The European corn borer (Ostrinia nubilalis Hübner), or ECB, is a major pest of hemp (Cannabis sativa L.). During the course of a study of hemp germplasm and cultivar accessions, the ECB attacked the vertical stem leader of hundreds of plants. At the site of invasion the main stem was typically destroyed, and the plant became strongly branched. Although the damaged plants were an average 9% shorter, mean shoot weight was 20% heavier. Seed productivity was also greater, based on a visual scale. The practical significance of such an “overcompensation” response to insect damage, with damaged plants growing more robustly and productively than their undamaged counterparts, is controversial. Certainly, some aspects of productivity, such as fibre quality, are detrimentally affected by the ECB. The insect showed a preference for larger plants, but was indifferent to the level of tetrahydrocannabinol, the chief intoxicant of C. sativa. Key Words: Cannabis sativahempEuropean corn borerOstrinia nubilalisovercompensation

The pathogenicity of eight Fusarium species causing fusarium head blight (FHB) in barley was studied under controlled conditions. Six barley genotypes varying in resistance to FHB were artificially inoculated with six isolates each of F acuminatum, F avenaceum, F crookwellense, F culmorum, F. equiseti, F. graminearum, F. poae and F. sporotrichioides 10-14 d after heading. Symptoms of FHB were rated as disease severity using a 0-9 scale, 4, 7, 14, 21 and 28 d after inoculation, and as percentage of infected spikelets (IS) after 21 d. All species tested caused head blight symptoms on the barley genotypes, but only F crookwellense, F culmorum and F graminearum resulted in severe disease development (> 65% IS) and were considered highly pathogenic. Fusarium avenaceum had 48% IS, which was significantly lower than those of the three highly pathogenic species and was moderately pathogenic. The remaining species had < 15% IS and were weakly pathogenic. There were significant differences (P < 0.05) in aggressiveness among isolates within species and in susceptibility among barley genotypes, suggesting that screening for resistance to FHB requires the use of aggressive isolates or a mixture of several isolates. This is the first report showing that F crookwellense is highly pathogenic and F avenaceum is moderately pathogenic on barley.

The pedigree method is often used for developing inbred lines in maize (Zea mays L.). This study was conducted to assess the effectiveness of pedigree selection for improving resistance to Gibberella ear rot in four maize populations. Selection was based on the severity of ear rot symptoms after inoculation with macroconidial suspensions of Fusarium graminearum (Schwabe) into the silk channel (for two populations) and into the developing kernels (for two other populations). Samples of the selfed families (S-1 to S-5), recovered from remnant seed from the selection programs, were evaluated for disease resistance during three years, using inoculation and evaluation protocols similar to those used during selection. Among-family selection was effective in both of the populations selected after silk inoculation and in one of the populations selected after kernel inoculation. Responses to selection were more evident in later than in earlier generations for both types of inoculation. Changes in the estimated genetic gain over generations were consistent with changes in the variances among families, which tended to increase in early generations and to decrease in later generations. Selection after kernel inoculation seemed to have been more effective than selection after silk inoculation in developing families with more stable resistance. Based on the results obtained here, it seems that responses to family selection could be accelerated without increasing operational costs by increasing selection intensity in later generations and inoculating fewer plants per family.

Defined broadly, pre-processing involves many potential steps that are essential for successful microarray experimentation. The need for some steps (e.g., experimental design, image analysis) is unquestionable. Other steps are less dogmatic. Data transformation, inspection, and filtering should occur based on individual analytical goals and data management systems. These steps may take on new meaning as different techniques for analysis become widely accepted. A complete and perfect recipe for pre-processing and analyzing microarray experiments does not exist. Therefore, each experimenter must develop systems and procedures that are both appropriate and correct. We hope that the concepts introduced in this chapter will help the reader to better understand the detailed presentations found in later chapters.

The alkane content of the silks of nine maize genotypes was analyzed to investigate the role of silk wax in resistance to Fusarium graminearum. Silk samples were collected 2, 4, 6, and 8 days after silk emergence and divided into three sections: exposed silk, silk channel silk, and silk that is under the husk and overlying the kernels. Four major unbranched alkanes (C-25, C-27, C-29, and C-31) and three isoalkanes (C-27i, C-29i, and C-31i) were identified. Total alkane contents were highest in the exposed silk followed by the silk channel silk, with the lowest in the youngest silk closest to the kernels. In the silk channel and overlying kernel silks, the moderately resistant inbred CO272 consistently had the highest alkane content. None of the other inbreds with improved resistance had as high a level of alkanes as CO272, indicating that alkane content is not a major mechanism of resistance.