The maize (Zea mays) kernel plays a critical role in feeding humans and livestock around the world and in a wide array of industrial applications. An understanding of the regulation of kernel starch, protein, and oil is needed in order to manipulate composition to meet future needs. We conducted joint-linkage quantitative trait locus mapping and genome-wide association studies (GWAS) for kernel starch, protein, and oil in the maize nested association mapping population, composed of 25 recombinant inbred line families derived from diverse inbred lines. Joint-linkage mapping revealed that the genetic architecture of kernel composition traits is controlled by 21-26 quantitative trait loci. Numerous GWAS associations were detected, including several oil and starch associations in acyl-CoA:diacylglycerol acyltransferase1-2, a gene that regulates oil composition and quantity. Results from nested association mapping were verified in a 282 inbred association panel using both GWAS and candidate gene association approaches. We identified many beneficial alleles that will be useful for improving kernel starch, protein, and oil content.Maize (Zea mays) is the world's most important production crop (faostat.fao.org): Its starch, protein, and oil are essential in supplying adequate food and nutrition to both humans and animals, and maize starch has recently become an important feedstock for ethanol production. Altering starch content can lead to higher yields, specialty industrial applications, and improved sweet corn varieties, while increased protein content and augmented levels of essential amino acids improve nutritional quality. Growing demand for healthy cooking oil can be met by improved oil content and composition.Substantial effort has been spent to develop maize varieties that meet market demands for modified kernel composition. Specialty maize germplasm with unique kernel composition traits has been developed by exploiting mutations affecting kernel grain composition and quality, including opaque2 (o2), which increases Lys content (Mertz et al., 1964), amylose-free waxy1 (wx1; Lambert, 2001), sugary1 (su1), sugary enhancer (SE), and shrunken2 (sh2), which are responsible for sweet corn (Schultz and Juvik, 2004), and linoleic acid1 (ln1) with an altered fatty acid ratio (Poneleit and Alexander, 1965). Use of specialty maize germplasm with unique kernel composition has been limited, however, due to difficulties in developing agronomically superior germplasm. Future progress in kernel composition improvement will depend on understanding and exploiting quantitative trait loci (QTLs) for kernel composition traits.The complex genetic architecture of starch, protein, and oil content has been demonstrated in the inbred line (IL) long-term selection experiment, in which more than 100 generations of recurrent selection has increased oil and protein content to approximately 20% and 27%, respectively (Moose et al., 2004). The continued phenotypic response of kernel composition provides convincing evidence that these traits are...

Wheat stem sawfly (WSS), Cephus cinctus N., is a major insect pest of winter and spring wheat, Triticum aestivum L., in areas of the northern Great Plains. The primary control measure is use of resistant cultivars containing solid stems. Environmental effects on expression of the trait can be problematic, thus genetic markers would be useful. In this study, a doubled haploid (DH) winter wheat population derived from a ‘Rampart’ (solid stems) × ‘Jerry’ (hollow stems) cross was analyzed to identify molecular markers linked to genes controlling stem solidness. The DH population was genotyped with GWM and BARC microsatellite primers that spanned the wheat genome. To genotype the population efficiently, bulked segregant analysis (BSA) was used to identify polymorphism between groups of solid stem and hollow stem individuals. Four microsatellite markers (GWM247, GWM340, GWM547, and BARC77) were found linked to a single solid stem QTL (designate Qss.msub‐3BL) on chromosome 3BL. However GWM247, GWM340, and GWM547 were found to be more closely linked to the QTL than BARC77. Single marker analysis showed Qss.msub‐3BL contributes at least 76% of the total variation for stem solidness. Additionally, no significant relationship existed between Qss.msub‐3BL and other agronomic traits, including yield. These microsatellite markers (GWM247, GWM340, and GWM547) will be useful for selecting solid‐stemmed wheat cultivars to help control the wheat stem sawfly.

The CRX (cone-rod homeobox) gene is specifically expressed in developing and mature photoreceptors and encodes an otd/Otx-like paired homeodomain protein. Mutant alleles of the CRX gene have recently been associated with autosomal dominant cone-rod dystrophy (CORD) as well as dominant Leber congenital amaurosis (LCA). Since LCA is more commonly inherited in an autosomal recessive manner, we examined a cohort of recessive LCA patients for CRX mutations. A homozygous substitution of arginine (R) at codon 90 by tryptophan (W) was identified in the CRX homeodomain of one of the probands who was nearly blind from birth. A group of 48 control individuals and 190 previously characterized CORD probands did not reveal this sequence change. The mutant CRXR90W homeodomain demonstrated decreased binding to the previously identified cis sequence elements in the rhodopsin promoter. In transient transfection experiments, the mutant protein showed significantly reduced ability to transactivate the rhodopsin promoter, as well as lower synergistic activation with the bZIP transcription factor NRL. Heterozygosity of the mutant CRX (R90W) allele was detected in both parents and in an older sibling. Ophthalmologic examination and electro-retinography revealed a subtle abnormality of cone function in both the parents. These data suggest that the R90W mutation results in a CRX protein with reduced DNA binding and transcriptional regulatory activity and that the subsequent changes in photoreceptor gene expression lead to the very early onset severe visual impairment in LCA.