Variability Of Phytate And Phytase Levels Among Culitivars From The Yellow And Huai River Valleys Winter Wheat Region And The QTL Mapping

Quality improvement of micronutrients as Fe and Zn is one of the most important targets for wheat breeding. Increasing the bioavailability is crucial to solve the human health problem related with Fe and Zn deficiency. Phytate primarily exists as insoluble complexes with nutritionally important divalent cations including Fe2+and Zn2+, hence reducing their bioavailability, while it can be degraded by the native phytases in cereal grains under environments with controlled pH and temperature, and significantly positive correlation between native phytase activity and micronutrient bioavailability has been reported. The objectives of this study were to determine the levels of phytate and phytase in grain of current Chinese leading wheat cultivars and advanced lines from the Huang and Huai River Valleys Winter Wheat Region, and to map QTLs of Fe, Zn, and phytate content, and phytase activity using71doubled haploid (DH) lines derived from zhongyou9507/CA9632, with the main results as follows:1. Two hundred and twenty one wheat cultivars and advanced lines from the Yellow and Huai River Valleys Winter Wheat Region, were collected and sown at Anyang, Henan province in two cropping seasons from2009to2011, to determine the phytate and phytase levels. The cultivars performed large variations on phytate content and phytase activity, ranged from3.5to12.2g/kg for phytate content and from10to2857U/kg for phytase activity, respectively, with the mean value of phytate content being of5.0g/kg and phytase activity being of906U/kg. Phytate content and phytase activity were significantly influenced by genotype, season, and their interaction effects, with genotype effect being the predominant, followed by genotype by season interaction effect. On the basis of the performance of phytate and phytase levels,221cultivars were clustered into6classes, with significant difference among classes observed. The class of42cultivars including Hengguan35, Shixin828, Zheng7698, Pingan8, Jimai22, and Taishan064199performed low phytate content with high phytase activity, and would play an important role with the objective being to improve Fe and Zn bioavailability in breeding program for nutrition quality.2. Seventy one DH lines derived from Zhongyou9507/CA9632were sown at Anyang, Henan province in two cropping seasons from2009to2011, to determine Fe, Zn, phytate, and phytase levels for QTL mapping. Five QTLs were identified on chromosomes1A,1B,2A,3B, and4B, closely related to Fe content, explaining7.6-15.4%of the phenotypic variance, respectively. Six QTLs were identified on chromosomes1A (2),2A,3B,4B, and7A, closely related to Zn content, explaining1.2-16.4%of the phenotypic variance, respectively. One QTL was identified on chromosome7B, closely related to phytate content, explaining10.8%of the phenotypic variance. Three QTLs were identified on chromosomes2A,4B, and5A, closely related to phytase activity, explaining7.6-13.7of the phenotypic variance, respectively. The QTLs on chromosomes1A,2A, and4B for Fe content located at the same marker interval as those of Zn content, and no consistent QTLs were found across seasons for Fe, Zn, phytate, and phytase levels. It is necessary to map QTLs furher for Fe, Zn and phytate content, and phytase activity, for nutrition quality improvement of Fe and Zn content, and their bioavailabilty.