Browsing by Author "Isutsa, Dorcas Khasungu"

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The analogy of simple and inter simple sequence repeat markers in the assessment of genetic diversity of pumpkin accessions in Kenya
(Innspub, 2020-09) Kiramana, James; Isutsa, Dorcas Khasungu; Nyende, Aggrey Bernard; ; ;
Pumpkin is found growing in many parts of Kenya although its genetic variation has not been determined using available molecular markers. This study compared SSR and ISSR efficacy in assessing diversity of 139 pumpkin accessions using the multiplex ratio (MR), polymorphic information content (PIC), effective multiplex ratio (EMR), marker index (MI), different (Na) and effective (Ne) alleles, Shannon index (I), expected (He) and unbiased expected heterozygosity (UHe), analysis of molecular variance (AMOVA), clusters and mantel correspondence. DNA ranged from 27-2992ng/µl and 0.45-2.1 of 260/280nm. SSR detected 23 total alleles and 4.6 average alleles of 100-700bp. ISSR detected 152 total alleles and 21.7 average alleles of 200-2000bp. Amplified and polymorphic DNA bands were 437 and 117 for SSR, 512 and 391 for ISSR, respectively. Total and polymorphic bands MR was 87.4 and 29.4 for SSR, 73.1 and 55.9 for ISSR, respectively. PIC, EMR and MI for ISSR were higher than for SSR. Markers with high polymorphism portrayed high EMR and MI. SSR PKCT-122 and ISSR 17899A had the highest polymorphism, PIC, EMR and MI. Ne, I, He and UHe was high for SSR, while Na was high for ISSR. AMOVA revealed significant (P=0.01; P=0.02) differentiation. Genetic diversity was 14% and 7% among, 86% and 93% within accessions for SSR and ISSR, respectively. Three clusters independent of geographic origin were revealed. SSR and ISSR Euclidean matrices showed positive significant (r=0.272, P=0.0001) correlation, which implied they reflected the same genetic diversity. Hence, the genetic diversity of pumpkins can be assessed effectively using either SSR or ISSR markers.
Climate change adaptation of potato (Solanum tuberosum L.): Influence of Biozyme® rate on potato yield, quality and mineral nutrient uptake
(2013-07) Karanja, Benard K.; Isutsa, Dorcas Khasungu; Aguyoh, Joseph Nyamori; ; ;
Potato (Solanum tuberosum L.) is an important food crop worldwide. Growers prefer potato because of its short growing season and tolerance to poor soils. Growers are using different agrochemicals so as to improve tuber yield, quality and maturity period under erratic and unreliable rain patterns. BiozymeÂ® foliar feed is widely used to hasten maturity and enhance yields of crops. BiozymeÂ® is said to be a storehouse of hormones and nutrients that improve the health of a crop. It contains major hormones along with primary and secondary mineral nutrients. This study determined BiozymeÂ® rate that is lower than the commercially recommended 500 ml/ha to curb overuse and misuse, but still enhance potato tuber yields under climate change deficit rainfall adaptation. The study was set up in split plots arranged in a randomized complete block design, replicated three times and repeated once. Main plots were assigned to two contrasting potato cultivars (Tigoni and Asante), while subplots were assigned to BiozymeÂ® rate (0, 125, 250, 500 and 750 ml/ha). Each subplot was planted with 28 seed potato tubers spaced at 30 cm Ã— 70 cm in four rows. A distance of 1 m separated plots. The 750 ml/ha BiozymeÂ® significantly (P<0.05) increased total potato tuber yields by 3Ã— to 7Ã—, reduced unmarketable tubers by up to 3Ã—, enhanced dry matter by 10% and starch by >2Ã— compared to the 0 ml/ha BiozymeÂ®. The 0 ml/ha BiozymeÂ® produced 2-11 t/ha and 7-14 t/ha in "Tigoni' and "Asante', while the 750 ml/ha BiozymeÂ® produced 25-33 t/ha and 39-43 t/ha in "Tigoni' and "Asante', respectively. The 750 ml/ha BiozymeÂ® also increased leaf tissue N by >1%, P by >100 ppm and K by > 9 ppm in both seasons and cultivars. The difference in performance for 500 and 750 ml/ha BiozymeÂ® was always not significant (P>0.05). Thus, it is not advisable to foliar-feed potato plants using BiozymeÂ® rates eÃ—ceeding 500 ml/ha since this will amount to overuse and misuse and eÃ—acerbate tuber perishability. Slightly lower BiozymeÂ® rates than 500 ml/ha may be recommended to guarantee production of "hardier" potatoes ideal for safe handling
