Tomato: a crop species amenable to improvement by cellular and molecular methods

Tomato is a crop plant with a relatively small DNA content per haploid genome and a well developed genetics. Plant regeneration from explants and protoplasts is feasable which led to the development of efficient transformation procedures. In view of the current data, the isolation of useful mutants at the cellular level probably will be of limited value in the genetic improvement of tomato. Protoplast fusion may lead to novel combinations of organelle and nuclear DNA (cybrids), whereas this technique also provides a means of introducing genetic information from alien species into tomato. Important developments have come from molecular approaches. Following the construction of an RFLP map, these RFLP markers can be used in tomato to tag quantitative traits bred in from related species. Both RFLP's and transposons are in the process of being used to clone desired genes for which no gene products are known. Cloned genes can be introduced and potentially improve specific properties of tomato especially those controlled by single genes. Recent results suggest that, in principle, phenotypic mutants can be created for cloned and characterized genes and will prove their value in further improving the cultivated tomato.

Glyphosate-Resistant Soybean Cultivar Yields Compared with Sister Lines

Herbicide-resistant crops like glyphosate resistant (GR) soybean [Glycine max (L.) Merr.] are gaining acceptance in U.S. cropping systems. Comparisons from cultivar performance trials suggest a yield suppression may exist with GR soybean. Yield suppressions may result from either cultivar genetic differentials, the GR gene/gene insertion process, or glyphosate. Grain yield of GR is probably not affected by glyphosate. Yield suppression due to the GR gene or its insertion process (GR effect) has not been reported. We conducted a field experiment at four Nebraska locations in 2 yr to evaluate the GR effect on soybean yield. Five backcross-derived pairs of GR and non-GR soybean sister lines were compared along with three high-yield, nonherbicide-resistant cultivars and five other herbicide-resistant cultivars. Glyphosate resistant sister lines yielded 5% (200 kg ha21) less than the non-GR sisters (GR effect). Seed weight of the non-GR sisters was greater than that of the GR sisters (in 1999) and the non-GR sister lines were 20 mm shorter than the GR sisters. Other variables monitored were similar between the two cultivar groups. The high-yield, nonherbicide-resistant cultivars included for comparison yielded 5% more than the non-GR sisters and 10% more than the GR sisters

Decay of Re188

The gamma rays in Os188 following beta decay of 18-h Re188 have been studied using coincidence and directional correlation techniques. The results agree with the principal features of the decay scheme proposed by Johns et al.1). A number of new, weak transitions are observed and an additional level is proposed at 1.750 MeV. Directional correlation measurements were made on six cascades. From the directional correlation measurements, spins 2, 2, 0, 2, 0, 2 are assigned to the levels at 0.155 MeV, 0.633 MeV, 1.086 MeV, 1.461 MeV, 1.765 MeV and 1.941 MeV, respectively. The 0.478-MeV gamma ray is a dipole--quadrupole mixture with Q [less, double equals] 99%. The 0.828-MeV and 1.308-MeV gamma rays are pure dipole.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/32427/1/0000508.pd