Many students start college intending to pursue a career in the biosciences, but too many abandon this goal because they struggle in introductory biology. Interventions have been developed to close achievement gaps for underrepresented minority students and women, but no prior research has attempted to close the gap for first-generation students, a population that accounts for nearly a fifth of college students. We report a values affirmation intervention conducted with 798 U.S. students (154 first-generation) in an introductory biology course for majors. For first-generation students, values affirmation significantly improved final course grades and retention in the second course in the biology sequence, as well as overall GPA for the semester. This brief intervention narrowed the achievement gap between first-generation and continuing generation students for course grades by 50% and increased retention in a critical gateway course by 20%. Our results suggest that educators can expand the pipeline for first-generation students to continue studying in the biosciences with psychological interventions.

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Potato early dying (PED), also known as Verticillium wilt, caused by Verticillium dahliae, is a seasonal yield-limiting disease of potato worldwide, and PED-resistant cultivars currently represent only a small percentage of potato production. In this study, we developed a real-time quantitative polymerase chain reaction (Q-PCR) approach to detect and quantify V. dahliae. The efficiency of the designed primer pair VertBt-F/VertBt-R, derived from the sequence of the beta-tubulin gene, was greater than 95% in monoplex Q-PCR and duplex (using Plexor technology) procedures with primers PotAct-F/PotAct-R, obtained from the sequence of the actin gene, designed for potato. As few as 148 fg of V. dahliae DNA were detected and quantified, which is equivalent to five nuclei. Q-PCR detected V. dahliae in naturally infected air-dried potato stems and fresh stems of inoculated plants. Spearman correlations indicated a high correlation (upward of 80%) between V. dahliae quantifications using Q-PCR and the currently used plating assays. Moreover, Q-PCR substantially reduced the variability compared with that observed in the plating assay, and allowed for the detection of V. dahliae in 10% of stem samples found to be pathogen free on the culture medium. The described Q-PCR approach should provide breeders with a more sensitive and less variable alternative to time-consuming plating assays to distinguish response of breeding lines to colonization by V. dahliae.

Young, visually symptomless leaves from potato (Solanum tuberosum) plants infected with Verticillium dahliae exhibited reduced carbon assimilation rate, stomatal conductance, and intercellular C02, but no increase in dark respiration, no change in the relationship between carbon assimilation rate versus intercellular C02, and no change in light use efficiency when intercellular CO2 was held constant. Therefore, the initial decrease in photosynthesis caused by V. dahliae was caused by stomatal closure.Errors in the intercellular CO2 calculation caused by uneven distribution of carbon assimilation rate across the leaf were tested by "4CO2 autoradiography. Patchiness was found at a low frequency. Low stomatal conductance was correlated with low leaf water potentials. Infection did not affect leaf osmotic potentials.on the biochemistry of photosynthesis can be ruled out, especially if the relationship is determined at several light levels. If differences are found between control and infected plants, these differences can be interpreted using biochemically based models of photosynthesis (9,20).Using this analysis can be complicated when stomata close unevenly across the leaf (6,23). This patchiness has been observed in water-stressed plants (6, 21). The occurrence of patchy photosynthesis can be checked by autoradiography.We have tested for patchy photosynthesis using autoradiography in control and Verticillium infected potatoes. We determined the relationship between photosynthesis and Ci at three light levels. Then we compared the relationship between stomatal conductance and water potential. MATERIALS AND METHODSThe potato early dying disease causes losses of 30 Inoculum PreparationInoculum was produced from pathogenic cultures of Verticillium dahliae which were isolated from potato. In experiment 1, eight cultures were grown on 10% strength Difco potato dextrose agar for 2 weeks. The agar containing the fungal colonies was homogenized in a blender, then mixed with peat-vermiculite at the rate of 1 mL/L of soil mix. The infested soil was dried and stored 5 months at room temperature prior to use.In experiments 2 through 4, three isolates of V. dahliae from potato were grown on autoclaved rye grain at 20°C for 4 weeks. The infested grain was dried for 2 weeks at room temperature, then ground in a Wiley mill. Dried, ground rye www.plantphysiol.org on May 12, 2018 -Published by Downloaded from

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