Contribution of multi-purpose pumpkin (Cucurbita moschata Duch.) to the economy of selected Kenyan small-scale households
(Science Publishing Group, 2019-03-19) Kiharason, Jedidah Wanjiku; Isutsa, Dorcas Khasungu; ; ;
Pumpkin (C. moschata Duch.) fruit is a highly nutritious horticultural crop with great potential for commercialization. However, in Kenya many households do not buy and utilize pumpkins regularly, leading to low demand. These scenarios increase post-harvest losses and provide no incentive for farmers to increase production in Kenya, which has an abundance of pumpkin landraces that unfortunately remain under-exploited and under-utilized. Their distribution and marketing is a great challenge due to easy perishability. Horticultural crops experience losses in quality and quantity in between harvest and consumption. The magnitude of post-harvest losses in fresh fruits and vegetables is estimated to range from 20% to 50% in developing countries. The present study determined marketability of fresh fruit, and the spoilage rate of fresh fruit in the various presentation formats (eighth, quarter and half slices and a control of whole fruit either wrapped or not with cling film). Selling was facilitated by four market women in Nyeri County of Kenya. Statistical analysis showed significant differences (P<0.05) in number of spoilt pieces over time, and between number of days to spoilage of whole fruit, compared to slice fruit. More quarter and half slices got spoiled after a few days of presentation to buyers. Nonetheless, quarter slices had the highest (54.5%) pieces sold, while half slices had the fewest (9.8%) pieces sold. However, no significant differences occurred in average number of pieces sold, or in amount of money from sale of fruit pieces of different presentation formats. Most consumers preferred buying smaller slices. Therefore, adoption and promotion of pumpkin presentation formats that effectively increase shelf-life is recommended to enhance production and utilization in Kenya.
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, Dorcas Khasungu; ; ;
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 (P > 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.
Effects of Integration of Irrigation Water and Mineral Nutrient Management in Seed Potato (Solanum Tuberosum L.) Production on Water, Nitrogen and Phosphorus Use Efficiencies
(Springer, 2015-11) Gathungu, Geofrey; Aguyoh, Joseph; Isutsa, Dorcas Khasungu
Inorganic fertilizers have become extremely important in correcting declining soil fertility in seed potato (Solanum tuberosum L.) production in Kenya. Unreliable rainfall has also limited seed production. Knowledge on water and nutrient use efficiencies in potato grown under different irrigation regimes with different nitrogen and phosphorus levels will help predict the best application rates for optimal seed potato production and yield. A study was conducted at Egerton University, Horticultural Research and Teaching Farm to determine the effect of integrated application of irrigation water, nitrogen (N) and phosphorus (P) use efficiencies of water, N and P. In a split-split plot design, the irrigation water was applied to maintain soil water at 40, 65 and 100 % field capacity in the main plots, N (0, 75, 112.5 and 150 kg N/ha) to subplots and P (0, 115, 172.5 and 230 kg P2O5/ha), which translated into 0, 50.6, 75.9, 101.2 kg P/ha) to sub-subplots, with each treatment replicated three times and the trial repeated once. The irrigation water was applied throughout the potato growth period through drip tube lines, with N supplied as urea (46 % N) in two splits, and P as triple superphosphate (46 % P2O5) at planting time. Data on seed potato yield was collected from each treatment at harvest and used to calculate water, N and P use efficiencies. High irrigation water at 100 % compared to 65 and 40 % rate resulted in relatively high N and P use efficiencies, but decreased water use efficiency. Application of intermediate to high N and P nutrient increased the water, N and P use efficiencies. It is recommended to apply low to intermediate irrigation water, intermediate to high N and P to increase their use efficiencies during seed potato production.
