Department of Plant Science

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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.
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.
Malus germplasm varies in resistance or tolerance to apple replant pathogens in a mixture of New York orchard soils.
(American Society for Horticultural Science, 2000-04) Isutsa, Dorcas K. 1; Merwin, Ian A.; ; ;
We tested 40 seedling lots and 17 clonal accessions - representing 941 genotypes and 19 species or interspecific hybrids of Malus - for their resistance or tolerance to apple replant disease (ARD) in a mixture of five New York soils with known replant problems. Total plant biomass, root necrosis, root-infesting fungi, and root-lesion nematode (RLN; Pratylenchus penetrans Cobb) or dagger nematode (DN; Xiphinema americanum Cobb) populations were evaluated in apple seedlings and clones grown for ≃60 days in the composite soil. In addition to phytophagous nematodes, various Pythium, Cylindrocarpon, Fusarium, Rhizoctonia and Phytophthora species were isolated from roots grown in the test soil. Plant growth response was categorized by a relative biomass index (RBI), calculated as total plant dry weight in the pasteurized field soil (PS) minus that in an unpasteurized field soil (FS), divided by PS. Nematode reproduction on each genotype was defined by a relative reproduction index (RRI), calculated as final nematode populations in roots and soil (Pf) minus initial soil populations (Pi), divided by Pi. The RBI, RRI, and other responses of accessions to ARD soil were used to rate their resistance, tolerance, or susceptibility to apple replant disease. None of the accessions was completely resistant to ARD pathogens in our test soil. Seedling accessions of M. sieversii Roem. and M. kirghisorum Ponom. appeared to have some tolerance to ARD, based upon their low RRIs and RBIs. Three clonal rootstock accessions (G.65, CG.6210, and G.30), and four other clones (M. baccata Borkh. - 1883.h,M. xanthocarpa Langenf. - Xan, M. spectabilis Borkh. - PI589404, and M. mandshurica Schneid. - 364.s) were categorized as tolerant to ARD. The disease response of other accessions was rated as susceptible or too variable to classify. We concluded that sources of genetic tolerance to ARD exist in Malus germplasm collections and could be used in breeding and selecting clonal rootstocks for improved control of orchard replant pathogens.
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.
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.
Effects of mulch and cultivar on strawberry productivity under tropical highland conditions.
(2006) Isutsa, Dorcas Khasungu *; ; ;
A study was conducted to determine effects of four mulches (cut grass, clear polyjilm, black polyjilm, and none) on productivity of four strawberry (Fragaria x ananassa Duch) cultivars (Pajaro, Aiko, Fern and Douglas) under tropical hig~land conditions. It was hypothesized that polyjilm would hasten growth and increase yield more than cut stargrass (Cynodon dactylon), or no mulch, through warming soil, improving nutrient uptake and conserving moisture. The experiment was set up as split plots in randomised complete block design; mulches were assigned to main plots, whereas cultivars were assigned to sub-plots. Each of the sixteen treatments was replicated three times. Cultivars were planted at the beginning of long rains in March 2002. Data were recorded from the fourth month after planting (MAP) and analysed. Polyjilm hastened growth from 2 to over 5 stolons, 18 to 30 leaves, 31 cm to 35cm diameter at 4 MAP, and increased flowering and yield from 9 to 12 flower stalks, 22 to 29 berries, and 30 g to 35 g berry fresh weight at 9 MAP. Most of the time, black polyjilm growth and yield parameters were higher than those for cut grass or no mulch. Positive effects of cut grass mulch developed slowly, while those of clear polyjilm mulch diminished over time. Nine months after planting, black polyjilm gave significantly (P0.05) interact with cultivar, implying that it does not alter the potential of cultivars grown under tropical highland conditions.
Current characteristics of cassava mosaic disease in post-epidemic’ areas increase the range of possible management options.
