Chemeda Fininsa

Relationship between common bacterial blight severity and bean yield loss in pure stand and bean?-?maize intercropping systems

Field experiments were conducted in the 1999 and 2000 seasons to determine the relationship between common bacterial blight (CBB) (caused by Xanthomonas campestris pv. phaseoli) and bean (Phaseolus vulgaris) yield in different cropping systems. Different levels of disease severity were created using natural epidemics by spraying copper hydroxide (Kocide 101) at 7-, 14- and 21-day intervals beginning at the first observation of CBB symptoms. The susceptible cultivar Red Wolaita was grown in broadcast, mixed and row bean - maize intercropping and pure stand. The bean growth stage at which the disease severity was correlated with seed yield varied among the cropping systems. In broadcast and mixed intercroppings, CBB appeared to be correlated with seed yield at later growth stages. In row intercropping, disease was correlated at preflowering to 50% flowering and in pure stand at 50% flowering to pod filling. In intercropping systems, both relative and predicted seed yield and 100-seed weight losses to CBB were, generally, less than in pure stand. Single-point regression models in 1999 predicted that for each per cent increase of CBB severity in broadcast and mixed intercropping, about 5.2 and 9.1 kg ha1 seed yield loss, respectively, occurred at physiological maturity. In pure stand, for each percentage increase in CBB at an earlier growth stage, 73 days after planting (DAP) in 2000, a yield loss of 38.8 kg ha1 occurred. Similarly, in row intercropping a 71.1 kg ha1, seed yield loss was estimated at 52 DAP in 1999. Decreasing seed weight was correlated with yield loss to CBB. The type of cropping system influenced CBB severity and the amount of loss in yield attributable to CBB. Variation in CBB and its relation to yield between years was influenced by difference in seasonal weather between years.

Association of bean rust and common bacterial blight epidemics with cropping systems in Hararghe highlands, eastern Ethiopia

Surveys of common bean rust and common bacterial blight (CBB) diseases were conducted in the Habro, Chercher and Wobera areas of the Hararghe highlands, Ethiopia during the 1998 and 1999 cropping seasons in four different bean cropping systems. Intercropping constituted 91% of the cropping systems. Bean proportions in intercropping ranged from 13 to 55%. In intercropping, the mean rust incidence and severity was reduced by 25 and 16%, respectively, compared with sole cropping. Similarly CBB incidence was reduced by 29% while severity was reduced by 20%. Single and multiple variable logistic regression analyses were used to determine the association of rust and CBB diseases with cropping systems and practices, geographical areas, cropping years and altitude. The analyses indicated that cropping system, geographical area and cropping year were important variables and affected both rust incidence and severity. In Habro during 1998 there was a high probability of rust incidence and severity greater than 25%. The probability of rust incidence and severity exceeding 25% inHabro was about 11 and4 times greater than in Chercher and Wobera areas, respectively. Less than 50% bean proportions in intercropping were significantly associated with low (<25%) rust severity. Similarly geographical area, altitude and cropping system affected CBB incidence and severity. In Habro and at lower altitudes there was a high probability ofgreater than 25% CBB incidence and severity. Bean plants at podding and or maturity were closely associated with high rust and CBB severity. Intercropping systems were more associated with lower CBB and rust intensity than sole cropping.

Sources of Resistance to Stem Rust (Puccinia graminis f. sp. tritici) in Ethiopian Tetraploid Wheat Accessions

