Screening for resistance to Diaporthe toxica in lupins by estimation of phomopsins and glucoseamine in individual plants

Abstract

Immunological and biochemical assays were developed for screening for resistance to Diaporthe toxica in individual plants of narrow‐leafed lupins (Lupinus angustifolius). The former was an enzyme‐linked immunosorbent assay (ELISA) for measuring phomopsin mycotoxins and the latter gave an estimation of glucoseamine in infected stem pieces. Stems of L. angustifolius seedlings were inoculated with conidia from D. toxica cultures and, as expected with this latent disease, remained symptomless for 21 days after inoculation. At this time, phomopsins were measured in excised stems that had been incubated for 6 or 8 days to allow mycelial growth from latent infection structures, thereby increasing the phomopsins to detectable levels in individual plants. The estimation of glucoseamine was carried out on the same stems that had been assayed for phomopsins. The method was based on the alkaline deacetylation of chitin to chitosan, the glucoseamine residues of which are de‐aminated with nitrous acid, yielding an aldehyde which is determined colorimetrically. At six days after excision, both tests clearly distinguished the very resistant, resistant, intermediate and susceptible lines and they may be useful in large‐scale resistance screening in lupin breeding programmes. The ELISA of phomopsins is easier to use and would be particularly useful in the elimination of susceptible plants and those plants expressing intermediate levels of resistance during early generations of the breeding programme.

Evaluation of Daphne Germplasm for Resistance to Daphne Sudden Death Syndrome Caused by the Soil-borne Pathogen Thielaviopsis basicola

“…For example, Nicotiana glauca Graham was identified as resistant to T. basicola and subsequently incorporated into a tobacco (N. tabacum) breeding program (Trojak-Goluch, 2005). In another germplasm screen, Gossypium arboreum L. PI 1415 was found to be resistant to T. basicola and subsequently incorporated into a diploid cotton-breeding program (Berbec and Berbec, 1976;Shankara and Cowling, 1999;Wheeler et al, 1999). Based on these reports, evaluating Daphne germplasm for resistance to DSDS, through controlled screens, is a reasonable approach to identify host plant resistance to this pathogen.…”

Growth and toxin production of phomopsin A and ochratoxin A forming fungi under different storage conditions in a pea (Pisum sativum) model system

“…The present study does not find a direct correlation of growth and toxin formation as growth (measured by numbers [CFU/g]) declined around day 7, but PHOA production was still increasing. Both Lanigan et al ( 1979 ) in liquid media, and Shankar et al ( 1999 ) in lupine plant parts taken from latently infected plants, also found that PHOA production by P. leptostromiformis , similarly to A. westerdijkiae ’s OTA production, did not correlate well with mycelium growth.…”

Scientific Opinion on the risks for animal and public health related to the presence of phomopsins in feed and food

“…As well as displaying toxicity in mammalian species, phomopsin A has also been shown to have phytotoxic properties, presumably also due to its anti-microtubule action, and the phomopsins are likely to have evolved in some Phomopsis species to facilitate colonisation of host plants (Edgar, 2004). For example, resistance of lupin cultivars to colonisation by D. toxica correlated with the level of phomopsins found in lupin seedlings six days after inoculation with the fungus (Shankar et al, 1999). More than 60 species of Phomopsis are pathogenic on host plants of economic importance (Uecker, 1988).…”