Douglas A. Johnson

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The mechanisms responsible for soil-N-mediated species replacement of native perennial grasses by the invasive annual grasses cheatgrass (Bromus tectorum L.) and medusahead (Taeniatherum caput-medusae [L.] Nevski) on rangelands are not completely understood. In addition, the contributions of distinct forms of inorganic N (i.e., NH4 + and NO3 -) to these(More)
Agropyron desertorum, a grazing-tolerant bunchgrass introduced to the western U.S. from Eurasia, and Agropyron spicatum, a grazing-sensitive bunchgrass native to North America, were examined in the field for photosynthetic capacity, growth, resource allocation, and tiller dynamics. These observations allowed identification of physiological characteristics(More)
A substantial amount of between and within cultivar genetic variation was detected in all the 13 registered modern Canadian durum wheat (Triticum turgidum L. ssp. durum (Desf.) Husn.) cultivars based upon amplified restriction fragment polymorphism (AFLP). Of the approximately 950 detected AFLP markers, only 89 were polymorphic, with 41 between cultivars(More)
Genetic variability in RAPDs (Randomly Amplified Polymorphic DNA) was studied in 104 genotypes of wild barley, Hordeum spontaneum from 21 populations sampled in Israel, Turkey and Iran, seven population from each country. The band (= loci) frequencies were calculated for each population and correlated with ecogeographical variables. In general, high RAPD(More)
We analyzed the genetic diversity in 88 genotypes from 20 populations of wild barley (Hordeum spontaneum C. Koch) from Israel, Turkey and Iran, by randomly amplified polymorphic DNA (RAPD). Twenty two of the 33 primers used yielded scorable products with 1–11 polymorphic bands. No duplicate patterns were found except for four haplotypes.When the total(More)
The expression pattern of tissue-specific promoters in transgenes can be influenced by promoter/enhancer elements employed for the expression of selectable marker genes or elements found in DNA flanking the insertion site. We have developed an analytical system in Arabidopsis thaliana to investigate strategies useful in blocking or reducing nonspecific(More)
cDNA and genomic clones of a new pollen-specific gene, Bnm1, have been isolated from Brassica napus cv. Topas. The gene contains an open reading frame of 546 bp and a single intron of 362 bp. A comparison of the deduced amino acid sequence with sequences in data banks did not show similarity with known proteins. Northern blot analysis of developing pollen(More)
We describe a gene, SCB1 (Seed Coat BURP-domain protein 1), that is expressed specifically within the soybean (Glycine max [L.] Merrill) seed coat early in its development. Northern blot analysis and mRNA in situ hybridization revealed novel patterns of gene expression during seed development. SCB1 mRNA accumulated first within the developing thick-walled(More)
The extent of sequence identity among clones derived from monomorphic and polymorphic AFLPTM polymorphism bands was quantified. A total of 79 fragments from a monomorphic band of 273 bp and 48 fragments from a polymorphic band of 159 bp, isolated from individuals belonging to different populations, varieties, and species of Echinacea, were cloned and(More)
Although seeds have been the subject of extensive studies for many years, their seed coats are just beginning to be examined from the perspective of molecular genetics and control of development. The seed coat, plays a vital role in the life cycle of plants by controlling the development of the embryo and determining seed dormancy and germination. Within(More)