Molecular-Marker-Mediated Characterization of Favorable Exotic Alleles at Quantitative Trait Loci in Maize

Exotic maize (Zea mays L.) germplasm, shown to be useful for developing improved temperate cultivars, has remained little used partly because of many inherent shortcomings. Five F2 populations, developed from South American and U.S. germplasm, were used to detect favorable factors of exotic origin at quantitative trait loci (QTL) with isozymes and RFLPs. A number of traits of agronomic importance, including grain yield, were measured on F2 individuals and/or F3 families grown in several environments. Many QTLs, mostly with small effects, were identified. Major QTLs for grain yield and number of ears per plant were located on chromosomes 3 and 6. Stability of QTLs across environments was high. Favorable alleles of exotic origin were found at QTLs for several traits including grain yield and number of ears per plant. Most of these alleles also showed undesirable effects on other traits, however. Nevertheless, the superiority of exotic alleles over adapted alleles was demonstrated clearly at a few QTLs, re-affirming the usefulness of exotic germplasm for temperate maize breeding

Subscale Test Methods for Combustion Devices

Stated goals for long-life LRE s have been between 100 and 500 cycles: 1) Inherent technical difficulty of accurately defining the transient and steady state thermochemical environments and structural response (strain); 2) Limited statistical basis on failure mechanisms and effects of design and operational variability; and 3) Very high test costs and budget-driven need to protect test hardware (aversion to test-to-failure). Ambitious goals will require development of new databases: a) Advanced materials, e.g., tailored composites with virtually unlimited property variations; b) Innovative functional designs to exploit full capabilities of advanced materials; and c) Different cycles/operations. Subscale testing is one way to address technical and budget challenges: 1) Prototype subscale combustors exposed to controlled simulated conditions; 2) Complementary to conventional laboratory specimen database development; 3) Instrumented with sensors to measure thermostructural response; and 4) Coupled with analysi

A supramolecular helix that disregards chirality

The functions of complex crystalline systems derived from supramolecular biological and non-biological assemblies typically emerge from homochiral programmed primary structures via first principles involving secondary, tertiary and quaternary structures. In contrast, heterochiral and racemic compounds yield disordered crystals, amorphous solids or liquids. Here, we report the self-assembly of perylene bisimide derivatives in a supramolecular helix that in turn self-organizes in columnar hexagonal crystalline domains regardless of the enantiomeric purity of the perylene bisimide. We show that both homochiral and racemic perylene bisimide compounds, including a mixture of 21 diastereomers that cannot be deracemized at the molecular level, self-organize to form single-handed helical assemblies with identical single-crystal-like order. We propose that this high crystalline order is generated via a cogwheel mechanism that disregards the chirality of the self-assembling building blocks. We anticipate that this mechanism will facilitate access to previously inaccessible complex crystalline systems from racemic and homochiral building blocks

Molecular-Marker-Mediated Characterization of Favorable Exotic Alleles at Quantitative Trait Loci in Maize

Exotic maize (Zea mays L.) germplasm, shown to be useful for developing improved temperate cultivars, has remained little used partly because of many inherent shortcomings. Five F2 populations, developed from South American and U.S. germplasm, were used to detect favorable factors of exotic origin at quantitative trait loci (QTL) with isozymes and RFLPs. A number of traits of agronomic importance, including grain yield, were measured on F2 individuals and/or F3 families grown in several environments. Many QTLs, mostly with small effects, were identified. Major QTLs for grain yield and number of ears per plant were located on chromosomes 3 and 6. Stability of QTLs across environments was high. Favorable alleles of exotic origin were found at QTLs for several traits including grain yield and number of ears per plant. Most of these alleles also showed undesirable effects on other traits, however. Nevertheless, the superiority of exotic alleles over adapted alleles was demonstrated clearly at a few QTLs, re-affirming the usefulness of exotic germplasm for temperate maize breeding