Crop Science and Production Collection

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    Studies on the Influence of Altitude on Abundance of Fall Armyworm (Spodoptera Frugiperda (Je Smith)) (Lepidoptera: Noctuidae) in Tanzania
    (Society for Science and Education, 2023-08-25) Mbemba, Kiva F.; Rwegasira, Gration M.; Tryphone, George M.
    Fall armyworm (FAW) (Spodoptera frugiperda) is one of the most devastating polyphagous field crop pests in many parts of the world, including Tanzania. Influence of altitude on the abundance of S. frugiperda was studies by using Pheromone (Frugilure S. frugiperda, Chemtica international, S.A) embedded cup traps. The study was conducted along sites of Mt. Uluguru slopes including; SUA (525 masl), Mlali (579 masl), Mgeta (1050 masl) and Nyandira (1691 masl) located in Morogoro Region, Tanzania. A total of 16 cup traps (four at each site equidistantly arranged at 100 m apart) were used. Weather data were recorded using Hygrocron i-button hung on a tree at equidistant from the four traps. Data on S. frugiperda counts and weather variables were recorded weekly for duration of six months from January to June 2020. Results showed that S. frugiperda was abundantly recorded across he tested altitude albeit at varied abundance. There was significant difference (p < 0.001) among altitude on S. frugiperda abundance, whereby at low altitude, S. frugiperda abundance was high compared to medium and high altitude. Rainfall had positive correlation on S. frugiperda abundance (r = 0.16, r = 0.04) for SUA and Mlali and negative correlation (r = -0.44) and (r = -0.03) for Mgeta and Nyandira. Temperature had positive correlation (r = 0.21) on S. frugiperda abundance at Nyandira while SUA (r = -0.03), Mlali (r = -0.35) and Mgeta (r = -0.28) had negative correlation. Relative humidity for all four locations showed negative correlation with S. frugiperda abundance. Thus, appropriate and effective management practices of S. frugiperda should be considered throughout maize production areas and across crop production seasons regardless of the altitude.
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    Management plan for fruit Fly (Diptera: Tephritidae) pests in Tanzania
    (Sokoine University of Agriculture, Directorate of Research and Postgraduate Studies., 2013) Prof. Maulid Mwatawala; Dr. Marc De Meyer; Dr. Zuberi Seguni; Dr. Gration Rwegasira; Ms. Janet Muganyizi; Mr. Frank Senkondo; Ms. Lilian Shechambo
    Tanzanian economy largely depends on agriculture which provides employment to almost 75 percent of Tanzanians, particularly the rural populations. Furthermore, agriculture accounts for about 24 percent of the GDP (URT 2012a) and about 35 percent of export earnings (URT, 2012b). However, agriculture in Tanzania is dominated by smallholder farmers (peasants) who cultivate an average of between 0.9 ha and 3.0 ha farm sizes. Furthermore, sixty-four (64%) percent of the agricultural land is cultivated by hand hoe, 24 percent by animal power and 14 percent by tractor (URT, 2012a). Most of the crops are predominantly grown under rain-fed condition whereas 5 percent of the cultivated land area (about 10.2 million hectares) is under irrigation. Women are believed to constitute a larger part of agricultural labour force.
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    Facilitating International Agricultural Trade Through Science: the Case of Tephritid Flies
    (Sokoine University of Agriculture, 2018) Prof. Maulid Walad Mwatawala
    International agricultural trade is important in addressing spatial and temporal food shortages across the globe. Agricultural trade generates income and contributes to economies of many countries. Unfortunately, there are various risks associated with the movement of agricultural commodities across borders. The spread of pests across countries is one of the great risks. The International Plant Protection Convention (IPPC), which is an agreement between nations, aims at preventing and controlling the introduction and spread of pests of plants and plant products across national boundaries. IPPC formulates various standards and guidelines that can be adopted by member states to formulate municipal phytosanitary laws against the introduction of pests. Countries normally conduct Pest Risk Analysis (PRA) in order to facilitate agricultural trade. This process requires scientific evidence on the identity and occurrences of pests in an area and a possible entry and the establishment and the spread of those pests into exotic places. Fruits and vegetable trade is important for food and security among the global population. However, fruit trade introduces the risk of the spread of pests, including fruit flies. Most fruit flies cause heavy losses to the fruit industry and these are therefore of quarantine importance. Research which has been conducted across the globe provided scientific evidence on the possible spread of fruit flies in order to facilitate trade. The Sokoine University of Agriculture (SUA) collaborated with various partners in the world to generate important information that is a prerequisite for conducting PRA. This inaugural lecture highlights key findings that include identification of new species, resolution of cryptic species, host range and preference, spatial and temporal distribution, and mitigation options against the selected economically important fruit flies.
