Effect of alloy treatment and coiling temperature on microstructure and bending performance of ultra-high strength strip steel

Two different high strength B-containing microalloyed steel strips produced in industrial processing conditions, one treated with Ti and the other treated with Al, processed by controlled rolling, accelerated cooling and coiling in two different temperatures ranges [723 K to 733 K (450 °C to 460 °C)] and [633 K to 653 K (360 °C to 380 °C)] were subjected to bend testing. The Ti treated steel coiled at the higher temperature 733 K (460 °C) showed the best bending performance. The relatively softer (tensile strength of and even {112} in the sub-surface region as well as uniformity of through thickness texture of the rolled sheet improve the bendability. In the presence of crack initiators, like coarse and brittle TiN particles found in the Ti treated steel, a harder microstructure and the presence of Cube and Goss texture in the sub-surface layer, seen for the lower coiling temperature can cause local transgranular cleavage cracking. Finally the post-uniform elongation obtained from tensile testing and bendability follow a good correlation

Indole is an essential herbivore-induced volatile priming signal in maize

Herbivore-induced volatile organic compounds prime non-attacked plant tissues to respond more strongly to subsequent attacks. However, the key volatiles that trigger this primed state remain largely unidentified. In maize, the release of the aromatic compound indole is herbivore-specific and occurs earlier than other induced responses. We therefore hypothesized that indole may be involved in airborne priming. Using indole-deficient mutants and synthetic indole dispensers, we show that herbivore-induced indole enhances the induction of defensive volatiles in neighbouring maize plants in a species-specific manner. Furthermore, the release of indole is essential for priming of mono- and homoterpenes in systemic leaves of attacked plants. Indole exposure markedly increases the herbivore-induced production of the stress hormones jasmonate-isoleucine conjugate and abscisic acid, which represents a likely mechanism for indole-dependent priming. These results demonstrate that indole functions as a rapid and potent aerial priming agent that prepares systemic tissues and neighbouring plants for incoming attacks

The Present and Future Role of Insect-Resistant Genetically Modified Maize in IPM

Commercial, genetically-modified (GM) maize was first planted in the United States (USA, 1996) and Canada (1997) but now is grown in 13 countries on a total of over 35 million hectares (\u3e24% of area worldwide). The first GM maize plants produced a Cry protein derived from the soil bacteriumBacillus thuringiensis (Bt), which made them resistant to European corn borer and other lepidopteran maize pests. New GM maize hybrids not only have resistance to lepidopteran pests but some have resistance to coleopteran pests and tolerance to specific herbicides. Growers are attracted to the Btmaize hybrids for their convenience and because of yield protection, reduced need for chemical insecticides, and improved grain quality. Yet, most growers worldwide still rely on traditional integrated pest management (IPM) methods to control maize pests. They must weigh the appeal of buying insect protection “in the bag” against questions regarding economics, environmental safety, and insect resistance management (IRM). Traditional management of maize insects and the opportunities and challenges presented by GM maize are considered as they relate to current and future insect-resistant products. Four countries, two that currently have commercialize Bt maize (USA and Spain) and two that do not (China and Kenya), are highlighted. As with other insect management tactics (e.g., insecticide use or tillage), GM maize should not be considered inherently compatible or incompatible with IPM. Rather, the effect of GM insect-resistance on maize IPM likely depends on how the technology is developed and used

Genetic variation at bx1 controls DIMBOA content in maize

The main hydroxamic acid in maize (Zea mays L.) is 2-4-dihydroxy-7-methoxy-1,4-benzoxazin-3-one (DIMBOA). DIMBOA confers resistance to leaf-feeding by several corn borers. Most genes involved in the DIMBOA metabolic pathway are located on the short arm of chromosome 4, and quantitative trait loci (QTLs) involved in maize resistance to leaf-feeding by corn borers have been localized to that region. However, the low resolution of QTL linkage mapping does not allow convincing proof that genetic variation at bx loci was responsible for the variability for resistance. This study addressed the following objectives: to determine the QTLs involved in DIMBOA synthesis across genetically divergent maize inbreds using eight RIL families from the nested association mapping population, to check the stability of QTLs for DIMBOA content across years by evaluating two of those RIL families in 2 years, and to test the involvement of bx1 by performing association mapping with a panel of 281 diverse inbred lines. QTLs were stable across different environments. A genetic model including eight markers explained approximately 34% of phenotypic variability across eight RIL families and the position of the largest QTL co-localizes with the majority of structural genes of the DIMBOA pathway. Candidate association analysis determined that sequence polymorphisms at bx1 greatly affects variation of DIMBOA content in a diverse panel of maize inbreds, but the specific causal polymorphism or polymorphisms responsible for the QTL detected in the region 4.01 were not identified. This result may be because the causal polymorphism(s) were not sequenced, identity is masked by linkage disequilibrium, adjustments for population structure reduce significance of causal polymorphisms or multiple causal polymorphisms affecting bx1 segregate among inbred lines.This research was supported by the National Science Foundation Plant Genome Award DBI0321467 and by research funds provided by the USDA Agricultural Research Service to MDM.Peer reviewe

S1 vs. Reciprocal recurrent selection response in maize populations

Resumen del trabajo presentado en Utah, en octubre de 1999.Peer Reviewe

Molecular genetic analysis of resistance to Aspergillus flavus in maize: QTL for husk tightness and silk maysin F2:3 lines

Resumen del trabajo presentado en Atlanta, en octubre de 1999.Peer Reviewe

Recurrent selection for corn earworm resistance in three corn synthetics

Corn (Zea mays L.) grown in the Southeastern U. S. is often severely damaged by corn earworm (Helicoverpa zea Boddie), which feed on developing kernels on the ear. Natural resistance to this insect due to husk cover and chemicals in the silks has been identified. we studied the improvement in the resistance to ear injury by the corn earworm in the population 10LDDSR after 10 cycles of S1 recurrent selection and in the population cross DDSA x DDSB after seven cycles of reciprocal recurrent selection. We evaluated progress for increased resistance over a two-year period. The linear response to selection for improved resistance to corn earworm in the 10LDDSR population and DDSA x DDSB population cross was 0.06 cm of damage per cycle. Only three cycles of S1 and reciprocal recurrent selection for ear damage and husk tightness to improve resistance reduced ear damage by the corn earworm while maintaining other desirable agronomic traits. Therefore, future efforts to reduce ear damage in 10LDDSR(C3) should probably be focused on increasing silk maysin content. Antibiosis is also proposed as a potential trait to improve the resistance of breeding populations DDSA(C3) and DDSB(C3).Peer reviewe