|M.Sc Student||Igal Dalia|
|Subject||Genetic Studies of "High Oil" and "High Available|
Phosphate" Traits in Maize
|Department||Department of Biology||Supervisors||Professor Gadi Schuster|
|Dr. Nurit Katzir|
|Dr. Yaakov Tadmor|
The objective of this thesis was to examine the combination of two nutritional improvigenetic traits giving better nutritional value to corn kernels: increased oil and available phosphate contents. Higher oil content means more energy stored in every kernel, enabling faster and cheaper livestock growth. Increased available phosphate accompanied by less phytic acid in the kernel positively affect the nutritional value of the kernels and environmental phosphate pollution due to animal waste A single recessive gene mostly governs this trait. In most plants, including corn, phosphate is stored in the form of phytic acid. Its molecule contains myo-inositol-6-phosphate, which is usually precipitated in the seed as salt with several different cations. Phytic acid is nutritionally unavailable to non-ruminants, causes decrease in the bioavailablity of cations in the intestine and can cause phosphate and other nutrient deficiencies in humans and animals because of its strong chelation capacity. It can also cause phosphate pollution of the environment by microbial discharge of inorganic phosphate from phytic acid in the waste. A mutation called ‘low phytic acid’ (lpa) has recently been found that decreases the amount of phytic acid in the seed and increases inorganic phosphate content without significant effects on the mutant plant. The goal of this thesis is to evaluate the mutual influence of the two traits and the influence of both of them together on the mutant plant and seeds. For this purpose I combined the two traits in the same plants in two ways. One way is chemical mutagenesis of high oil corn and screening for a mutant with high inorganic phosphate content. Utilizing this method we identified two mutants; however we could not stabilize them in their homozygous state. The second way is cross breading high oil corn and lpa corn to build a segregating population for the two traits. The segregating population will enable us to estimate the influence of the lpa genotype on different measures of high oil plant and seed. I created 6 informative populations from different genetic backgrounds. Data processing reveals that combining the two traits does not significantly influence seed weight, protein content and total phosphate content of the seeds. Significant influence of the lpa genotype had been found on oil content. The genetic background of the plant in which the two traits are expressed influenced the level of the effect of the trait. Thus, a combination of the two traits is possible; however, the genetic background has a strong effect and thus selection for the parental lines should be conducted carefully .The populations I created can serve as a source for the identification of genes affecting high oil.