Host plant resistance and linear furanocoumarin content of Apium accessions

Linear furanocoumarin contents and antibiotic resistance to Liriomyza trifolii (Burgess) were documented for Apium species being investigated in a celery breeding program. In no-choice tests, L. trifolii fed more, produced more offspring, and had the highest pupal and adult productivity on the widely planted cultivar 'Tall Utah' 52-70R (Apium graveolens L.). Antibiotic effects of the commercial cultivar 'Tall Utah' 52-70 HK and University of California families 87A-147 and 87A-338, derived from A. chilense Hook and Arn., were intermediate. Only A. nodiflorum (L.) Lag (accession 87A-236) did not allow survival beyond the larval stage. Concentrations of the carcinogenic and mutagenic linear furanocoumarins varied by location within plants (leaves usually greater than petioles), by specific compound (trend: psoralen less than xanthotoxin less than bergapten or isopimpinellin), and between accessions. A. nodiflorum had the lowest foliar levels of phototoxic furanocoumarins (11.8 micrograms/g fresh weight) and the best potential for use in the breeding program. Foliar levels of phototoxic furanocoumarins (psoralen, bergapten, and xanthotoxin) in plants 87A-147-3 (406 micrograms/g), 87A-147-2 (292.9 micrograms/g), and the family 87A-338 (265.9 micrograms/g) were 22.6, 16.3, and 14.8 times higher, respectively, than the concentration known to produce contact dermatitis (18 micrograms/g). Even with such variability in concentration, the foliar content of linear furanocoumarins (individually or total) and L. trifolii adult production were not correlated.     

Untersuchungen zum Einflufß von Aluminiumfosetyl auf den pflanzlichen Phenolstoffwechsel in den Pathogen-Wirt-Beziehungen Phytophtbora fragariae – Erdbeere und Bretmia lactucae - Salat

Investigations on the influence of aluminium ethyl phosphite on the plant phenolic metabolism in the pathogen-host-interactions Phytophthora fragariae - strawberry and Bremia lactucae - lettuce Aluminium ethyl phosphite exhibited pronounced preventive and very good curative activities. In strawberries, 4000 ppm of the compound affected an eminent protection against Phytophthora fragariae after root and leaf applications; the earlier the fungicide treatment was carried out, the more distinct was the control effect. Similar relations were established in the pathogen-host-interaction Bremia lactucae, in which 5000 ppm of the fungicide proved to be highly active following pre- and postinfectional applications. In both parasite-host-interactions, an enrichment of phenolics in consequence of a de-novo-synthesis in diseased plant tissue was observed only very late and exclusively, when fungicide and parasite had come together; inoculation on one hand or fungicide treatment on the other resulted in no remarkable effect. With great certainty, however, the augmentation of phenolics was not the cause, but rather the consequence of fungicidal efficiency which resulted in killing of the fungus and partial destruction of host tissue after direct influence of aluminium ethyl phosphite on the parasite itself. A clear proof for a main and causal evidence of aluminium ethyl phosphite-induced phenolics for protection of strawberries against Phytophthora fragariae and of lettuce against Bremia lactucae could not be furnished.