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    Fungi intercepted in seeds of pigeon pea ( (cajanus cajan (l.) grown in Northern Tanzania and relation to quality attributes of the seeds
    (International Research Journal of Biological Sciences, 2019) Tarmo, Theophili; Msuya, Dunstan; Njau, Paul
    Fungi associated with Pigeon pea seed were studied using 80 seeds samples of pigeon pea collected from Babati and Karatu districts in northern Tanzania. The standard moist blotter test was used to detect fungi on seeds. The tested pigeon pea samples yielded d more than 12 different fungal species. Fusarium udum which is a pathogen of seed health certification significance was detected in 33 samples from Babati (equivalent to 82.5%) and 36 samples from Karatu districts (equivalent to 90%) of the samples. Eleven n other seed infesting fungi were also intercepted, with Rhizopus spp appearing in all samples and having the highest incidence of 23.2% for Karatu and 16.1% for Babati district followed by Aspergillus flavus having the incidence of 20.3% and 15.7% for Karatu atu and Babati districts, respectively. The other species ranged between 1.1% and 10.1% for Babati and 0.7% and 13.7% for Karatu. Significant correlation existed between seed purity and incidence of Cladosporium spp and between seed moisture content and in incidence cidence of Fusarium moniliforme; but the correlation with purity was positive against expectation. Even though farm farm-saved saved seeds may be localized with the practicing farmer or within a restricted locality, generally it is suggested that in those areas where seed borne pathogens are endemic and farm-saved farm seeds is predominant farmers’ awareness on Fusarium wilt disease should be created. It is also suggested that farmers should be trained on how to reduce seed transmission of the diseases at least by rouging the infected plants in the field and selective harvesting of the crop to be used as seed.
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    Bacterial leaf spot of sweet pepper caused by Xanthomonads-. incidence, pathogen characterization, epidemiology and management options
    (Sokoine University of Agriculture, 2011) William, Magdalena Nchagwa Magere
    A study was conducted in sweet pepper growing regions (Morogoro. Arusha, Tanga and Mbeya) in Tanzania to determine incidence and epidemiology of bacterial leaf spot disease (BLS), characterize bacterial spot-causing xanthomonad (BSX) strains and screen for resistance of the locally available sweet pepper varieties. One hundred sweet pepper fields were surveyed and diseased samples were collected for laboratory analysis. Bacterial isolates were identified based on physiological, biochemical, PCR and pathogenicity tests. Races were determined based on compatible or hypersensitive response on differential sweet pepper near-isogenic lines ECW-10R, ECW-20R and ECW- 30R. Results indicated that, BLS disease was wide-spread in farmers' fields in the surveyed regions. Disease incidence ranged between 10—100%, while the overall mean disease incidence was 69.3 %. Disease severity was statistically significant on village basis and the overall mean score was 4.6. High mean disease incidence (93.3 %) and disease severity score (6.5) were recorded in Lukozi and Kivulul villages, respectively. The lowest mean disease incidence (12 %) and severity (1.2) were recorded in Utengule village. Poor cultural practices and epiphytic survival of BSX on host and non-host plants were found to be the sources of inocula for successive crops. The RST2/RST3 primer sets detected 59 strains to genus level and the effector/avirulence gene primer sets detected 68 out of the 74 strains tested. The species-specific primer sets identified 63 out of 68 BSX to species level and were pathogenic on the susceptible cultivar Early Calwonder (ECW). The BSX were X. euvesicatoria (30), X. perforans (10) and X. gardneri (23). Xanthomonas euvesicatoria and X. perforans dominated in Tanga region whereas Xanthomonas gardneri dominated in Arusha region. Five strains were not pathogenic on cv. ECW. Seven sweet pepper races (P0 - P6) were identified. Race P3 (50 %) dominated the strains of BSX in Morogoro, Arusha and Tanga regions. Race P6 (27.9 %) dominated in Tanga and Morogoro regions. Frequencies of races PO, Pl, P2, P4 and P5 were considerably low. All the locally available sweet pepper varieties were susceptible to BLS disease. This is the first report to characterize BSX of sweet pepper in Tanzania.
