Co-inoculation effect of rhizobia and plant growth promoting rhizobacteria on common bean growth in a low phosphorus soil

Open Access JournalNitrogen (N) fixation through legume-Rhizobium symbiosis is important for enhancing agricultural productivity and is therefore of great economic interest. Growing evidence indicates that other soil beneficial bacteria can positively affect symbiotic performance of rhizobia. Nodule endophytic plant growth promoting rhizobacteria (PGPR) were isolated from common bean nodules from Nakuru County in Kenya and characterized 16S rDNA partial gene sequencing. The effect of co-inoculation of rhizobium and PGPR, on nodulation and growth of common bean (Phaseolus vulgaris L.) was also investigated using a low phosphorous soil under greenhouse conditions. Gram-positive nodule endophytic PGPR belonging to the genus Bacillus were successfully isolated and characterized. Two PGPR strains (Paenibacillus polymyxa and Bacillus megaterium), two rhizobia strains (IITA-PAU 987 and IITA-PAU 983) and one reference rhizobia strain (CIAT 899) were used in the co-inoculation study. Two common bean varieties were inoculated with Rhizobium strains singly or in a combination with PGPR to evaluate the effect on nodulation and growth parameters. Co-inoculation of IITA-PAU 987 C B. megaterium recorded the highest nodule weight (405.2 mg) compared to IITAPAU 987 alone (324.8 mg), while CIAT 899 C B. megaterium (401.2 mg) compared to CIAT 899 alone (337.2 mg). CIAT 899 C B. megaterium recorded a significantly higher shoot dry weight (7.23 g) compared to CIAT 899 alone (5.80 g). However, there was no significant difference between CIAT 899 C P. polymyxa and CIAT 899 alone. Combination of IITA-PAU 987 and B. megaterium led to significantly higher shoot dry weight (6.84 g) compared to IITA-PAU 987 alone (5.32g) but no significant difference was observed when co-inoculated with P. polymyxa. IITA-PAU 983 in combination with P. polymyxa led to significantly higher shoot dry weight (7.15 g) compared to IITA-PAU 983 alone (5.14 g). Plants inoculated with IITA-PAU 987 and B. megaterium received 24.0 % of their nitrogen demand from atmosphere, which showed a 31.1% increase compared to rhizobium alone. Contrast analysis confirmed the difference between the co-inoculation of rhizobia strains and PGPR compared to single rhizobia inoculation on the root dry weight. These results show that co-inoculation of PGPR and Rhizobia has a synergistic effect on bean growth. Use of PGPR may improve effectiveness of Rhizobium biofertilizers for common bean production. Testing of PGPR under field conditions will further elucidate their effectiveness on grain yields of common bean

The State of Agricultural Mechanisation in Uasin Gishu District, Kenya, and its Impact on Agricultural Output

Rosana G. Moreira, Editor-in-Chief; Texas A&M UniversityThis is a paper from International Commission of Agricultural Engineering (CIGR, Commission Internationale du Genie Rural) E-Journal Volume 9 (2007): The State of Agricultural Mechanisation in Uasin Gishu District, Kenya, and its Impact on Agricultural Output. Invited Overview. Vol. IX. June, 2007

Socioeconomic constraints to sustainable cocoyam production in the Lake Victoria Crescent

Cocoyam production has the potential of significantly improving the food security status and income levels of farmers in the Lake Victoria region. The study covered various areas of the three East African states, Kenya, Uganda and Tanzania as follows: Kisumu, Kakamega and Siaya districts in Kenya; Bukoba in Tanzania; and Mukono, Wakiso and Kampala in Uganda. Structured questionnaires were used to collect data from a total of 283 respondents. Results showed that farmers had an adequate level of education that enabled them utilize cocoyam production technologies. However, land scarcity was the major factor limiting cocoyam cultivation. This was attributed to the fact that cocoyam cultivation was restricted to wetlands, which was already a limited resource in the region. Other factors such as diseases, weeds, pests, scarcity of labour, unavailability of extension services and planting material and improved varieties, among others influenced the production of the crop. Research and development agencies in the study area need to develop appropriate cocoyam production technologies to mitigate existing constraintsKey words: Cocoyam production, social and economic constraints, Lake Victoria region

