engleski

Symptom expression of Citrus tristeza virus monophyletic isolates in Satsuma mandarin

Citrus tristeza virus (CTV) causes tristeza, one of the most damaging diseases of citrus. CTV isolates can be classified in several phylogenetic groups based on the coat protein (CP) gene sequence. Depending on the genotype, scion/rootstock combination and environmental conditions, CTV may induce the development of three syndromes: quick decline (QD), stem pitting (SP) and seedling yellows (SY). The aim of this study was to investigate the effect of different CTV genotypes on symptoms expression in Satsuma mandarins scions grafted on Poncirus trifoliata rootstock in greenhouse conditions, as this combination of plants is the most common in Croatia. CTV monophyletic isolates were molecularly characterized by SSCP-analysis of CP variants, separated by cloning, and sequenced. Six tested isolates, clustered to six different monophyletic groups (Gp:1, 2, 3a, 4, 5, M), were used for the infection of S. mandarin/P. trifoliata hosts. Infected plants were monitored for all changes that could be related to CTV infection. SP were observed in plants infected with Gp3a and Gp4, while those infected with Gp2 developed chlorosis, retarded growth and shortened internodes. The most severe reactions were associated with Gp3a and Gp4 isolates that displayed SP, and Gp2 that developed SY reactions. Although P. trifoliata is known as CTV resistant rootstock, our findings showed that some CTV isolates are able to break the resistance to symptom expression in S. mandarin/P. trifoliata combination.

CTV genotypes; disease symptoms; Poncirus trifoliata; Satsuma mandarin

ISSn 1848-5553