Genetic Diversity of a Global Population of Colletotrichum Coccodes Using Amplified Fragment Length Polymorphism Markers

The present study tested the hypothesis that the global C. coccodes population is genetically differentiated by region of origin. A total of 855 isolates, originating from North America (475), Europe (147), Israel (66), Australia (86), South Africa (14) and additional testers (67), which previously were assigned to VCGs (21 international VCGs) were examined for their genetic diversity. Using the previously assigned North American VCGs as the leading sub-population, and with the aid of amplified fragment length polymorphism (AFLP) markers, the isolates were grouped into five VCG/AFLP sub-populations (1, 2, 3, 4/5 and 6/7). These were distributed between two phylogeny clusters, designated Cc-A and Cc-B. Cluster Cc-A was unique and composed of isolates from VCG/AFLP6/7 only, whereas cluster Cc-B was composed of the remaining four VCG/AFLP sub-populations, which was further divided into 17 sub-clusters. VCG/AFLP4/5 was the most common VCG globally, followed by VCG/AFLP2. Most of the variation among the four geographic regions originated from the within population differentiation (84 %). It is concluded from these studies that the global population of C. coccodes exists as one large population with five main VCG/AFLPs worldwide and that they are probably of the same origin, however, geographic isolation caused these populations to differentiate and form distinct sub-clusters.     

Dakota Pearl: An attractive, bright white-skinned, cold-chipping cultivar with tablestock potential

Dakota Pearl (ND2676-10) is a medium-maturing chipping cultivar with uniform, round, bright white-skinned tubers with shallow eyes. Dakota Pearl has the ability to produce commercially acceptable chips following long-term storage at 5.5 C without the need for reconditioning. It yields well under both dryland and irrigated trial conditions in North Dakota. North Central Regional Potato Variety Trial and Snack Food Association Trial results indicate it has wide adaptability. Yield and specific gravity under dryland conditions are similar to Norchip; Dakota Pearl has a low percentage of external defects. Average set is 12 to 14 tubers per hill. Dakota Pearl demonstrates wide consumer appeal as a tablestock cultivar due to attractive tuber appearance and bright-white skin. Sensory evaluation scores for baking, boiling, and microwaving are comparable to those of standard chip cvs Atlantic, NorValley, and Snowden. The specific gravity of Dakota Pearl is similar to cvs Norchip and NorValley, lower than for Atlantic or Snowden. Total glycoalkaloid levels are low, at 1.5 mg/100 g fresh tuber tissue. The North Dakota Agricultural Experiment Station released Dakota Pearl on 23 April 1999.     

Influence of tillage and method of metam sodium application on distribution and survival ofVerticillium dahliae in the soil and the development of verticillium wilt of potato

The effect of plowing and deep-rip tillage, in combination with chemigation or shank injection of metam sodium, onVerticillium dahliae populations and disease development was assessed in two fields with differing soil types and potato rotations. Soil samples were collected on a geo-referenced basis at depths of 0 to 10 cm and 10 to 20 cm before tillage, after tillage, after chemical application, and before planting and assayed for the presence of the pathogen. Propagules ofV. dahliae were detected at 140 of 141 sites sampled prior to tillage. Most (74.4% in heavy, sandy loam; 63.1% in light, loamy sand) were concentrated in upper 10 cm of the soil profile. Plowing redistributed inoculum vertically while deep-rip tillage did not. In the non-chemical treated areas of both fields, theVerticillium population reached a maximum between 25 July and 8 August before declining to near pre-tillage levels. Overall, the population generally was lower in the field with heavy soil, higher organic matter content, and a 3-year crop rotation. Metam sodium appeared to be most effective when shank injected, as the levels of inoculum in both fields declined by 60% to 80% following this application method. Chemigation was ineffective in the lighter soil, but the inoculum density in the deep-rip tillage area of the field with the heavier soil declined by nearly 20% in the upper and 60% in the lower strata following this treatment. The number ofV. dahliae propagules at the 10- to 20-cm depth in the plowed area of the same field was reduced by 25% following chemigation, but remained unchanged in the upper strata. Wilt was reduced in both fields by as much as 50% with shank injection of metam sodium with concomitant increases in total yield, marketable yield and gross income. Increases in total yield were significant (P<0.05) for the main effect of chemical, in the plowed area of the field with the heavier soil type following shank injection. These data suggest that growers might benefit from altering their tillage and chemical application practices as part of an integrated approach to managing Verticillium wilt.     

The effect of ethylene and abscisic acid on symptom expression of bacterial ring rot in eggplant and potato

Studies were performed to determine the effect that plant hormones involved with plant senescence (i.e., ethylene and abscisic acid) and photoperiod have on disease development and symptom expression of bacterial ring rot (BRR) caused byCorynebacterium sepedonicum (Spieck & Kotth.) Skapt & Burkh. Potato plants were grown either under a long (14 hr.) or short (10 hr.) photoperiod, while eggplants were grown only under a short (10 hr.) photoperiod. Disease severity ratings of BRR were found to be significantly higher (P=0.05) on potato plants grown under a short photoperiod compared to a long photoperiod. Plant heights of BRR infected plants were found to be significantly greater under the long photoperiod. Endogenous levels of ethylene were found to be significantly (P=0.05) greater in inoculated potato plants grown under a long photoperiod than inoculated plants grown under a short photoperiod. Results suggest that the plant hormones ethylene and abscisic acid do not significantly affect the disease development and symptom expression of BRR.     

A High-Temperature Electrical Conduction Mechanism in the Lower Mantle Phase (Mg,Fe)1-xO

Measurements of electrical conductivity at high pressure and temperature were taken on the lower mantle phase magnesiowustite with varying Fe3+ content. Although previous measurements at atmospheric pressure suggest Fe2+-Fe3+ hopping (small polaron) as the dominant conductivity mechanism, the present experiments show a change in charge transport mechanism with temperature. The lower temperature measurements are consistent with small polaron conduction, but at higher temperatures, which are more applicable to the lower mantle, a large polaron mechanism is suggested. Because these mechanisms have different temperature and compositional dependencies, this transition has important implications for extrapolation to mantle conditions.     

Unitary control in quantum ensembles: maximizing signal intensity in coherent spectroscopy

Experiments in coherent magnetic resonance, microwave, and optical spectroscopy control quantum-mechanical ensembles by guiding them from initial states toward target states by unitary transformation. Often, the coherences detected as signals are represented by a non-Hermitian operator. Hence, spectroscopic experiments, such as those used in nuclear magnetic resonance, correspond to unitary transformations between operators that in general are not Hermitian. A gradient-based systematic procedure for optimizing these transformations is described that finds the largest projection of a transformed initial operator onto the target operator and, thus, the maximum spectroscopic signal. This method can also be used in applied mathematics and control theory.