Agricultural Biotechnology

1. Introduction 2. Microbial inoculation of plants 3. Recycling of organic wastes 4. Plant cell and tissue culture 5. Fermentation and enzyme technology 6. Transformation of plants and animals 7. Crop protection through pest resistance genes 8

Diversity and abundance of nematodes in agroecosystems of Kenya

A review of nematodes associated with crops has revealed that almost every crop or group of crops is attacked by one or several nematode pests, which cause economic losses in heavily infested fields. The most commonly reported nematodes belong to the genera Meloidogyne Goeldi, Pratylenchus, Filip'jev, Helicotylenchus, Steiner Scutellonema, Andrassy, Tylenchorhynchus, Cobb Xiphinema, Trichodorus, Cobb, Radopholus Thorne, Aphelenchoides, and Ditylenchus. Overall, populations of plant parasitic nematodes and their diversity decreases with intensity of land cultivation especially if the same crop or where a narrow range of crops is cultivated. The distribution of plant parasitic nematodes is influenced by many factors which include soil properties, environmental factors, susceptibility of crops and cultivars grown, cropping systems, type of nematodes and their interactive effects. A handful of studies show that plant parasitic nematodes form synergistic complexes with other soilborne pathogens resulting in more severe disease manifestations that lead to high yield losses. For instance, root-knot nematodes interact with Fusarium oxysporum to cause more severe wilt in pyrethrum. Journal of Tropical Microbiology Vol.3 2004: 24-3

Effect of phosphate rock fertilization and arbuscular mycorrhizae(AM) inoculation on growth and Nodulation of agroforestry tree seedlings

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The Diversity of Biological Nitrogen Fixing Systems in Kenya

This paper outlines efforts to utilize Biological Nitrogen Fixation (BNF) technology through the utilization of microbial and plant components of symbiotic nitrogen-fixing systems that are encountered in a tropical environment. It underscores the immense potential that exists in the application of BNF research in tropical farming systems using the diverse array of nitrogen fixing systems found in Kenya and some of the factors that influence BNF such as the prevalent stress conditions (acid stress, nutritional needs) that exist between rhizobia at the genera, species, and strain levels. The contribution of non-leguminous systems such as Frankia, and the free-living and associative nitrogen fixing systems have also been considered as have the other symbiotic nitrogen fixing systems: Azolla, and Blue green algae. Key Words: Rhizobium, Bradyrhizobium, Sinorhizobium, Azorhizobium, Legumes, Nitrogen Fixation Journal of Tropical Microbiology Vol.3 2004: 35-4

Fertilisation continue des Oxisols acides non humifères du

Crop rotation system of maize and beans, established at Rubona (Rwanda) from 1984 to 1992, was used to evaluate different types and rates of fertilizers in improving the productivity of acid Oxisols. Continuous cropping of maize followed by beans for a period of 8 years gave no yield in control plots. Asingle application of 2 t per ha of lime increased significantly (p = .01) the soil pH, Ca2+ content, cationic exchange capacity, and decreased the level of the exchangeable aluminium. This quantity of lime when applied every two years for a period of eight years led to overliming. The application of more than 8 t per ha of fresh farmyard manure (annually), combined to 300 kg per ha of NPK 17:17:17 (every six months) significantly improved soil organic C and crop production at Rubona. The high rate (35 t per ha) of fresh manure or the combination of “lime, manure and NPK fertilizers” gave the best crop performance. Ten tons of farmyard manure (dry matter) per ha and per year seems to be the minimum acceptable amount which can effectively substitute for inorganic fertilizers

Assessing the role of organic soil amendments in management of rootknotnematodes on common bean, Phaseolus vulgaris L.

A greenhouse study was conducted to determine the effectiveness of animal manures, cow and chicken manures, and green manures, Mucuna pruriens, Azadirachta indica and Tagetes minuta in root knot nematode suppression. The organic materials were mixed with soil at the rate of 5% (w/w) and placed in 5- kg plastic pots. The soil was infested with 4000 second-stage Meloidogyne juveniles and galling was assessed using a scale of 1 to 9. Galling was reduced in soil treated with organic amendments and ranged from 1.5 to 4.4 compared to 5.8 in the control. The amendments were ranked as chicken manure, neem, marigold, and cow manure in descending order of effectiveness in root-knot disease suppression. All the amendments were mo re effective than carbofuran, with the exception of cow manure. An analysis of the correlation between available ammonium nitrogen (NH4-N) and phosphorous (P) in amended soil done on one hand and nematode parameters on the other, showed significant (p < 0.01) negative relationships. The correlation coefficient (r = -0.85) between NH4-N and juvenile numbers in the soil was significant (p < 0.01). Similarly, phosphorous was negatively and significantly (p < 0.01) correlated to nematode egg mass (r = -0.79) and juvenile (r= -0.44) numbers. Microbial activity, measured using microbial biomass, carbon and nitrogen, was higher in organically amended soils than the control, with the highest figures being recorded on chicken manure. This is a clear demonstration of the potential of organic amendments in triggering the natural mechanisms that regulate plant nematodes in the soil. Journal of Tropical Microbiology Vol.3 2004: 14-2