The maize brown midrib6 (bm6) mutation encodes a functional GTP Cyclohydrolase1

Brown midrib mutations in maize (Zea mays L.) and sorghum (Sorghum bicolor L.) alter lignin composition and enhance cell wall digestibility. These mutations are prime candidates for silage breeding. Six brown midrib mutants are currently known, brown midrib1 (bm1) to brown midrib6 (bm6). The bm1 and bm3 mutations are being used commercially for silage. The underlying genes responsible for five of the six bm mutations in maize (bm1, bm2, bm3, bm4, and bm5) are known. Chen and co-workers (2012) characterized the bm6 mutation, demonstratingthat bm6 increases cell wall digestibility and physically mapped bm6 within a 180 kilobase region on chromosome 2. The present investigation utilized map-based cloning to identify the candidate gene responsible for the bm6 phenotype as GTP Cyclohydrolase1 (GCH1) and validated the candidate gene through reverse genetics. Orthologs of bm6 include at least one paralogous gene in maize on chromosome 10 and various homologs in other grasses and dicots. The discovery that GCH1 is  responsible for the maize bm6 phenotype suggests that GCH1 plays a role in the tetrahydrofolate biosynthetic process

Genetic and agronomic assessment of cob traits in corn under low and normal nitrogen management conditions

With rising energy demands and costs for fossil fuels, alternative energy from renewable sources such as maize cobs will become competitive. Maize cobs have beneficial characteristics for utilization as feedstock including compact tissue, high cellulose content, and low ash and nitrogen content. Nitrogen is quantitatively the most important nutrient for plant growth. However, the influence of nitrogen fertilization on maize cob production is unclear. In this study, quantitative trait loci (QTL) have been analyzed for cob morphological traits such as cob weight, volume, length, diameter and cob tissue density, and grain yield under normal and low nitrogen regimes. 213 doubled-haploid lines of the intermated B73 × Mo17 (IBM) Syn10 population have been resequenced for 8575 bins, based on SNP markers. A total of 138 QTL were found for six traits across six trials using composite interval mapping with ten cofactors and empirical comparison-wise thresholds (P = 0.001). Despite moderate to high repeatabilities across trials, few QTL were consistent across trials and overall levels of explained phenotypic variance were lower than expected some of the cob trait × trial combinations (R2 = 7.3–43.1 %). Variation for cob traits was less affected by nitrogen conditions than by grain yield. Thus, the economics of cob usage under low nitrogen regimes is promising

Isozyme variation in "helminthosporium-type" species pathogenic on maize

The population structure of three species of fungi pathogenic on Zea mays L.; Cochliobolus carbonum, C. heterostrophus, and Septosphaeria turcica were studied using isozyme analysis. Forty isolates of S. turcica were evaluated using nineteen enzyme stains. Polymorphisms were identified with aspartate aminotransferase (EC 2.6.1.1), fumarase (EC 4.2.1.2), glucose-6-phosphate dehydrogenase (EC 1.1.1.49), and mannose-6-phosphate isomerase (EC 5.3.1.8). Associated electrophoretic and virulence phenotypes were found, indicating that populations exist in S. turcica as asexually propagated clonal groups. Use of the UPGMA method to calculate overall similarity between isolates found that isolates of race 1 were more similar to race 2 than isolates of race 3.Isolates of C. carbonum were found to be polymorphic for aspartate aminotransferase, esterase (EC 3.1.1), glucose phosphate isomerase (EC 5.3.1.9), leucine aminopeptidase (EC 3.4.11), and mannitol dehydrogenase. Races of C. carbonum were found to be associated with specific electrophoretic phenotypes. Phenograms generated by the UPGMA method showed similarity between races 1 and 3, which are highly virulent on maize. Both races were less similar to isolates of race 2, a weak pathogen of maize. No isozyme polymorphisms were detected in isolates of race 0 of C. heterostrophus. One race T isolate showed polymorphisms with esterase and hexokinase.U of I OnlyETDs are only available to UIUC Users without author permissio

Genetic and agronomic assessment of cob traits in corn under low and normal nitrogen management conditions

With rising energy demands and costs for fossil fuels, alternative energy from renewable sources such as maize cobs will become competitive. Maize cobs have beneficial characteristics for utilization as feedstock including compact tissue, high cellulose content, and low ash and nitrogen content. Nitrogen is quantitatively the most important nutrient for plant growth. However, the influence of nitrogen fertilization on maize cob production is unclear. In this study, quantitative trait loci (QTL) have been analyzed for cob morphological traits such as cob weight, volume, length, diameter and cob tissue density, and grain yield under normal and low nitrogen regimes. 213 doubled-haploid lines of the intermated B73 × Mo17 (IBM) Syn10 population have been resequenced for 8575 bins, based on SNP markers. A total of 138 QTL were found for six traits across six trials using composite interval mapping with ten cofactors and empirical comparison-wise thresholds (P = 0.001). Despite moderate to high repeatabilities across trials, few QTL were consistent across trials and overall levels of explained phenotypic variance were lower than expected some of the cob trait × trial combinations (R2 = 7.3–43.1 %). Variation for cob traits was less affected by nitrogen conditions than by grain yield. Thus, the economics of cob usage under low nitrogen regimes is promising.This article is published as Jansen, Constantin, Yongzhong Zhang, Hongjun Liu, Pedro J. Gonzalez-Portilla, Nick Lauter, Bharath Kumar, Ignacio Trucillo-Silva et al. "Genetic and agronomic assessment of cob traits in corn under low and normal nitrogen management conditions." Theoretical and applied genetics 128, no. 7 (2015): 1231-1242. 10.1007/s00122-015-2486-0. Posted with permission.</p

Genetic and agronomic assessment of cob traits in corn under low and normal nitrogen management conditions

AbstractKey message Exploring and understanding the geneticbasis of cob biomass in relation to grain yield undervarying nitrogen management regimes will help breedersto develop dual-purpose maize.Abstract With rising energy demands and costs for fossilfuels, alternative energy from renewable sources suchas maize cobs will become competitive. Maize cobs havebeneficial characteristics for utilization as feedstock includingcompact tissue, high cellulose content, and low ashand nitrogen content. Nitrogen is quantitatively the mos