Browsing by Author "Isutsa, D. K."

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Climate change adaptation of potato (Solanum tuberosum L.) 2: Influence of Biozyme® rate on potato growth and development.
(2013-07-31) Karanja, B. K.; Isutsa, D. K.; Aguyoh, J. N.; ; ;
Potato is an important food crop worldwide. Growers adopt potato production due its short growing season and poor soils tolerance. They use agrochemicals to improve growth under unreliable rainfall. Biozyme® foliar feed is widely used to hasten maturity and enhance yields of crops. It is said to be a storehouse of hormones and nutrients that improve crop health. It contains major hormones along with primary and secondary nutrients. This study determined if Biozyme® could overcome deficit rainfall and enhance potato growth to adapt to climate change. The arrangement was split plots in randomized complete block design replicated three times and repeated once. Main plots were assigned to potato cultivar (Tigoni and Asante) and subplots to Biozyme® rate (0, 125, 250, 500 and 750 ml/ha). Each subplot was planted with 28 tubers spaced at 30 cm x 70 cm in four rows. A distance of 1 m separated plots. Plant growth in height, stem diameter and aboveground biomass increased with increase in Biozyme® rate. The 750 ml/ha rate increased height by 41%, stem diameter by 55.34%, chlorophyll by 19.45 spads, flowers by 21.86%, as compared to the control rate (0 ml/ha), but was not significantly different from 500 ml/ha rate. Increased height, leaf area index, chlorophyll content, aboveground biomass is good as it enhances photosynthate synthesis and translocation to edible tubers. Thus, foliar-feeding potato plants with at most 500 ml/ha Biozyme® is recommended for hastening growth in regions with deficit rainfall.
Determination of Factors Influencing Cultivation and Utilisation of Pumpkins Among Smallholders in Kakamega and Nyeri Counties, Kenya
(Taylor and Francis, 2019-06-27) Kiramana, J. K.; Isutsa, D. K.; ; ;
Pumpkin is becoming an important fruit-vegetable, although its potential remains unexploited in Kenya. This study aimed at enhancing conservation, preservation and production of naturalized pumpkins through the cataloguing of accessions and documentation of indigenous traditional knowledge influencing cultivation and utilization. In 2012 an expedition led to the collection of 155 accessions of Cucurbita moschata (Lam.) Poir., with 70 from Kakamega and 85 from Nyeri. Variegated accessions were significantly (p<0.05) the most popular and highly utilized, compared to the exotic green-leafed ones. Significantly (p<0.05) more green-leafed accessions were collected in Nyeri, and variegated in Kakamega. There was significant (p<0.05) variation in fruit shape and skin colour. Fruit-form ranged from ovate to globose or elliptical, and the predominant skin colour was dark to pale-green. Intercropping was the main cropping system. Food provision and income generation significantly (p<0.05) influenced cultivation and utilization of the pumpkins. Most variegated accessions were inherited from past generations and have become naturalized. The green-leafed accessions were introduced by farmers and other stakeholders. Fruits and leaves were significantly (p<0.05) utilized by farmers, compared to seeds and whole plants. The quality of fruits and leaves, cooking method and recipes were significantly (p<0.05) considered by farmers when selecting accessions to cultivate. These factors were significant (0.05) in sustaining genetic diversity and conservation. Interventions to preserve positive factors and overcome constraining ones should be promoted to enhance growing of naturalised pumpkin for good health and income generation.
Effect of pruning time and resting period on total non-structural carbohydrates, regrowth, and yield of tea (Camellia sinensis L.).
(Taylor and Francis, 2015-11-07) Bore, J. K.; Isutsa, D. K.; Itulya, F. M.; Ng'etich, W. K.; ; ;
An experiment was conducted at Kipkebe Estate, Sotik, Kenya, with the aim of establishing the effects of pruning time and resting period on total non-structural carbohydrate (TNC) reserves, regrowth and yield of tea. In this experiment, tea bushes were freely left unplucked for 45 and 90.d before pruning. Control treatments were continuously plucked until pruning. Results showed that TNC was significantly (P≤0.05) increased at pruning time. October pruning significantly increased leaf, stem, and root TNC. A longer resting period of 90.d significantly increased leaf and root TNC to 294 and 230.gkg–1, respectively. Generally, TNC declined after pruning and thereafter increased. Root TNC significantly correlated with regrowth period, diebacks and yield. Generally, the best resting period for increased TNC, regrowth and yield, is between 45 and 90.d. The best pruning time is October, if drought stress can be avoided.