(Association of Applied Biologists, 2006-06-05) Mallowa, S. O.1; Isutsa, D. K.1; Kamau, A. W.1; Obonyo, R.2; Legg, J.P 2,3; ; ;
As a case study to document the current characteristics of cassava mosaic virus disease (CMD) in postepidemic areas, surveys were carried out, in 2003 and 2004, in Siaya District of western Kenya. This was an area affected by a severe CMD pandemic in the late 1990s. Data recorded on cassava varieties were CMD incidence, severity index and number of adult whiteflies. Farmers (174) were interviewed on their understanding of the disease and their knowledge and practice of management interventions. Cassava cultivation was being reestablished, but local landraces predominated. Resistant varieties were present 13% in 2003, and 4% in 2004, of the surveyed fields. Adhiambolera was the most common variety, occurring in 35% and 40% of fields in 2003 and 2004, respectively, and had an average CMD incidence of 82% in 2003 and 73% in 2004. By contrast, the CMD-resistant variety Migyera had a low mean incidence (28% in 2003). The overall incidence for both years was 71%, consisting of 61% as a result of infection through planting diseased cuttings and 10% as a result of whitefly infection. In 2003, the total incidence was 72% and the average severity 2.7 (severity index), while in 2004 the incidence was 78% and the severity 2.6. There were significant severity variations in each division of the Siaya District during the 2 years except for Karemo and Ukwala. The abundance of whiteflies on the top five leaves of plants was low in 2003 but high in 2004, with means of 1 and 16, respectively, over the same seven divisions in both years, although this variation was thought to be because of seasonal factors. East African cassava mosaic virus-Uganda was the predominant geminivirus present in every division. Phytosanitation by farmers was minimal, as evidenced by 29% of farmers using a selection of CMD-free stems for planting and 15% using hand-roguing for CMD management. Occurrence of more than 25% CMD-free plants in 2004, moderate CMD severity and limited spread provide a conducive environment for the use of phytosanitation as a CMD control measure that can be immediately used by farmers growing their own cassava varieties.
Effects of integrated nutrient sources on growth and yield of strawberry grown under tropical high altitude conditions.
(Horticultural Association of Kenya, 2008) Odongo, T.; Isutsa, Dorcas K.; Aguyoh, J. N.; ; ;
Strawberries are popular both in fresh and processed forms because of their enormous values. Low soil fertility is among major factors constraining strawberry productivity in Kenya. Consequently, effects of cattle farmyard manure (FYM) (0, 18, 36, and 54t/ha) in combination with triple super phosphate (TSP), equivalent to 0, 17, 34 and 68kg/ha phosphorus on strawberry productivity, were tested in split plots embedded in randomized complete block design, replicated three times. Farmyard manure formed main plots, whereas TSP formed sub-plots. Each treatment had 10 plants spaced at 0.3m´0.45m in double rows per plot, measuring 0.6m´1.5m. The plots were mulched with black polyfilm, irrigated with 2.5.cm diameter drip lines, and separated with a 0.5m trench. The study was done in three seasons (August 2003-July 2004, Feb. 2004-Jan. 2005, and July 2005-June 2006). Each season was conducted in new plots. Growth and fruit yield were assessed from 3 to 6 and 6 to 12 month after planting, respectively. Since seasons 1 and 2 data were not significantly different they were pooled and reported as season 1, whereas the different season 3 data were reported separately as season 2. Generally, the 54t/ha FYM promoted the highest growth, although not significantly different. Phosphorus (P) significantly (P<0.05) increased root biomass, and root: shoot biomass ratio. The effects of FYM, P and interaction on fruit yield were not consistent. The 36 and 54t/ha FYM resulted in the highest fruit weight in seasons 1 and 2, respectively. Phosphorus did not significantly (P>0.05) influence fruit weight, although 17 and 34kg/ha P yielded highest in seasons 1 and 2, respectively. The effect of interaction on cumulative yield was not significant in both seasons. Thus the observed variation was also attributed to soil and seasonal effects. Based on the current results, 36 t/ha to 54t/ha FYM and 17 kg/ha to 34kg/ha P are recommended for enhancing strawberry productivity under conditions similar to the ones for the present study. Phosphorus should only be applied where soil tests show deficiency.
Growth of ranunculus cutflower under tropical high altitude conditions. 2: Effects of GA3 and shade on light intensity and temperature modification
(Horticultural Association of Kenya, 2009) Mayoli, Rose N.; Isutsa, Dorcas K.; Tunya, G.O; ; ;
Customer needs of a different flower are increasing over time worldwide. Many bulbous plants including ranunculus fit the category of a different flower because they are not known. Ranunculus(Ranunculus asiaticusL.),commonly known as Persian Buttercup or Asiatic Crowfoot,is a bulbous plant native of the cool Mediterranean basinregion. The growth of GA3and shade-treated ranunculus cutflower in relation to lightintensity (LI) and temperature under tropical high altitude conditions is not documented. An experiment was conducted to determine these relationships.The fixed factors were four GA3levels (0, 100, 500, 1500 mg/L) and three shade levels (0%, 40% and 80%shade). The experiment was set up in split plots arranged in randomised complete block design, replicated three times and repeated once. Tuberous roots were soaked in the respective GA3solutions for 10 minutes followed by planting under the shaded plots.Data were recorded from sprouting through tuberous root formation stages.The relationship of sprouting was negative quadratic with LI, positive linear with soil temperature (ST) in season 1 (cool), and negative linear with ST in season 2 (warm). The relationship of time to flower formation with LI was negative linear in season 1 and positive linear in season 2. The relationships of flower stem length with LI and air temperature (AT) were negative linear. The relationships of flower buds per stem, flower stem diameter, flower head diameter and tuberous root fresh weight with either LI or AT were negative quadratic. Therefore, shade modifies both LI and temperature that then interact in influencing growth of GA3-treated ranunculus. About 40000 lux LI and moderate seasonal temperature, both prevailing under 40% shade are ideal for best growth of ranunculus. Shade should be applied as follows: 0%, 40% and 80% in cool, warm and hot seasons, respectively.
