Fine Mapping A Major QTL For Kernel Number Per Row Under Different Phosphorus Regimes In Maize (Zea Mays L.)

Phosphorus (P) is one of the essential macronutrients for plant growth anddevelopment. Grain yield is the primary trait of interest in maize breeding programs.Maize grain yield and yield-related traits are seriously affected by P deficiency. Kernelnumber per row (KN), as one of the major components of grain yield, has attracted theattention of more and more breeders. 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 thedemand of plants. Phosphorus deficiency is one of the most important abiotic factors thatlimited maize production. The effective approach to solve this problem is breeding andpopularizing variety for phosphorus tolerance. With the development and application ofmolecular markers, MAS (molecular assistant selection) supply a useful tool to thebreeding for phosphorus tolerance. In our previous study, one major QTL, controlling KN,was mapped to the interval between bnlg1360and umc1645on chromosome10using aF2:3population derived from the cross between178and5003(107) under different Pregimes. In order to understand its genetic basis, we developed a near isogenic line (NIL)to map and characterize the QTL. The major results are as follows.(1) We developed a near isogenic line (NIL) and two P regimes were used to mapand characterize the QTL(named qKN).(2) SSR Hunter1.3was used to search SSR primers and PRIMER5.0was used todevelop new markers,133SSR markers were designed and finally30new markers thatrepresented good polymorphism in parents were used to narrow down the major QTL.(3) In BC4F2populations, We located the major QTL at umc2203and umc1450,Using30new markers we developed, qKN was limited between SSR11and SSR27. InBC4F3populations, the qKN was precisely defined in a~480kb region by SSR15andSSR19. The major QTL qKN region was20times smaller than the initial F2:3 populations.(4) The genetic effect of qKN was researched using BC4F1, BC4F2, BC4F3populations during the year2008-2010. As expected, plants carrying the qKN regionshowed higher KN than those without qKN. A single qKN allele derived from178couldsteadily increase the KN by6.08%to10.76%in the5003(107) background; the qKNacted in a partially dominant manner.(5) Our results will be helpful for future identification and isolation of the candidategene; the tightly linked markers that we have developed for qKN will be a useful tool inthe marker-assisted selection of this gene in maize improvement programs.