Effect of time of pruning and lungs on non-structural carbohydrates of tea (Camellia sinensis L.).
(2003-03) Bore, John K.; Ng'etich, Wilson; Isutsa, D. K.; ; ;
An experiment was conducted at Kipkebe Estate, Sotik, Kenya, with the aim of establishing the effects of pruning time and resting period on total non-structural carbohydrate (TNC) reserves, regrowth and yield of tea. In this experiment, tea bushes were freely left unplucked for 45 and 90.d before pruning. Control treatments were continuously plucked until pruning. Results showed that TNC was significantly (P<0.05) increased at pruning time. October pruning significantly increased leaf, stem, and root TNC. A longer resting period of 90 d significantly increased leaf and root TNC to 294 and 230 g kg -1, respectively. Generally, TNC declined after pruning and thereafter increased. Root TNC significantly correlated with regrowth period, diebacks and yield. Generally, the best resting period for increased TNC, regrowth and yield, is between 45 and 90 d. The best pruning time is October, if drought stress can be avoided.
Enhancing preharvest physiology of multi-purpose pumpkin using combined nitrogen, mulch and gibberellic acid
(Chuka University, 2022-03) Isutsa, D. K.; Mwaura, M. M.; ; ;
In recent times, it has become apparent that multi-purpose pumpkin (Cucurbita moschata Duch.) is a very important crop since its leaves, fruits and seeds can be eaten as vegetables, snacks and blended dishes to boost household food and nutritional security. However, it is regarded as a low value crop, leading to poor cultivation, comprehension of preharvest physiological behaviour, and maximization of productivity in Kenya. Consequently, a study was conducted to assess the effects of combined nitrogen, mulch and gibberellic acid (GA3) in enhancing its preharvest physiology of pumpkin. Four N rates of 0, 50, 100 and 150 kg N/ha supplied as CAN, three mulch types as none, unpainted, and black-painted rice straw, and three GA3 rates of 0, 40 and 80 mg/L were assessed. The experiment was arranged in split-split plots in randomized complete block design, replicated three times in two seasons, and each plant occupied 2 m x 2 m space. Nitrogen was applied to main plots, mulch to sub-plots, and GA3 to sub-sub plots. Pre-harvest physiological variables measured were stomatal conductance, chlorophyll, photosynthesis, and transpiration. Data values were subjected to analysis of variance using SAS Version 9.3. Separation of significant means was done using the least significant difference test at α = 0.05. Results showed that nitrogen and mulch individually and interactively did not significantly (P > 0.05) affect most preharvest physiological parameters. The effect of GA3 was not significant on stomatal conductance and leaf chlorophyll, but it was negative and significant on both photosynthesis and transpiration in season 1 which was drier than season 2. Based on the present results, the influence of combined nitrogen, mulch and GA3 on multi-purpose pumpkin cannot be entirely depicted by analysing preharvest physiology. Adoption and application of treatments that promote desired preharvest physiology of multi-purpose pumpkin is recommended, including 50 kg N/ha to enhance stomatal conductance and leaf chlorophyll, and unpainted rice straws to enhance leaf chlorophyll content and photosynthesis.
Enhancing preharvest physiology of multi-purpose pumpkin using combined nitrogen, mulch and gibberellic acid
(African Journal of Horticultural Science, 2022-03) Isutsa, D. K.; Mwaura, M. M.; ; ;
In recent times, it has become apparent that multi-purpose pumpkin (Cucurbita moschata Duch.) is a very important crop since its leaves, fruits and seeds can be eaten as vegetables, snacks and blended dishes to boost household food and nutritional security. However, it is regarded as a low value crop, leading to poor cultivation, comprehension of preharvest physiological behaviour, and maximization of productivity in Kenya. Consequently, a study was conducted to assess the effects of combined nitrogen, mulch and gibberellic acid (GA3) in enhancing its preharvest physiology of pumpkin. Four N rates of 0, 50, 100 and 150 kg N/ha supplied as CAN, three mulch types as none, unpainted, and black-painted rice straw, and three GA3 rates of 0, 40 and 80 mg/L were assessed. The experiment was arranged in split-split plots in randomized complete block design, replicated three times in two seasons, and each plant occupied 2 m x 2 m space. Nitrogen was applied to main plots, mulch to sub-plots, and GA3 to sub-sub plots. Pre-harvest physiological variables measured were stomatal conductance, chlorophyll, photosynthesis, and transpiration. Data values were subjected to analysis of variance using SAS Version 9.3. Separation of significant means was done using the least significant difference test at α = 0.05. Results showed that nitrogen and mulch individually and interactively did not significantly (P > 0.05) affect most pre- harvest physiological parameters. The effect of GA3 was not significant on stomatal conductance and leaf chlorophyll, but it was negative and significant on both photosynthesis and transpiration in season 1 which was drier than season 2. Based on the present results, the influence of combined nitrogen, mulch and GA3 on multi-purpose pumpkin cannot be entirely depicted by analysing preharvest physiology. Adoption and application of treatments that promote desired preharvest physiology of multi-purpose pumpkin is recommended, including 50 kg N/ha to enhance stomatal conductance and leaf chlorophyll, and unpainted rice straws to enhance leaf chlorophyll content and photosynthesis.