Improving seed potato leaf area index, stomatal conductance and chlorophyll accumulation efficiency through irrigation water, nitrogen and phosphorus nutrient management.
(Macrothink Institute, 2016-01) Gathungu, Geofrey Kingori; Aguyoh, Joseph Nyamori; Isutsa, Dorcas Khasungu; ; ;
A study was conducted in a Rainshelter (RTrial) at Horticultural Research and Teaching Farm, Egerton University to determine the effect of integration of irrigation water, nitrogen (N) and phosphorus (P) application on seed potato leaf area index (LAI), stomatal conductance and chlorophyll content. The treatments arranged in a split-split plot layout in a completely randomised block design, consisted of three irrigation water rates (40%, 65% and 100% field capacity), four N rates (0, 75, 112.5 and 150 kg N/ha) supplied as urea (46% N), and four P rates (0, 50.6, 75.9, 101.2 kg P/ha) supplied as triple superphosphate, replicated three times and repeated once. During the growth leaf area, stomatal conductance, and chlorophyll content were measured. Data collected were subjected to analysis of variance and significantly different means separated using Tukey’s Studentized Range Test at P≤0.05. Leaf area index was greater with high irrigation water at 100%, N at 150 kg N/ha and P at 101.2 kg P/ha, which was 2.6 and 1.3 at 51 days after planting (DAP) and 3.5 and 3.1 at 64 DAP. Furthermore, low irrigation water rate at 40% together with low N and P rates of 0 kg N/ha and 0 kg P/ha had the least LAI, which was 0.28 and 0.19 at 51 DAP and 0.28 and 0.24 at 64 DAP both in RTrials I and II, respectively. Subjecting potato to 100% compared to 40% irrigation rate increased stomatal conductance at 87 days after planting (DAP) by 32.82 and 31.99 mmolm⁻²s⁻¹, leaf chlorophyll content index by 16.2 and 16.5, 19.8 and 19.6, and 15 and 20.3, when integrated with high compared with low N and P application rates at 59, 73 and 87 DAP, in RTrials I and II respectively. Irrespective of N and P rates LAI, stomatal conductance and chlorophyll content were significantly greater with high irrigation water at 100% followed by 65% and was lowest with 40% irrigation water rate.
Increasing leaf harvest intensity enhances edible leaf vegetable yields and decreases mature fruit yields in multi-purpose pumpkin.
