\ue9 \ue0 Gofa au Sud de l\u2019Ethiopie, pour \ue9valuer la variabilit\ue9 g\ue9n\ue9tique, pour r\ue9sistance \ue0 la s\ue9cheresse dans quarante quatre g\ue9notypes de petits grains de haricot rouges, tous d\u2019origine locale et exotique. Les g\ue9notypes \ue9taient \ue9valu\ue9s sous deux r\ue9gimes d\u2019humidit\ue9 de sol, non-stress (NS) et stress hydrique (DS). Le stress hydrique \ue9tait initi\ue9 \ue0 la floraison par la r\ue9duction de l\u2019eau d\u2019irrigation. A l\u2019aide de la m\ue9thode de la moyenne des liens des groupements, quarante neuf g\ue9notypes plant\ue9s en condition de stress hydrique \ue9taient class\ue9s en cinq groupes. La distance maximale \ue9tait trouv\ue9e entre le groupe-I et le groupe-III. Le mode de variation examin\ue9 par l\u2019analyse de la composante principale (PCA) impliquant des traits morpho-physiologiques a montr\ue9 que les quatre premiers PCs comptaient pour plus de 74% de la variation totale parmi lesquels 59.9% \ue9taient induits par les deux premiers PCs. Le premier composant principal expliquait seul 49.9% et \ue9tait hautement correl\ue9 avec le rendement en grains, l\u2019index de r\ue9colte et la moyenne g\ue9om\ue9trique. Le second PC a expliqu\ue9 9.7% de la variation totale et \ue9tait hautement corr\ue9l\ue9 avec les jours \ue0 la maturit\ue9 et l\u2019index de susceptibilit\ue9 \ue0 la s\ue9cheresse. Tous les PCs offraient des contributions \ue9lev\ue9es \ue0 la diversit\ue9 totale et \ue9taient celles qui avaient diff\ue9renci\ue9es le plus les g\ue9notypes

Alternate furrow irrigation of four fresh-market tomato cultivars under semi-arid condition of Ethiopia – Part II: Physiological response

Understanding the variation in physiological response to deficit irrigation together with better knowledge on physiological characteristics of different genotypes that contribute to drought adaptation mechanisms would be helpful in transferring different irrigation technologies to farmers. A field experiment was carried to investigate the physiological response of four tomato cultivars (Fetan, Chali, Cochoro and ARP Tomato d2) to moderate water deficit induced by alternate furrow irrigation (AFI) and deficit irrigation (DI) under semi-arid condition of Ethiopia during 2013 and 2014. The study also aimed at identifying physiological attributes to the fruit yield of tomato under different deficit irrigation techniques. A factorial combination of irrigation treatments and cultivar were arranged in a complete randomized design with three replicates. Results showed that stomatal conductance (g_s) was significantly reduced while photosynthetic performance measured as chlorophyll fluorescence (Fv’/Fm’), relative water content (RWC) and leaf ash content remained unaffected under deficit irrigations. Significant differences among cultivars were found for water use efficiency (WUE), g_s, chlorophyll content (ChlSPAD), normal difference vegetation index (NDVI), leaf ash content and fruit growth rate. However, cultivar differences in WUE were more accounted for by the regulation of g_s, therefore, g_s could be useful for breeders for screening large numbers of genotypes with higher WUE under deficit irrigation condition. The study result also demonstrated that cultivar with traits that contribute to achieve higher yields under deficit irrigation strategies has the potential to increase WUE