Evaluation of endogenous phytocomponents and amino acids associated with direct somatic embryogenesis of coffee (Coffea arabica L.).
(Khalsa Publications, Punjab, India, 2018-03-01) Isutsa, D. K.; Mayoli, R. N.; Nyende, A. B.; Mweu, C. M.; ; ;
Coffee is one of the most important crops cultivated in the world for use in beverages and confectionaries. Embryogenesis is a complex process that begins with a single cell and ends with the formation of mature embryos. Somatic embryo development involves accumulation of complex metabolites and storage reserves. This present experiment identified and quantified endogenous phytocomponents and amino acids present during somatic embryogenesis of ‘Ruiru 11’. Laboratory experiments for this study were set up in the Coffee Research Institute, Kenya at Ruiru. Third leaf pair explants were excised from 8-month-old greenhouse-grown mother plants sterilized and cultured in half strength Murashige and Skoog basal salts augmented with Thidiazuron. Once embryos had developed, the cultures were analysed for phytocomponents using GCMS and HPLC. The results showed that palmitoleic and stearic acids were highest (23.3 µg/g and 69.9 µg/g respectively) in brown embryogenic cultures. Cis 7,8 epoxy-2-methyl octadecane was highest (253 µg/g) in green embryogenic cultures. (Z)-3-Tetradecene was highest (25 µg/g) in brown non-embryogenic cultures. Z, Z-3,13- Octadecedien-1-ol and (Z)-7-Hexadecenal were highest (32.1 µg/g and 70.2 µg/g respectively) in green embryogenic cultures. Alanine content was highest (4.4 µg/g) in embryos of brown cultures. Amino acids, fatty acids and their derivatives are potential biomarkers for embryogenesis. Other phytocomponents should be identified and their role in coffee somatic embryogenesis determined. Further studies regarding the status of the phytocomponents identified in the present study, especially in particular stages of embryo development are needed to propose treatments to improve coffee somatic embryo development. Keywords: Amino acids, Biomarkers, Fatty acids, Somatic embryos
Irrigation and mulch significantly enhance yield but not quality of purple passion fruits
(2011) Gaturuku, J. K.; Isutsa, D. K.; ; ;
Purple passion fruit (Passiflora edulis f. edulis Sims.) is an important fruit in the juice industry but its yields can drastically decline under drought stress. The present study evaluated the effects of irrigation and mulch on drought stress amelioration in purple passion fruits. The experiment was set up in a rain shelter in randomized complete block design, replicated four times and repeated once. The study had four irrigation rates (2.5, 5, 10 and 20 L/plant) and three mulches (black plastic film, wheat straw and none). Each treatment had 12 plants in 45cm x 45cm holes spaced at 1.5m x 1.5m and trellised onto posts and wires. A trench lined with plastic film prevented water seepage across treatments. Plants were maintained uniformly until the fifth week when treatments were imposed. Data were recorded up to 56 weeks after planting (WAP) and subjected to analysis of variance using the SAS software. Irrigation significantly increased fruit number at 52 WAP only, and fruit weight at 48, 52 and 56 WAP. The effect of irrigation on cumulative fruit weight (6016 g/plant) for 20 L was significantly (P<0.05) greater than the 5052 g/plant for 2.5 L. Black plastic mulch significantly increased fruit number and weight at 43 WAP only. Irrigation and mulch did not significantly (P>0.05) affect passion fruit quality traits which were nevertheless within standard magnitudes. Generally, when irrigating with over 5 L, there was no additional benefit of mulching but mulch ameliorated drought stress when deficit irrigation (2.5 L) was applied. Wheat straw and 10 L/plant once per week is generally optimal and should be used in mitigating drought stress to enhance purple passion fruit yields. Irrigation is more effective in enhancing passion fruit yield than mulching and hence it should be given first priority.
