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Wisconsin Quality Synthetic (WQS) is a maize population that has undergone four cycles of S2-topcross selection for increased silage yield and feed quality. This study evaluated forage yield and quality for each cycle of WQS per se as well as testcrosses to two Stiff Stalk-type testers. Linear improvement was seen in whole plant yield, stover yield, and whole-plant quality both in the population per se and in testcrosses. stover quality has not improved through selection. Starch content has increased while crude protein has decreased. Milk yields on a Mg dry matter and hectare basis have increased with selection. Changes in silage dry matter yield have been greater on a percent basis than changes in silage quality, suggesting that the current selection protocol of selecting S2-top crosses first for yield then for quality may be more efficient at improving yield than quality. Selection directly focused on stover quality may be necessary if more rapid improvement in stover composition is desired. [ABSTRACT FROM AUTHOR]

Maize hybrids with improved stover yield and quality are needed to support the emerging cellulosic biofuels industry. Knowledge of the genetic variation, covariation, and genetic architecture of agronomic and cell wall traits will help maize breeders improve relevant traits through selective breeding and genetic engineering. We utilized the maize intermated B73 × Mo17 (IBM) recombinant inbred line (AlL) population to map quantitative trait loci (QTL) and to evaluate the genetic relationships among traits relevant for cellulosic biofuel production, including grain yield, stover yield, neutral detergent fiber digestibility (NDFD), and glucan, xylan, and hgnm concentration. Intermated B73 × Mo17 AlL were evaluated per se and as testcrosses to W604S to assess how well performance and QTL effects correspond between inbreds and hybrids. There were no unfavorable correlations between agronomic and cell wall traits within the testcross progeny. Polysaccharide content was either positively correlated to, or not correlated to, NDFD, indicating that increasing both carbohydrate content and convertibility is feasible. Quantitative trait loci were identified for all traits evaluated, but few QTL were in common between inbred per se and testcross evaluations despite moderate to high genotypic correlations between progeny types. This study provides information that will support the development of dual-purpose maize hybrids that are high in grain yield and also high in yield of digestible cellulosic feedstock. [ABSTRACT FROM AUTHOR]

The use of maize (Zea mays L.) stover as a feedstock for cellulosic biofuels production will create demand for maize hybrids with greater stover yield. It is expected that grain yield will remain the most critical trait and continue to drive hybrid sales, requiring that any increases in stover yield be made without sacrificing grain yield potential. The objective of this review was to determine the relationship between grain yield, harvest index, and stover yield to illuminate the potential for increasing both grain and stover yield through breeding. In contrast to what has been observed in other crops, gains in maize grain yield over time in the U.S. Corn Belt have been accompanied by increases in stover yield. Where recurrent selection on grain yield has been most successful, stover yield also increased while harvest index has been relatively stable. The opposite situation has been observed in tropical germplasm, where gains in grain yield have been associated with increasing harvest index and relatively constant biomass yield. We expect that stover yield of Corn Belt hybrids will continue to increase along with grain yield, resulting in future hybrids capable of producing both more food and biofeedstock for energy production. If maize breeders pursue selection for increased stover yield, we found no evidence to suggest that breeding for stover yield will necessarily reduce rate of gain in grain yield. [ABSTRACT FROM AUTHOR]

Maize (Zea mays L.) stover has been identified as an important feedstock for the production of cellulosic ethanol. Our objectives were to measure hybrid effect and combining ability patterns of traits related to cellulosic ethanol production, determine if germplasm and mutations used for silage production would also be beneficial for feedstock production, and examine relationships between traits that are relevant to selective breeding. We evaluated grain hybrids, germplasm bred for silage production, brown-midrib hybrids, and a leafy hybrid. Yield and composition traits were measured in four environments. There was a 53% difference in stover yield between commercial grain hybrids that were equivalent for other production- related traits. Silage germplasm may be useful for increasing stover yield and reducing lignin concentration. We found much more variation among hybrids than either in vitro ruminal fermentability or polysaccharide concentration. Correlations between traits were mostly favorable or nonexistent. Our results suggest that utilizing standing genetic variation of maize in breeding programs could substantially increase the amount of biofuels produced from stover per unit area of land. [ABSTRACT FROM AUTHOR]

While maize silage is a significant feed component in animal production operations, little information is available on the genetic bases of fiber and lignin concentrations in maize, which are negatively correlated with digestibility. Fiber is composed largely of cellulose, hemicellulose and lignin, which are the primary components of plant cell walls. Variability for these traits in maize germplasm has been reported, but the sources of the variation and the relationships between these traits in different tissues are not well understood. In this study, 191 recombinant inbred lines of B73 (low-intermediate levels of cell wall components, CWCs) × De811 (high levels of CWCs) were analyzed for quantitative trait loci (QTL) associated with CWCs in the leaf sheath. Samples were harvested from plots at two locations in 1998 and one in 1999 and assayed for neutral detergent fiber (NDF), acid detergent fiber (ADF) and acid detergent lignin (ADL). QTL were detected on all ten chromosomes, most in tissue specific clusters in concordance with the high genotypic correlations for CWCs within the same tissue. Adjustment of NDF for its subfraction, ADF, revealed that most of the genetic variation in NDF was probably due to variation in ADF. The low to moderate genotypic correlations for the same CWC across leaf sheath and stalk tissues indicate that some genes for CWCs may only be expressed in certain tissues. Many of the QTL herein were detected in other populations, and some are linked to candidate genes for cell wall carbohydrate biosynthesis. [ABSTRACT FROM AUTHOR]