Distribution, characterization and the commercialization of elite Rhizobia strains in Africa

Grain legumes play a significant role in smallholder farming systems in Africa because of their contribution to nutrition and income security and their role in fixing nitrogen. Biological Nitrogen Fixation (BNF) serves a critical role in improving soil fertility for legumes. Although much research has been conducted on rhizobia in nitrogen fixation and their contribution to soil fertility, much less is known about the distribution and diversity of the bacteria strains in different areas of the world and which of the strains achieve optimal benefits for the host plants under specific soil and environmental conditions. This paper reviews the distribution, characterization, and commercialization of elite rhizobia strains in Africa

Flowering and maturation periods of Finger Millet as influenced by phosphorus and variety in different agro-ecologies in Kenya

Phosphorus is important for finger millet production in many tropical African soils with low phosphorus fertility. Knowledge of redirection of this limited resource for reproduction is fundamental in realization of potential yields. The effect of four phosphorus levels (0, 12.5, 25.0 and 37.5 kg ha-1 P2O5) and three varieties (U-15, P-224 and a local check) on the days to flowering and maturity of finger millet were evaluated in three agro-ecologies in Kenya during the raining seasons of 2014-2015. Phosphorus application significantly (P<0.05) increased early flowering and physiological maturity in Kakamega and Busia. The varieties elicited significantly different days to 50% flowering and maturation periods in all the study sites. The days to flowering and maturity were found to be lowly but negatively correlated with the grain yield of finger millet in all the sites

Phosphorus influence on nitrogen uptake, nutrient and yield attributes of finger millet in semi-arid region of Kenya

An understanding of P efficiencies of finger millet is very important in soil management and selection of varieties adaptable to P-deficient soils. Therefore, on-station experiments were conducted at the ICRISAT-Kiboko research station to evaluate the effect of differential levels of P on nitrogen uptake, nutrient content and yield. There were four P levels (0, 12.5, 25 and 37.5 kg ha-1 P2O5) and three varieties (U-15, P-224 and Ekalakala). Ekalakala was the local check while 0 kg/ha P2O5 was the control. The trial was laid out in a randomized complete block design in factorial arrangement with three replicates. Soil analytical results showed moderately available P but very low N, organic carbon and zinc. Significant differences (P<.05) were observed between the phosphate levels on the nitrogen contents, where the control had the lowest with 4.95% and 4.90% for the short and long rains respectively; while the 25 kg ha-1 P2O5 rate had the highest, with 5.66% in the short rains and 5.14% in the long rains. The protein content significantly increased with phosphorus application, peaking at 11.00 g/100 g on the 25 kg ha-1 P2O5treatment. The newly released variety (U-15) responded positively to P supplemented at 25 kg ha-1 P2O5 , with a maximum grain yield of 3,410 kg ha-1. It can, thus, efficiently utilize N in soils with low N and is highly recommended. The application of P beyond 25 kg ha-1 P2O5 would not be translated into profitable yields, but losses to the farmer

Effect of Phosphate Levels on Soil Rhizosphere Nutrient Balances and Finger Millet Yield

Soil infertility is one of the main factors leading to low finger millet production in the semi-arid tropics of Kenya. About 50-80% of P applied as fertilizer is adsorbed by soil and the amount of P needed to achieve maintenance of its adequate status and influence on other soil properties has not been well documented. An on-station experiment was therefore conducted at the KALROKiboko research station during the 2014 long and 2015 short rain seasons to investigate the influence of phosphorus rates on soil rhizosphere chemical properties and yield of three finger millet varieties. The experiment was laid out in a Randomized Complete Block Design in factorial arrangement and replicated three times. There were four P levels (0, 12.5, 25 and 37.5 kg ha-1 P2O5) and three varieties (U15, P-224 and local check-Kat FM1). Phosphorus application reduced the soil pH significantly for both seasons with the 37.5 kg ha-1 P2O5 rate eliciting the greatest pH from 9.26 to 7.90 (1.36 units) during the long rain season. As expected, soil phosphorus increased with the highest rate with 11 ppm during the long rain season and 9 ppm for the short rains. The organic carbon increased by 0.28% for the long rain season on the 25 kg ha-1 P2O5 rate while the highest rate increased total N by 0.05%. The 25 kg ha-1 P2O5 rate and U-15 indicated the highest yield for both seasons with a maximum of 3.71 t ha-1 realized during the short rain season. Monitoring change in soil nutrient status is important for prescribing P fertilization in order to maintain or replenish soil fertility. The application rate of 25 kg ha-1 P2O5 led to the optimal yields under the improved variety and hence the study recommends this rate