Irrigation rate and mulch type significantly affect growth and flowering of purple passion fruit (Passiflora edulis f. edulis Sims).
(2011) Gaturuku, G. K.; Isutsa, D. K.; Aguyoh, J. N.; ; ;
Purple passion fruit (Passiflora edulis f. edulis Sims.) is an important fruit in the tropics, but its growth can be adversely affected by drought stress. This study evaluated effects of irrigation rate and mulch type on drought stress amelioration in purple passion fruits. The experiment was set up in a rain shelter in a randomized complete block design, replicated four times and repeated once. The irrigation rates were: 2.5, 5, 10 and 20 L/plant, while mulch types were: black plastic film, wheat straw and mulch-free control. Each treatment had 12 plants in 45 cmx45 cm planting holes spaced at 1.5 mx1.5 m and trellised onto posts and wires. The plants were subjected to different treatments from the fifth week after planting. Data were recorded bi-weekly and subjected to analysis of variance using the SAS software. The 16.8 laterals, leaf area of 122 cm2/leaf, and leaf biomass of 2.4 g/leaf for 20 L were significantly greater than the 11.3 laterals, leaf area of 106.5 cm2/leaf, and leaf biomass of 2.0 g/leaf for 2.5 L at P<0.05. Black plastic and wheat straw mulches significantly increased leaf biomass to 2.3 g/leaf. The 20 L significantly increased combined florals to 332 and dropped flowers to 241, compared to 250 and 171, respectively, for the 2.5 L. Black plastic mulch significantly increased combined florals to 326, dropped flowers to 235 and immature fruits to 76, compared to 263, 188, and 59, respectively, for 2.5 L. The 10 L and 20 L, as well as the black plastic and wheat straw effects were correspondingly not significantly different. When irrigating with at least 5 L, no additional benefit of mulching was observed, but mulch ameliorated drought stress when deficit 2.5 L was applied. The 10 L and the biodegradable wheat straw mulch are recommended for maximizing growth and flowering of purple passion fruits.
Irrigation rate and mulch type significantly affect some physiological processes of purple passion fruit (Passiflora edulis f. edulis Sims.) under drought stress.
(2011-12) Gaturuku, G. K.; Isutsa, D. K.; Aguyoh, J. N.; ; ;
Purple passion fruit (Passiflora edulis f. edulis Sims.) is an important fruit in the tropics, but its growth can be adversely affected by drought stress. This study evaluated effects of irrigation rate and mulch type on drought stress amelioration in purple passion fruits. The experiment was set up in a rain shelter in a randomized complete block design, replicated four times and repeated once. The irrigation rates were: 2.5, 5, 10 and 20 L/plant, while mulch types were: black plastic film, wheat straw and mulch-free control. Each treatment had 12 plants in 45 cmx45 cm planting holes spaced at 1.5 mx1.5 m and trellised onto posts and wires. The plants were subjected to different treatments from the fifth week after planting. Data were recorded bi-weekly and subjected to analysis of variance using the SAS software. The 16.8 laterals, leaf area of 122 cm2/leaf, and leaf biomass of 2.4 g/leaf for 20 L were significantly greater than the 11.3 laterals, leaf area of 106.5 cm2/leaf, and leaf biomass of 2.0 g/leaf for 2.5 L at P<0.05. Black plastic and wheat straw mulches significantly increased leaf biomass to 2.3 g/leaf. The 20 L significantly increased combined florals to 332 and dropped flowers to 241, compared to 250 and 171, respectively, for the 2.5 L. Black plastic mulch significantly increased combined florals to 326, dropped flowers to 235 and immature fruits to 76, compared to 263, 188, and 59, respectively, for 2.5 L. The 10 L and 20 L, as well as the black plastic and wheat straw effects were correspondingly not significantly different. When irrigating with at least 5 L, no additional benefit of mulching was observed, but mulch ameliorated drought stress when deficit 2.5 L was applied. The 10 L and the biodegradable wheat straw mulch are recommended for maximizing growth and flowering of purple passion fruits.
Morphological characterization of naturalised pumpkin (Cucurbita moschata (Lam.) Poir.) accessions in Kenya. African Journal of Horticultural Science, 12:61-83.
