Dependence on alcohol and illicit drugs frequently co-occur. Results from a number of twin studies suggest that heritable influences on alcohol dependence and drug dependence may substantially overlap. Using large, genetically informative pedigrees from the Collaborative Study on the Genetics of Alcoholism (COGA), we performed quantitative linkage analyses using a panel of 1717 SNPs. Genome-wide linkage analyses were conducted for quantitative measures of DSM-IV alcohol

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Stomatal length and frequency and pollen grain diameter were examined as indirect methods for identification of 4x, 6x and 8x ploidy levels in Bromus inermis. The study was conducted in the greenhouse on seedlings and mature plants. Mean stomatal lengths were 40.4, 43.0, 53.1, and 66.6 µ for mature 4X (clonal), 4X (selfing), 6X and 8X plants, respectively. Coefficients of variation among observations within each ploidy level were relatively low. Stomatal frequency decreased with increasing ploidy while pollen‐grain diameter increased, but considerable overlapping occurred among ploidies for both characters. Greater ploidy differences and smaller standard deviations were associated with stomatal length rather than with stomatal frequency and pollen‐grain diameter. Therefore, the former is recommended as a rapid method for identification of ploidy level.

The cyclic hydroxamate, 2,4‐dihydroxy.7‐methoxy‐l,4‐benzoxazin‐ 3‐one (DIMBOA), has been implicated in the resistance of corn (Zea mays L.) to fungi and insects. In our study, bioassay and field experiments tested the relationship between hydroxamate concentration and resistance to corn leaf aphid (Rhopalosiphum maidis (Fitch)).In the bioassay, various concentrattons of DIMBOA were added to an artificial diet fed to corn leaf aphids. DIMBOA concentrations of 0.1, 0.25, and 0.5 mg/g diet caused 5.1, 12.8, and 20.8% mortality, respectively. In field trials, 12 inbred lines were evaluated for corn leaf aphid resistance under natural infestation. Aphid infestation was evaluated at mid‐silking stage with a visual rating scale and index system. Cyclic hydroxamate concentration in a separate set of the same lines was estimated by a rapid procedure based upon the colorimetric reaction of hydroxamates with ferric chloride. Aphid infestation values ranged from 119 to 366. Hydroxamate concentration ranged from 0.08 to 1.48 mg/g fresh weight. A highly significant correlation (r = 0.72) was obtained between aphid infestation and hydroxamate concentration.Eighteen hybrids derived from crosses among 12 inbred lines were also evaluated for corn leaf aphid resistance in the field. Aphid infestation values from high ✕ high, intermediate ✕ intermediate, and low ✕ low DIMBOA lines were generally low, intermediate, and high, respectively. Hybrids derived from crossing high ✕ low, high ✕ intermediate, and intermediate ✕ low DIMBOA lines produced infestation values between the parental extremes.