EFFECT OF DROUGHT STRESS ON BARLEY - WHEAT INTERCROPPING

Vol. 14. No. 3, pp. 185-195, 2006

A. WOLDEAMLAK, M.J. KROPFF1 and P.C. STRUIK1

(Received 17 August, 2005; accepted 7 July, 2006

Abstract

The effects of drought or moisture stress (MS1- no stress; MS2- stress at seedling stage and MS3- stress at heading stage) was studied for different crop ratios of barley (Hordeum vulgare) and wheat (Triticum aestivum) mixtures sown in additive and replacement series at Halhale Research Station (Eritrea) during the off-seasons of 1998 and 1999. The objective was to identify crop ratios with higher productivity and to analyse the competition and niche differentiation of component crops in mixtures grown under stress. Competition and niche differentiation were assessed by analysing the data using a hyperbolic competition model. The best yields were obtained from the crop ratios 50% barley / 50% wheat and 25% barley / 100% wheat when averaged over two years. One barley plant was as competitive as about seven wheat plants. The relative competitive ability was higher in barley than in wheat. Inter-specific competition was larger than the intra-specific competition for wheat while for barley the intra-specific competition was greater than the inter-specific. The component crops shared the same resources in a complementary way. The Niche Differentiation Index (NDI) > 1 was related to Relative Yield Total (RYT) > 1 showing that the yield advantage was due to complementary use of resources. Key Words: Eritrea, Hordeum vulgare, mixed cropping, Triticum aestivum
Click here to download full version

EFFECT OF DROUGHT STRESS ON BARLEY - WHEAT INTERCROPPING

Vol. 14. No. 4, pp. 263-273, 2006

G. Otto Dangasuk, P. O. Odago, B.A. Were and S. Gudu
Department of Botany, Moi University, P. O. Box 1125, Eldoret, Kenya

(Received 1 May 2006; accepted 25 November, 2006)

Abstract

Polymerase Chain Reaction (PCR) analysis based on Internal Franscribed Spacers (ITS) and Random Amplified Polymorphic DNA (RAPD) were carried out on sixteen provenances of Faidherbia albida currently growing in a provenance trial in semi-arid Baringo district in Kenya. The objectives of the study were to: (i) determine the phylogenetic relationship among the 16 provenances in order to establish the species centre of origin, and (ii) determine the extent of genetic diversity in F. albida using PCR markers. ITS data did not produce any consistent regional or geographic pattern. RAPD data produced a dendrogram clearly grouping the provenances into Western, Southern and Eastern African regions. The study revealed the utility of RAPD markers in understanding geographic variation and phylogenetic relationships among F. albida populations in Africa. Key Words: DNA, Genetic diversity. Click here to download full version

INCIDENCE AND SEVERITY OF CASSAVA MOSAIC DISEASE IN THE REPUBLIC OF CONGO

Vol. 15, No. 1, pp. 1 - 9

P. NTAWURUHUNGA, G. OKAO-OKUJA, A. BEMBE1, M. OBAMBI2, J. C. ARMAND MVILA1
and J.P. LEGG3
International Institute of Tropical Agriculture Uganda, Kampala, Uganda

(Received 29 December, 2006; accepted 19 March, 2007)

Abstract

Diagnostic surveys were conducted in 2002 and 2003 in order to provide a comprehensive and detailed assessment of the status of cassava mosaic disease (CMD) in the Republic of Congo (ROC) and to determine if the disease was spreading. In 2002, 105 farmers’ fields were assessed in the four major cassava-producing regions of the country. In 2003, 163 fields were sampled in nine regions and Brazzaville Commune. Incidence of cassava mosaic disease was generally high, averaging 80 and 86 % for 2002 and 2003, respectively; while damage was moderate to severe. In 2002, disease incidence was moderate in Pool (73%) but high in Brazzaville (81%), Cuvette Centrale (82%) and in Plateaux Region (84%). Pool region still had the lowest incidence (78%) in 2003, while Sangha (95%) had the highest incidence. The greatest disease severity was recorded in Niari region in the south and Cuvette Ouest region in the north in 2003. East African cassava mosaic virus Uganda variant (EACMV-UG) occurred virtually throughout the country, commonly in dual infections with African cassava mosaic virus. The high incidence of disease in plants considered to be the results of cutting infection (74% in 2002 and 82% in 2003), relatively low incidence of disease in plants considered to be infected by whiteflies and wide distribution of EACMV-UG points to the fact that the CMD pandemic is a chronic in the country and the areas sampled are currently in a stable post-epidemic phase. This situation is comparable to that in areas of East Africa affected by a pandemic during the 1990s, including Uganda, parts of western Kenya and north-western Tanzania. These findings clearly verify the assertion that the CMD pendemic has expanded across Central Africa and provide a basis for designing interventions and control strategies for the entire region..
Click here to download full version

POTENTIAL MALE GAMETOPHYTE COMPETITION AMONG CAMELLIA SINENSIS

Vol. 15, No. 2, pp. 59 - 66

R.C. MUOKI, F.N. WACHIRA1*, R. PATHAK2 and S.M. KAMUNYA

(Received 17 February, 2007; accepted 17 June, 2007)

Abstract

Male fertility of crop plants is a function of pollen production and viability. In breeding, it is a requirement that there be similar fertilities among breeding parents within seed orchards. An in-vitro germination method was used in this study to determine variation in pollen viability among eight tea (Camellia sinensis) genotypes, over three flowering seasons in four isolated biclonal seed orchards located at two sites. The effect of environmental conditions on pollen germination was also studied on two popular genotypes, i.e. AHP SC31/37 (an assamica variety) and GW Ejulu-L (a sinensis variety) that were planted in both sites. Significant variation (P < 0.05) in pollen viability among the eight genotypes indicated a potential for male gametophyte competition. There was significant genotype by environment interaction and positive correlation between pollen viability and temperature. Pollen germination was, however, not affected by rainfall and humidity. The variations in pollen viability may contribute to the variable genetic composition of seed produced in the isolated seed orchards of tea. Key Words: In-vitro germination, male fertility, pollen viability .
Click here to download full version