(2017-06) Kiramana, J. K.; Isutsa, D. K.; ; ;
Pumpkin is an emerging important indigenous vegetable in Kenya, although its sale and consumption remain low, while distribution and diversity are systematically studied and reported to a limited extend. The present study sought to provide information that could spur enhanced conservation, preservation and production of preferred multi-purpose pumpkin accessions among smallholder farmers in Kenya. A survey done in 2012 collected 155 accessions, belonging to Cucurbita moschata (Lam.) Poir.), which comprised 70 and 85 from Kakamega and Nyeri regions, respectively. The accessions were grown in the Chuka University farm and used for morphological characterization. All 26 morphological characters evaluated were significantly (P=0.000) different. Principal Component Analysis (PCA) reduced them to 9 Principal Components (PCs) that accounted for 82.4% total variation. The first PCs explained 50.5% variation, comprising 27.7% PC 1, 14.4% PC 2 and 8.8% PC 3. The PCA differentiated accessions by plant growth, productivity, maturity, fruit yield, seed yield, and quality factors. The high phenotypic variation explained by the PCs indicates that the discriminating traits could be used as good genitors and priority indices in pumpkin germplasm screening, selection and improvement. Total fruit weight was 0.3 kg in NY-155 and 19.3 kg in KK-65. Cluster analysis classified the accessions into four groups, with 63, 29, 25 and 6 accessions in clusters one, two, three and four, respectively. A close relationship among the variegated accessions was observed. The green-leafed accessions were grouped in cluster three. The best yielding accessions KK-65 and KK-54 were clustered separately. The sparse distribution of the green-leafed accessions was attributed to crossing-breeding with the variegated accessions in the farms. The present study showed that phenotypic characterization can be used as an inexpensive means for distinguishing related pumpkin species. Since naturalised pumpkin germplasm is slowly becoming endangered in many farming systems and the current pumpkin germplasm is highly diverse, there is need to conserve it to serve as resources for future pumpkin improvement. Kenyan farmers need to be sensitised on production and conservation of pumpkin. Interventions to strengthen informal on-farm conservation should be adopted and promoted to ensure germplasm availability in future.
Multivariate analysis techniques reveal significant morphogenetic variability in pumpkin landraces in Kenya
(Shamokal Publications, 2018-07-30) Kiramana, J. K.; Isutsa, D. K.; ; ;
Documented information on naturalized pumpkin landraces in Kenya to identify useful variability is insufficient. The present study assessed variability using quantitative characters of 155 accessions, with 70 and 85 from Kakamega and Nyeri regions, respectively. The accessions were grown in one farm in a completely randomized design with three replications. Analysis of variance showed significant (P<0.05) variation in all characters. Lowest and highest variables in mean and range were leaf length/width ratio and seed number that were 0.8 and 0.4, and 837 and 4,111, respectively. Eight factors accounted for 79.4% of total variation. The highly variable factors were fruit flesh thickness, length, width and length/width ratio, size, total weight, average weight and number, as well as seed number, 100-seeds weight, length, width, and thickness. Phenotypic coefficients of variation (PCV) were slightly higher or equal to genotypic ones (GCV). High GCV and PCV, heritability and genetic gain resulted for fruit size, total fruit weight, fruits and seeds. Over 70 positive correlations in fruit size, number and seeds with total fruit weight were observed in genotypic and phenotypic variabilities. Maximum positive direct effects on total fruit weight were observed in seeds, fruit average weight, length, and size, while indirect effects were observed in fruit number, flesh thickness, length, peduncle length and days to first flower. Multivariate analysis revealed fruit size, number, total weight, and seeds were characters of great genetic variability, which should be considered as primary components for achieving high yields in pumpkins when screening accessions for selection and improvement.