(Asian Research Publishing Network (ARPN), 2013-08) Isutsa, Dorcas Khasungu; Malowa, Sally O.; ; ;
The popular Pumpkin (Cucurbita moschata Duchsene) in Kenya is the multi-purpose type, grown for its edible tender leaves, mature fruits and seeds. It requires appropriate management to realize high yields. Pumpkin is an important crop because most plant parts are rich in nutrients and are edible. Leaves are preferred in African countries. In West Africa, seed consumption is common. In Asian countries, pumpkin seeds have several medicinal applications. Pumpkin is rich in carotenoids that keep the immune system strong and healthy. Its beta-carotene is a powerful antioxidant and antiinflammatory agent that helps prevent build-up of cholesterol in arteries, thus reducing chances of strokes. Its alphacarotene slows down aging, prevents cataract formation and reduces the risk of muscular degeneration that usually results in blindness. Its high fibre improves bowel health, potassium lowers hypertension risk, and zinc boosts immune system and bone density. The high demand for tender pumpkin leaves consumed as a vegetable accompanying the main meal brings about excessive defoliation that terminates the life of the plant prematurely. This research established optimum leaf harvest intensity (LHI) that maximizes either the tender leaf or mature fruit yields. Pumpkin seeds were grown for 3 weeks in a nursery bed followed by transplanting and growing each seedling singly at a spacing of 2 m x 4 m. The layout was completely randomized design with 4 LHI (0, 1, 2 and 3), replicated four times and repeated once. Data collection started when plants had 5-true leaves and it continued for 29 weeks (season 1) and 21 weeks (season 2). Data collection entailed defoliating up to 3 tip-most leaves, with the entire leaf stalk attached, from each vine once per week and then counting. Mature fruits were harvested as their colour started to turn yellowish-brown, counted and weighed. Data were subjected to analysis of variance and regression using Minitab version 15 program. Leaf yield significantly (P<0.05) increased with increase in LHI, but fruit yield significantly decreased. The highest yields were 580 edible leaves for 3-LHI and 20 kg fruits (25 t/ha) for 0-LHI. Fruit yield had a significant (P<0.05) negative relationship with LHI. Thus, the pumpkin leaf and fruit yields depend on leaf harvest intensity. If fruit production is desired, then LHI should be kept to a minimum. If edible leaves are desired then fruit yields should be forfeited. Maximum fruit productivity requires minimum leaf defoliation.
Interactive effects of irrigation rate and leaf harvest intensity on edible leaf and fruit yields of multipurpose pumpkin (Cucurbita moschata Duchesne).
(ISDS LLC, Japan, 2017) Isutsa, Dorcas Khasungu; Mwaura, Margaret Mahiga; ; ;
Pumpkin (Cucurbita moschata Duchsene) is rapidly gaining popularity in dishes in Kenya. The fruits, leaves and seeds are becoming popular due to their nutritional and medicinal properties. However, water stress and irregular leaf harvesting constrain optimal yields. The present study determined effects of irrigation rate and leaf harvest intensity in sustaining enhanced growth and quality. A split-block embedded in Randomized Complete Block Design with four replications was set up in a rain shelter that blocked rain from plots. Irrigation was applied to main plots and leaf harvest intensity to split-blocks. The treatments were 1, 2, 3 and 4 litres applied once per week through drip tubes and 0, 1, 2 and 3 leaves harvested once per fortnight per branch. One plant spaced at 2mx2m and replicated four times formed a treatment. The variables measured were: leaf and fruit growth; male and female flowers; fruit quality; seed number, weight, germination and vigour. Data were subjected to analysis of variance using JMPIN 5.1 software. Tukey’s Studentized Range Test at P=0.05 was used to separate means. Leaf harvest intensity had a significant P<0.05 was used to separate means. Leaf harvest intensity had a significant (P 0.05) decreasing effect on flower, leaf and fruit growth and quality. Irrigation rate had a significant (P 0.05) increasing effect on branches, flowers and seedling vigour. Interaction had a significant (P 0.05) increasing effect on leaves, seeds and male flowers. Irrigating with 3 L sustained the best performance and hence is recommended. Harvesting two leaves is recommended for producing many edible leaves, and one or no leaf for high quality fruits and seeds.
Nematodes and fungi associated with apple replant disorder in sampled New York State orchards.
