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- ItemOpen AccessAssessment of Occupational Exposure Hazards on Farmers Due to Insecticide Control of Cacao Mirids (Insecta: Hemiptera) in Southwestern Nigeria(2015-06-05) Sosan, Mosudi BabatundeThe study investigated the risks involved in applying selected insecticides to control mirids in cacao (Theobroma cacao L.) plantations in southwestern Nigeria. A field survey was conducted in 15 major cacao-producing villages from which 150 farmers were randomly selected for interview. Structured questionnaires were administered to the respondents while oral interviews were also conducted. Five exposure duration periods were identified based on number of years of involvement in insecticide application as < 5 years, 5-9years, 10-14 years, 15-19 years and > 20 years. The blood erythrocyte acetylcholinesterase enzyme (AChE) activities, haematological profile, and insecticide residue analyses were carried out to determine the possibility of insecticide poisoning, establish any relationships between haematological profile and exposure, and detect the presence of residues in the blood, and the farmers' sources of drinking water. The results showed that the cacao farmers used lindane formulated as Gamalin 20ECo; diazinon (Basudin 600 ECo); endosulfan (Sulfonex 35 ECo); and propoxur (Unden 20ECo) for mirid control. Sources of exposure identified included eating/chewing habits and drinking during application, non-adherence to the use of protective clothing, improper storage and disposal of used insecticide containers. Varying proportions of the farmers experienced the common symptoms that could be ascribed to insecticide exposure hazards. The results from the baseline AChE activity measurement of 76 cacao farmers revealed that eight of them had a relatively low AChE activity ranging from 33% to 50% N which is indicative of chronic poisoning. The baseline and post-insecticide application AChE activities determined among 40 of these farmers, showed that 90% of them experienced AChE activity inhibition ranging from < 20% to 50%. The duration of exposure had no significant effect on the PCV and WBC of the farmers but their WBC differential counts (eosinophil, neutrophil and lymphocyte) differed; farmers in the 15-19 and above 20 years exposure periods showed a marked prevalence of abnormal counts. The farmers also generally showed significant decreases in haemoglobin values between the pre-(13.9g/dl) and post-(12.9g/dl) insecticide application periods. The residue analyses revealed that 42 (53.3%) out of the 76 farmers had residues of diazinon, endosulfan, propoxur and lindane in their blood out of which 47.6% belonged in the >20 years exposure duration period. Nineteen percent of the farmers had diazinon in their blood, while 15% had endosulfan, 14% propoxur, and 8% lindane. Only 5% had no residues at all while 39% had unknown residues and possible metabolites of these insecticides in their blood. About 67% and 9% of the farmers that had diazinon and propoxur, respectively, in their blood exceeded the No Observable Effect Level (NOEL) of 0.02 ppm (diazinon) and 0.2 ppm (propoxur). The diazinon and propoxur detected in the farmers' sources of drinking water also exceeded the Acceptable Daily Intake (ADI) of 0.002 ppm and 0.02 ppm respectively. It was concluded from the study that cacao farmers had been occupationally exposed due to insecticide application for mirid control; and the exposure was sometimes of such magnitude as to be hazardous to the farmers and their respective communities.
- ItemOpen AccessEfficiency of Germination and Vigour Tests in Predicting Field Performance of Different Genotypes of Maize (Zea Mays L.)(2015-05-11) Olosunde, Akinloye AdamEighteen varieties of maize (Zea mays L.) were used to evaluate the efficacy of germination and vigour tests in predicting maize emergence under field conditions as well as to investigate whether differential response to the tests exist among the maize varieties. The study was designed to establish which among the tests could be used to reliably predict field emergence of maize. The four tests used were the standard germination, accelerated ageing, tetrazolium staining and conductivity. Each test was evaluated with 4 replicates of 25 seeds per variety. The tests were conducted in the Seed Science Laboratory of the Department of Plant Science. In addition, the maize varieties were evaluated in a 4-replicate field trial, laid out as randomised complete-block design at the Teaching and Research Farm of the University during the 2004 late season. The results showed that eleven out of eighteen varieties evaluated had standard germination above 80%. The viability of seed as determined by tetrazolium staining was also above 80% for seventeen varieties. Germination for accelerated ageing test varied between 5% and 72% while conductivity test results ranged from 48.4 μs/cm/g to 146.6 μs/cm/g. Field emergence varied from 62% to 90%. There was variation in the results of relative ranking of each vigour test as well as the grand rank summation. Field emergence of varieties 18 (TZEEY — SR BC5) and 7 (TZE WPop X 1368 STR CI) could be reliably predicted by these vigour tests but predictions for varieties 9 (SIN 9432) and 12 (TZEE — SR Damascus) would be unreliable. Results of the relative ranking of the varieties within each test and the significant variety x test interactions observed in the study suggested that evaluation of seed vigour involving several maize varieties should be done under several seed quality tests in order to minimize the chances of taking wrong decisions. Furthermore the significant positive correlation coefficients of field emergence with tetrazolium (r = 0.62, P < 0.01) as well as accelerated ageing (r = 0.48, p < 0.05) indicated that these two tests could be used to predict maize emergence and seedling vigour in the field. The performance of the maize varieties in the field trial showed few significant con-elation coefficients between the laboratory tests and mature plant traits. Tetrazolium test had significant negative correlation with grain yield (r = -0.49, p < 0.05). For the standard germination test, there were significant negative correlations with days to 50% tasseling, pollen shed and Bilking (r = -0.64 to 0.62, p < 0.01) while accelerated ageing had significant correlation with days to 50% tasseling and pollen shed. Therefore, seedlots with high germination in the laboratory had a tendency to flower early. In conclusion, tetrazolium and accelerated ageing tests reliably predicted field emergence and flowering dates of the 18 maize varieties evaluated.