Plant Propagation: A Teaching Resource Packet with Emphasis on Agroforestry and Fruit Trees in East Africa
(Cornell University, Ithaca, NewYork, USA, 1992) 68. Mudge, K. W; Mwaka, A.; Isutsa, D. K.; Musoke, R.; Foster, D.; Ngoda, B. J. M.; ; ;
The products and services provided by trees have always been used in farming. In the past, trees grew naturally on farm lands. The rise in population, and resulting increased demand for wood products, has led to loss of tree cover through cutting down of trees without replacement. Land shortage is common in most parts of Uganda, and therefore land for establishing separate wood plantations is not available. Agroforestry becomes the most obvious and appropriate alternative. Agroforestry is a term used for land-use systems in which trees or shrubs are grown together with crops or combined with livestock. Trees can be combined with other components, either simultaneously being grown in a field with crops, or in rotation where trees are grown first then cut and replaced with crops. Agroforestry is a technology through which the problems of poor agricultural production, wood shortages and environmental degradation can be addressed. Trees provide many products such as fuelwood, poles, shade, fodder, fruits, medicine and timber. Trees planted as contour hedges for soil and water conservation help reduce water and soil loss and improve infiltration rate. Trees also maintain soil fertility through nutrient recycling, nitrogen fixation and improving soil structure. Trees are also used as windbreaks, for providing shade and beautifying the landscape. Trees suitable for agroforestry should have characteristics that are highly beneficial to farmers. This usually depends on the technology or tree arrangement desired by the farmer and the final products needed. For instance, a fast-growing aggressive tree species may be very useful for rotational systems but may compete too much with crops. Table 9. Desirable characteristics of agroforestry trees for selected practices Tree characteristics Improved Boundary Scattered in Contour fallow planting crop fields planting Nitrogen fixing – – Fast growing – – – Coppicing – – – Deep rooted – – – Light canopy – – Suitable for fodder – – Compatibility with crops – – – Quick recovery – – – Lots of biomass – – 6.3 Propagation of trees There are three methods of propagating trees: ● Seed ● Vegetative propagation ● Collecting wild seedlings (wildings). Most trees are raised from seed. Successful raising of seedlings and growing of trees depends on timely availability of good-quality seed.
PRODUCTION OF MINERAL NUTRIENT-RICH MULTIPURPOSE PUMPKIN LEAFY VEGETABLESUSING INTEGRATED RESOURCE MANAGEMENT
(Chuka University, 2022) Mwaura, M. M.; Isutsa, D. K.; Munyiri, S. W.
Enhancing mineral nutrient composition in multipurpose pumpkin (Cucurbita moschata Duch.) is important since it contributes to household food security. To respond to this need, an experiment arranged in split-plot in randomized complete block design and replicated three times was conducted at Chuka University for two seasons from January 2019 to July 2020. The main plots were assigned to nitrogen (CAN) (0, 50, 100 and 150 kg N/ha), sub-plots to mulch (no mulch, black-painted and unpainted rice straws), while split-plots to gibberellic acid (GA3) (0 mg/L, 40 mg/L and 80 mg/L). Nitrogen for each rate was applied in two equal doses at three weeks post-emergence and at the beginning of flowering. The black-painted and unpainted rice straws were placed on plots after land preparation. The GA3 solution was sprayed onto plants using a knapsack sprayer, starting with 40 mg/L followed by 80 mg/L, once during the fourth week after emergence. Data collection was done fortnightly from the fourth week after emergence and data values were subjected to analysis of variance using SAS software. Means were separated using the least significant difference test at α=0.05. Highest levels of potassium and magnesium were obtained for 100 kg N/ha. On the other hand, phosphorus and beta-carotene were highest in treatments where unpainted rice straw mulch was used, while application of 80 mg/L of GA3 gave high phosphorus and potassium contents. Results further showed that combined N fertilizer, mulch and GA3 had a significant (P<0.05) effect on nitrogen, phosphorus, potassium, magnesium and beta-carotene contents during both seasons, implying that they are useful factors in evaluation of mineral nutrient contents in leaves of multi-purpose pumpkins.
A protocol for rooting and growing apple rootstock microshoots.