(2014) Isutsa, Dorcas Khasungu; Merwin, Ian A.; ; ;
The factors associated with unthrifty growth of apple are not fully determined, resulting i n inadequate diagnosis of apple replant disorder (ARD). The present study isolated and identified nematodes and fungi from ARD -infested soils to determine factors that interacted to cause ARD. Nematodes were extracted and identified in several orchard soil subsamples. The remaining soils were mixed to give composite soil. Transformed and non-transformed apple host seedlings were planted in the composite soil in a greenhouse, harvested after 10 weeks, and processed for isolation and identification of fungi. Pratylenchus and Xiphinema nematodes were present in the soils. Root-lesion nematode (RLN) frequency was always 100%, and dagger nematode (DN) frequency ranged from 40-70%. The RLN and DN ranged from 56-350 and 5-58 per 100 cm 3 of soil, respectively. Isolation frequency of Pythium species was highest (29%), followed by 10% for Pythium cryptogea, 4% for Pythium cambivoraand Pythium catorum, 3% for Pythium megasperma , and 2% for Phytophthora species. Both transformed and non-transformed apple hosts were infested by at least several fungi. Of the six apple hosts tested, Pythium sp. and F. oxysporum colonized six each, Pythium cryptogea, C. lucidum and C. destructans colonized three each, Pythium cactorum, Pythium cambivora and Pythium megasperma two each, and Phytophthora sp., F. solani, F. equiseti, F. acuminatum and Rhizoctonia sp. one each. Consequently, the ARD symptoms observed on diverse apple hosts were associated with combined effects of RLN, DN and various species of Pythium, Phytophthora, Cylindrocarp on, Fusarium and Rhizoctonia. Whenever unthrifty growth is observed in soil especially that under perennial fruits and continuously cultivated annual crops, similar diagnostic isolation of multiple pathogens should be performed. In developing management st rategies, germplasm for the crop in question should be evaluated in multiple sites or in composite soil in order to identify germplasm with broadspectrum resistance or tolerance to the pathogens.
Optimization of seed potato specific density, starch and dry matter contents and tuberization capacity of resultant plants through integrated irrigation, nitrogen and phosphorus management.
(Science Publishing Group, 2015-08-01) Gathungu, Geofrey Kingori; Nyamori, Aguyoh Joseph; Isutsa, Dorcas Khasungu; ; ;
A study was conducted in a Rainshelter (RTrial) at the Horticultural Research and Teaching Farm of Egerton University to determine the effect of integrated application of irrigation water, nitrogen (N) and phosphorus (P) on seed potato physiological quality and performance of plants resulting from them. The treatments arranged in a split-split plot in a completely randomized block design, consisted of three irrigation water rates (40%, 65% and 100% field capacity), four N rates (0, 75, 112.5 and 150 kg N/ha) supplied as urea (46% N), and four P rates (0, 50.6, 75.9, 101.2 kg P/ha) supplied as triple superphosphate with experiment replicated three times and repeated once. After harvest seed specific density, starch and dry matter contents were determined after which 15 seed tubers per treatment were stored for 90 days under diffuse-light sprouting conditions for postharvest (PTrial) evaluation. Later, three potato tubers were selected per treatment and planted to study growth vigour and tuberization capacity of resultant potato plants both in PTrials I and II. Data collected were subjected to analysis of variance and significantly different means were separated using Tukey’s Studentized Range Test at P=0.05. Specific density, starch and dry matter contents increased from 40% to 65% irrigation water. Application of irrigation water beyond 65% reduced the specific density, starch and dry matter contents by 0.03, 2.6%, 3.7% and 0.04, 3.7%, 5.2% in RTrials I and II, respectively. The 100% compared to 65% irrigation rate reduced post-treatment evaluation stem number, density and height at 57 DAP by 1.3 and 1.1, 15.1 and 12.6, and 13.4 cm and 10.3 cm, and tuberization capacity in resultant plants by 5 and 8.7 tubers, in PTrials I and II, respectively. Application of N and P significantly increased seed potato specific density, starch and dry matter contents but application of N and P beyond 112.5 kg N/ha and 75.9 kg P/ha respectively reduced the same both in RTrials I and II, respectively. In postharvest evaluation integration of N at 0 to 112.5 kg N/ha with 65% irrigation rate increased the number of tubers produced by the resultant plants by 3.4 and 5.4, while high P rate at 75.9 kg P/ha increased tuberization by 8.4 and 10.7, in RTrials I and II, respectively. Integration of 65% irrigation rate, 112.5 kg N/ha and 75.9 kg P/ha rates optimized potato growth, and vigour of resulting potato plants.