QTL Analysis For Grain Yield And Its Components To Phosphorus Deficiency Tolerance In Maize

Maize (Zea mays L.) is one of the most important crops. High grain yield is the first breeding target pursued by breeder. Phosphorus (P) is one of essential macronutrients for plant growth and development. Plants usually take up P from the soil solutions, however the concentration of P in the soil solution is low, which in turn cannot satisfy the demand of plants. Phosphorus deficiency is one of the most important abiotic factors that limited maize production. The effective approach to solve this problem is breeding and popularizing variety for phosphorus tolerance. With the development and application of molecular markers, MAS (molecular assistant selection) supply a useful tool to the breeding for phosphorus tolerance. In order to investigate the molecular genetic basis of phosphorus tolerance, a set of 210 F_2:3 families developed from 5003(107) and 178 were used to identify quantitative trait loci (QTL) under high and low phosphorus treatments at Taian and Yantai. The major results are as follows.1. Six agronomic traits, including grain yield per plant (GY), 100-kernel weight (100KW), ear length (EL), row number per ear (RN), kernel number per row (KN) and ear diameter (ED) were evaluated under high and low phosphorus treatments at Taian and Yantai. Significant correlations were mostly positive except for correlations between RN and EL and between RN and KN, which had low, negative correlations.2. 207 polymorphic SSR markers were placed on 10 linkage groups which represented 10 maize chromosomes. The genetic map spanned 1,755.1 cM in length with an average interval of 8.48 cM between adjacent markers. Compared with other published maize linkage maps in chromosome bin locus, the linkage map established in this study was consistent with them. The SSR linkage can be used for QTL mapping.3. A total of 69 QTLs with LOD>2.5 were identified for the six traits by composite interval mapping under high and low phosphorus treatments at Taian and Yantai. Thirty six distinct QTLs were identified from Taian, in which 7 out of 36 for GY, 7 for 100KW, 5 for EL, 5 for RN, 6 for KN and 6 for ED, while thirty three distinct QTLs were identified at Yantai, in which 6 out of 33 for GY, 5 for 100KW, 5 for EL, 7 for RN, 5 for KN and 5 for ED. QTL mapping revealed that the majority of loci for grain yield and yield components were positively contributed by 178.4. This result also show that some QTLs trend to cluster the same chromosome regions. The key chromosome regions for yield and its components under phosphorus tolerance mostly were detected on chromosome 1, 5 and 10. And three common loci are in the interval umc2215-bnlg1429, umc1464-umc1829 and umc1645-bnlg1839.5. The most important QTL effects were detected on chromosome 1, 5 and 10 for grain yield and yield components under HP and LP treatments at two sites. The QTLs contain genes controlling several traits and it is important to address here that in this case these QTLs are extremely stable. The presence of these QTLs may contribute to fine-mapping, identification of candidate genes and MAS strategies for maize improvement purposes under phosphorus deficiency combining traditional breeding approaches.