B‐genome derived resistance to Leptosphaeria maculans in near isogenic Brassica napus lines is independent of glucosinolate profile

Abstract

The role of the glucosinolate‐myrosinase system in resistance to Leptosphaeria maculans was studied by monitoring changes in glucosinolate profiles in leaf tissue surrounding the site of inoculation. Susceptible Brassica napus cv. Hanna, resistant B. nigra and near isogenic lines derived from interspecific hybrids between the two species were compared. Expression of myrosinase binding protein and presence of genetic markers were also assayed. No correlation between degree of resistance and amount of sinigrin or other aliphatic glucosinolates was found. However, in time course experiments the glucosinolate profile of the L. maculans inoculated plants differed significantly from the water‐inoculated control plants in the amount of 4‐methoxy‐glucobrassicin observed. Five to eight days post‐inoculation an increased level of 4‐methoxy glucobrassicin, ranging from 30% to 47% on average, was found in the inoculated plants, whilst controls varied between 7.6% and 9.2%. This increase was seen both in susceptible and resistant material. Other changes observed could mainly be assigned as effects of wounding. Although inoculation with L. maculans elicited changes in the leaf indolyl glucosinolate profiles, in the material studied, these changes could not be correlated to resistance against the fungus.

Leptosphaeria maculans Alters Glucosinolate Profiles in Blackleg Disease–Resistant and -Susceptible Cabbage Lines

“…MGBS levels have previously been reported to increase by 30–47% in response to L. maculans infection in Brassica napus after 5–8 days of inoculation (Wretblad and Dixelius, 2000 ). In an in vitro study, Mithen et al ( 1986 ) also reported anti-fungal activity for MGBS along with two other glucosinolates, SIN and GBS.…”

“…Nevertheless, no obvious relationship between glucosinolate profiles and L. maculans resistance has been established, possibly due to the fact that these studies focused on total glucosinolate levels rather than individual glucosinolate compounds (Mithen and Magrath, 1992 ; Giamoustaris and Mithen, 1997 ; Sexton et al, 1999 ; Kliebenstein et al, 2002 ). Previous studies concluded that the glucosinolate-myrosinase system is not a major determinant of blackleg resistance (Wretblad and Dixelius, 2000 ; Andreasson et al, 2001 ). This conclusion was supported by an earlier report in resynthesized B. napus F 2 progeny, in which disease resistance and glucosinolate profiles did not co-segregate (Mithen and Magrath, 1992 ).…”

Altered Glucosinolate Profiles and Expression of Glucosinolate Biosynthesis Genes in Ringspot-Resistant and Susceptible Cabbage Lines

“…The quantity of GSLs in leaf tissues is a result of concomitant activation of myrosinases (biosynthesis and catabolism), which can upregulate the contents of the GSL components at a specific time period. MGBS levels increased by 30–47% in response to Leptospharia maculans after 5–8 days of infection in B. napus [ 57 ]. In vitro studies have reported the antifungal activity of MGBS, as well as SIN and GBS [ 58 ] and increased accumulation of MGBS conferred moderate resistance in cabbage plants to L. maculans .…”

Altering glucosinolate profiles modulates disease resistance in plants

“…In vitro studies have demonstrated that ITCs can inhibit growth of fungal and bacterial pathogens (Brader et al, 2001;Manici et al, 1997;Mithen et al, 1986;Tierens et al, 2001). Earlier in vivo studies of disease resistance of Brassica napus cultivars bred for altered levels of GSs were not conclusive with respect to the role of the individual GSs (Giamoustaris and Mithen, 1997;Li et al, 1999;Wretblad and Dixelius, 2000).…”