DNA microarray-based discovery of molecular markers for the improvement of tomato color and nutritional quality

Color is among the most important attributes of tomato for processing into whole and diced products.  Both color and color uniformity are affected by yellow shoulder disorder (YSD), a ripening disorder that results in discoloration of the proximal end tissues of the fruit.  We show that lycopene and b-carotene concentrations are reduced by 18% and 22%, respectively, in fruits affected by YSD.  Variance partitioning suggests that YSD incidence and severity is affected by both genetics and environment.  The objectives of this project were to: (1) develop single nucleotide polymorphisms (SNPs) as molecular markers and (2) elucidate the genetic basis of YSD.  We hypothesized that a QTL mapping approach would identify loci that affect both color and color uniformity.  SNP discovery in breeding populations was based on both analyses of large public EST databases and on hybridization to a custom oligonucleotide array.  The array was hybridized with target cDNA from S. lycopersicum (Ohio 7814) and S. pimpinellifolium (LA1589).  We developed algorithms to detect outliers and identified 1,296 potential SNPs.  These putative SNPs are being verified by sequencing, screened for utility as markers on a collection of 99 S. lycopersicum lines and wild relatives, and applied to the genetic dissection of YSD.  Implementing SNP-based marker technology has the potential to dramatically alter our approach to genetic characterization.  Results and interpretation from this study will help bridge the gap between the goals of genetic and crop improvement research by facilitating the use of population structures that favor simultaneous genetic analysis and crop improvement.OARDC Research Enhancement Competitive gran

Breeding for Grain Amino Acid Composition in Maize

Improving the amino acid balance of grain has been a long-standing objective of plant-breeding research. In this chapter, we review the history of maize breeding for improved amino acid balance. Following this, we present results of our experiments involving divergent selection for the levels of the amino acids tryptophan and methionine in random-mated populations

Variability and genetic effects for tryptophan and methionine in commercial maize germplasm

Maize (Zea Mays L.) is a major food and feed crop; however, maize proteins are nutritionally imbalanced due to low levels of certain essential amino acids, including tryptophan and methionine. The objectives of this study were (1) to determine the variability in methionine and tryptophan levels present in commercial maize inbred lines, (2) to characterize the genetic groups of commercial maize breeding germplasm for their methionine and tryptophan content, (3) to estimate general combining ability, specific combining ability, and reciprocal genetic effects for tryptophan and methionine content in this germplasm. Seventy-six inbred lines representing nine different genetic groups (B14/B73 - 5 lines, B14/B73/Iodent - 16 lines, B73 - 16 lines, OH43/W153R - 6 lines, OH43/Iodent - 4 lines, Mo17 - 10 lines, European Flint - 8 lines, Plata - 6 lines, Unrelated - 5 lines) were evaluated .. There was significant variability among the genetic groups and among the inbreds in some of the groups. A six-parent diallel mating design was completed with three parents selected for low metionine methionine and three parents selected for high methionine levels. A second diallel mating design was carried out with three parents selected for high tryptophan levels and three parents selected for low tryptophan levels. Analysis of the diallel crosses revealed significant general and specific combining ability effects, as well as reciprocal effects. These effects were of greater magnitude in the methionine diallei than in the tryptophan diallel. These studies suggest that methionine should respond better to selection than tryptophan. Maize breeders may be able to exploit these genetic effects to develop hybrids with elevated levels of tryptophan or methionine

Recurrent Selection to Alter Grain Methionine Concentration and Improve Nutritional Value of Maize

Methionine is an essential amino acid that is limiting in maize- (Zea mays L.) based diets. The objective of this work was to determine whether we could alter grain methionine concentration in random-mated maize populations by mass selection for methionine concentration using a microbial assay. In one study, we developed two populations by selecting for high or low methionine concentration (HM or LM, respectively) for three generations starting from the random-mated population BS11. Grain from these populations was used to formulate diets for a feeding trial in which 15 rats were fed HM grain and 15 rats were fed LM grain. Rats on the HM diet had a 0.018 higher feed efficiency (g gain/g feed) than rats on the LM diet. In a second study, we performed three cycles of selection for high or low methionine concentration starting with two random-mated populations, BS11 and BS31. We evaluated each cycle of selection in a field trial with two replications in each of two years. Methionine concentration was significantly correlated with the cycle of selection, changing on average 0.004 g methionine/100 g grain per cycle. Kernel mass, %N, oil, protein, starch, tryptophan, and lysine concentration did not exhibit significant correlations with cycle of selection. We conclude that recurrent selection for grain methionine concentration using a microbial assay is an effective method to alter methionine content

Breeding for Grain Amino Acid Composition in Maize

Improving the amino acid balance of grain has been a long-standing objective of plant-breeding research. In this chapter, we review the history of maize breeding for improved amino acid balance. Following this, we present results of our experiments involving divergent selection for the levels of the amino acids tryptophan and methionine in random-mated populations.This is a chapter from Darrigues, A., Lamkey, K. R. and Scott, M. P. (2006) Breeding for Grain Amino Acid Composition in Maize, in Plant Breeding: The Arnel R. Hallauer International Symposium (eds K. R. Lamkey and M. Lee), Blackwell Publishing, Ames, Iowa, USA. doi: 10.1002/9780470752708.ch24.</p

Variability and genetic effects for tryptophan and methionine in commercial maize germplasm

Maize (Zea Mays L.) is a major food and feed crop; however, maize proteins are nutritionally imbalanced due to low levels of certain essential amino acids, including tryptophan and methionine. The objectives of this study were (1) to determine the variability in methionine and tryptophan levels present in commercial maize inbred lines, (2) to characterize the genetic groups of commercial maize breeding germplasm for their methionine and tryptophan content, (3) to estimate general combining ability, specific combining ability, and reciprocal genetic effects for tryptophan and methionine content in this germplasm. Seventy-six inbred lines representing nine different genetic groups (B14/B73 - 5 lines, B14/B73/Iodent - 16 lines, B73 - 16 lines, OH43/W153R - 6 lines, OH43/Iodent - 4 lines, Mo17 - 10 lines, European Flint - 8 lines, Plata - 6 lines, Unrelated - 5 lines) were evaluated .. There was significant variability among the genetic groups and among the inbreds in some of the groups. A six-parent diallel mating design was completed with three parents selected for low metionine methionine and three parents selected for high methionine levels. A second diallel mating design was carried out with three parents selected for high tryptophan levels and three parents selected for low tryptophan levels. Analysis of the diallel crosses revealed significant general and specific combining ability effects, as well as reciprocal effects. These effects were of greater magnitude in the methionine diallei than in the tryptophan diallel. These studies suggest that methionine should respond better to selection than tryptophan. Maize breeders may be able to exploit these genetic effects to develop hybrids with elevated levels of tryptophan or methionine.This article is from Maydica 50 (2005): 147–156. Posted with permission.</p