The possibility of spreading Leptosphaeria maculans and Leptosphaeria biglobosa by rapeseed seed

Abstract

Stem canker (blackleg) is economically the most important disease of oilseed rape world­wide. This disease is caused by two species of pathogenic fungi of the genus Leptosphaeria: Leptosphaeria maculans (Desm.) ces. and de Not anamorf Phoma lingam (Tode. Fr.) Desmas, that causes stem canker and blackleg root and Leptospaeria biglobosa Shoem and Brun, that causes symptoms such as cancers of the upper part of the stem usually causing less damage, and can cause serious damage in countries with higher summer temperatures. Pathogenic fungi from one area to another are transmitted by ascospores and contaminated (infected) seed. In order to prove the modes of transmission of parasites, the test is done transmitting the parasite by seeds. Disinfected seeds of oilseed rape cultivars Quinta were submerged in the suspension of pycnospores. Submerged seeds were kept at 20 º C ± 1 º C and 12 h photoperiod for 48 h. After planting in plastic containers seeds were kept at 25 º C ± 1 º C and 12h photoperiod. In this experiment the following isolates were used: C-5, L-5, K-7, LJ-3, S-11, St-1, GS-3 and Lm as a reference isolate (L. maculans) fol­lowed by K-113, K-115 and Lb as a reference isolate (L. biglobosa). The symptoms were as­sessed after 7 and 14 days after emergence. Ratings were made with + which meant visible symptoms on cotyledons or hypocotyl and - what referred to healthy plants. After 7 days, the isolates (Lm, C-5, L-5, K-7, LJ-3, S-11, St-1, GS-3) were caused disease symptoms on plants of oilseed rape. This pathogenicity is reflected in the number of seedlings, leaf spots and stalk lodging cotyledons. At izolate Lb (reference isolate L. biglobosa) K-113 and K-115 after 7 and 14 days was not observed pathogenicity on rapeseed plants. The control variety seeds were soaked in distilled water. The trial was set in 6 reps, and pathogenicity of fungal isolates in relation to the control was tested using Dunette's test. After 14 days re-isolation of pathogen was done.

Rak stabla (crna noga) je najznačajnije oboljenje uljane repice širom sveta. Bolest mogu prouzrokovati dve vrste patogenih gljiva iz roda Leptosphaeria: Leptosphaeria maculans (Desm.) ces. i de Not, anamorf Phoma lingam (Tode. Fr.) Desmas, koja prouzrokuje rak stabla i crnu nogu na korenu i Leptospaeria biglobosa Shoem and Brun, koja prouzrokuje simptome slične raku ali na gornjim delovima stabla obično prouzrokujući manje štete. Ozbiljnije štete mogu nastati u zemljama sa višim letnjim temperaturama. Patogene gljive se iz jedne oblasti u drugu prenose askosporama i zaraženim semenom. Da bi se utvrdili načini prenošenja parazita testirana je mogućnost prenošenja semenom. Dezinfikovano seme uljane repice, kultivara Quinta je potopljeno u suspenziju piknospora. Ovakvo seme je držano na 20ºC ± 1ºC i 12h fotoperiodu tokom 48 sati. Posle setve seme je preneto u plastične posude a temperatura čuvanja je bila 25ºC ± 1º C i fotoperiod od 12h. U ovom eksperimentu korišćeni su sledeći izolati: C-5, L-5, K-7, LJ-3, S-11, St-1, GS-3 i Lm kao referentni izolat (L. maculans) kao i K-113, K-115 i Lb kao referentni izolat (L. biglobosa). Ocena prisustva simptoma je rađena posle 7 i 14 dana od nicanja. Sa znakom + su se obeležavale biljke sa vidljivim simptomima na kotiledonima ili hipokotilu a znakom - biljke bez pojave simptoma. Posle 7 dana izolati Lm, C-5, L-5, K-7, LJ-3, S-11, St-1 i GS-3 su izazvali simptome bolesti na biljkama uljane repice. Patogenost se ogledala kroz broj oštećenih klijanaca, lisnih pega i povijenih kotiledona. Kod izolata Lb (referentni izolat L. biglobosa) K-113 i K-115 posle 7 i 14 dana nije primećena patogenost na biljkama uljane repice. Kontrolna varijanta semena je potapana u destilovanu vodu. Ogled je postavljen u 6 ponavljanja, i patogenost izolata gljive u odnosu na kontrolu je izražena Danetovim testom. Posle 14 dana izvedena je ponovna izolacija patogena.