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    Banana xanthomonas wilt: occurrence and means of transmission in Kagera, Mwanza and Mara regions of Tanzania
    (2016-02) Hashim, Ibrahim; Mabagala, Robert B
    Abstract: Banana Xanthomonas wilt (BXW) disease is a major constraint of banana production in the Lake zone (Kagera, Mwanza and Mara) regions of Tanzania where banana plays an important role as a staple food and cash crop. Infected plants die and fruits rendered inedible. To assess the current status of BXW disease field surveys were conducted from December, 2011 to January, 2012 in Kagera, Mwanza and Mara regions. Twenty eighty banana samples with BXW disease symptoms were randomly collected from a total of 147 surveyed fields. Farmers’ knowledge of BXW disease was assessed using a checklist, discussions and direct field observations. Isolation of bacteria was done on Yeast Peptone Glucose Agar and identification was done based on morphological, biochemical and pathogenicity test. Results indicated that the incidence of BXW disease was highest (56.7 %) at Ihangiro and the lowest (10 %) at Ruhija and Mulela, in Muleba District; Nakamwa and Busagami, in Ukerewe District. Such results implied that, BXW disease is still a constraint to banana production in the surveyed districts. The results also indicated that BXW pathogen transmission was through infected farming tools (65.4 %) in Muleba District and infected planting materials in Tarime (50.5 %) and Ukerewe (45.8 %) Districts implying that these were the major means by which BXW disease was spread in the study area. About 58.33 % and 41.67 % of the farmers in Ibare and Kishanda villages, respectively, in Muleba District associated pied crow (Corvus albus L.) with the transmission of BXW causing pathogen. Results based on morphological, biochemical and pathogenicity test indicated that, four out of 16 bacteria isolated from infected banana samples were Xanthomonas campestris pv. musacearum (Xcm). Further studies on the relationship between the pied crow and Xcm transmission in Kagera, Mara and Mwanza regions, are recommended.
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    Seasonal variations of nematode infection in Small East African goats and their crosses with Boer and Saanen reared under extensive and semi- intensive systems
    (2010-04) Muhikambele, Vedasto; Chenyambuga, Sebastian; Mbaga, Said
    A study was conducted in Turiani (sub-humid environment) and Mlali (semi-arid environment) to assess the seasonal variation of nematode infection in Small East African (SEA) goats and F 1 crosses of SAE with Saanen and Boer. The SEA goats were kept under extensive system while the crossbreds were kept under semi-intensive system. In Mlali 37 SEA goats and 30 SEA x Boer crosses while in Turiani 30 SEA goats and 33 SEA x Saanen crosses were included in the study. Worm burden was assessed using faecal egg count (FEC) and packed cell volume (PCV) as indicator traits. Faecal and blood samples were collected at the end of dry season, mid and end of rain season. The dominant worm species were identified by faecal culture. The results indicated that fewer animals (30 – 66.7%) were infected at the end of the dry season than at the mid and end of the rain season (69.7 – 100%). The FEC values differed significantly between periods of the year (P< 0.001) and between locations (P<0.05). The geometric mean faecal egg count (GFEC) ranged from 71.3 to 200.9, 185.8 to 516.4 and 273.5 to 924.7 eggs per gram (epg) at the end of dry season, mid and end of rain season, respectively. The GFEC values of SEA goats reared under extensive system were slightly higher (80.5 – 924.7 epg) than those of crossbred goats (71.3 – 690.2 epg) reared under semi-intensive system. The PCV values differed significantly (P<0.001) between locations, periods of the year and breeds. In Mlali, the PCV values ranged from 18 to 45% while in Turiani, the values ranged from 10 to 43%. The dominant parasite in the study areas was Haemonchus spp and accounted for 47.5 and 48.9% of total worms in Turiani and Mlali, respectively. This was followed by Trichostrongylus spp (21.3 and 19.8% in Mlali and Turiani, respectively) and Oesophagostomum spp (18.2 and 20.7% in Turiani and Mlali, respectively). The proportions of Strongyloides spp (6%), Bunostomum spp (4%) and Cooperia spp (3%) were small in all periods and locations. It is concluded that the level of nematode infection is highest at the end of the rain season and low during the dry season. The crossbred goats kept under semi-intensive grazing system had lower level of nematode infection than the local goats kept under the free-range grazing system