(1998) Isutsa, D. K.; Pritts, M. P.; Mudge, K. W.; ; ;
Microshoots of apple (Malus domestica Borkh.) rootstocks G. 65, G.30 and G.11 were transferred from stage II axillary shoot cultures to stage III rooting media containing 10 levels of indole-butyric acid (IBA) for four weeks to determine optimal conditions for rooting. Microshoots were inverted or left in an upright position. Rootstocks and microshoot position affected rooting and survival; the highest rooting was 30% for G.65 inverted with 2 mgcntdotL-1 I13A, 100% for G.30 upright with 3 mgcntdotL-1 IBA, and 100% for G.11 inverted with 1 or 2 mgcntdotL-1 IBA. No single set of conditions provided consistent rooting in vitro, and plants were not always of high quality. In a second experiment, microshoots were rooted and acclimatized ex vitro in a custom-built fog chamber to assess the effect of two carbon dioxide levels (450 or 1350 mumolcntdotmol-1) and three light levels (30, 50 or 100 mumolcntdotm-2cntdots-1). All rootstocks rooted equally well ex vitro, but survival varied. Plantlets had the highest dry mass, leaf area and growth rates under high light conditions compared to medium light or low light conditions. Supplemental carbon dioxide had no consistent effect. If plants survived fog chamber conditions, subsequent survival in the fog tunnel and greenhouse was 100%. Thus, these rootstocks can be rooted successfully in the fog chamber at high light conditions, which yielded high quality plants. A third experiment was conducted to evaluate the effect of chilling for four weeks at 3.3degreeC, or spraying with gibberellic acid 3 (GA3) on post-rooting dormancy, a problem which frequently occurs with recently rooted apple microshoots. Chilled plants had greater dry mass than control or GA3 plants, and the GA3 effect was short-lived. The ex vitro procedure suggested by these experiments could reduce the time associated with rootstock micropropagation to at most 6 months.
Rapid micropropagation of passion fruit (Passiflora edulis Sims.) varieties.
(2004-02) Isutsa, D. K.; ; ;
Lack of adequate, healthy plants can hamper production of passion fruits (Passiflora edulis Sims.). Seed propagation results in undesirable variability, inadequate and seasonal supply. This research aimed at rapid generation of P. edulis plants through modified ex vitro rooting techniques. Yellow (P. edulis var. flavicarpa) and purple (P. edulis var. edulis) passion fruit shoot tops were proliferated in vitro to stage II shoots, half of which were rooted ex vitro and the other half were conventionally rooted in vitro. The design was completely randomized for each variety. Plantlets were assessed after 30 days. Data were analyzed using the MSTAT programme. After proliferating yellow passion fruit on a medium containing 22.2 μM 6-benzylaminopurine (BAP), its rooting ex vitro was significantly better (96% rooting, three roots per shoot, 92% survival) than rooting in vitro (62% rooting, one root per shoot on 24.5 μM indole-3-butyric acid medium, 50% survival). Purple passion fruit proliferated satisfactorily only on a medium containing both 22.2 μM BAP and 11.6 μM gibberellic acid 3. Like difficult proliferation, and compared to yellow passion fruit, its rooting and survival also proved difficult and poor (47% rooting, one root per shoot on 21.5 μM naphthalene acetic acid medium in vitro, 32% survival) and (66% rooting, two roots per shoot ex vitro, 60% survival). Thus, the various passion fruit varieties have different requirements for micropropagation. The key finding was that ex vitro rooting is possible and significantly better than in vitro rooting of passion fruit shoots.
Response of strawberry quality and profitability to farmyard manure and triple super phosphate under tropical high altitude conditions
(2011) Odongo, T.; Isutsa, D. K.; Aguyoh, J. N.; ; ;
Quality of strawberries in the tropics is partly limited by poor soil fertility, while profitability of different nutrient management strategies has not been established. The present study determined the effect of 0, 18, 36, and 54 t/ha farmyard manure (FYM) and triple super phosphate (TSP), equivalent to 0, 17, 34 and 68 kg/ha phosphorus (P) on quality and profitability of strawberries. The study was done in three seasons on field 3 of Tatton farm-Njoro, Kenya. The design was split-plots embedded in randomised complete blocks, replicated three times. The FYM and TSP were broadcasted to main plots and sub-plots, respectively. Each treatment had 10 plants, spaced at 0.3 m x 0.45 m in 0.6 m x 1.5 m plots, mulched with black polyfilm and irrigated with drip lines. Berry fruit size, brix index and storage life were determined from 26 to 42 weeks after planting (WAP). Profitability was calculated using berry yield-income and input-costs at the end of the study. Results varied depending on response variable. High FYM and TSP significantly (P < 0.05) increased fruit size, but lowered storage life. High FYM significantly lowered brix index. Low FYM plus moderate P significantly lowered fruit size. Thus, 54 t/ha FYM plus 34 kg/ha P and 36 t/ha FYM plus 17 kg/ha P are recommended for large-sized and sweetest, long-storing berries, respectively. Manure alone increased profitability more than TSP alone. Highest FYM and TSP did not always result in highest profitability. The relationship between treatments and profitability was sigmoid, and dependent on site and season. Thus, profitable strawberry mineral nutrition packages will have to be developed for each site and season in Kenya.