Browsing by Author "Fakorede, M. A. B."

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    Estimating Kernel Weight in Maize
    (Faculty of Agriculture, University of Ife, 1981) Fakorede, M. A. B.; Orisadare, S. S.
    In an experiment involving 20 maize (Zea mays L.) cultivars and five sample sizes (100,500,750 and 1000 kernels) replicated four times, it was found that sample weight increased linearly (r2 = 0.81) as sample size increased. This suggests that mean weight/kernel did not differ significantly among sample sizes. In similar trials involving 21 S1 lines developed from two maize cultivars (FARZ 23 and FARZ 27) but utilising sample sizes of 25, 50, 75, 100 and 125, mean weight/kernel showed a curvilinear response to increased sample size with the point of inflection at approximately the sample size of 100 kernels. This suggests that mean weight/kernel was variable for sample sizes less than 100 kernels. It seems, therefore, that kernel weight in maize can be estimated from small sample sizes (e.g. 100 and 125) kernels in order to save time and expenses when evaluating a large number of lines in a breeding programme.
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    Genetic Variability and Predicted Responses to Four Types of Progeny Selection in a Nigeria Maize (Zeamays L.) population.
    (Obafemi Awolowo University, 1986) Adeyemo, Moses Olusegun; Fakorede, M. A. B.
    Genetic variability and predicted responses to full-sib (FS), half-sib (HS), Si and S1 testcross (TCH) selection methods were studied in the open-pollinating maize variety, TZSR-Y-1. Evaluation of progress after one cycle of selection was also done. Grain yield and seven agronomic traits were investigated. Mean grain yield ranged from 3.4 to 9.2 t/ha for FS, 2.9 to 7.5 t/ha for HS, 1.75 to 8.0 t/ha for S1 and 3.2 to 8.8 t/ha for TCH. Genetic variances ( 4;2) were largest for S1 families but there were no consistent trends for c2 among the other progeny types. Additive genetic variance constituted- the major portion of the total genetic variance for grain yield and the agronomic traits. Heritability estimates were moderate to high for nearly all agronomic traits of the four progeny types. Generally, only the correlations of yield with ear number per plot and ear length had coefficients appreciably larger than 0.50; these two traits were therefore the primary determinants of grain yield. Largest predicted direct gain per season of selection for grain yield was obtained for S1 families followed by TCH and FS which differed little. HS selection gave the smallest predicted gain. Predicted correlated responses in grain yield assuming selection was done for agronomic traits were generally smaller than predicted direct responses to selection for grain yield. After one cycle of selection, yield improvements of the derived populations relative to the source population were -2.5% for SI, 8.8% for HS, 13.5% for FS, and 14.6% for TCH selection methods. On the basis of operational efficiency and predicted versus realized gains from selection, FS family selection would be more effective than the other selection methods studied for improving the maize variety TZSR-Y-1.
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    Genotype X Environment Component of Variance and its Implications in Maize (Zeamays L.) Yield Trials.
    (Obafemi Awolowo University, 1985) Adisa, Aramide Omolara; Fakorede, M. A. B.
    Grain yield data obtained from yield trials conducted in 1981 and 1982 for five open-pollinating cultivars and eight varietal hybrids of maize (Zea mays L.) were used to investigate the effectiveness of 3 different yield trial methods. These included experiments A: 2 years, 2 locations, 1 planting date; experiment B: 1 year, 2 locations, 3 planting dates, and experiment C: 2 years, 1 location, 3 planting dates. Variance components were obtained for each method and optimum combinations of numbers of years, locations, planting dates and replications for varietal testing were determined by calculating theoretical standard error of the mean (SEM). Analysis of variance for the three methods showed highly significant location, year, planting date and genotype effects. SEM of 0.256 was obtained for 2 years, 2 locations, 1 planting date and 4 replications, and this was used as the standard for comparing the other two methods. When planting dates were substituted for years in experiment B, the SEM of 0.256 was obtained for combinations ranging from 1 year, 8 locations, 2 planting dates and 1 replication, to 1 year, 2 locations, 2 planting dates, and 4 replications. Substituting planting dates for location in experiment C however, resulted in the use of a larger number of planting dates than in experiment B, and not less than a 1-year period of testing to obtain the minimum SEM of 0.256. Planting dates can therefore be effectively substituted for years in order to reduce the time for conducting preliminary maize yield trials. Planting dates can also be substituted for locations where funds but not time, are limiting.
