To determine the effect of nitrous oxide on chromosome doubling in diploid red dover ( Trifolium pratense L.), excised heads were treated at 6 bars atmospheric pressure. Treatment commenced2 4 hours after crossing and continued for the following 24 hours. Of the plants which flowered, 71% were classified as tetraploid based on pollen size. Subsequent root‐tip and PMC chromosome counts of 136 of these plants revealed that 119 were tetraploid, 3 were diploid, and 12 were aneuploid. Two plants died before chromosome counts were made. The technique produced 49 and 79% tetraploids in T. alpestre L. and T. rubens L. respectively. The chromosome numbers of T. noricum Wulf. and T. pallidum Wald. and Kit. were successfully doubled also. Ease and frequency of chromosome doubling was considerably higher and production of mixaploids was lower than in previously‐reported colchicine treatments. The treatment was toxic to T. hirtum All. and T. heldreichianum Hausn.
A diallel cross involving 10 I 0 red clover ( Trifolium pratense L.) clones was evaluated for survival on two dates, total season yield in 1970, vigor, and days to first bloom on three different dates. General combining ability was the most important and the only significant source of genetic variance for all the characters. The additive genetic variance constituted 81% or more of the total genetic variance for each character. Nonadditive genetic variance may not be important enough to warrant production of hybrid red clover varieties, but other justifications exist. Parents for hybrids could be developed by selection and progeny testing, and little emphasis should be placed on examination of specific combinations among selected parents.
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Read moreTaylor, N. L., Ghabrial, S. A., Pederson, G. A., and McLaughlin, M. R. 1995. Quantification of yield benefits from incorporation of virus-resistant white clover germ plasm into grass-legume systems. Plant Dis. 79:1057-1061. The performance of the virus-susceptible white clover (Trifolium repens) cultivar Regal was compared in broadcast and spaced-plant plots with three experimental breeding populations (Southern Regional Virus Resistant synthetic [SRVR], Brown Loam Synthetic No 2 [BL Syn. 2] and Florida Experimental No. 4 [FL Exp. 4]) expressing varying levels of resistance to viruses endemic to forage legumes in the southeastern United States. The experimental plots were established with and without grasses in fields at Lexington, Ky., and Mississippi State, Miss., with the objective of comparing the magnitude of yield losses from virus diseases in spaced-plant nurseries with those in broadcast plots that more closely resemble farm conditions. Data from virus incidence in spaced plants in both locations indicated that SRVR had significantly (least significant difference, P = 0.05) lower incidence of peanut stunt virus (PSV) and clover yellow vein virus (CYVV) than Regal. Although significantly lower estimates of PSV and/or CYVV incidence were also obtained with BL Syn. 2 and FL Exp. 4 at some testing dates, there were little or no differences at others. Furthermore, higher estimates of PSV and CYVV incidence were determined for spaced plants grown in plots without grass than those with grass. Unlike PSV and CYVV, incidence of alfalfa mosaic virus was similar among treatments. Data on yield, stand, and virus incidence in broadcast plots closely paralleled those of spaced plants. Percentage of virus incidence in broadcast plots in Kentucky, however, was generally lower than that in the spaced plants. The overall data indicated that the performance of SRVR, based on yield (14 to 55% higher than Regal) and resistance to PSV and CYVV, was superior to the other germ plasms and suggest that without virus resistance improved white clover yields and persistence cannot be obtained.
Abstract A mixture of four squalestatins was separated and characterized by gradient‐packed capillary liquid chroma‐tography combined with dynamic liquid secondary‐ion mass spectrometry (LSIMS). Thioglycerol/glycerol matrix was added post‐column. Negative‐ion LSIMS was found to afford spectra typified by strong molecular ions with structurally informative fragments. The new method showed improvements in sensitivity and specificity for this class of compound when compared to existing thermospray methods.
Samples of red clover ( Trifolium pratense L.) pollen were cultured in vitro or analyzed for 21 amino acids. Pollen rated at more than 50% in germination capacity had about twice as much gamma aminobutyric acid, glycine, isoleucine, leucine, ornithine, serine, tyrosine, glutamic acid, and phenylalanirie and less proline than pollen which germinated at less than 50%. Supplements of proline, glycine, and alpha aminobutyric acid to the medium enhanced germination of pollen from plants grown in the greenhouse but not from plants grown in the field. Tube elongation of pollen from plants in the greenhouse and field was enhanced by proline and alpha or gamma aminobutyric acid supplements to the medium.
Read moreThe effects of inbreeding and heterosis in red clover ( Trifolium pratense L.) were investigated in two experiments. Objectives were to study the effects of one generation of selfing on pseudo‐self‐compatibility (PSC) and on seed and forage characteristics, and to ascertain the degree of hybrid vigor obtained and its relation to persistence in single crosses of I 1 parents. In the first experiment, five I 0 parental clones and four I 1 clones from each of the five parents were compared in spaced‐planted field plots for PSC, cross‐compatibility, florets per head, and heads per plant. In all characteristics, some inbred families contained clones which equalled or exceeded their non‐inbred parents. In the second experiment, a diallel cross was made among four I 0 clones, and another among four I 1 clones (one from each I 0 ). Plants from these crosses and from open‐pollinated seed of the four I 0 's, and three varietal checks were compared for yield and persistence in spaced‐planted field plots, which also included vegetative propagules of the four I 0 and four I 1 clones. Hybrid vigor was expressed in the I 1 single crosses, but their yields were no greater than the single crosses of the parental I 0 clones. I 1 clones yielded as much and were as persistent as I 0 clones, but both yield and persistence were less than other non‐inbred materials, except for the varietal checks and O.P.'s of I 0 clones. It was inferred that inbred parental lines may be maintained either by seed through PSC or by vegetative reproduction, and that yield and persistence lowered by selfing will be regained in single crosses.
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