Grouping of environments for testing navy bean in Ethiopia

Common bean variety selection within its production environment is often challenged by the occurrence of significant genotype-by-environment interactions (GEI) in the variety development process. Grain yield performance of 16 navy bean (Phaseolus vulgaris L.) lines was tested in a multi-environment variety trial during 2010 and 2011 main growing seasons of Ethiopia. Field experiments were conducted in Randomized Complete Block Design (RCBD) with three replications in 14 rainfed environments of the major common bean growing areas. The objectives were to assess the line by environment interactions (LEI), determine stable genotypes, and grouping of test environments. Significant differences were found among the lines for grain yield on each environment and combined over environments. The combined analysis of variance across environments indicated that both environment and LE interactions were significantly influenced lines yield. All interactions in relation to L×E showed high significant difference (P<0.01) for grain yield. Statistical methods as AMMI, GGE and some stability parameters were used to describe the LE interaction and to define stable lines in relation to their yield. The highest yield (2435 kg ha-1) was obtained from the line ICA BUNSI X SXB 405/1C-C1-1C-87. The stability analysis also identified lines ICA BUNSI X SXB 405/1C-C1-1C-87 and ICA BUNSI X SXB 405/1C-C1-1C- 37 as the most stable lines. Lines identified as superior differed significantly from the standard varieties and can be recommended for use by farmers in the bean growing areas of Ethiopia. Cluster analysis, based on grouping of locations showed that Melkassa, Alemtena and Haramaya as potential and high yielding, but Jimma, Bako, Pawe, Areka, Assosa and Sirinka as low to medium yielding locations

Genotype X Environment Interaction and Stability Analysis of Seed Yield in Navy Bean Genotypes

Genotype x environment interactions, genotype response to environments and stability for seed yield of navy bean genotypes (Phaseolus vulgaris   L.) were studied. Sixteen genotypes were grown in a randomised complete block design with three replications at four locations in Ethiopia. Genotype x environment (G X E) interactions were analysed using linear regression. There was considerable variation in seed yield within and across environments. Genotype x environment interaction was present, the highest being the linear component. The significance of the linear proportion demonstrated the adequacy of the regression model in describing the stability of the bean genotypes. Two genotypes, G 17450 and PAN 134 with respective regression coefficient values of 1.04 and 1.09, smaller S2d values, and a relatively high seed yield could be considered the most widely adapted genotypes. The other test genotypes were sensitive to production-limiting factors, their wider adaptability, stability and general performance to the fluctuating growing conditions within and across sites being lowered

Effects of Drought Stress on Growth, Water-Use Efficiency and Leaf Gas-Exchange of Common Bean (Phaseolus vulgaris L.) Genotypes Differing in Drought Resistance

Growth, water-use efficiency (WUE) and leaf gas exchange responses of common bean (Phaseolus vulgaris L.) genotypes differing in degree of drought  resistance were assessed when plants were subjected to drought stress at vegetative and early pod filling stages. A drought-resistant inbred line (SEA 15)  and a drought-susceptible cultivar (BrSp) selected from an earlier screening trial were used for the study. The two genotypes were grown in a vegetation  hall under drought stress and non-stress conditions during the summer of 2004. Despite differential genotypic responses found to the stress imposed, drought initiated at both growth stages had an adverse effect on leaf area expansion, above-ground biomass yield and biomass partitioning of the two  genotypes. Seed yield reduction due to drought imposed during early pod-fill stage was 72% and 33% for BrSp and SEA 15, respectively. Drought stress at  the vegetative stage increased the WUE of both genotypes, although the increase was considerably higher for SEA 15 (3.12 mg g-1) compared with  BrSp (2.45 mg g-1). On the other hand, seed yield based water-use efficiency (WUESY) was significantly higher for SEA 15 (1.81 mg g-1) compared with  BrSp (0.33 mg g-1) under drought stress imposed at early pod-fill stage. Drought stress initiated during the reproductive phase significantly reduced the  net photosynthetic rate (A) and stomatal conductance (gs) of the two genotypes. Despite the similar response in leaf gas-exchange parameters (A and gs)  between the two genotypes, the stress resulted in a significant and consistent decrease in Ci/Ca ratio of SEA 15 implying that the stress thresholds at  which stomatal and metabolic limitations to A occurred differed between the two genotypes. Some of these specific adaptation traits related to growth,  artitioning and water-use can be used in tandem with seed  yield as selection criteria in breeding beans for drought conditions. &nbsp