Typescript. / Digitized by Kansas Correctional Industries

Thesis--Ohio State University. / Includes bibliographical references. Available online via OhioLINK's ETD Center

In recent years Zaire has changed from a net exporter to a net importer of maize. Four districts of South Central Zaire were selected to investigate factors which limit the production and the supply of marketed maize grain in Zaire. Farmers in this area were interviewed to collect data on the number of crops planted, the peak periods for agricultural operation, the division of labor within the household and the labor force available for agricultural work. Survey procedures were also used to determine when and where farmers sell maize and who buys marketed maize. The effects on maize production of the policies of the central and regional governments were also investigated. During the sixties and early seventies, national investment policy has heavily favored the urban based manufacturing and mining sectors, undoubtedly contributing to the fact that many Zairians migrated from rural to urban areas. In the absence of a compensating increase in labor productivity, these migrations reduced agricultural output and the quantities of food crops sold, particularly, the quantity of maize delivered to urban markets. At the producer's level, this study indicates that low maize production is a consequence of inadequate storage for seed and consumption maize. The use of seeds of low quality for germination combined with production practices that result in untimely planting, weeding and harvesting contribute to low maize yields. This study also indicates that one of the factors which has contributed to limit the quantity of maize produced is a shortage of labor during peak periods of agricultural operations. Labor shortages exist because of the limited number of household members involved in agricultural work, and because of the division of labor in the household which assigns some agricultural tasks almost exclusively to women. The study also indicates that the effectiveness of the marketing system in providing incentives for maize production has been limited by weak transportation and communication links between production and consumption centers and by efforts of some traders to gain oligopsonistic power in their relations with maize producers in the more isolated areas. This study also indicates that national price policies have negatively affected maize production. Other regional and local policies have served to restrict interregional trade. The policy implications of this study suggest that a number of government programs may be helpful in increasing maize production and the supply of marketable surplus. These may include: (1) government information programs designed to improve maize storage, seed quality and the efficiency of the marketing system;. (2) diffusion of information on the appropriate times for planting, weeding and harvesting maize; (3) further promotion of the technological package developed by Programme National Mais and the provision of inputs and incentives favorable to the adoption of this technology; (4) providing incentives for the promotion of a greater participation of all household members in agricultural production; and (5) some mechanical assistance for plowing such as is now provided by two government supervised production organizations, CAKO and TABAZAIRE. Indications from this study also suggest that a successful implementation of such programs would necissitate some reorganization of the extension service and diverting a larger share of government current and investment expenditures to agriculture. / Graduation date: 1977

Aspergillus flavus is a fungus pathogen of maize that causes contamination of maize with aflatoxin. Aflatoxin is a carcinogenic toxin that can cause harm to human and animal health. Several management practices have been developed, such as cultural, chemical, biological and breeding, for host resistance. Development of host plant resistance has been the most desirable but this has been hampered by several factors, such as environmental influence, time consuming phenotyping and costly inoculation and field evaluations. Because of the problems associated with breeding for aflatoxin resistance, heritability estimates along with genetic correlations for aflatoxin and its secondary traits were estimated in this study. This experiment was conducted in two Texas locations (College Station and Weslaco) and phenotypic data were collected for aflatoxin concentration, maturity, endosperm texture, percentage of rotten ears and grain yield per ear. The heritability was moderate to high for aflatoxin and secondary traits such as endosperm texture and percentage of rotten ears. Aflatoxin was observed to be negatively correlated to grain yield and positively correlated to percentage of rotten ears. A population of recombinant inbred line derived from a cross between CML161 and B73o2 were evaluated in replicated trials in two environments for resistance to aflatoxin contamination. The families were genotyped using simple sequence repeat (SSR) markers. The mapping Recombinant Inbred Line population was used to detect and characterize Quantitative Trait Loci associated with aflatoxin accumulation. Alleles for reducing aflatoxin contamination came from both parents across the chromosomes. Thirty-eight epistatic interactions were detected for aflatoxin resistance. Several other QTLs were identified for other traits such as grain yield, endosperm texture, and percentage of rotten ears. The QTLs reported in this experiment are promising and need to be validated in other environment and genetic backgrounds for further use in marker assisted selection. Inheritance studies using generation mean analysis in six crosses showed additive and dominance effects to be mainly responsible for aflatoxin resistance. Two inbreds, CML176 and CML161, were identified as sources of resistance in breeding programs and use for selection.

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Characteristics of inbred plants were sought which might indicate the maturity pattern of their F1 progeny. Observations were also made on the influence of xenia and cytoplasm from the female on ear moisture loss (of F1 kernels and plants). [...]

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