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    Impact of spatio-temporal simulations of rat damageon yield of rice (Oryza sativa L.) and implications forrodent pest management
    (Taylor & Francis, 2014-11-29) Mulungu, L.S; Lagwen, P.P; Mdang, M.E; Kilonzo, B.S; Belmain, S.R
    Rodents often damage crops throughout the growing season, from germination to harvest, thus making it difficult to understand the cumulative effects of rodent damage for crops such as rice that are able to partially compensate for damage. Compensation can make it difficult to understand the impact of variable rodent damage in terms of when the damage occurs, its severity and thus when, whether and how rodent pests should be controlled. The compensatory responses of rice to simulated rat damage carried out at different growth stages and at different spatial levels of severity showed that higher yield was recorded during the wet season in comparison to the dry season. However, yield loss was observed during all cropping stages for all levels of simulated damage for wet and dry season crops, with significant compensation noted at the transplanting [14 days after sowing (DAS)] and vegetative (45 DAS) stages. Only damage at the maturity (110 DAS) stage resulted in significant reductions in rice crop yield. Seasonal differences suggest water availability was an important factor that perhaps enhanced rice production. The ability of rice to compensate for early rodent damage could potentially reduce a farmer's perception of damage. However, failing to control rodents at these earlier crop growth stages could lead to increased rodent populations at the time of maturity when compensatory effects are limited.
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    Effect of final moisture content, cooling time and paddy variety on milling quality of rice (Oryza sativa, L.)
    (Pearl Research Journals, 2016) Furahisha, Kulwa; Chove, Lucy Mlipano; Chaula, Davis
    The study was carried out to establish the effects of three factors -final moisture content (FMC), shade-cooling time (CT) and paddy variety on rice milling quality. Paddy was sun dried to final moisture contents ranging from 9.0 to 15.5% (on wet basis) and shade-cooled for 0, 6, 12, 18, and 24 h at ambient temperature (27.20 to 35.10 o C). Five paddy varieties, TXD 88, TXD 306, SUPA, IRRITA 1, and IRRITA 2 were studied. The milling tests were carried out using a laboratory rice mill. Latin square design with 5 replications (5x5 orders) was used. Physical properties and milling quality in terms of total rice yield (TRY), head rice yield (HRY) and whiteness index (WI) were analyzed. The physical properties differed significantly (P<0.05) among varieties. SUPA had good size, shape and chalkiness whereas TXD 88 had poor quality for all these parameters. IRRITA 1 and IRRITA 2 produced higher TRY compared to other tested varieties. TXD 88 had higher whiteness index but lower HRY compared to other tested varieties. Higher yields, which were significantly different for TRY and HRY (P<0.05) were obtained at moisture content between 9.0 to 12.5% for TRY, but between 10.5 to 14.0% for HRY
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    Fatty acid profiles and lipid oxidation status of sun dried, deep fried, and smoked sardine (Rastrineobola argentea) from Lake Victoria, Tanzania
    (Taylor & Francis, 2019) Chaula, Davis; Laswai, Henry; Chove, Bernard; Dalsgaard, Anders; Mdegela, Robinson; Hyldig, Grethe
    Freshwater fishes contain long chain omega-3 and omega-6 polyunsaturated fatty acids (PUFAs) of highest nutritional value. PUFAs in fish are susceptible to oxidative damage during processing and subsequent storage. Sardines (Rastrineobola argentea) are an important fish species of Lake Victoria, constitut- ing 72.3% of the total landings by weight on the Tanzanian side of the lake. Fatty acid profiles and lipid oxidation status of sun-dried, deep-fried, and smoked sardines were investigated. Lipid oxidation was assessed by peroxide value, thiobarbituric acid reactive substances (TBARS), and free fatty acids. Fatty acids were analyzed by gas chromatography with flame ionization detector. The three omega-3 PUFAs: docosahexaenoic acid (C22:6n-3), docosapentaenoic acid (C22:5n-3), and eicosapentaenoic acid (C20: 5n-3) contributed 57–60, 63, and 38% of PUFAs in sun-dried, smoked, and deep-fried sardines, respectively. Lipid oxidation reactions were more pronounced in sardines dried on sand and rocks, with TBARS values 97.87 and 84.18 μmolMDA/kg, respectively. The polyene index was significantly lower (p < 0.05) in deep-fried sardines, indicating lower retention of PUFAs in the product. Lake Victoria sardines are a rich source of omega-3 PUFAs. PUFAs in sun-dried sardines are prone to oxidative damage. Smoking resulted in relatively higher retention of omega-3 fatty acids in products.
