Variation for resistance to Puccinia hordei in Ethiopian barley landraces

Summary Up to 100 single plant derived lines of 18 Ethiopian barley landraces were evaluated for infection type in the seedling and adult plant stage, and for latent period in the adult plant stage only. A low infection type indicates the presence of race-specific resistance genes of the hypersensitive type, while the latent period is the major component of the polygenic, partial resistance.In the seedling stage 1721 of these single plant derived landrace lines were assessed for infection type against two barley leaf rust races. In the adult plant stage 1227 from these 1721 lines were evaluated for infection type against one race. In the seedling stage 2 (against race 1-2-1) and 29 against race A) out of the 1721 lines showed an infection type lower than 6–7 on the 0 to 9 scale. In the adult plant stage none of the 1227 lines had an infection type lower than 6–7 against race 1-2-1.The variation between and within the landraces for latent period in the adult plant stage was large. Some landraces such as landrace 212845 showed a highly significant and longer mean latent period than most other landraces. Virtually all plants in all landraces carry at least some partial resistance.The near-absence of race-specific, major, resistance genes and the high frequency of moderate levels of partial resistance indicates that the durability of leaf rust resistance in Ethiopian barley landraces is due to the latter type of resistance, and that the multiline principle does not operate.     

Extent and Pattern of Genetic Diversity for Morpho-agronomic Traits in Ethiopian Highland Pulse Landraces: I. Field Pea (<Emphasis Type="Italic">Pisum sativum</Emphasis> L.)

An experiment was conducted in 2001 at Holetta and Kulumsa, Ethiopia, to study the extent and pattern of genetic diversity in Ethiopian field pea (Pisum sativum L.) landraces. One hundred forty-eight germplasm accessions were grown in an alpha lattice design with 2 replications. Data on 12 traits were collected and analyzed. Differences among the accessions were significant for most of the traits (except number of seeds/ pod) at each location even though differences pooled over location were mostly non-significant. The accessions were grouped into five clusters of different sizes. Accessions from the southern part of the country (Arsi) distributed overall clusters while those from the northern half (North and South Wello, North Gonder and North Shewa) fell into clusters C₁ to C₃. Cumulative effects of a number of characters dictated differentiation of the accessions into clusters. There was no definite relationship between geographic diversity and genetic diversity as overlapping was encountered in clustering pattern among accessions from different parts of the country. Accessions from different regions might have similar genetic background and those from the same origin might also have different genetic background. Therefore, geographic diversity should not necessarily be used as an index of genetic diversity and parental selection should be based on a systematic study of genetic diversity in a specific population. Genetic distances among most of the clusters were significant that crosses between parents selected out of them are expected to generate desirable genetic recombination. Selection should also consider the special advantages of each cluster and each accession within a cluster. Future germplasm collection, conservation and breeding efforts should focus not only on inter-regional diversity but also on intra-regional diversity.     

Extent and Pattern of Genetic Diversity for Morpho-agronomic Traits in Ethiopian Highland Pulse Landraces II. Faba Bean (<Emphasis Type="Italic">Vicia faba</Emphasis> L.)

A field experiment was conducted in 2001 at Holetta and Kulumsa, Ethiopia, to study genetic diversity in Ethiopian faba bean (Vicia faba L.) landraces. One hundred sixty random germplasm accessions were grown in an alpha lattice design with two replications. Data on 12 traits were collected and analyzed. Significant differences were observed among the accessions for most of the traits (except number of pods/podding nodes) at each location even though differences pooled over location were mostly non-significant. Cluster analysis distinguished seven diversity classes of different sizes. Accessions from the northern half of the country (North and South Wello, North Gonder and North Shewa) were closely related while those from the southern part of the country (Arsi) were highly diverse. Cumulative effects of a number of characters dictated differentiation of the accessions into clusters. Some overlapping were encountered between accessions from the northern and those from the southern parts of the country. The study revealed that accessions from different regions might have similar genetic background and those from the same origin might also have different genetic background. Therefore, geographic diversity should not necessarily be used as an index of genetic diversity and parental selection should be based on a systematic study of genetic diversity in a specific population. Genetic distances between most of the clusters were significant that crosses between parents selected out of them are expected to generate desirable progenies. Future germplasm collection, conservation and utilization strategies should put more focus not only on inter-regional diversity in the country as a whole but also on intra-regional diversity in Arsi.     

