Changes in phenolic constituents of maize silk infected with Fusarium graminearum

Abstract

The concentration of phenolic compounds in the silks of five maize inbred lines ('CO272', 'F7', 'F2', 'A641', and 'CO266') of varying susceptibility to Fusarium graminearum was determined at three stages of silk development. The level of phenolic compounds in noninoculated silk tissue increased with silk development for only two of the inbreds. A suspension of F. graminearum spores was sprayed on the exposed silk of the same inbreds. Silk tissue collected from the silk channel 1 to 14 days after this inoculation was analyzed for phenolic compounds. The level of phenolic compounds increased relative to a water control in the most resistant line 'CO272' and decreased relative to water controls in susceptible lines. From thin layer chromatography of the phenolic extracts, flavones were the major phenolic compounds present. Five flavones were identified using high performance liquid chromatography: iso-orientin, iso-vitexin, maysin, luteolin, and apigenin. Key words: maize, corn, Fusarium graminearum, silk, phenolic, flavone.

Natural mechanisms for cereal resistance to the accumulation of Fusarium trichothecenes

“…Phenolic compounds have been shown to inhibit the in vitro growth and reproduction of a wide array of fungal genera (Guiraud et al 1995;Aziz et al 1998). Several reports suggest that resistance to Fusarium is correlated with kernel phenolic content in maize at maturity (Reid et al 1992;Assabgui et al 1993;Bily et al 2003) andwheat (McKeehen et al 1999;Siranidou et al 2002). In these studies, the phenolic compounds associated with FHB resistance are flavonoids (Reid et al 1992) and phenolic acids, especially ferulic and p-coumaric acid (Assabgui et al 1993;McKeehen et al 1999;Siranidou et al 2002;Bily et al 2003).…”

Inhibition of non‐enzymatic glycation by silk extracts from a Mexican land race and modern inbred lines of maize (Zea mays)

“…It is important to note that exposure to fungal pathogens (F. graminearum and/or U. maydis) enhances the production of active phenolic compounds in maize silk, particularly among more resistant inbreds (Reid et al, 1992). Furthermore, Reid et al (1992) demonstrated that phenolic levels in maize do not correlate with resistance to infection by F. graminearum when this fungus is not introduced.…”

“…Furthermore, Reid et al (1992) demonstrated that phenolic levels in maize do not correlate with resistance to infection by F. graminearum when this fungus is not introduced. It is therefore possible that, if maize silk is not exposed to fungal spores, fewer inducible phenolics will be produced and correspondingly less antiglycation activity will be observed.…”

“…Corn silk contains phenolic compounds of which flavonoids, such as luteolin and maysin, are abundant (Reid et al, 1992;Snook et al, 1989). In vitro glycation studies have identified flavones as the most effective inhibitors of AGE formation among flavonoids with luteolin being exceptionally active (Wu and Yen, 2005;Matsuda et al, 2003).…”

“…In addition to 13 inbred genotypes of maize, the study included a Mexican land race, Zapalote chico (ZC), whose maysin content in silk has been correlated with earworm resistance (Waiss et al, 1979). Moreover, the concentration of phenolic compounds in silk invaded by fungal spores has been inversely correlated with the plant's susceptibility to disease (Reid et al, 1992). For these reasons, it is hypothesized that antiglycation activity will vary among maize genotypes according to phenolic content and resistance levels of the silk, with genotypes of high phenolic content and resistance levels displaying the greatest antiglycation activity.…”