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Extracts of pure cultures of Penicillium roqueforti isolated from toxic feed samples and of P. roqueforti NRRL 849 were lethal to rats by either intraperitoneal or oral administration. Purification studies guided by this test led to the isolation of a major toxin which showed intraperitoneal and oral median lethal dose values in weanling rats of 11 and 115 mg/kg, respectively. Partial characterization of the crystalline compound, C 17H2006, by infrared, ultraviolet, PMR, and mass spectroscopy, and by several chemical transformations indicated the presence of three C-methyl substituents plus one acetoxy, one aldehyde, and one a, a-unsaturated ketone group. Two oxygen atoms are present either in epoxide or ether form.

cDNA clones of the two non-allelic sucrose synthase (Ss) genes, Ss2 and Sh, have been isolated from λgt11 expression libraries derived from immature kernel poly(A)(+) RNA of sh-deletion and Sh/Sh genotypes of maize respectively. Recombinant clones containing the longest Ss2 and Sh cDNA inserts, each of approximately 2.5 kb size, were characterized and comparatively analyzed. Although the Sh cDNA insert expresses as a sucrose synthase-1 (SS1) β-galactosidase fusion protein (∼ 200 kD) in λ lysogens, the Ss2 cDNA failed to form such a chimeric protein and instead showed a ∼ 70 kD SS2 polypeptide. The Ss2 and Sh cDNAs as hybridization probes on RNA blots of immature kernels detected a larger Ss2 transcript (∼ 2900 b) than the Sh transcript (∼ 2750 b). Because SS1 and SS2 protein subunits are known to be of identical size, the significance of difference in transcript size is not apparent. A comparative restriction enzyme mapping of the two cDNA clones and a genomic Ss2 clone show sequence diversity over the entire lengths of Ss2 and Sh clones. Interestingly, restriction endonuclease sites around the 3' ends are more conserved than the 5' ends of these two genes. Genetic data indicate that the Ss2 locus is on chromosome 9 and molecular mapping using the Ss2 cDNA clone on recombinant inbred lines and B-A translocations stocks suggest that Ss2 is about 20 map units away from the Wx locus on 9L.

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Highly morphogenic callus cultures were isolated from stamens of a wild peanut species, Arachis paraguariensis. These cultures were initiated on modified N6 medium containing 0.2 mg 1-4amino-3,5,6-trichloro-picolinic acid (picloram) and 0.5mgl -l 6-benzylaminopurine (BAP) and were maintained on modified N6 medium with 0.008 mg 1-' picloram and 0.25 mg 1-i BAP. Buds formed on the calli growing on the maintenance medium developed into shoots when they were transferred to a MS salts based medium with no hormones. The cultures could also be maintained as a suspension culture in N6 liquid medium. When cell clumps larger tham 840/zm were collected from the suspension culture and transferred to MS medium without hormones, they formed shoots in liquid culture. Root formation rarely occurred in agar or liquid cultures. Therefore, grafting to stems of rooted seedlings was used to obtain plants from regenerated shoots. Eight out of 50 field grown plants produced viable seed.