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    Inheritance of Yield and Agronomic Traits in a Maize (Zeamays L.) Population at Two Levels of Inbreeding.
    (Obafemi Awolowo University, 1986) Ajala, Samson Oyewole; Fakorede, M. A. B.
    Hybrids resulting from diallel crosses of ten radom lines at the second (S2) and fifth (S5) generations of inbreeding in the TZSR-W population of maize (Zea mays L.) were studied. Eight of the lines were common to both generations. At both generations, general combining ability (gca) was more important than specific combining ability (sca) for most traits. For grain yield however, gca and sca were nearly equal. Therefore, recurrent selection methods that utilize both additive and non-additive gene actions should be used to improve the population. Generally, lines with positive gca effects at the S2 generation also had positive gca at the S5 generation with line 013 being the best at both generations. However, the relative performance of crosses (sca) differed between the two generations. Appreciable inbreeding depression had occurred at the S2 generation with little further depression at the S5 generation. The preponderance and relative stability of gca effects, and the magnitude of inbreeding depression at the S2 generation suggest that good inbred lines can be selected as from the S2 generation. However, the inconsistent ranking of hybrids for sca effects at both generations implies that the yielding ability of such selected lines must be specifically tested to identify the best hybrid combinations. Correlation, stepwise multiple regression and path-coefficient analyses indicated that vigorous lines that mature early, with long rather than wide ears will be high-yielding in hybrid combinations. These analyses also showed that shelling percentage, emergence percentage and numbers of days to silking of S2 X S2 hybrids positively influenced grain yield in the S5 X S5 hybrids. Therefore, these traits could be used as indirect selection criteria for high-yielding hybrids.
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    Predicted responses to recurrent selection in maize (Zea mays L.)
    (Faculty of Agriculture, University of Ife, 1979) Fakorede, M. A. B.; Obilana, A. Tunde
    Previous studies with computer simulation models have shown that standardised correlated response in one trait, y, to selection for another trait, x, should be the same in one generation regardless of whether selection is for x or for y. In the study reported herein, we tested the hypothesis that direct response to selection for trait x should be the same as standardised correlated response in trait x when selection is based on trait y. Additionally, we compared, observed and predicted correlated responses to seven cycles of reciprocal recurrent selection for grain yield in two maize populations Results obtained indicated that predictions of direct and standardised correlated responses showed poor agreement. Direct response to mass selection, however, agreed more closely with standardised correlated responses than did half-sib selection and S1 testing, whereas direct response to S1 testing agreed more closely with conventional correlated response than did the other two selection methods. Also, observed and predicted correlated response to reciprocal recurrent selection for grain yield showed poor agreement. However, predictions based on parameters obtained in the fourth cycle of selection agreed more closely with observed changes than similar estimates obtained from the original populations. Implications of these results in determining indirect selection criteria are discussed.
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    A Proposed Procedure for Rapid Development of Inbred Lines for the Production of Hybrid Maize in Nigeria
    (Faculty of Agriculture, University of Ife, 1982) Fakorede, M. A. B.
    A procedure is described for the rapid development of inbred lines to be used as parents of high-yielding hybrid cultivars of maize (Zea mays L.). This procedure involves the production of S1 lines from three unrelated populations A, B, C whose Fl hybrids are known a priori to demonstrate significant yield heterosis. The S, lines are evaluated per se and S2 lines obtained from the best performing 5 or more S1 lines from a population are intercrossed with those-from the other populations to give 75 or more S2 x S2 crosses. The S2 x S2 crosses are evaluated with check cultivars (e.g. cultivar hybrids, the best widely grown cultivar and single-cross hybrids, if available) and the top 5 are selected for the National Zonal Maize Yield Trials (NZMYT) coordinated by the National Cereals Research Institute (NCRI), Ibadan. S4 x S4 hybrids of these top 5 selections are evaluated in the NZMYT as well as several other locations available to the researcher and inbred lines of the best 1 or 2 hybrids are released as parent materials. The advantages of this procedure include (i) simultaneous inbreeding and evaluation trials, (ii) flexibility for concurrent population improvement and extraction of inbredlines, and (iii) with two rainfed cropping seasons and an off-season with irrigation facilities, near-homozygous inbred lines (F 0.99) can be obtained within 3 calendar years.