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    In situ pectin engineering as a tool to tailor the consistency and syneresis of carrot purée
    (Elsevier, 2012) Christiaens, Stefanie; Buggenhout, Sandy Van; Chaula, Davis; Moelants, Katlijn; David, Charlotte C.; Hofkens, Johan; Loey, Ann M. Van; Hendrickx, Marc E.
    To investigate whether in situ pectin engineering would be a helpful tool in tailoring the consistency and syneresis of vegetable purées, carrot was selected as a plant tissue in which the textural properties are largely influenced by pectin methylesterase-induced pectin changes. The effect of low-temperature and high-temperature blanching, as well as the effect of two types of mechanical disruption, blending and high-pressure homogenisation, on the flow properties of carrot purée was explored. The influence of these different purée preparation steps on pectin was examined via physicochemical analysis of fractionated walls and isolated polymers, and via anti-pectin antibodies entailing in situ and ex situ analyses. Purée prepared by blending non-pretreated carrots showed a rather high consistency and pronounced syneresis. Treatments that solubilise pectin, such as high-pressure homogenisation and, in particular, high-temperature blanching, limited syneresis phenomena. In contrast, when the intercellular adhesion in carrot tissue was strengthened via low-temperature blanching, the degree of syneresis increased. High-pressure homogenisation was useful to reduce the carrot tissue particle size and, consequently, resulted in a lower consistency carrot purée. Low-temperature blanching on the other hand increased the consistency of carrot purée as the higher level of intercellular adhesion presumably led to an increased resistance to particle disintegration upon blending or high-pressure homogenisation
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    Effect of improved tomato cultivars on productivity and profitability in Morogoro region, Tanzania
    (Journal of Animal &Plant Sciences, 2016) Msogoya, T. J.; Mamiro, D.
    The objective of this study was to assess yield, revenue and profit from F1 hybrid tomato cultivars compared to farmers' preferred open pollinated local tomato cultivars grown in Tanzania. Seeds of local and F1 hybrid tomato varieties were sourced from local agro-dealers. The experiment was laid out in a randomized complete block design with four treatments (cv. Assila, Eden, Shanty and Oxyl Premium) and four controls consisting of local tomato cultivars (cv. Tengeru 97, Tanya, Cal-J and Riogrande). A treatment was replicated three times each with 12 plants. The seedlings were planted at a spacing of 60 cm x 60 cm in an open field at Sokoine University of Agriculture during the rainy and dry seasons. Data on total and marketable fruit yields were analyzed using Genstat statistical software version 15 and treatment means were separated based on Fisher’s unprotected LSD test at p< 0.05. Seed and production costs were computed based on real cost while revenues and net profits were estimated based on fruit marketable yield and retail prices of TSh. 700 and 1000 per kilogram (One USD = TSh. 2000). Results indicated that cv. Assila significantly (p = 0.002) produced higher total and marketable fruit yields than all local tomato cultivars during both the dry and rainy seasons. Moreover, cv. Eden significantly (p = 0.002) produced higher total and marketable fruit yields than all local cultivars during the dry season only while cv. Shanty produced higher marketable yields than all local cultivars during the rainy season only. The production costs of F1 hybrid tomato cultivars were higher than those of local tomato cultivars during both seasons. Tomato cv. Assila produced higher revenue and net profit than all local cultivars during both seasons while cv. Shanty produced higher revenue and net profit than all local tomato cultivars during the rainy season only. It is therefore recommended that farmers in Morogoro region should grow cv. Assila during both the rainy and dry seasons, and cv. Shanty during the rainy season only.