ANTAGONISTIC EFFECTS OF BIOCONTROL AGENTS AGAINST Phytophthora infestans AND GROWTH STIMULATION IN TOMATOES

Late blight disease is a major cause of economic losses in tomato ( Lycopersicon esculentum L.) production in eastern Africa. The objective of this study was to evaluate the efficacy of Trichoderma species in controlling late blight disease and their role on the growth of tomato. Trichoderma asperellum and T. harzianum were isolated from two commercial products containing the antagonistic species. Culture-based and molecular approaches, genomic DNA isolation and amplification, using ITS1 and ITS4 universal primers, and sequencing, were used to characterise the products. Trichoderma antagonistic effects against Phytophthora infestans (causative of tomato late blight) experiments were conducted in vitro and in the greenhouse. The greenhouse experiment had five treatments; namely, a negative control, Metalaxl-M, T. asperellum, T. harzanium and mixture of the two biocontrol agents, laid out in a randomised complete block design. The experiment was carried out for 12 weeks, with 3 weeks measurements intervals. Morphological and molecular characterisation confirmed the organism in most of the commercial products as T. harzianum and T. asperellum. An inhibiting action was observed on the P. Infestans mycelial growth, by the effect of T. asperellum (30.7%), and T. harzianum (36.9%).Trichoderma spp. suppressed late blight disease in the greenhouse experiment. These effects were specific to soil type, with the higher effectiveness realised in Ferralsols (27% disease severity) and least in Nitisols (36% disease severity). Trichoderma harzianum and T. asperellum resulted in higher above ground biomass of tomato of 31 and 19% increase over the control, respectively. There is potential of biocontrol agents in reducing P. infestans effects in tomatoes and in stimulating growth.La maladie du mildiou est une cause majeure de pertes \ue9conomiques dans la production de tomate ( Lycopersicon esculentum L.) en Afrique de l\u2019Est. L\u2019objectif de cette \ue9tude \ue9tait d\u2019\ue9valuer l\u2019efficacit\ue9 des esp\ue8ces de Trichoderma dans la lutte contre le mildiou et leur r\uf4le sur la croissance de la tomate. Trichoderma asperellum et T. harzianum ont \ue9t\ue9 isol\ue9s de deux produits commerciaux contenant les esp\ue8ces antagonistes. En se basant sur la culture et des approches mol\ue9culaires, l\u2019isolement de l\u2019ADN g\ue9nomique et l\u2019amplification, en utilisant des amorces universelles ITS1 et ITS4, et le s\ue9quen\ue7age ont \ue9t\ue9 utilis\ue9s pour caract\ue9riser les produits. Des effets antagonistes de Trichoderma contre Phytophthora infestans (causant le mildiou de la tomate) ont \ue9t\ue9 men\ue9s in vitro et en serre. L\u2019exp\ue9rience en serre a eu cinq traitements; \ue0 savoir, un contr\uf4le n\ue9gatif, Metalaxl-M, T. asperellum, T. harzanium et un m\ue9lange des deux agents de lutte biologique, dispos\ue9s dans un mod\ue8le de bloc complet randomis\ue9. L\u2019exp\ue9rience a dur\ue9 12 semaines, avec des intervalles de mesure de 3 semaines. La caract\ue9risation morphologique et mol\ue9culaire a confirm\ue9 l\u2019organisme dans la plupart des produits commerciaux comme T. harzianum et T. asperellum. Une action inhibitrice a \ue9t\ue9 observ\ue9e sur la croissance myc\ue9lienne de P. Infestans, sous l\u2019effet de T. asperellum (30,7%) et T. harzianum (36,9%). Trichoderma spp. supprim\ue9 la maladie du mildiou dans l\u2019exp\ue9rience en serre. Ces effets \ue9taient sp\ue9cifiques au type de sol, avec une efficacit\ue9 plus \ue9lev\ue9e r\ue9alis\ue9e dans les Ferralsols (27% de gravit\ue9 de la maladie) et moins dans les Nitisols (36% de gravit\ue9 de la maladie). Trichoderma harzianum et T. asperellum ont entra\ueen\ue9 une augmentation de la biomasse a\ue9rienne de la tomate de 31 et 19% par rapport au t\ue9moin, respectivement. Les agents de lutte biologique peuvent r\ue9duire les effets de P. infestans sur les tomates et stimuler la croissance