Growth of ranunculus cutflower under tropical high altitude conditions.
(Horticultural Association of Kenya, 2009) Mayoli, Rose N.; Isutsa, Dorcas K.; Tunya, G.O; ; ;
Cutflower production and marketing is partly challenged by lack of new, exciting and improved varieties to satisfy customer needs of a different flower. Ranunculus (Ranunculus asiaticus L.) is a bulbous plant that originated in the Mediterranean basin region where growth and development take place optimally in cool, moist winter season. The extent of dormancy breaking and growth of this flower in tropical conditions is not known. Consequently, the present research studied the effects of shade and gibberellic acid (GA3) in breaking dormancy and reducing high light intensity and high temperature so as to assure optimal growth of R. asiaticus under tropical conditions. The fixed factors were: four GA3 levels (0, 100, 500 and 1500 mg/L) and three shade intensities (0%, 40% and 80% shade). The experiment was laid out in split plots arranged in randomised complete block design, replicated three times and repeated in two seasons. Tuberous roots were soaked in the respective GA3 concentrations for 10 minutes followed by planting under shaded plots. Data were recorded from sprouting through tuberous root formation stages. Season 1 (June to November 2006) was characterised by cool temperatures, whereas season 2 (December 2006 to April 2007) was characterised by warm temperatures. The 80% shade promoted significantly longer stems. Nevertheless, early flowering, highest quality flower stem diameter, flower bud initiation, flower head diameter and tuberous root fresh weight resulted for 40% shade. These quality parameters were highest in tuberous roots that had been soaked in 100 mg/L GA3 pre-plant. Therefore, growers in tropical high altitudes should use 80%, 40% and 0% shade in hot, warm and cool seasons, respectively. Pre-soaking of the tuberous roots in 100 to 500 mg/L GA3 is optional, depending on the desired growth magnitude and speed desired.
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.
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.
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.
Effectiveness of phytosanitation in cassava mosaic disease management in a post-epidemic area of western Kenya
(2011-07) Mallowa, S. O. 1; Isutsa, D. K.1; Kamau, A. W.1; Legg, J. P.2; ; ;
The effectiveness of phytosanitation in managing cassava mosaic disease (CMD) was studied in a post-epidemic area of western Kenya. Four varieties [MM96/4466 (resistant), TMS 30572 (Migyera, moderately resistant), Bukalasa 11 (Serere, moderately susceptible) and Karemo (susceptible)] and four phytosanitation approaches (roguing, cutting selection, roguing plus cutting selection, and none) were studied at two sites (Alego and Ugunja) for two seasons. With no phytosanitation, resistant varieties had very low levels of CMD infection, and infected plants expressed very mild symptoms. By contrast, the most susceptible variety became heavily diseased, with incidences of > 90%, whether phytosanitation measures were applied or not. Tuberous root yields were highest for CMD-resistant varieties. Roguing susceptible varieties resulted in significantly reduced root yields compared to the 'do nothing' control, largely as a result of the greatly reduced plant population. However, plots of CMD-susceptible varieties where selection was applied gave tuberous root yields that exceeded those of the control and that were comparable to those of the resistant variety with the equivalent treatment. These data clearly demonstrate the value of selection as an approach for maintaining the production of local varieties under the CMD post-epidemic conditions that are now prevalent across large areas of East and Central Africa. Conversely, the results show that roguing provides no tuberous root yield benefit under any of the tested circumstances. Raising awareness amongst farming communities of the potential advantages of selection of healthy planting material should be an important component of CMD management programmes, in tandem with efforts to multiply and disseminate planting materials of resistant varieties.
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.
Variation of micronutrients in pumpkin fruit varieties grown by smallholder farmers within Lake Victoria Basin.
