Generation, Genetic Characteristics And Grain Quality Of Low Phytic Acid Germplasm In Maize (Zea Mays L.)

In order to obtain low phytic acid (lpa) mutant in maize, the dried seeds of 20Chinese key inbred lines (including Huang C, Zheng 58 etc.) were firstly treatedwith 200 Gyγ-rays from a ⁶⁰Co facility, at the Irradiation Centre of ZhejiangUniversity, at a dose rate of 5 Gy/min. Seeds were indirectly screened by using thecolorimetric assay for high inorganic phosphorus (HIP). Meanwhile, the thesis didsome systematic research on genetic characteristics, agronomic traits and nutritionalquality of the lpa mutants. The main results were as follows:1. The result of screening to the offspring that was approximately 40,000 M₂plants from 20 Chinese key inbred lines in maize indicated that, the actual frequencyof HIP mutations may reach about 0.1%. Eight homozygous lpa mutant lines wereobtained from 8 inbred lines: DH25-lpa, X178-lpa, K22-lpa, K12-1pa, HC-lpa,Z58-lpa, Q319-lpa, HZ4-lpa. The F₂ populations of crosses between mutants (DH25and K12) and their wild type (WT), and backcross populations, the segregation ofHIP type and WT plants fit into 1:3 and 1:1, respectively, which indicated the lpamutations were controlled by single recessive genes. Allelism tests showed themutations in DH25-1pa, X178-lpa, Z58-lpa and HZ4-lpa was mutually allelic, andthe mutations in K22-lpa, K12-lpa and Q319-lpa was mutually allelic, which maybea new type of lpa mutant.2. Compared with the wild parent, the Pi content of 8 mutants doubled, whichreached 2.9～6.6 times, however, the content of phytic acid phosphorus wasremarkably lower than the counterpart, decreased approximately by 15%～48%, thetotal phosphorus content was not remarkably changed.3. On the agronomic characters, the adult plant of the mutants became short,duration growth period lengthened 5～11 days, the seedling fresh growing trend wasweak, the field rate of seedlings emergence decreased approximately by 20%, kernelnumber overall had remarkably reduced, but the Z58-lpa and the HZ4-lpa had noremarkable change, in comparison with their corresponding WT. The ear length, ear diameter, the number of lines and the weight of hundred grains of mutant appear thedrop tendency, however, various mutants agronomic characters changed differently,which indicated it was possible to cultivate the ideal lpa maize lines.4. The research on nutritional quality discovered that in comparison with thecorresponding WT, protein content of mutant increased, and that of K12-lpa andZ58-lpa got 46% and 49%, respectively. About the content of the total starch, fivemutants, such as DH25-lpa, HC-lpa, X178-lpa, K12-lpa and Z58-lpa decreasedobviously, and HZ4-lpa, K22-lpa, Q319-lpa were similar to WT. About the contentof amylose, K12-lpa decreased by 45.2%, and other 7 were similar to their parents.However, about the content of fat, it didn't change obviously. Consequently, thecontent of many amino acids in all mutants was increased; the concentration ofLysine was increased by 13%～26% except Q319-lpa and X178-lpa. About thecontent of EAA, the Z58-lpa increased by 30%, and Ile/Leu of DH25-lpa, HC-lpa,X178-lpa, K12-lpa was increased by 5%～6%. In addition, the concentrations ofmineral macronutrients (K, Ca, Na and Mg) and mineral micronutrients (Fe, Mn, Cu,Zn and Se) in mutations were more than or similar to their corresponding WT.5. The content of phosphorus of lpa mutants and wild type grains which wereproduced in Hainan was higher than the corresponding type which were produced inHangzhou, and the content was 21.5% higher than average, but inorganicphosphorus content had a little effect by environment, and Hainan and Hangzhouhad no change, i.e., the mutants still displayed the high inorganic phosphorusphenotype, while wild type maintained the low inorganic phosphorus content.Therefore, the mutants of high inorganic phosphorus content with low phytic acidphosphorus content between two places were relatively stable.