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    Assessment and management of post harvest losses of fresh mango under small-scale business in Morogoro, Tanzania
    (JAPS, 2011) Msogoya, T. J.; Kimaro, E. S.
    This study was conducted to assess postharvest losses and the effect of shade during wholesale market and hot water treatments on storage of mango cv. ‘Dodo’. To assess postharvest losses, mature fruits were packed on semi-rigid bamboo cartons, loaded on a truck without separators in between cartons and transported from Mkuyuni ward to Morogoro urban, Tanzania. The effect of heat stress during the wholesale market was evaluated by storing mango fruits under the sun, woven polypropylene shade and black net shade at Sokoine University of Agriculture. Mango fruits dipped in hot water at 60° C for 10 minutes were compared with untreated ones as control. Results showed that the fruit total postharvest losses were 43.8 % with the wholesale market, transport and harvest stages accounting for 30.6 %, 10.6 and 2.6 % of the total losses, respectively. The main features of fruit deterioration during the wholesale market stage were softening and microbial decay each accounting for 50.7 and 39.6 % of the total losses within the stage, respectively. Microbial decays of 7.2 % and mechanical injuries of 2.0 % were the major features of mango fruit deterioration during the transport and harvest stages. Storing fruits for three days under the woven polypropylene and black net shades significantly reduced fruit postharvest losses by 52.7 and 38 %, respectively in comparison with fruit storage under the sun. Hot water treatment reduced the incidence of microbial decay by 85 % and improved fruit total soluble solids content by 15 % in comparison to untreated fruits. However, hot water treatment reduced fruit firmness and shelflife by 56.0 and 71.4 %, respectively. In the short term, wholesale traders are advised to store fruits under the polypropylene shade while in the long term, municipal and council authorities are argued to construct cold storage facilities for fresh fruits. Furthermore, farmers are advised to disinfect mangoes with hot water, especially those purported for immediate marketing.
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    Identification and management of microbial contaminants of banana in vitro cultures
    (Journal of Applied Biosciences, 2012) Msogoya, T. J.; Kanyagha, H.; Mutigitu, J.; Kulebelwa, M.; Mamiro, D.
    Microbial contamination is one of the major challenges hampering the application of in vitro micropropagation technique for mass production of pest-free banana planting materials at the Sokoine University of Agriculture in Tanzania. Objectives: The objectives of this study were to identify bacterial and fungal contaminants of banana in vitro cultures and to test the efficacy of selected antibiotics and antifungal agents in the elimination of such contaminants. Methodology and results: Purified bacterial isolates were identified based on vegetative cell shape, gram reaction, fluorescent pigment and standard biochemical tests. On the other hand, pure fungal isolates were microscopically identified based on structural and morphological characters. Four antibiotics, namely rifampicin, gentamicin, chloramphenicol and vancomycin each at 100, 150 and 200mg /litre and three antifungal agents, namely ketoconazole, fluconazole and nystatin each at 100, 150 and 200 mg/litre were used in the culture susceptibility tests of the identified bacteria and fungi, respectively. The bacterial contaminants of banana in vitro cultures were Proteus spp., Erwinia spp., Klebsiella spp. and Staphylococcus spp. while the fungal contaminants were Aspergillus spp., Fusarium spp,. Penicillium spp. and Candida spp. Culture susceptibility tests revealed that gentamicin, rifampicin and chloramphenicol each at 150mg/litre effectively suppressed the growth of all the identified bacteria while only ketoconazole at 200mg/litre inhibited the growth of all the identified fungal contaminants. Conclusion and application of results: Proteus, Erwinia, Klebsiella and Staphylococcus are the major bacterial contaminants while Aspergillus, Fusarium, Penicillium and Candida are the main fungal contaminants of banana in vitro cultures. These contaminants can effectively be eliminated by incorporation in the growth media of gentamicin, rifampicin and chloramphenicol each at 150mg/litre and ketoconazole at 200mg/litre. Further studies are required to investigate the negative side-effects of these antibiotics and antifungal agents on the growth and genetic stability of banana in vitro cultures.