- ItemOpen AccessSeed Setting under Controlled Natural Cross Pollination in Three Populations of Coconut (Cocas Nucifera L.)(2015-04-20) Enaberue, LouisThe purpose of this study was for high rate production of coconut natural hybrids resulting from controlled natural pollination. The primary objective of this study was to evaluate the seed setting percentage resulting from controlled natural pollination in various cross combinations of coconut (Cocos nucifera L.). A secondary objective was to estimate the effect of climatic factors on number of bunches, number of buttons and number of nuts produced by the cross combinations. Four coconut types: West African Tall (WAT), Malayan Green Dwarf (MGD), Malayan Yellow Dwarf (MYD) and Malayan Red Dwarf (MRD) were planted in 1987 in an isolated coconut seed garden in Field 42 of the main station of the Nigerian Institute for Oil Palm Research (NIFOR) near Benin-City. The goal was to produce different types of Dwarf (D) x Tall (T) hybrids through open pollination. The male flowers of the selected dwarf mother palms were emasculated, while the male flowers of the tall mother palms were not, allowing the tall palms to cross pollinate the emasculated dwarf palms. Controlled natural pollination of these selected dwarf mother palms was carried out for four years (1997-2000) and seed setting percentage (S%) was recorded during the period. The various cross combinations (populations) studied were MGD x WAT (population 1), MYD x WAT (population 2), and MRD x WAT (population 3). Data collected included number of bunches (NOB), number of buttons (NOBT) and number of nuts (NON). The relationship between climatic factors and NOB, NOBT, NON and S% in the various populations was evaluated using correlation and regression techniques. The climatic Factors included, temperature, rainfall. relative humidity, solar- radiation and sunshine hours. Data were subjected to the analysis of variance (ANOVA) for a complete randomized design. The Least Significant Difference (LSD) was used for separation of means of traits that had significant F-test. Data on S% were subjected to aresine transformation before analysis. Analysis of variance showed significant mean squares for palms and years for NOB. NOBT, NON and S%(p< 0.01).The mean S% for the four years of investigation was 51.4%, with a range of 48.2-54.3%. Maximum S% was 54.3% in population 3, 51.7% in population 1 and 48.2% in population 2. Broadsense heritability for the four traits ranged from a low value of 3.020/o for NON in population I to a fairly moderate value of 56.22% for NOB in population 2. Statistically significant positive correlation coefficients of 0.85, 0.80, 0.72, 0.71, 0.06 and 0.04 occurred between NOB vs NOBT, NOBT vs NON, NOB vs NON, NON vs S%, NOB vs S% and NOBT vs S% at 0.05 and 0.01 level of probability respectively. The climatic factors were correlated with NOB, NOBT. NON and S%. Amongst the live climatic factors, only rainfall and sunshine hours were significantly correlated (-0.96 and -0.96) with seed setting percentage. Coefficients of determination (R2) of rainfall, temperature, relative humidity, sunshine hours and solar radiation investigated on the seed setting percentage across populations were 54%, 44%, 5 8 % , 64% and 74%, respectively. In conclusion, controlled natural cross- pollination method was effective in the production of high D x T hybrid seed setting in coconut palms.
