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Allotetraploid rapeseed ( Brassica napus L., AnAnCnCn, 2 n = 4x = 38) is extraordinarily susceptible to boron (B) deficiency, a ubiquitous problem causing severe losses in seed yield. The breeding of B-efficient rapeseed germ plasm is a cost-effective and environmentally friendly strategy for the agricultural industry; however, genes regulating B efficiency in allotetraploid rapeseed have not yet been isolated. In this research, quantitative trait locus (QTL) fine mapping and digital gene expression (DGE) profiling were combined to identify the candidate genes underlying the major-effect QTL qBEC-A3a, which regulates B efficiency. Comparative phenotype analyses of the near-isogenic lines (NILs) indicated that qBEC-A3a plays a significant role in improving B efficiency under B deficiency. Exploiting QTL fine mapping and DGE analyses revealed a nodulin 26-like intrinsic protein (NIP) gene, which encodes a likely boric acid channel. The gene co-expression network for putative B transporters also highlighted its central role in the efficiency of B uptake. An integration of whole-genome re-sequencing (WGS) with bulked segregant analysis (BSA) authenticated the emerging availability of QTL-seq for the QTL analyses in allotetraploid rapeseed. Transcriptomics-assisted QTL mapping and comparative genomics provided novel insights into the rapid identification of quantitative trait genes (QTGs) in plant species with complex genomes. [ABSTRACT FROM AUTHOR]

Root nodule organogenesis is described. Plant regulated aspects of nodulation and N2 fixation are reviewed and discussed. Since the effective N2 fixing symbiosis requires the interaction of the host plant and bacterium in an appropriate environment (the rhizosphere and the root nodule) it is essential that research aimed at improving N2 fixation involve a knowledge and understanding of the plant genes that affect nodule development, growth, and function. Current knowledge of host plant genes involved in N2 fixation is summarized. Various experimental approaches to the study of the host plant's contribution to nodulation are noted. The functions of nodule specific proteins (nodulins) in symbiosis are delineated. Future areas of research are suggested. [ABSTRACT FROM AUTHOR]