Nigussie Dechassa

Phosphorus Efficiency of Cabbage (Brassica oleraceae L. var. capitata), Carrot (Daucus carotaL.), and Potato (Solanum tuberosumL.)

Plant species and genotypes within the same species may differ in phosphorus efficiency. The objective of this research was to study phosphorus efficiency of cabbage (Brassica oleraceae L.), carrot (Daucus carota L.), and potato (Solanum tuberosum L.) and to quantify the contribution of morphological root characteristics to P uptake of the plant species. An experiment was conducted in a glasshouse with six P levels: 0, 12, 27, 73, 124 and 234 mg P kg−1 soil, and with six replications. Cabbage attained 80% of its maximum yield already at the level of no P supply, whereas carrot and potato reached only 4 and 16% of their highest yields respectively at this level of P supply. This indicated that cabbage was P-efficient compared to carrot and potato. Root/shoot ratio (cm root g−1 shoot d. m.) increased in the order of cabbage < carrot < potato, and was enhanced at lower P levels. Root hair length was not affected by P level, and averaged 0.22, 0.03 and 0.18 mm for cabbage, carrot, and potato, respectively. Predicting P uptake by a mechanistic simulation model revealed that root hairs contributed about 50% to the total P uptake of cabbage and potato, but only 0.3% to that of carrot. The relationship between the observed P uptake and the predicted P uptake of the plants revealed that model parameters explained nearly 4/5th of the total P uptake of carrot and potato, but only 2/5th of that of cabbage. This showed that the P uptake of cabbage was strongly under-predicted, whereas that of carrot and potato was predicted well. Therefore, it was hypothesised that cabbage may have the ability to mobilise and take up soil P additionally by other root mechanisms such as exudation of organic acids.

Effects of plant growth regulators on in vitro cultured nodal explants of cassava ( Manihot esculenta Crantz) clones

Cassava ( Manihot esculenta Crantz) is one of the major food security crops in Ethiopia. Recently, clean planting materials of improved cassava cultivars are in high demand. A limitation, however, is the low multiplication ratio (1:10) of the crop via conventional methods. Thus, a study was undertaken to develop an efficient in vitro mass propagation protocol for two elite cassava clones, 44/72-NR and 44/72-NW. Combination of different plant growth regulators (PGRs); four concentrations of 6-benzylaminopurine (BAP) and kinetin (Kin) on shoot multiplication and that of α-naphthaleneacetic acid (NAA) and BAP each at four concentration combination on root induction were assessed. The experiments were factorial laid out in a completely randomized design (CRD) with PGRs as one-factor and clones as another, replicated five times. Significant (p< 0.05) interaction effects were observed in response to shoot multiplication and root induction treatments within six weeks of culture. Murashige and Skoog (MS) medium containing BAP and Kin each at 0.75 mg/L gave an average of 7.30 shoots per explant than other media combinations. Consecutively, the regenerated cassava shoots produced an average of 6.14 roots within four weeks in a 0.5 mg/L NAA medium and were successfully acclimatized and transferred to field. Keywords: Cassava, Manihot esculenta , clone, in vitro, nodal bud, plant growth regulators. African Journal of Biotechnology Vol 13(28) 2830-2839

In vitro screening of potato genotypes for osmotic stress tolerance

Abstract Potato (Solanum tuberosum L.) is a cool season crop which is susceptible to both drought and heat stresses. Lack of suitable varieties of the crop adapted to drought-prone areas of the lowland tropics deprives farmers living in such areas the opportunity to produce and use the crop as a source of food and income. As a step towards developing such varieties, the present research was conducted to evaluate different potato genotypes for osmotic stress tolerance under in vitro conditions and identify drought tolerant genotypes for future field evaluation. The experiment was carried out at the Leibniz University of Hannover, Germany, by inducing osmotic stress using sorbitol at two concentrations (0.1 and 0.2 M) in the culture medium. A total of 43 genotypes collected from different sources (27 advanced clones from CIP, nine improved varieties, and seven farmers’ cultivars) were used in a completely randomized design with four replications in two rounds. Data were collected on root and shoot growth. The results revealed that the main effects of genotype, sorbitol treatment, and their interactions significantly (P < 0.01) influenced root and shoot growthrelated traits. Under osmotic stress, all the measured root and shoot growth traits were significantly correlated. The dendrogram obtained from the unweighted pair group method with arithmetic mean allowed grouping of the genotypes into tolerant, moderately tolerant, and susceptible ones to a sorbitol concentration of 0.2 M in the culture medium. Five advanced clones (CIP304350.100, CIP304405.47, CIP392745.7, CIP388676.1, and CIP388615.22) produced shoots and rooted earlier than all other genotypes, with higher root numbers, root length, shoot and root mass under osmotic stress conditions induced by sorbitol. Some of these genotypes had been previously identified as drought-tolerant under field conditions, suggesting the capacity of the in vitro evaluation method to predict drought stress tolerant genotypes. Most of the genotypes collected from Ethiopia were found to be susceptible to osmotic stress, except one farmers’ cultivar (Dadafa) and two improved varieties (Zemen and Belete). Field evaluation of the tested materials under drought conditions would confirm the capacity of osmotic stress tolerant genotypes to perform well under drought-prone conditions and the potential interest of in vitro evaluation as a pre-screening component in potato breeding programs.