Infectious bursal disease: seroprevalence and associated risk factors in major poultry rearing areas of Ethiopia

The study was conducted in eight districts of Ethiopia with the objectives of determining the seroprevalence and associated risk factors of infectious bursal disease (IBD). From the total of 2,597 chicken serum samples examined using ELISA, 83.1 % were found positive. The highest seroprevalence was found at Mekele (90.3 %) while the lowest was recorded at Gondar district (69.8 %). These differences among the study areas were statistically significant (p?<?0.05). Highest seroprevalence was found in crossbreed of chicken (91.4 %) while the lowest was recorded in indigenous breed of chicken (81.4 %). This difference was statistically significant (p?<?0.05) among the three breeds of chickens, but sex was not statistically significant (p?>?0.05). The seroprevalence of the disease was found high in young (≤8 weeks) age group (86.6 %) while the lowest prevalence was recorded in adults (>8 weeks) (72 %). This is also statistically significant (p?<?0.05) between young and adult age groups. The prevalence of IBD in different production system indicated that higher seroprevalence was recorded in intensive production system (85.9 %) while the lowest was recorded in extensive production system (81.6 %). This difference is also statistically significant (p?<?0.05).     

Occurrence of aphid vector and genetic tolerance to infection by potyvirus in hot pepper

The productivity and marketable quality of hot pepper (Capsicum annuum var. annuum L.) are low in tropical regions mainly due to virus infections and lack of effective virus management strategies. The absence of effective virus management strategies could be attributed to lack of information on virus vectors and host resistance. Parental (P₁ and P₂) and progeny (F₁, B₁, B₂ and F₂) generations of five hot pepper crosses were grown in Ethiopia at three sites (Bako, Hawasa and Melkasa) to monitor number and species of potential aphid vectors, disease incidence levels with regards to natural infections by Potato virus Y (PVY) and Ethiopian pepper mottle virus (EPMV) complex, and to determine genetic tolerance of the crop to the viruses. Disease incidence was assessed before the flowering stage of the crop plants using visible disease symptoms due to infections by PVY and EPMV. The serological tests revealed presence of symptomless genotypes of the crop to the virus infections. Aphid species potentially transmitting the viruses, such as Acyrthosiphon pisum (Harris), Aphis fabae (Scopoli), and Myzus persicae (Sulzer), were identified from specimens caught by yellow water traps. The highest number of aphids from yellow water traps was recorded at a dense foliage growth stage of the crop at Melkasa. Highly significant variation was observed among generations of the five crosses in response to infections by PVY and EPMV complex. The most susceptible parents had the levels of disease incidences ranging from 80 to 90%, whereas their progenies had only below 30% incidence levels. The most tolerant parent remained symptomless to the natural infections of PVY- and EPMV-complex. Incidence levels in progenies of a cross from the most susceptible and tolerant parents remained below 20%. Based on serological test, the proportion of PVY-positive plants ranged from 0 to 75% and of EPMV-positive plants from 0 to 25%, with 0 to 17% co-infection by the two viruses. Availability of virus sources in the vicinity, efficiency of aphids in vectoring, weather conditions during the growth period, genetic tolerance and the growth stage of the crop affected natural infection by PVY- and EPMV-complex. Exploitation of the genetic potential of introduced elite genotypes and their progenies along with breeding elite local cultivars for resistance and excluding aphid vectors at young (seedling) stage of the crop plants could be helpful for minimizing losses in yield and quality of hot pepper due to infections by PVY- and EPMV-complex.     

