Hessian fly is one of the world's most destructive insect pests of wheat Triticum aestivum L. We have used the combination of near-isogenic lines (NIL) and random amplified polymorphic DNA (RAPD) analysis to screen up to 2,000 primers to identify DNA markers that are linked to gene H6 that confers resistance to biotype B of the insect. This screen produced six primers that show polymorphic fragments associated with resistance by H6. We have screened 440 F(2) individuals from a cross of the susceptible cultivar Newton and a NIL that contains H6 to verify the linkage between these markers and the resistance gene. A high-resolution genetic map was constructed based on recombination frequency. Two of the markers were tightly linked to the gene with no recombination observed, three were within 2.0 cM, and one was 11 cM from the gene. Three of the six markers were successfully converted to sequence tagged site (STS) markers. Both RAPD and STS primers were used to screen for the presence or absence of the resistance gene in wheat varieties. The identification of markers and construction of the genetic high resolution map provide the first steps toward localization of this resistance gene.

The generation of ions in air has several useful applications, such as electrohydrodynamic (EHD) pumping, air purification and isolation breakdown prevention. In this paper, ion generation processes in atmospheric air are simulated using a Direct Simulation Monte Carlo (DSMC) method. Details of the collision model are discussed. A C++ code is developed to implement the Monte Carlo method with cross-section data compiled from the literature. Self-sustaining discharge and ionization can be reproduced in the simulation under sufficient voltage bias, and the associated trends obtained are similar to those predicted by Paschen’s curve for a parallel-plate configuration.

The geminiviruses are a group of plant DNA viruses characterized by having one or two copies of a single-stranded, circular DNA genome and frequent occurrence of geminate, quasi-isometric particles as observed by transmission electron microscopy. The Geminiviridaefamily is classified into three genera (Mastrevirus, Curtovirus and Begomovirus)based on the number of DNA components, the plant hosts, and the transmission vectors. Maize streak virus (MSV), the type member of the Mastrivirusgenus, is transmitted by the leafhopper and infects Gramineaespecies. Wheat dwarf virus, Digitaria streak virus, and Chloris striate mosaic virus (CSMV) are examples of other members of the Mastrivirusgenus. The Nigerian strain of MSV (MSV-N) contains one copy of a singlestranded, circular DNA molecule (2687 nucleotides). Two protein products, VI and V2, are coded by the MSV-N genome.2 V2 (244 amino acids) is the only coat protein found in virions.