Reaction to phytotoxins in a potato population derived from mesophyll protoplasts

Abstract

Alternaria solani, the causal agent of early blight disease in potato, produces two host-specific, li idlike toxins in culture. Both compounds are required in tgie leaf bioassay for the elicitation of typical early blight symptoms, but the compounds are individually inactive. The procedures for the preparation of both compounds are outlined. These compounds can be used effectively to select for toxin-insensitive and sensitive clones of a Russet Burbank potato cultivar that have been regenerated from single mesophyll protoplasts. Furthermore, both sensitivity and insensitivity to the toxins in these clones is well correlated with susceptibility and resistance to A. solani. Potato clones that have been produced by somatic cell regeneration techniques maintain their reaction type to these fungal toxins for at least two generations of vegetative propagation. The genetic basis for this variation among these potato clones remains to be explained.Alternaria solani (Ell. and Marten) Jones and Grout is the causal agent of early blight of potato and is recognized in many areas of the world as a limiting factor in potato production. The disease is characterized by the appearance of sunken necrotic spots on the leaves, which enlarge to dark blotches (possessing a typical target design), usually surrounded by a chlorotic area. Earlier workers (1) supposed that A. solani produced a toxin that would cause some or all of the symptoms associated with the disease. Brian et al. (2) described alternaric acid as a phytotoxic compound in cultures of A. solani, and subsquently numerous other toxic products have been isolated from various species of Alternaria (3). While certain of these compounds possess broadly based plant toxicity (3), others-such as the host-specific toxin from A. alternata (4), the A. kikuchiana toxin (5), and the A. malh toxin (6)-are extremely host specific. To date, no host-specific toxins (3) have been isolated from A. solani. This report describes isolation procedures for the hostspecific A. solani toxins and provides evidence that at least two compounds are required for the elicitation of the chlorotic and necrotic symptoms typically associated with the early blight disease.Russet Burbank is the oldest and the most widely grown potato cultivar in the United States. Unfortunately, this cultivar, along with many other potato cultivars, does not possess a high level of resistance to important potato diseases, including early blight. Not only has it been difficult to obtain genetic resistance through classical breeding techniques, but also growers are generally reluctant to accept new potato cultivars for production. The successful regeneration of potato plants from single mesophyll protoplasts by Shepard and Totten (7) may offer an alternative, namely intracultivar improvement without the requirement for plant breeding procedures. This notion was made possible by the finding that, while the majority of the several hundred regenerated potato plants appeared to express a "normal" phenotype, there was also...

Wheat plants regenerated from embryo cell cultures.

“…With wheat (Triticum aestivum), only a very few plants have been obtained sporadically from wheat cultures derived from various organs (Shimada et al 1969;Dudits et al 1975). Stable, regenerated plants in wheat should be possible, since disease-resistant plants of maize (Gengenbach et al 1977) and potato (Matern et al 1978), and herbicide-resistant plants of tobacco (Chaleff and Parsons 1978) have been obtained by tissue culture techniques.…”

Effect of Phytophthora Parasitica Var Nicotianae (Race 0) Culture Filtrate on Direct Organogenesis in Tobacco Stem Explants

“…Mycelial plugs (10 mm in diameter) of the isolate of Ppn grown on oatmild agar were placed in 500 ml flasks, containing 100 ml specific liquid medium that is suitable for most Phytophthora species (10). The flasks were kept in incubator at 28 oc in dark for 14 days.…”

The Structure of Zinnolide, a New Phytotoxin from Alternaria solani

“…The IR spectrum showed absorption bands at 3200 cm -1 due to a hydroxyl group and at 1720 cm -1 due to a carbonyl group and at 1600 cm -1 due to a phenyl group. 3.90 (3H, s) attributable to a methoxyl group, it was deduced that the phytotoxin had a closely related structure to that of zinniol (2), which has been isolated from the phytopathogenic fungus Alternaria zinniae. SI Extensive comparison between zinnolide (1) and zinniol (2) by the 'H NMR spectrum revealed that two hydroxymethyl groups in 2 were completely missing in 1. fnstead, the presence of a lactol moiety (15 6.60, IH, O-CHOCO) was deduced in zinnolide 2.…”

“…3.90 (3H, s) attributable to a methoxyl group, it was deduced that the phytotoxin had a closely related structure to that of zinniol (2), which has been isolated from the phytopathogenic fungus Alternaria zinniae. SI Extensive comparison between zinnolide (1) and zinniol (2) by the 'H NMR spectrum revealed that two hydroxymethyl groups in 2 were completely missing in 1. fnstead, the presence of a lactol moiety (15 6.60, IH, O-CHOCO) was deduced in zinnolide 2. In fact, reduction of 1 with LiAIH4 in ether afforded a diol, whose spectral data were completely identical with those of authentic (2) in all respects.…”

“…(1) to zinniol (2). To a solution of zinnolide (20 mg, 0.072 mmol) in anhydrous ether (0.4 ml) was added dropwise a suspension of LiAIH4 (8 mg, 0.211 mmol) in anhydrous ether (0.1 ml), and the mixture was refluxed for 4 hr under a nitrogen atmosphere.…”