Abstract
Low boron (B) seriously limits the growth of oilseed rape (Brassica napus L.), a high B demand species that is sensitive to low B conditions. Significant genotypic variations in response to B deficiency have been observed among B. napus cultivars. To reveal the genetic basis for B efficiency in B. napus, quantitative trait loci (QTLs) for the plant growth traits, B uptake traits and the B efficiency coefficient (BEC) were analyzed using a doubled haploid (DH) population derived from a cross between a B-efficient parent, Qingyou 10, and a B-inefficient parent, Westar 10. A high-density genetic map was constructed based on single nucleotide polymorphisms (SNPs) assayed using Brassica 60 K Infinium BeadChip Array, simple sequence repeats (SSRs) and amplified fragment length polymorphisms (AFLPs). The linkage map covered a total length of 2139.5 cM, with 19 linkage groups (LGs) and an average distance of 1.6 cM between adjacent markers. Based on hydroponic evaluation of six B efficiency traits measured in three separate repeated trials, a total of 52 QTLs were identified, accounting for 6.14–46.27% of the phenotypic variation. A major QTL for BEC, qBEC-A3a, was co-located on A3 with other QTLs for plant growth and B uptake traits under low B stress. Using a subset of substitution lines, qBEC-A3a was validated and narrowed down to the interval between CNU384 and BnGMS436. The results of this study provide a novel major locus located on A3 for B efficiency in B. napus that will be suitable for fine mapping and marker-assisted selection breeding for B efficiency in B. napus.
Highlights
Boron (B) is one of the essential microelements for plant growth and development [1]
Plant materials and hydroponics A doubled haploid (DH) population containing 70 lines derived from a cross between the B-efficient parent Qingyou 10 and the B-inefficient parent Westar 10, which is more sensitive to B deficiency than the B-inefficient parent Bakow [32], named the QW DH population, was used to construct a high-density genetic map and identify QTLs associated with plant growth, B uptake and B efficiency coefficient (BEC)
For the increment of primary root length (IPRL), Westar 10 was longer than Qingyou 10 under the high B (HB) condition; the opposite trend was observed at low B (LB) (Table 2)
Summary
Boron (B) is one of the essential microelements for plant growth and development [1]. Low B soils are present in many regions of the world, with B deficiency reported in over 80 countries and for 132 crops [6]. B. napus has a high requirement for B and is sensitive to B deficiency [9]. Over the past 20 years, the application of B fertilizers for crop production has been a standard measure to solve the problem of B deficiency in soils with a hot water soluble B (HWB) concentration below 0.5 mg kg21 [10]. Boron can be toxic to some crops at soil B levels only slightly above those required for normal growth in other crops. Breeding new B-efficient varieties represents an important and practical method to improve the production of B. napus in B-deficient soils
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