Maize silage is a significant energy source for animal production operations, and the efficiency of the conversion of forage into animal mass is an important consideration when selecting cultivars for use as feed. Fiber and lignin are negatively correlated with digestibility of feed, so the development of forage with reduced levels of these cell-wall components (CWCs) is desirable. While variability for fiber and lignin is present in maize germplasm, traditional selection has focused on the yield of the ear rather than the forage quality of the whole plant, and little information is available concerning the genetics of fiber and lignin. The objectives of this study were to map quantitative trait loci (QTLs) for fiber and lignin in the maize stalk and compare them with QTLs from other populations. Stalk samples were harvested from 191 recombinant inbred lines (RILs) of B73 (an inbred line with low-to-intermediate levels of CWCs) × De811 (an inbred line with high levels of CWCs) at two locations in 1998 and one in 1999 and assayed for neutral detergent fiber (NDF), acid detergent fiber (ADF), and acid detergent lignin (ADL). The QTLs were detected on nine chromosomes, mostly clustered in concordance with the high genetic correlations between NDF and ADF. Adjustment of NDF for ADF and ADF for ADL revealed that most of the variability for CWCs in this population is in ADF. Many of the QTLs detected in this study have also been detected in other populations, and several are linked to candidate genes for cellulose or starch biosynthesis. The genetic information obtained in this study should be useful to breeding efforts aimed at improving the quality of maize silage. [ABSTRACT FROM AUTHOR]

The open-pollinated maize (Zea mays subsp. mays) population Golden Glow [GG(MP)] provides excellent material for the study of morphological and genetic changes associated with selection for prolificacy. Late generations of the GG(MP), when planted at low densities, resemble the architecture of teosinte (Z. mays subsp. parviglumis), the ancestor of maize. Our objectives were (i) to identify molecular markers linked to chromosomal regions that influenced prolificacy and related morphological traits, (ii) to determine whether genes previously shown to influence branching patterns in maize were associated with quantitative trait loci (QTLs) influencing these traits, and (iii) to determine whether epistatic interactions among putative QTLs influenced prolificacy and correlated traits. A mapping population was developed from the cross of inbred A679 and a highly prolific S1 plant from Cycle 23 of GG(MP). Simple sequence repeat (SSR) and amplified fragment length polymorphism (AFLP) markers were combined for the linkage map construction. Thirty-three QTLs were found for 14 of the 16 traits analyzed. A region located on Linkage Group 1 (LG 1) shared similarities with the pattern of development suggested for the teosinte branchedi (thi) mutant. This suggests that genetic control of prolificacy and associated traits in GG(MP) may resemble the genetic changes underlying branching morphology that occurred during maize domestication. No evidence for additive-by-additive epistatic interactions was found. [ABSTRACT FROM AUTHOR]

The Wisconsin Quality Synthetic (WQS C3) is a corn breeding population under selection at the University of Wisconsin for improved NDF digestion and silage yield. A recessive allele, floury2, increases floury endosperm in corn grain, and its starch has been found to be more ruminally degradable than dent corn. Population WQS C3, and two near-isogenic hybrids, W64AXOH43 (ISO) and W64AXOH43 fl2 (fl2), were harvested from isolated 0.5 ha plots as whole-plant corn silage at approximately 35% DM. Treatment silages were fed in TMR to six cows assigned randomly to a replicated 3x3 Latin Square design with 21-d periods. However, only two periods were completed due to unforeseen silage shortages. Data were analyzed using a mixed models procedure. The ISO, fl2, and WQS C3 corn silages averaged 35.9, 35.7, and 35.7 % NDF, respectively. Diets were formulated to meet or exceed NRC (2001) protein, mineral, and vitamin requirements and averaged 30.8% NDF. Diets were comprised of 54% corn silage, 36% concentrate, and 10% alfalfa hay (DM basis). Lactation performance and digestion data are presented in Table 1. Intake and milk production did not differ among treatments. Ruminal 48-h in situ DM and NDF disappearance were greater for WQS C3, but total tract NDF digestibilities were not in agreement with our in situ results or prior in vitro measurements. Reduced total tract NDF digestibility for ISO relative to fl2 was unexpected based on previous in vitro measurements and our in situ measurements, and cannot be explained. Starch in situ disappearance and total tract digestibility will be determined. [ABSTRACT FROM AUTHOR]