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  Effects of Azolla and inorganic nitrogen application on growth and yield of rice in mwea irrigation scheme

  (International Journal of Agronomy and Agricultural Research (IJAAR), 2019-03-24)

  Oyange, W. A

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  Chemining’wa, G. N

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  Kanya, JI

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  Njiruh, Nthakanio P.

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  Use of inorganic fertilizers constitutes 20% of the rice production cost in Mwea. Azolla fern, which grows in Mwea Irrigation paddies, has the potential to supplement the nitrogen requirement, thus reducing the fertilizer costs. A field experiment was conducted in Mwea Irrigation Scheme during 2015 long and short rains to determine the effect of Azolla incorporation and inorganic nitrogen on growth and yield of rice. The treatments comprised three nitrogen fertilizer levels (0, 30 and 60kg N ha-1) and three Azolla biomass levels (0, 7.5 and 15tons ha-1) laid out in a randomized complete block design with a split-plot arrangement. Data on plant height and number of tillers per plant were collected at 21, 35, 45, and 65 and 75 days after transplanting rice while yield and yield components were determined at 120 days after transplanting rice. Soil was analysed for N, P and K, before and after termination of the experiment. Data were subjected to analysis of variance using SAS and means separated using the least significant difference test at p ≤ 0.05. Azolla incorporation significantly increased residual soil phosphorus, grain weight, % grain filling and grain yield. Inorganic nitrogen significantly increased plant height, tiller numbers, neck node, and panicle length, number of panicle m-2 and grain yield. Grain yield increase from Azolla treatment ranged from 5 to 42% compared to that of inorganic nitrogen which ranged from 18 to 36%. Application of 15t ha-1 of Azolla biomass recorded the highest yield, however, it was not significantly different from that of 7.5t ha-1.

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  Effects of inorganic nutrient P and N application on Azolla biomass growth and nutrient uptake

  (International Journal of Agronomy and Agricultural Research (IJAAR), 2019-02-28)

  Oyange, W. A

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  Chemining’wa, G. N

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  Kanya, JI

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  Njiruh, Nthakanio P.

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  Rice farmers in Mwea Irrigation Scheme routinely apply P and N fertilizers which affect water nutrient levels. A study was conducted to establish the effects of nutrient N and P application on Azolla biomass accumulation. The study was conducted in a batch culture experiment, using 5g of fresh Azolla biomass samples from each of the six major paddy schemes namely: Mwea, Ahero, West Kano, Bunyala, TARDA, and Taveta. Treatments consisted of 0 and 3mg P l-1 and 0 and 200mg N l-1, laid out in a randomized complete block design replicated three times. Azolla samples were grown in batch culture plastic pots of 8.4 x 10-3m3 for 10 days using canal water, which was replenished every three days. Fresh Azolla biomass weight was recorded at 0, 5 and 10 days after inoculation. Data was subjected to analysis of variance using SAS statistical package version 9.1 and means separated using the least significant difference test (p≤0.05). The pH levels in irrigation water averaged 7.2 while N, P and K levels were 20.2, 11.6 and 15ppm respectively. Tissue N and K for Azolla accession averaged 4.2% and 1.6% respectively. Biomass accumulation and doubling time of Azolla were significantly affected by exogenous P and N nutrient application. Doubling time ranged from 5.5 days to 6.7. Application N and P significantly reduced Azolla biomass accumulation and increased biomass doubling time.

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  Effects of azolla biomass growth on flood water temperature and ph, tillering and yield of paddy rice.

  (Tropical and Subtropical Agroecosystems, 2019-08-22)

  Oyange, W.A.

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  Chemining’wa, G.N.

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  Kanya, J.I.

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  Njiruh, Nthakanio P.