Profitability of potato (Solanum tuberosum L.) as affected by NP nutrition and variety in Southern Ethiopia

Profitability of different rates of nitrogen (N), phosphorus (P) and five potato varieties (Bellete, Gudene, Jalene, Marachere and local check) was investigated in southern Ethiopia to find out rates of the nutrients and varieties that would give acceptable returns and likely to be adopted by smallholder farmers in the locality. Factorial combination of N (0, 55.5 and 111 kg/ha) and P (0, 19.5 and 39 kg/ha) were applied to the main plots while the five varieties were to the sub plots of split-plot design and replicated three times. Both factors had significant effect on tuber yield, but there were no significant interaction effect. Significant treatments of this experiment were, therefore, subjected to economic analysis using partial budget procedure. Economic analysis showed that 0:19.5, 55.5:19.5 and 55.5:39 kg NP/ha and varieties Bellete, Jalene and Marachere were economically superior and stable even within a price variability range of 20% in the locality. In conclusion, application of NP nutrients with the rate of 0:19.5, 55.5:19.5 or 55.5:39 kg/ha for the varieties Bellete, Jalene and Marachere were identified profitable treatments for lucrative production of potato in the study area. Key words: Dominance analysis, economic analysis, partial budget, smallholder farmers, tuber yield.

Influence of Nitrogen and Phosphorus Application on Bulb Yield and Yield Components of Onion (Allium Cepa L.)

RESEARCH ARTICLE Influence of Nitrogen and Phosphorus Application on Bulb Yield and Yield Components of Onion (Allium Cepa L.) Negasi Tekeste, Nigussie Dechassa, Kebede Woldetsadik, Lemma Dessalegne and Abuhay Takele Aksum University, College of Agriculture, P O Box 314, Shire, Ethiopia Department of Plant Sciences, Haramaya University, P O Box 138, Dire-Dawa, Ethiopia Melkassa Agricultural Research Centre, P O Box 2500, Adama, Ethiopia

Phosphorus Use Efficiency of Common Bean Cultivars in Ethiopia

ABSTRACT Phosphorus (P) deficiency in the soil is one of the major factors limiting common bean production in Ethiopia. A pot experiment was conducted in a glasshouse at Hawassa University in southern Ethiopia to evaluate twelve common bean cultivars for P use efficiency at three phosphorus rates (0, 120, and 240 kg P2O5 ha−1). The results of the study revealed that the interaction effect of cultivar and P rates significantly (P < 0.01) influenced grain yield efficiency index (GYEI), grain yield and yield attributing traits, leaf P concentration, root length, diameter and surface area. Grain yield efficiency index at low and medium phosphorus rates indicated that Red-Wolaita, Dinkinesh, Tabour, Nasir and Haramaya are P-efficient, whereas Chore was found to be P-inefficient. These genotypic variations could be exploited for sustainable production of the crop by fitting suitable varieties to soils with variable P availability. Thus, the P-efficient cultivars indicated above could be recommended for cultivation by smallholder farmers in soil with low P availability that is dominant in the study area.

Effects of different dormancy-breaking and storage methods on seed tuber sprouting and subsequent yield of two potato (Solanum tuberosum L.) varieties