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    Paths of influence among components of yield in sorghum (Sorghum bicolor (L) Moench, cv Tegemeo) grown in the semi arid area of Dodoma Region, Tanzania
    (1998) Reuben, S.O.W.; Rwehumblza, F.B.R.; Mahoo, H.F.; Hatibu, N.; Makungu, P.; Ashimogo, G.C.
    Sorghum is a food security crop in tropical marginal areas. Improvement strategies for yield under such conditions are important. Genetic improvement for yield is done thr0ll:gh improvement of its components. Due to yield component compensation, this improvement strategy is made less rewarding. It is therefore important to know compe1J.satory mechanisms existing for better improvement strategies. Studies on the nature of component compensations in sorghum are limited and virtually lacking under Tanzanian conditions. A field experiment was conducted to investigate the nature of interrelationships among components of yield in sorghum at the experimental plots of Hombolo Research Station in the semi-arid zone of Dodoma Region, Tanzania. Six treatment combinations, of rain water harvesting techniques and fertilizer were laid out in a randomized comple,te block design (ReED) with four replications during the growing season of 1996/97. Number of grains was an important component which was significantly correlated (r=O. 982***) with grain yield and had a high positive direct effect (0.979) on yield. Average grain weight was not import~nt in influencing yield of sorghum. Plant biomass had a negative direct effect (-1.2997) on average grain weight but was not important in influencing number of grains. Plant height and percent light intercepted directly influenced number of grains and average grain weight negatively. The negative influence (- 0.8712) of plant height on number of grains was compensated to a low relationship (r= -0.337) mainly by its positive indirect influence (0.3780) through light interception. Improvement strategies should aim at shorter plants with more grains, of lesser canopy development and biomass in these semi arid areas.
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    Genetic characterization of heat tolerant (HT) upland mutant rice (Oryza Sativa L.) lines selected from rice genotypes
    (Sokoine University of Agriculture, 2015) Yona, Neema
    Rice (Oryza sativa L.) is the one of the most important cereal crop and staple food of over half the world’s population that provides 45-60% of the dietary calories . The global climate changes including increased heat affect negatively rice production and other crops resulting into increased food insecurity. The analysis of Induced gamma rays mutations from upland rice mutant lines was done to discover mutations in heat tolerant genes (HSPs genes). Out of 64 putative heat HT mutant upland rice lines characterized for mutations in HSPs genes, 34 lines discovered to have mutations in that gene by using TILLING (Targeting Induced Local Lesions IN Genomes) technique with SNP Markers; gene specific primers. The results of nucleotides sequenced of mutant rice lines DNA, indicated that most mutations discovered were base pair substitution and InDels 50% and 41% in OS_HSP90_1 and 23% and 35% in OS_HSP17.9 respectively. Mutant rice lines identified to have HSPs genes were evaluated for growth performance, yield and yield components in order to select the promising HT mutant rice lines which can produce economic yield under heat and drought stress conditions. The 8 Mutant rice lines produced economical yield under heat stress condition selected for further breeding as donor materials for heat tolerant. This study aimed to determine the genetic factors associated with heat tolerance in mutant upland rice lines for variety development by Marker Assisted Selection (MAS). Understanding genetic mechanisms for heat stress tolerance in mutant rice lines will help further breeding and selection of suitable rice breeding materials for heat tolerance in order to improve rice productivity hence to reduce food insecurity.