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  Azolla is a floating pteridophyte, which forms an association with an endosymbiont, the nitrogen-fixing cyanobacterium Anabaena azollae. In Mwea Irrigation Scheme paddies, Azolla biomass coverage ranges from 25 to 50 % with a high biomass growth rate and this has caused a challenge in its management. Knowledge on the effect of Azolla biomass on rice tillering, root development and grain yield are important in order to exploit its potential benefits in Mwea Irrigation Scheme, where nearly 60 % of the total rice in Kenya is produced. The effect of Azolla on tillering, plant biomass, adventitious roots development, basal internode growth and yield of rice, was studied during 2015/2016 short and long rains. Azolla was inoculated in 30 cm x 30 cm plastic pots planted with rice variety Basmati 370. Controls where no Azolla was inoculated were included. Tiller number, plant height, flood water temperature and pH were determined at 21, 32, 42, 60 and 75 days after transplanting (DAT). At 120 DAT, grain yield and yield components were determined. Length of basal node and adventitious root were measured and dry biomass weights of, root and above ground biomass determined. Water temperature in Azolla inoculated pots were significantly lower than in controls by 0.8 °C and 1.3 °C in the second and first seasons respectively with a daily fluctuation of 2 °C. The pH of flood water in potted rice inoculated with Azolla was significantly lower than in control. Azolla inoculated potted rice had significantly higher number of tillers/m2, spikelets per panicle-1, panicle size m-2, 1000 grain weight and plant biomass than in non-inoculated controls. Adventitious roots were significantly longer and more per unit area in all treatments than in controls. The basal stem node length was significantly shorter while root biomass was less for the Azolla inoculated potted rice than in controls. In all treatments, Azolla doubled its biomass within an average of 5 days.

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  Overexpression of rice thaumatin-like protein (Ostlp) gene in transgenic cassava results in enhanced tolerance to Colletotrichum gloeosporioides

  (Journal of Genetic Engineering and Biotechnology, 2017-12-16)

  Ojola, Patroba Odeny

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  Nyaboga, Evans N.

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  Orinda, George

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  Njiruh, Nthakanio P.

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  Cassava (Manihot esculenta Crantz) is the most important staple food for more than 300 million people in Africa, and anthracnose disease caused by Colletotrichum gloeosporioides f. sp. manihotis is the most destructive fungal disease affecting cassava production in sub-Saharan Africa. The main objective of this study was to improve anthracnose resistance in cassava through genetic engineering. Transgenic cassava plants harbouring rice thaumatin-like protein (Ostlp) gene, driven by the constitutive CaMV35S promoter, were generated using Agrobacterium-mediated transformation of friable embryogenic calli (FEC) of cultivar TMS 60444. Molecular analysis confirmed the presence, integration, copy number of the transgene all the independent transgenic events. Semi-quantitative RT-PCR confirmed high expression levels of Ostlp in six transgenic lines tested. The antifungal activity of the transgene against Colletotrichum gloeosporioides pathogen was evaluated using the leaves and stem cuttings bioassay. The results demonstrated significantly delayed disease development and reduced size of necrotic lesions in leaves and stem cuttings of all transgenic lines compared to the leaves and stem cuttingss of non-transgenic control plants. Therefore, constitutive overexpression of rice thaumatin-like protein in transgenic cassava confers enhanced tolerance to the fungal pathogen C. gloeosporioides f. sp. manihotis. These results can therefore serve as an initial step towards genetic engineering of farmer-preffered cassava cultivars for resistance to anthracnose disease.

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  Occurrence and genetic variability of partial coat protein gene of Sweet potato leaf curl virus (SPLCV) in Kenya

  (African Journal of Biotechnology, 2017-06-09)

  Maina, S

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  Miano, D. W

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  Mbogo, E.

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  Amimo, J. O.

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  Irungu, J.

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  A survey was conducted to determine the occurrence of sweet potato leaf curl virus (SPLCV) infecting sweet potato in Kenya. Vine cuttings of sweet potato were collected in 2011 from fields in Central, Western and Coastal regions of the country. The cuttings were grown in an insect-proof screen-house and scion grafted to Ipomoea setosa indicator plants. DNA was extracted from leaf samples of graft inoculated I. serosa and tested for the presence of SPLCV by polymerase chain reaction (PCR) using degenerate and specific primers. The virus was detected in all the regions with incidence rates of 33, 17.0 and 2.6% from Western, Coastal and Central regions, respectively using specific primers. Coat protein gene AV1 from isolates collected from each region was sequenced and their comparison revealed >88.4% nucleotide identity. Phylogenetic grouping using nucleotide and amino acid sequences showed that four Kenyan isolates (Coast3, Central13, Coast15 and Western14) clustered together, while the other remaining five grouped a long with isolates from different parts of the world. The results reveal that Kenyan SPLCV isolates have a clear diversity and are also closely related with other isolates from different parts of the world. The wide distribution of the virus within the country means that urgent measures are needed to clean the farmers planting material to reduce possible losses incurred due to the presence of the virus.

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