Regeneration of vascular tissues in relation to Fusarium wilt resistance of carnation

Abstract

Fusarium wilt-resistant 'Novada' carnations responded both to stem inoculation with a conidial suspension ofFusarium oxysporum f. sp. dianthi or E oxysporum f. sp. lycopersici and to root inoculation by planting in soil infected with E oxysporum f.sp. dianthi by means of a localization mechanism comprising gel formation in the xylem vessels and hyperplasia of adjacent parenchyma cells. Dye translocation experiments showed that xylem transport was limited by the presence of vascular gels, although wilting did not occur. Overcapacity of the vascular system apparently allowed for sufficient water transport to compensate for local vascular dysfunction. Also, vascular regeneration in the hyperplastic tissue next to occluded xylem vessels created new pathways for water transport to compensate for those lost by occlusion. Regeneration of xylem vessels was eventually followed by regeneration of xylem fibers, xylem parenchyma, cambium, and phloem cells.'Early Sam' carnations, susceptible to Fusarium wilt, responded to stem inoculation with E oxysporum f. sp. lycopersiciby similar localization of infection and vascular regeneration. Stem inoculation with E oxysporum f. sp. dianthi, however, resulted in colonization of the xylem vessels followed by lysis of the vascular tissues. Vascular gelation, hyperplasia of parenchyma cells, and vascular regeneration did generally not occur. However, if some hyperplasia occurred in attempted defence, some differentiation of hyperplastic cells into single xylem vessel elements was observed which only rarely resulted in complete vascular regeneration next to colonized xylem. In the absence of hyperplasia, differentiation of medulla parenchyma cells bordering destroyed vascular tissue into xylem vessel elements was even more exceptional. Apparently, vascular regeneration in carnation is a normal defence reaction to fungal invasion.

Verticillium Infection Triggers VASCULAR-RELATED NAC DOMAIN7–Dependent de Novo Xylem Formation and Enhances Drought Tolerance in Arabidopsis

“…This is reminiscent of the de novo xylem formation reported for carnations resistant to Fusarium wilt (Baayen, 1986). In this interaction system, nonfunctional xylem was also substituted by transdifferentiation of xylem parenchyma and pith cells into xylem cells, but this transdifferentiation was preceded by cell division.…”

“…A different strategy to substitute infected, nonfunctional xylem was described for wilt-resistant carnation (Dianthus caryophyllus) plants infected with the vascular pathogen Fusarium oxysporum f sp dianthi. In this interaction, xylem parenchyma and pith cells adjacent to obstructed xylem were described to undergo renewed cell division and subsequent differentiation into xylem (Baayen, 1986). These two anatomical studies provided early descriptive evidence for pathogen-induced developmental reprogramming of host plant vascular tissues and were interpreted as a compensatory response to maintain functionality.…”

Evaluation of the virulence of races 1, 2 and 4 of Fusarium oxysporum f.sp. dianthi in carnation

“…Resistance to Fusarium wilt was introduced by the Institute for Horticultural Plant Breeding (IVT), Wageningen as well as by carnation breeders in France, Italy and USA . The mechanism of resistance has been the subject of several histopathological studies (Baayen & Elgersma, 1985 ;Harling & Taylor, 1985 ;Baayen, 1986) . Parallel investigations were carried out on the spread and control of the fungus (Rattink, 1977(Rattink, , 1983) and on the variation within the population of the pathogen (Garibaldi, 1975(Garibaldi, , 1977Matthews, 1978) .…”

Slow wilting components in pigeonpea (Cajanus cajan(L.) Millsp.)

“…Major components of partial resistance seemed to be those that restrict the growth of pathogen on or within host tissues (Lancashire and Jones 1985). Localization of the wilt pathogen (F. oxysporum s. sp dianthi) in carnation was ascribed to occlusion of xylem vessels, gel formation and phytoalexins accumulation (Baayen and van der Plas 1992), and regeneration of vascular tissues (Baayen 2005), which directly or indirectly restrict pathogen growth, and the property varied by cultivar. In pigeonpea, it appears that wilt resistance is attributed to slow growth and localization of the pathogen.…”

“…Resistance components reflect underlying histological and physiological role on resistance mechanisms and they may be used as early selection criteria in resistance breeding (Baayen and van der Plas 1992). Resistance components against the important vascular wilt in carnation has been studied by Baayen et al(1991) and three resistance components, localization ability, latent period and wilting rate have been evaluated as early selection criteria (Baayen and van der Plas 1992;Baayen 2005). The prospect of increasing the level of partial resistance by combining apparently different mechanisms of resistance to provide a more stable protection against a pathogen seems attractive as a breeding strategy (Parlevliet and Kuiper 1985).…”