The sporadic occurrence of Sclerotinia stem rot in soybeans often is attributed to the sensitivity of Sclerotinia sclerotiorum to environmental factors. Environmental sensitivity in soybean response to the pathogen also could contribute to the unpredictable nature of this disease. We used stability analysis to determine whether soybean cultivar response to S. sclerotiorum was sensitive to light and temperature. Five greenhouse experiments examined the response of seven cultivars to limited-term inoculation with S. sclerotiorum. The cultivars, selected at random from Pennsylvania variety trials, represented maturity groups grown in Pennsylvania and other states sharing that latitude. Photon flux density of photosynthetically active radiation (PAR) and temperature were recorded hourly and varied among experiments. Environmental sensitivity was detected in the response of five cultivars to S. sclerotiorum when individual cultivar disease ratings (assessed 6 days after inoculation) were regressed against the mean disease rating of each experiment. Stability analysis with temperature during the 48-h inoculation period as the environmental index found that all cultivars responded similarly to the number of hours that temperatures were <19 degrees C, 19 to 22 degrees C, or >22 degrees C. In contrast, cultivars separated into PAR-sensitive and PAR-insensitive groups when the environmental index was moles of PAR at a photon flux density >/=475 mumol m(-2) s(-1) during the inoculation period. The photon flux density of PAR on a cloudy day in the field is

Crownvetch (Coronilla varia L.) has been reported to contain antiquality constituents. Feeding trials were conducted to determine the feasibility of using the weanling meadow vole (Microtus pennsylvanicus) as a bioassay to assess the effects of these antiquality constituents on feed intake, body‐weight change, and ration digestibility. The feeding value of crownvetch forage was compared with that of alfalfa (Medicago sativa L.), birdsfoot trefoil (Lotus corniculatus L.), and sainfoin (Onobrychis viciaefolia Scop.) incorporated at 15% dry weight into a nutritionally adequate and balanced diet. Voles had lower intake and lost weight when fed crownvetch than when fed the other legume forages. No relationship existed between intake or weight loss and apparent digestibility. However, not all crownvetch forages resulted in lower intake and weight loss, and samples differed in their capacity to cause adverse vole responses from year to year. Voles also differed in their responses to forage fed from individual plants of the ‘Chemung’ cultivar. Low intake appeared to be the primary reason for the weight loss and death which occurred on many samples. The information presented indicates the presence of an antiquality constituent(s) in crownvetch forage that should be thoroughly investigated for its effects upon other animal species, especially rapidly growing monogastrics.

Increased use of land for “disposal” of industrial wastes and animal wastes such as poultry and swine manure from flocks and herds fed high levels of trace elements will require soil monitoring methods to maintain safe levels of these elements with respect to both crop production and the food chain. The objectives of this investigation were to: 1) measure Cu ion potentials, pCu, associated with minimum and maximum Cu ion activities for growth of corn (Zea mays L.) seedlings; 2) evaluate the influence of the chelator DTPA (diethylenetriaminepentaacetic acid) on plant uptake of Cu; and 3) relate pCu to uptake of Cu and other elements by single‐cross corn hybrids selected for genetic controlled accumulations of relatively high and low concentrations of leaf Cu. Two corn hybrids were grown in the greenhouse using solution cultures of varying pCu. Other essential elements were held constant in solution or supplied by frequent application to 100 g of soil supporting the plants above the solution. For the constantly aerated solutions, pCu, as calculated from formation constants of Cu‐DTPA complexes and pH and as measured with a Cu specific ion electrode, was biologically equivalent to those obtained for solutions devoid of DTPA. For both hybrids, root and top growth were reduced due to Cu toxicity when pCu was ≤ 5.78. A deficiency of Cu was associated with a pCu > 13. While Cu concentrations in plant tops increased with decreasing pCu for both hybrids, the hybrids were different as predicted from the performance of the parental inbred lines. At high levels of Cu (pCu of 5 to 7) hybrid differences and changes in plant concentrations of Cu with pCu in solutions indicated that plant composition could not be used to indicate toxic substrate levels of Cu.

Crownvetch, Coronilla varia L., is relatively self‐incompatible. Plants selected to represent the full range of self‐fertility of a large sample of C. varia L. ‘Penngift’ were used in greenhouse experiments to locate the site or sites of incompatibility of self‐pollinations. Pollen germination and pollen tube growth in pistils after self‐ and cross‐pollinations were observed employing UV fluorescence microscopy.Pollen germination on the stigma and pollen tube penetration of the style occurred within the first 12 hours after self‐ and cross‐pollination. Pollen tubes reached ovaries within 24 hours for both types of pollination.In one experiment, the average number of germinated pollen grains on stigmas was significantly higher after crossing than after selling. However, this relationship between the two types of pollination was not consistent over the plants studied. For most plants, pollen germination on stigmas after cross‐pollination was about twice that after self‐pollination. This suggested that self‐incompatibility existed on the stigma. In the second experiment, using a different pollen source, the average number of germinated pollen grains on the stigma after crossing was not significantly different from that after selfing and the site of incompatibility seemed to be in the style.Pollen tube behavior in the ovary was the same for selfing and crossing in both experiments. For selfing, less ovules matured as seed than were penetrated by pollen tubes. Thus, both fertilization failure and post‐fertilization ovule abortion could have affected the amount of seed set after selling.Pollen germination and pollen tube behavior were the same in flowers from excised stems and stems growing on plants.

Since crownvetch (Coronilla varia L.) does not flower under conditions conducive to flowering in alfalfa, (Medicago sativa L.), red clover (Trifolium pratense L.), and birdfoot trefoil, (Lotus corniculatus L.), four hypotheses were developed concerning flowering in this species. These included: (i) crownvetch requires exposure to cool or cold conditions (thermo‐induction) before flowering can occur; (ii) Thermo‐induction can occur under either long or short photoperiods, but long photoperiods are subsequently required for the initiation and development of floral primordia; (iii) A certain plant age is required before thermo‐induction can occur; and (iv) Crownvetch genotypes and cultivars differ in their need for thermoinduction. A series of field, greenhouse, and growth chamber studies indicated that all or nearly all 4‐ to 8‐week‐old plants of ‘Penngift’ crownvetch exposed to effective thermo‐inductive treatment (minimum temperatures of 10 or less for 12 to 15 hr per day) subsequently flowered in 5 to 7 weeks when tested under warm conditions (20 C or above) and long photoperiods (16 hr or longer). Plants weeks old when subjected to thermo‐inductive treatment required longer exposure (8 weeks) than 8‐week‐old plants, which required only 4 weeks of thermo‐inductive treatment. In these studies thermo‐induction occurred under both long (16‐ to 24‐hr) and short (9‐ to 12‐hr) photoperiods, but thermo‐induced plants flowered only when subsequently exposed to photoperiods of 15 hr or more. Nearly all 5‐ to 8‐week‐old plants of the cultivar Penngift could be thermo‐induced in 4 weeks. Plants of ‘Chemung’ and ‘Emerald’ cultivars needed to be both older (8 to 16 weeks) and thermo‐induced at 10 C or below for longer periods (8 weeks or more) for a comparable response. addition, some genotypes within different cultivars differed somewhat in their response to thermo‐inductive treatment. By using the above techniques, we were able to cause most plants of Penngift crownvetch to flower 13 to 16 weeks after seeding; plants of Emerald and Chemung, however, generally require 7 to 8 weeks longer.