- ItemOpen AccessDistribution of Seeds of Mimosa Invisa Mart (Giant Sensitive Plant) in Soils and Factors Affecting Germination(2015-04-20) Ekhator, FrankThis study was conducted to investigate the distribution of seeds of Mimosa invisa in the soil seed bank so as to develop effective control measures against this noxious weed. The specific objectives were to examine the distribution of seeds of M. invisa in 0-30 cm of soil depth; and, determine the effect of acid scarification, boiling water treatment, heat treatment, pH, planting depth and brine stress on germination and emergence of M. invisa seeds The experiments were laid out in a completely randomized design with four replications. Soil cores were collected from cultivated and fallow fields from the Nigerian Institute for Oil Palm Research (NIFOR) at three depths (0 – 7, 7 – 15 and 15 – 30 cm), processed and placed in germination trays 34 x 22 x 4 cm in the screenhouse for germination. Bulked seeds collected from oil palm plantation and fallow fields in NIFOR were used in investigating the effects of acid scarification, boiling water treatment, heat treatment, pH, planting depth and brine stress on germination and emergence of M. invisa. Data collected were subjected to analysis of variance and means compared using Least Significant Difference (LSD) at 5% level of probability, Shannon and Wiener index was used to estimate the weed species diversity. Results showed that there were no significant differences in the seed populations of M.invisa between depth of 7 to 15 cm and 15 to 30 cm in both cultivated and fallow fields. Although only significant (P<0.05,Fcal. = 196.16) on 0 to 7 cm depth in the fallow fields, the distribution of M .invisa seeds follow the same trend in soils of cultivated and fallow fields, decreasing down the depth (P<0.05, Fcal. = 196.16). However, seeds of M. invisa were significantly higher (P<0.05, Fcal. = 196.16) in fallow fields than in cultivated fields. Seeds of other weed species such as Panicum maximum Jacq., Chromolaena odorata (L.) R. M. King and Robinson, Cyperus species, Aspilia africana (Pers.) C.D. Adams and Boehavia coccinea Mill were found in the seed bank along with M. invisa. Shannon — Wiener diversity index showed that seeds of weed species were more diverse in the seed bank of cultivated than in the seed bank of the fallow fields. Percentage germination of M. invisa seeds treated with sulphuric acid were significantly higher (P<0.05, Fcal. = 1071.47) than those treated with hydrochloric and nitric acid at the different concentration rates of 0, 25, 50, 75 and 100%v/v of the acids used. Germination of M. invisa seeds was higher when seeds were immersed in boiling water for 2 minutes and no germination occurred when immersed in boiling water for 14 minutes. Germination of M. invisa increased with increase in temperature from 0°C (1.44%) up to 90°C (87%) and was totally inhibited at 110°C. M. invisa emerged better at soil depth of 0 cm (87%) and 5 cm (22.64%). M. invisa germinated over a wide range of pH (4 to 10), with the highest germination occurring at pH 6 (72.56%). While germination of M. invisa seeds was totally inhibited at 300 mM NaCl, over 80% germination occurred between 0 and 60 mM NaCl. In conclusion, seeds of M. invisa in the soil seed bank were found distributed through the 0 to 30 cm depths studied. Other weed species were found in association with M. invisa in the soil seed bank and the weed species diversity was greatest in the cultivated fields. Acid scarification, boiling water treatment and heat treatment were all effective in dormancy release of M. invisa seeds. Emergence of M. invisa was best at a planting depth of 0 cm. M. invisa germinated over a wide range of pH and NaCl solutions.
- ItemOpen AccessHeterotic Patterns of Early Maturing Inbred Lines of Maize (Zea mays L.) in Striga–Infested And Striga–Free Environments(2015-03-27) Agbaje, Samuel AdemolaThe study was designed to separate early maturing yellow- and white-endosperm inbred lines of maize (Zea mays L.) into heterotic groups; evaluate the effects of tester, location and infestation of Striga hermonthica (Del.) Benth on the heterotic groups; and rank the heterotic patterns of the inbreds in Striga-free and Striga-infested environments. Seventy yellow and 84 white endosperm testcrosses were generated by crossing 35 yellow and 42 white endosperm inbred lines to two testers each under irrigation in the dry season of 2004. The testers for the yellow inbred lines were 4001 and KU 14 l4 while those for the white inbred lines were 1368 and 907L The testcrosses plus 7 checks for the yellow and 4 for the white lines, were evaluated under Striga-free environments at Obafemi Awolowo University Teaching and Research Farm as well as under ,Striga-free and Striga-infected environments at IITA's experimental outstations in Abuja and Mokwa in 2005. Each trial was laid out as 11 x 7 and 11 x 8 randomised incomplete block design for the yellow and white testcrosses, respectively. Data were collected on flowering traits, root and stalk lodging, plant and ear heights, incidence of diseases (ratings), grain yield and yield components. Additional data were collected at 8 and 10 weeks after planting (WAP) on Striga damage rating on a 1 to 9 scale and Striga emergence count in the Striga-infested environments. Analysis of variance was performed for each set of testcrosses in each location as well as combined across the three locations. Line x tester analysis was performed from which values for general (GCA) and specific (SCA) combining ability effects were obtained. Correlation of GCA effects among the traits was computed also. The results revealed that, mean squares for location and line GCA effects were significant for grain yield and several other agronomic traits in both evaluation environments. In Striga-free environments, SCA effects were significant (f = 1.54, P<0.05) for blight and days to 50% anthesis among yellow testcrosses while for white testcrosses ear aspect and grain yield had significant SCA effects. Under Striga-infested conditions, SCA was significant only for Striga damage rating at 10 WAY among the white testcross hybrids. About 62% of the white and 77% of the yellow lines had large GCA effects for grain yield in the two evaluation environments. Only 13 of the 42 white inbred lines could be classified into heterotic groups based on the SCA effects and testcross mean grain yield in Striga-free environments. Three of these white inbreds maintained their heterotic group under the two evaluation environments. None of the yellow inbred lines could be classified into heterotic groups under any of the evaluation environments. It was concluded that the testers used in this study were not sufficiently effective in classifying the yellow inbred lines and most of the white lines into heterotic groups.