Abstract Potato is an important food and cash crop which in Ethiopia is produced two or more times in a year. However, its productivity is low owing to a number of constraints including a) limited availability of quality planting materials, and b) poor tuber sprouting due to long dormancy period of improved varieties at the time of planting. Two consecutive experiments were conducted from November 2013 to June 2014: 1) to assess the effects of gibberellic acid (GA3) and storage methods on seed tuber dormancy breakage of two potato varieties; and 2) to assess the effects of dormancy breakage treatments and storage methods on subsequent growth, yield and related traits of potato crop. The treatments in the first experiment consisted of two potato varieties (Bubu and Bate), three levels of GA3 [0, 10 and 20 parts per million (ppm)], and three storage methods [in diffused light store (DLS), in pit store (PS), and in farm-yard manure (FYM)]. The first trial was laid out as a complete randomized design with four replications and conducted at Haramaya University, Ethiopia. The second trial consisted of seed from each treatment in the first experiment, planted in randomized complete block design with three replications on a farmers’ field. The results showed that varieties, application of GA3 and storage methods as well as the interaction among the variety and treatments significantly affected tuber dormancy period, sprouting characteristics and subsequent tuber yield. When tubers were treated with 20 ppm GA3 and stored under FYM, the dormancy period was reduced from 102.5 and 52 to 36.5 and 31 days in improved and farmer’s variety, respectively. Tuber treatment with 20 ppm GA3 and stored under DLS, PS, and FYM, increased marketable tuber yield by 31.6%, 29.6%, and 33.6%, respectively for Bubu variety and by 92.5%, 78.4%, and 80.9% for Bate variety, respectively compared to non-GA3 treated tubers stored under DLS, PS, and FYM. However, tubers of improved variety Bubu treated with 20 ppm GA3 and stored under DLS produced the highest marketable tuber yield of 34.20 ton per ha. Tuber quality attributes (specific gravity, dry matter, and total starch content) were affected only due to interaction effects of variety and GA3 application with the highest values at 20 ppm GA3 for improved potato variety Bubu. In general, the research indicated that treating seed tubers with GA3 and storing under DLS, PS or FYM promoted early tuber sprouting and better tuber yield of both varieties. These results suggest that, use of GA3 treatment combined with different storage methods enhances early tuber sprouting and increases tuber yield. Nevertheless, further research should be continued to evaluate different potato varieties, GA3 treatment, and storage methods under different atmospheric conditions and production seasons.

DETERMINANTS OF ADOPTION OF POTATO PRODUCTION TECHNOLOGY PACKAGE BY SMALLHOLDER FARMERS: EVIDENCES FROM EASTERN ETHIOPIA

Potato production plays an important role in improving household income and nutrition and thereby contributes to food security. Despite of this, the current productivity of the crop is below the potential. Low level of use of improved potato technology package is among the causes for low productivity. In this context, this study analysed the factors influencing adoption of potato technology package by smallholder farmers in Gurawa, Haramaya, Kombolcha, Meta, and Habro districts of Eastern Ethiopia. The analysis was based on a household survey conducted on 214 randomly selected potato growing households. A two-limit Tobit model was used to analyse the factors affecting adoption which is measured in an index computed from five components of the technology package. Variation in districts, access to irrigation, farm size, membership to cooperatives, and annual income of the households were found to significantly affect the adoption of potato technology package. Policy makers, planners and development practitioners are required to give due attention to these determinants in order to support smallholder farmers in production and productivity improvements from potato production.

Evaluation of soil solarisation and bio-fumigation for the management of bacterial spot of tomato

Soil-borne plant pathogens cause heavy losses to all major crops, leading to reductions in both yield and quality. Soil solarisation and bio-fumigation offer disease management options that are safe and reduce the use of pesticides for soil-borne plant pathogens. Mustard plant releases antimicrobial hydrolysis products, notably isothiocyanates when used as a bio-fumigant. Bacterial spot of tomato caused by Xanthomonas campestris pv. vesicatoria (Xcv) can survive in soil and plant debris, which serve as a primary inoculum for infecting the next tomato crop. An experiment was carried out with the objective of evaluating effects of soil solarisation and the use of Ethiopian mustard ( Brassica carinata A. Braun) as a bio-fumigant to control bacterial spot disease and on yield of tomato. The treatments consisted of six types of potted soil medium (solarised at Haramaya and Dire Dawa, bio-fumigated, biofumigated as well as solarised at Haramaya and Dire Dawa, and untreated control as non-solarised non-biofumigated pots). Treated tomato seeds were planted and fruit yields were compared among treatments. Potted soil was inoculated with the pathogen, Xcv, belonging to T2P2 race group. The total microbial and Xcv counts were done before as well as after setting up the experiment. The results revealed that solarisation reduced the population of Xcv from 10.68 to 8.79 CFU g -1 , total bacterial population from 11.27 to 9.86 CFU g -1 , and total actinomycete counts from 11.69 to 9.44 CFU g -1 while bio-fumigation had a non-significant effect on Xcv and total microbial counts. None of the treatments exhibited a significant effect on fungal counts. The fruit yield of tomato grown on biofumigated as well as solarised soil was the highest (91.18 t ha -1 ) as compared to the other treatments. It can, therefore, be concluded that solarisation and bio-fumigation cannot be used as a bio-rational option for effective management of Xcv on tomato but the two methods could be used to increase tomato yield in the presence of the pathogen. Key words : bio-fumigation, solarisation, bacterial leaf spot