Seedlings of 41 emmer (Triticum dicoccon Schrank) and 56 durum (T. durum Desf.) wheat accessions were evaluated for their response to stem rust (Puccinia graminis f. sp. tritici) infection under greenhouse condition at Kulumsa Agricultural Research Center, Ethiopia. The objectives were to identify tetraploid wheat accessions that could serve as sources of resistance to stem rust, and postulate the stem rust (Sr) resistance genes through multipatotype testing. The test included screening of accessions for stem rust resistance and multipatotype testing. To ensure vigorous screening, a mixture of six isolates (Si-1a, Am-2, Ku-3, Dz-4a, Ro-4 and Na-22) that were collected from severely infected emmer, durum, and bread wheat (Triticum aestivum L.) varieties of major wheat growing areas of Ethiopia was used as inocula. Out of the tested accessions, 18 emmer and 6 durum accessions exhibited low infection types (0–2) response and hence selected as a source of resistance to stem rust infection. Multipatotype testing was done to postulate Sr genes in the selected accessions. In the test, 10 different stem rust races (A2, A9, A11, A14, A16, A17, B3, B7, B15, and B21), 33 stem rust differential lines, and a universal susceptible check variety, Morocco were used, The high (3–4) and low infection type reaction patterns of the tested accessions and differential lines were used to postulate the genes that exhibit gene-for-gene relationship. The presence of Sr 7b, 8b, 9a, 9b, 10, 14, 24, 27, 28, 29, 30, 31, 32 and Tt-3+10 genes were postulated in 16 selected emmer and 5 durum wheat accessions. Efforts to transfer these valuable Sr genes from cultivated tetraploid wheats could be rewarding to get stem rust resistant varieties and boost wheat production.

Association of maize rust and leaf blight epidemics with cropping systems in Hararghe highlands, eastern Ethiopia

Abstract Two hundred and eight fields in the Hararghe highlands (Habro, Chercher and Wobera areas), Ethiopia were surveyed during the 1998 and 1999 cropping seasons to determine the occurrence, distribution and importance of maize rust and leaf blight (LB) in five types of maize cropping systems. Sixty four percent of the surveyed fields were intercropped with the proportion of maize ranging from 24% to 68%. Rust incidence and severity among the areas and between years varied. Logistic regression was used to analyse the association of the diseases with cropping systems and practices, geographic area, season and altitude. Crop density, sowing date, variety, area, cropping system and year were significantly associated with rust incidence in a multiple variable model. Low rust incidence had a high probability of association to low crop density, early and optimum sowing, maize–bean intercropping and the 1998 cropping season. High rust incidence had a high probability of association to the Habro area, hybrid varieties and maize–sorghum intercropping. Cropping year and proportion of maize in intercrops were significantly associated with rust severity in a multiple variable model. The severity of rust was higher where the proportion of maize in the intercrop was 25–50%. The Habro area and the 1998 season had a high probability of association with high rust severity. Crop density, altitude and sowing date were significantly associated with LB incidence in a multiple variable model. Sowing at an optimum time had a high probability of association with low (

Yield loss of faba bean (Vicia faba) due to chocolate spot (Botrytis fabae) in sole and mixed cropping systems in Ethiopia

Two field experiments were conducted during 2004 and 2005 cropping seasons at Adet Agricultural Research Center, Ethiopia to assess yield losses caused by chocolate spot(Botrytis fabae) of faba bean in sole and mixed cropping systems using two cultivars. Cropping systems were sole faba bean (FB), faba bean mixed with field pea (FB: FP), barley (FB: BA) and maize (FB: MA). Mancozeb was sprayed at the rate of 2.5 kg a.i/ha at 7-, 14- and 21-day interval to generate different levels of chocolate spot disease in all the four cropping systems, and unsprayed control was also included. The treatments were arranged in a randomised complete block design (RCBD) with four replications. FB: MA mixed cropping significantly reduced disease severity and the area under disease progress curve (AUDPC) and increased faba bean grain yield. The highest faba bean grain yield among the three mixed croppings under different spray schedules was obtained from FB: MA mixed cropping in both 2004 and 2005 (2.56 and 3.74 t/ha, respectively) cropping seasons. There were highly significant yield differences (P < 0.05) among the spray intervals of mancozeb in both seasons. The highest grain yield (4.9 t/h) was recorded from the 7-day spray interval in 2005. The unsprayed faba bean had a lower grain yield (1.9 t/ha in 2004 and 2.3 t/ha in 2005) compared to the sprayed plots. The highest relative yield loss (67.5%) was calculated in 2005 from FB: FP mixed cropping in unsprayed plots. The relative yield losses in the unsprayed plots were in the range of 35.8–41.5% in 2004 and 52.6–67.5% in the 2005 cropping season. Severity and AUDPC were inversely correlated with faba bean grain yield. Significant differences were recorded in the 100-seed weight and days to maturity (DM). The unsprayed plots had shorter DM ranging from 126 to 128.5 day (except FB: MA mixed cropping) in 2004 and 122–123.9 days in 2005. In the sprayed plots DM was relatively longer than the unsprayed plots. A higher seed weight was recorded in the sole FB (56 g) and FB: MA (55 g) mixed cropping, and the lowest value of 100-seed weight was recorded from FB: FP (53 g) mixed cropping. The productivity of the mixed cropping evaluated by land equivalent ratio (LER) exceeded that of sole cropping. Faba bean grain yield was highly influenced by the severity of chocolate spot. The disease affects the DM, forcing early maturing of the plants.

