Lima beans are an important vegetable crop to the processing industry in Delaware, but yields in Delaware are below other areas due to heat. The objective was to correlate RAPD markers from heat-tolerant and intolerant cultivars with phenotypic data. Twenty-five primers were used, 10 of which generated 25 polymorphic bands among 11 cultivars. MDS analysis of genetic distance among the cultivars shows segregation into two major clusters, with Kingston as a distant outlier. Kingston's position can be correlated to published data reporting its consistently good yields even when temperatures are high. The results of this study indicate RAPD markers may be used to screen for cultivars that have high yield potentials despite high temperatures. Further studies to screen F, and inbreeds will determine the usefulness of these markers in breeding programs.
Kathryn R. Kleiner, John J. Frett, and James Nienhuis
Tracy L Wootten, John J. Frett, and W. Edwin Kee
In an effort to increase lima bean yields in Delaware, the documentation of lima bean plant development and the comparison of Delaware and California lima bean production was conducted. Delaware lima bean yields have averaged 1905 kg·ha-1 for the last 30 years. California averages 3923-4484 kg·ha-1. Cultivar M-15 is used by both states for production. Plant population density, plant fresh weight, and final yield was greater in California than in Delaware. Although plant populations were the same in 1992, yields remained higher in California than in Delaware. High night temperatures have an adverse affect on lima bean yields. Minimum temperatures from both states were compared. Minimum temperatures from the California planting were greater than the minimum temperatures for the late planting in Delaware.
Sharon J. Keeler, John J. Frett, and Sherry L. Kitto
Heat stress on field grown Phaseolus lunatus (lima bean) can have a significant influence on yield. Lima bean crops grown in Delaware typically yield less pounds per acre than the same cultivars grown in California. Part of this effect may be due to extreme heat conditions or fluctuations during Delaware's summers, which can affect blossom and pod set. Our purpose was to analyze the heat tolerance of various cultivars of P. lunatus using quick bioassays and to establish a relationship to yield in greenhouse temperature trials. Two assays were used. The first, a hypocotyl extension assay, consisted of a treatment of germinated seedlings at 25, 35, or 42 for 2 h and observations of hypocotyl extension at 72 and 96 h posttemperature treatments. Three cultivars [`Fordhook' 1072 (heat-sensitive), `Jackson Wonder' (heat-tolerant), and `Early Thorogreen' (heat tolerant)] were analyzed. Initial results indicated that `Jackson Wonder' and `Early Thorogreen' are capable of surviving the 42C heat shock, but `Fordhook 1072' is not. In the second assay, we measured electrical conductivity of a solution containing hypocotyl sections following incubation at various temperatures (R1). Tissue samples then were boiled and conductivity was measured again (R2). The ratios of R1/R2 × 100 were determined as percent injury. Preliminary data suggests that `Jackson Wonder' is more heat-tolerant in this assay than `Fordhook 1072'. Subsequent experiments will analyze the induction of specific heat shock proteins as a function of cultivar-specific heat tolerance.
David Devenney, John Frett, Wallace Pill, and Gary Smith.
Ten 10 wildflower species grew satisfactorily in a 1:1 (vol.) mix of Ironrich (IR, mineral co-product of the titanium dioxide industry) and Fairgrow (FG, co-composted sewage sludge and solid waste). Shoot fresh weights in the low fertility IR and in the high fertility FG averaged 35% and 157%, respectively, those grown in IR+FG. Wildflower establishment in 10cm-deep outdoor seedbeds of IR, FG, or IR+FG were compared to those in soil (control) plots. Maximum percentage seedling emergence and emergence rate and synchrony were lower in FG than in IR, values in IR+FG being intermediate and similar to those for control plots. Shoot fresh weights, however, were greater from the IR+FG than from IR, FG or the control plots. Total shoot dry weights of wildflowers from 1 m2 subplots after 3 months were FG > IR = IR+FG > control, being respectively 8.4, 8.5, 5.1 and 1.1% those of total shoot dry weights of weeds.
Sandra L. Barbour, Margaret J. McMahon, John J. Frett, and Dennis R. Decoteau
Similarities exist between the effects of phytochrome and cytokinins on plant growth and development (e.g., chloroplast development, amaranthin synthesis. seed germination, photomorphogenesis). It is unclear, however, if and how these two systems interact.
As a beginning step to determine cytokinin-phytochrome interactions, we developed a strategy utilizing ipt -transgenic tobacco in phytochrome/light treatment investigations. The sour-cc of the ipt gene was Agrobacterium tumefaciens Ti plasmid 15955. This gene encodes for isopentenyl transferase which is an enzyme active in cytokinin biosynthesis.
Ipt -transgenic tobacco cultures (grown on MS medium supplemented with kanamycin but no plant growth regulators) were treated with end-of-day red or far-red light for 15 minutes. After 30 days of treatment, the plant tissue was harvested and either homogenized for SDS-PAGE or fixed for transmission electron microscopic analysis.
Results from immuno-gold labelling using polyclonal antibodies specific to iptase will he used to Indicate the influence of phytochrome on cytokinin activity. Also, structural changes at the ultra-cellular level will be determined.