White or ladino clover (Trifolium repens L.) is an important forage or legume worldwide. However, lack of drought tolerance and disease resistance limit its usefulness. Although other Trifolium species express these traits, routine crossing to develop interspecific hybrids and introduce desirable traits has achieved limited success. The objective of this work was to culture embryos and ovules to rescue hybrids and regenerate plants in new interspecific hybrid combinations. A media regime is described that is generally useful with Trifolium hybrid embryos at the torpedo stage or later. Novel interspecific combinations include T. ambiguum Bieb. with T. montanum L. and T. occidental Coombe; T. isthmocarpum Brot. with T. repens and T. nigrescens Viv.; a trihybrid, designated RUO, of T. repens, T. uniflorum L., and T. occidentale with hexaploid T. ambiguum. The RUO‐T. ambiguum hybrid was produced in several genotypic combinations, one of which bloomed and yielded viable pollen. Interspecific hybridization in Trifolium offers a route to enhancement of forage germplasm by introducing traits that increase longevity while maintaining the superior forage quality of T. repens.
Widespread infection of tall fescue (Festuca arundinacea Schreber) by the endophytic fungus (Acremonium coenophudum Morgan‐Jones and Gams) is responsible for poor performance of grazing animals. Because infection results in changes in phenotypic means for numerous traits, changes in phenotypic variances could also be a result of infection. Phenotypic variances for forage and seed production were investigated in studies of polycross families from endophyte‐infected (El) and endophyte‐free (EF) clones of 20 tall fescue genotypes. No significant phenotypic variance for forage production was detected among El families during the study. In 1989, phenotypic variances for EF were greater than El for both harvests, suggesting that the endophyte can mask plant genotypic variance. Significant phenotypic variances were observed for all seed production traits in both El and EF. Phenotypic variances for total seed weight and seed numbers in 1990 were greater for El than for EF. Estimates of genetic variance for these traits were not greater than twice the standard error in the EF state but were greater than twice the standard error in the El state. The resulting heritability estimates reflected this difference. Endophyte presence could result in overestimates of plant genotypic variance for these traits. Breeding strategies should consider presence or absence of endophyte and the possible effects on variances.
Acremonium coenophialum, a fungal endosymbiont in tall fescue, is responsible for the production of alkaloid toxins. Animals grazing endophyte-infected tall fescue often show toxicosis. In marginal environments, the endophyte is important for long-term survival of tall fescue. Few differences in endophyte isolates from individual tall fescue plants have been reported. To aid development of a toxicosis-free tall fescue, it is important to identify differences in endophyte isolates. This report describes variation in nitrogen utilization in a defined culture medium by endophyte isolates from Kentucky-31 tall fescue. Overall, the best nitrogen sources for dry weight production of mycelium were proline and potassium nitrate. Thirty-four isolates grown on agar-solidified defined media with single nitrogen sources showed variation in nitrogen utilization. Fifty percent of the isolates were unable to utilize two or more amino acids. Manipulation of endophyte variation could lead to development of a toxicosis-free tall fescue cultivar.
A distance-delivered course in plant biotechnology targeted for high school science teachers was offered for graduate credit by Clemson University. Objectives of this course were to update and strengthen knowledge of molecular genetics, genetic engineering, and associated technology; to provide ideas for high school laboratory and science fair projects; and to increase awareness of modern technology used in agronomy and agriculture. Instructional strategies designed to facilitate and reinforce learning were incorporated into a comprehensive study guide that accompanied the 36 videotaped lessons. Students viewed these lessons independently according to a schedule provided in the course syllabus. During alternate weeks, a 1.5-h live interactive session with one-way video and two-way audio was broadcast. This session served as a tutorial to focus, reinforce, and clarify the learning objectives for the lessons covered. Two Saturday sessions on campus provided experience with laboratory techniques associated with recombinant DNA technology and plant tissue culture. Student response to this format was very favorable. This course is intended to promote literacy in biotechnology and appreciation of the potential solutions of modern agricultural problems.
Computer-assisted instruction (CAI) offers a valuable supplemental teaching aid for courses that require repetitious drill to develop problem-solving skills. Computer assisted genetics instructor (CAGI) help students and teacher identify weaknesses and misconceptions, provides interactive drill to encourage students to master problem-solving, and reduces the need for continuing teacher tutorial time. CAGI contains multiple-choice questions developed by the course instructor and immediately acknowledges correct responses. The performance of students using CAGI was evaluated in an introductory genetics course comprised of students from several majors. Students utilizing CAGI scored an average of between 6 and 10 points higher on hour exams than students in the same class who did not use CAGI. More than 96% of CAGI users received a grade of B (88 percentage points) or better; 67% of the nonusers received B or better. CAGI helps students focus on the key aspects of biological processes, diagnose misconceptions, and provides drill accompanied by immediate feedback.
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