Genetic analysis for some plant and fruit traits, and its implication for a breeding program of hot pepper (Capsicum annuum var. annuum L.).

Two separate field experiments were conducted on hot pepper in which the genetic, heritability and environmental components of variation for seven plant and fruit traits in 78 genotypes and gene effects for four fruit traits in six generations of five crosses were estimated. The objectives were to determine the variation and effects of genes controlling inheritance of plant and fruit traits, and to propose efficient breeding procedures for improving the crop. Analysis of variance in half-diallel crosses revealed the presence of total genetic variability for seven traits among the 78 experimental entries with an excess of over-dominance genes. The presence of unequal distributions of dominant genes with positive and negative effects was observed among the parents and indicated the need to be cautious while selecting hot pepper parents for breeding purposes. Significant variability was also revealed in environmental sensitivity among the 78 experimental entries for some traits along with high heritability, which could be an advantage for a plant breeder but provides less clear opportunities for an agronomist to achieve better plant and fruit traits. Progeny generations (F(1), F(2), B(1) and B(2)) were found to perform better for fruit traits than their parents (P(1) and P(2)). The presence of significant gene interactions indicated a polygenic inheritance of the fruit traits studied and the possibility of pyramiding favorable alleles in the required directions at different levels of progeny generations. Heterosis, backcrossing, multiple crossing and pedigree breeding methods with recurrent selection may facilitate simultaneous exploitation of the genetic components and gene effects obtained. Nevertheless, it is doubtful whether selection efforts within the current set of hot pepper parents would be beneficial to achieve superior fruit traits for developing new varieties.

Aspergillus and aflatoxin in groundnut (Arachis hypogaea L.) and groundnut cake in Eastern Ethiopia

ABSTRACT This study was conducted to assess major Aspergillus species and aflatoxins associated with groundnut seeds and cake in Eastern Ethiopia and evaluate growers’ management practices. A total of 160 groundnut seed samples from farmers’ stores and 50 groundnut cake samples from cafe and restaurants were collected. Fungal isolation was done from groundnut seed samples. Aspergillus flavus was the dominant species followed by Aspergillus parasiticus. Aflatoxin analyses of groundnut seed samples were performed using ultra performance liquid chromatography; 22.5% and 41.3% of samples were positive, with total aflatoxin concentrations of 786 and 3135 ng g−1 from 2013/2014 and 2014/2015 samples, respectively. The level of specific aflatoxin concentration varied between 0.1 and 2526 ng g−1 for B2 and B1, respectively. Among contaminated samples of groundnut cake, 68% exhibited aflatoxin concentration below 20 ng g−1, while as high as 158 ng g−1 aflatoxin B1 was recorded. The study confirms high contamination of groundnut products in East Ethiopia.