Longevity of <Emphasis Type="Italic">Juniperus procera</Emphasis> seed lots under different storage conditions: implications for ex situ conservation in seed banks

Juniperus procera Endl. is economically important timber species, but its populations are extremely small and fragmented in its natural habitat, thus, calling for immediate ex situ conservation. Here we examined the effects of seed sources and storage temperature on the longevity of Juniperus procera seed lots through collection and preservation of seeds in seed banks. Seeds were collected from nine sites across the species natural distribution in Ethiopia and stored in four warehouses: modern cold room (5℃), mud house (15℃), concrete block house (17℃ or corrugated iron house (20℃) for 42 months. Every three months, a random sample of stored seeds were drawn and tested for germination. A highly significant variation (p < 0.01) in germination of stored seeds was observed among different storage environments, seed lots, and duration of storage. Over the storage period, seeds stored in the cold room had the highest mean percentage germination, followed by the mud house, corrugated house and blocket house. The cold room (41%) and the mud house (38%) maintained the same level of germination as the intitial germination of the seedlotds (42%). The variation in longevity of stored seeds was significnatly correlated with the initial germination of seed lots (r > 0.80; p < 0.01). Cold storage also resulted in enhancement of germination through its stratification effect that terminated the non-deepphysiological dormancy of juniper seeds. In conclusion, seed lots with good initial germination can be effectively stored in cold room (5℃) up to four years. In the absence of modern cold stores, mud houses can be used as a good alternative to store seeds at local level.     

Mating biology,nuclear DNA content and genetic diversity in spider plant (Cleome gynandra) germplasm from various African countries

Cleome gynandra (L.) Briq. is an African leafy vegetable with a potential to improve food security and micronutrient deficiencies. Cytological traits, breeding biology and genetic diversity of 30 selected entries of C. gynandra from six African countries were investigated. The entries consisted of advanced lines, gene bank accessions and farmers’ cultivars. Our study revealed chromosome numbers of 2n = 34 in root tip metaphase cells from one entry. The 30 entries were found to be diploid with genome sizes ranging from 2.31 to 2.45 pg/2C. Hand pollination experiments were carried out to assess self‐incompatibility within the entries and revealed that they are self‐ and cross‐compatible. For genetic diversity studies within and among the entries, the pooled data of 499 polymorphic bands from 11 amplified fragment length polymorphism primer combinations and nine simple sequence repeat markers were used. The genetic distance among the entries ranged from 0.13 to 0.77. In a principal coordinate analysis, the farmers’ cultivars formed a cluster separate from the advanced lines and the gene bank entries, and the latter were not well resolved.     

Nutrient uptake and use efficiency of onion seed yield as influenced by nitrogen and phosphorus fertilization

Abstract

The experiment was conducted at Kulumsa, South East Ethiopia, using four levels of nitrogen (N) (0, 50,100 and 150?kg N ha^?1) and four levels of phosphorus (P) (0, 35, 70 and 105?kg P₂O₅ ha^?1) fertilizers arranged in 4?×?4 factorial arrangements in randomized complete block design with three replications. The available P was increased after harvest due to the application of N and P fertilizer at the rates of 100 or 150?kg N ha^?1 and 70 or 105?kg P₂O₅ ha^?1. More specifically, nutrients concentration and nutrient uptake were significantly (p?<?.01) varied among treatment combinations and nutrient use efficiency was declined by increasing N and P after optimum rates. The higher physiological efficiency of N (53.47?kg kg^?1) and P (580.41?kg kg^?1) and the highest apparent recovery of N (19.62%) and P (2.47%) was recorded from application of 50?kg N ha^?1 and P at 70?kg P₂O₅ ha^?1 and the highest agronomic efficiency of N (10.78?kg kg^?1) and P (15.25?kg kg^?1) was recorded from N at the rate of 50?kg N ha^?1 and P at 35?kg P₂O₅ ha^?1, respectively. The combination of N at 100?kg N ha^?1 and P at 70?kg P₂O₅ ha^?1 was promising combination that generated highest net benefit 488,878.5 ETB (Ethiopian birr) ha^?1 with the highest marginal rate of return (36638%) and gave the highest seed yield (1858.82?kg ha^?1) with yield increment of about 57.72% over the control.