Disease progression of Sclerotinia rot of carrot, caused bySclerotinia sclerotiorum, from shoot to root before and after harvest

Abstract

Sclerotinia rot of carrot, caused by Sclerotinia sclerotiorum, is an economically important disease that causes yield loss in stored carrots. To examine the relationship between infection of leaves in the field and disease development in roots, the histopathology of sclerotinia rot within carrot crowns was investigated. Petioles of mature greenhouse-grown carrots were inoculated with mycelium of S. sclerotiorum. Disease progression was monitored in carrots in the greenhouse and in carrots that were harvested and placed in cold storage at 4 °C. Disease progressed more rapidly through carrot crowns in storage than in carrots in the greenhouse, and this differential reaction was associated with changes in tissue response to infection. A thick layer of cells that stained red with safranin 0 and a zone of leaf abscission were observed at the base of infected petioles of carrots that remained in the greenhouse, and these responses were associated with restricted disease progress. Cellular staining occurred rarely and leaf abscission was not detected in carrots that were harvested and placed in cold storage. These results demonstrate a possible preharvest resistance response to S. sclerotiorum in carrot, which was absent in carrots that were harvested and placed in cold-storage conditions. This study contributes to an improvement in understanding of the differential development of this disease in carrots before and after harvest.Resume : La pourriture a sch~rote de Ia carotte, causee par Sclerotinia sclerotiorum, est une maladie importante sur le plan economique a cause des pertes de carottes entreposees qu'elle occasionne. Afin d'examiner Ia relation qui existe entre !'infection des feuilles au champ et !'incidence de Ia maladie sur les racines, on a etudie l'histopathologie de Ia pourriture a sclerote dans Ia couronne de Ia carotte. Des petioles de carottes matures cultivees en serre ont ete inocules avec du mycelium de S. sclerotiorum. La progression de Ia maladie a ete suivie chez des carottes cultivees en serre et chez d'autres qui avaient ete recoltees et entreposees a 4 oc. La maladie a progresse plus rapidement dans les couronnes des carottes entreposees que dans celles des carottes cultivees en serre, et cette reaction differentielle a ete associee aux changements dans Ia reponse des tissus a !'infection. Une epaisse couche de cellules, qui se colore en rouge au contact de Ia safranine 0, ainsi qu'une zone d'abscission des feuilles ont ete observees a Ia base des petioles infectes des carottes qui n'avaient pas encore ete recoltees. Ces reactions ont ete associees a une diminution de Ia progression de Ia maladie. La coloration cellulaire se produit rarement chez les carottes stockees dans un entrepot frigoritique. Quant a !'abscission des feuilles, on ne !'a pas observee sous ces memes conditions d'entreposage. Ces resultats demontrent une possible resistance de Ia carotte a S. sclerotiorum. au Stade de Ia prerecolte, resistance qui ne se manifeste pas chez les carottes soumises aux conditions de I'entreposage ...

Temperature adaptation in isolates of Sclerotinia sclerotiorum affects their ability to infect Brassica carinata

“…They concluded that temperature was not limiting to the disease. However, since then, temperature has been included as one of the variables in forecasting models for Sclerotinia diseases in several crops, including brassicas (Koch et al, 2007;Foster et al, 2008;Clarkson et al, 2014), although other models have excluded temperature and focused on moisture and inoculum levels (Twengstr€ om et al, 1998;Bom & Boland, 2000).…”

High Levels of CO 2 Induce Spoilage by Leuconostoc mesenteroides by Upregulating Dextran Synthesis Genes

“…severe spoilage. The postharvest soft rot of stored carrot roots is attributed to wellknown pathogens, such as Pectobacterium carotovorum (3)(4)(5), the fungus Sclerotinia sclerotiorum (6)(7)(8), and other microorganisms (9). We recently discovered an additional bacterium, Leuconostoc mesenteroides, responsible for deterioration of stored carrots (10).…”

Inoculum potential of Sclerotinia sclerotiorum sclerotia depends on isolate and host plant

“…In carrot, S. sclerotiorum has been reported in over 20 carrot-producing countries and affects both foliage and roots, causing substantial canopy die-back and subsequent crown rot (Jensen et al, 2008). This can also then lead to post-harvest epidemics in storage (Foster et al, 2008). Sclerotinia sclerotiorum also causes lettuce 'drop', where plants quickly wilt in the field due to infection of the stem base and lower leaf axils, followed by rapid rotting of the tissue (Young et al, 2004;Clarkson et al, 2014).…”