Pathogenic and genetic diversity of Botrytis fabae Sand. isolates from faba bean fields in different agro-ecological zones of Northern Ethiopia

The identity and genetic diversity of the causal agent of chocolate spot (Botrytis cinerea or Botrytis fabae) in Ethiopia is still poorly defined and this hinders efforts aimed at integrated management of the disease, especially breeding for resistance. Chocolate spot disease epidemics are more severe in the moist, humid western districts of northern Ethiopia (NW) compared to the sub-humid eastern districts (NE) but knowledge of pathogen identity and genetic diversity is needed to facilitate epidemiological studies. Of a total of 120 Botrytis isolates examined, all were found to be B. fabae and none fitted the morphological description of B.cinerea. In pathogenicity tests, representative isolates caused typical chocolate spot symptoms and were re-isolated from infected leaves, indicating that B. fabae is the causal agent of chocolate spot in Ethiopia. Marked differences were found among the isolates in colony morphology and growth rate but the morphology of isolates was unrelated to their pathogenicity. A preliminary virulence (=severity of disease) test with 76 isolates revealed differences in virulence of the B. fabae isolates, with NE isolates being generally more virulent than the NW isolates. Genetic analysis based on 129 amplified fragment length polymorphism (AFLP) markers showed that genetic differentiation among pathogen populations was low (GST = 0.02 to 0.03; θ = 0.02, p = 0.05), indicating limited geographic delimitation and significant gene flow. Total gene diversity (HT = 0.22) was mostly attributable to diversity within populations (HS = 0.21). Thus, only 4.5% of the total variability was attributable to frequency differences between agroecological zones. Genotypic diversity (GD), defined as the probability that two individuals taken at random had different genotypes, was high for populations from NW and NE, and from the moist and subhumid agro-ecological zones (GD = 0.99). However, cluster analysis showed high similarity among many isolates (>75% similarity index), suggesting that such isolates have a familial structure or are clonally related. The phenetic tree revealed groups with low bootstrap values that did not reflect the grouping of isolates based on virulence or agro-ecological zone. The implications of these findings for chocolate spot resistance breeding in Ethiopia are discussed.

Status of chickpea fusarium wilt (Fusarium oxysporum f.sp. ciceris) in northwestern Ethiopia

Surveys for incidence of fusarium wilt of chickpea were carried out in six districts of North and South Gondar, and East Gojam administrative zones, Amhara National Regional State in northwestern Ethiopia in 2006–2007 and 2007–2008 main cropping seasons. In each district, five representative peasant administrations (PAs) were selected based mainly on chickpea-growing area coverage, and, in each PA, disease was assessed in five randomly selected farmers’ fields. In the two cropping seasons, the mean incidences recorded in each district were as follows: Gondar Zuria, 34.16% and 34.11%; Dembia, 37.90% and 35.36%; Libo-Kemkem, 34.74% and 28.81%; Fogera, 34.74% and 28.81%; Dejen, 34.74% and 28.81% and Enemay, 33.34% and 37.64%. The result indicated that fusarium wilt is currently highly distributed in all surveyed chickpea-growing areas of northwestern part of Ethiopia. Therefore, possible management options are vital to alleviate the problem.

Relationship between stripe rust (Puccinia striiformis) and common wheat (Triticum aestivum) yield loss in the highlands of Bale, southeastern Ethiopia

Abstract The effect of stripe rust (Puccinia striiformis) on yield and yield components of three common wheat cultivars was studied in 2002 and 2003 in Bale highlands, Ethiopia. The objectives were to quantify amount of loss in yield and yield components incurred by stripe rust on common wheat, and assess the relationship between stripe rust and yield. Different severity levels were created by varying triademefon spray intervals. Stripe rust significantly affected grain yield, kernels per spike (NKPS) and thousand kernels weight (TKW) of the susceptible Wabe cultivar. Losses of 3819 kg ha−1 (71%) grain yield, 21.5 (35%) NKPS and 13.9 g (37%) TKW occurred on Wabe. Each unit increase in stripe rust severity resulted in yield reduction of 41 – 47 kg ha−1 at Agarfa. The study indicated that stripe rust causes intolerable high yield loss in common wheat production and the importance of using resistant cultivars and applying fungicide on susceptible cultivars.