(2013) Echessa, A.C. Peter1*; Nyambaka, Hudson 1, O; Ondigi, N. Alice 2; Omuterema, Stanley 3 ,; Toili, William 3; Sande, Anne 3
Food shortage is a common occurrence in the developing countries. The shortage is emancipated in both low quantity and poor quality resulting in deficiency based diseases. The fact that pumpkins have an easy production (3-4 month), long shelf life (over six month) and therefore available, should increase their likelihood incorporation in the diet. The study set out to establish the varieties and levels of micronutrients in the fruits of the pumpkins grown by small holder farmers in four districts of Busia, Gucha, Jinja and Tarime within the Lake Victoria Basin. A questionnaire was administered to determine information on the varieties. The levels of βcarotene, α-tocopherol and the B-complex vitamins were determined with RP HPLC. Vitamin C was analysed by titration while AAS was used for the analysis of trace elements (zinc, iron and selenium). Standards were run and calibration curve equations with 0.955 ≤ R2 ≤ 0.999 used to calculate the concentrations. Three species of pumpkins Cucurbita maxima, Cucurbitapepo and Cucurbitamoschata were widely distributed. Ten different varieties were sampled. The levels of micronutrients in different varieties (Fruits) showed significant differences that could not be accounted for by chance. At 95 % confidence limit, moisture (p = 0.001), β-carotene (p = 0.002), thiamine (p = 0.000), riboflavin (p = 0.001), niacin (p = 0.009) and pyridoxine (p = 0.000) varied significantly. Further comparison of the samples from each district equally showed significant differences (p < 0.05) in all micronutrients except vitamin C (p = 0.08) and selenium (p = 0.447) levels. These results indicate non universality in levels of micronutrients in different varieties and between locations enhancing the need for focusing on those superior varieties (like the banana variety) as established in this study. From the levels of the micronutrients (β-carotene 2.220-2.670 mg / 100 g, zinc 0.986-1.728 mg / 100g, iron 2.16-1.68 mg / 100g) established, it is appropriate to popularize the utilization of pumpkins as a conventional rich food source to supplement the traditional cereal based diets aimed at combating the problem of food shortages and malnutrition in the Lake Victoria Basin and developing countries in general.
Mechanisms and Sources of Resistance in Tropical Maize Inbred Lines to Chilo partellus Stem Borers
(2013) Munyiri, S. W. 1,2; Mugo, S. N. 3; Otim, M. 4; Mwololo, J. K. 1,5; Okori, P.
Developing maize with durable resistance to maize stem borers could be enhanced by identifying genotypes with different mechanisms of resistance and pyramiding the resistances into high yielding genotypes. This study was carried out on 120 CIMMYT tropical maize inbred lines to identify the most important mechanisms of resistance that could be used to discriminate the germplasm into resistant or susceptible categories. The experiment was laid in an α-lattice design, and replicated three times during the 2011/12 seasons. Traits measured were leaf toughness, stem penetrometer resistance, trichome density, stem sugar content, leaf damage, number of stem exit holes and stem cumulative tunnel length. A selection index was computed and categorized the 120 inbred lines into 33 resistant, 29 moderately resistant, 31 moderately susceptible and 27 susceptible. The most resistant lines were those derived from the CIMMYT multiple borer-resistant populations with CKSBL10039 being most resistant and CML395 most susceptible with indices of 0.49 and 1.84, respectively. Trichome density, leaf toughness and stem sugar content in that order were the most important traits in discriminating the lines into resistance and susceptible categories. More research is needed to classify the specific types of trichomes and sugars present in both resistant and susceptible inbred lines.
Responses of tropical maize landraces to Spotted stem borer damage in Kenya
(2013-03) Munyiri, S. W.1,2; Mugo, S. N.3*; Otim, M. 4; Tefera, T. 2; Beyene, Y. 2; Mwololo, J. K. 1,5; Okori, P. 1
The potential to manage insect pests using host-plant resistance exists, but has not been exploited adequately. The objective of this study was to determine the resistance of 75 tropical maize landraces through artificial infestation with Chilo partellus Swinhoe. The trial was laid in alpha-lattice design and each seedling was infested with five neonates three weeks after planting, over two seasons in 2009 and 2010. The number of exit holes, tunnel length, ear diameter, ear length, plant height, stem diameter, stem lodging and grain yield were measured and a selection index computed. GUAT 1050 was the most resistant with an index of 0.56, while BRAZ 2179 was the most susceptible with an index of 1.66. Ear characteristics were negatively correlated with damage parameters. The principal component biplot suggested that exit holes, cumulative tunnel length, leaf damage, cob diameter, stem lodging, selection index, ear and plant height contributed 71.2% of the variation in resistance. The mean number of exit holes and tunnel length for resistant landraces and resistant hybrid checks were similar; at 5.5 and 2.48 cm, respectively.
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
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.

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