Finger Millet (Eleusine coracana) Fodder Yield Potential and Nutritive Value under Different Levels of Phosphorus in Rainfed Conditions

Scarcity of fodder is the major limiting factor for increasing livestock production in Kenya. With rising energy costs and declining water levels in the semi-arid tropics and sub-tropics, crops that use less water like finger millet could become an alternate fodder crop. The fodder potential of three finger millet varieties (U-15, P-224 and a local check) were evaluated under four P fertilizer levels (0, 12.5, 25 and 37.5 kg ha-1 P2O5) at three sites in Kenya for two cropping seasons. The trials were laid in randomized complete block design in factorial arrangement and replicated three times. A maximum of 28,189 kg ha-1 fresh stover yield was realized in the 25 kg ha-1 P2O5 treatment and consequently 11,616 kg ha-1 dry stover yield. The 25 kg ha-1 rate elicited the highest fresh stover yield at Kakamega and Alupe for both seasons while at Kiboko a linear increase was observed on the stover yield with increasing rates where the highest rate had more than 15% yield compared to the control. The varieties also showed significant differences in all the sites with the local variety, Ikhulule, showing the highest fresh and dry stover yield at Kakamega and Alupe peaking at 28,852 and 12,826 kg ha-1 fresh and dry stover yields respectively. Interactions between variety and phosphorus rates were revealed on the crude protein content of the finger millet stover. At Kiboko, the highest crude protein (11.0%) on varieties P-224 and U-15 was exhibited at the highest rate while on the local variety, Ekalakala, the highest protein (10.9%) was realized at the 25 kg ha-1 P2O5. At Kakamega and Alupe, the highest protein was observed on the local variety, Ikhulule at 12.5 kg ha-1 P2O5 rate with variety P-224 and U-15 showing the highest at the 25 and 37.5 kg ha-1 P2O5 respectively. Therefore, finger millet can provide a unique opportunity to improve the availability of fodder to smallholder livestock farmers

Nitrogen and Phosphorus Uptake and Partitioning in Finger Millet as Influenced by Phosphorus Fertilization

Finger millet (Eleusine coracana) production in Eastern Africa remains low due to a variety of factors including soil nutrient depletion. As intensive row-crop production evolves, improvements in managing soil nutrient quantity and availability of less renewable nutrients like P becomes increasingly important. The yields in Kenya are typical of low input systems ranging below 1.0 t ha-1 against a potential of 5.0 t ha-1 in a season. In an attempt to overcome this constraint, On-station experiments were conducted at the Alupe research station during the long and short rain seasons of 2015 to investigate the influence of phosphate fertilizer rates (0, 12.5, 25 and 37.5 kg ha-1 P2O5) on nutrient uptake and partitioning in finger millet. Partitioning of N and P was significantly influenced (P30%) while the least to the roots (<19%). Variety U-15 had the greatest partitioning of nitrogen to the grains while the local variety, Ikhulule had the least. Application of phosphorus led to increase in the nitrogen and phosphorus uptake in finger millet with the most in the grains with a maximum of 106.5 kg ha-1 on the 37.5 kg ha-1 P2O5 rate during the short rains while the roots had the lowest uptake with 16.9 kg ha-1 and 22.1 kg ha-1 in the long and short rains seasons respectively on the control. This study on nutrient use provides an opportunity to further improve P fertilization to specific rates in relation to crops needs as farmers will be assured of greater yields, profitable and sustainable production. Limited use of P fertilizer restricts the uptake of phosphorus and nitrogen as well as the balance in partitioning and recommends application of 25 kg ha-1 P2O5 with improved varieties