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ARS Home » Southeast Area » Byron, Georgia » Fruit and Tree Nut Research » Research » Publications at this Location » Publication #306976
Title: A comparison of resistance to Asiatic citrus canker among different genotypes of Citrus spp. in a long-term canker-resistance screening experiment in Brazil

Author
item CARVALHO, SERGIO - Agronomical Institute Of Campinas (IAC)
item NUNES, WILLIAM - Universidade Estadual De Santa Cruz
item BELASQUE, JUNIOR - Universidad De Sao Paulo
item MACHADO, MARCOS - Agronomical Institute Of Campinas (IAC)
item FILHO, JOSE - Federal University Of Parana Polytechnic Center
item Bock, Clive
item Abdo, Zaid

Submitted to: Plant Disease
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/18/2014
Publication Date: 2/1/2015
Citation: Carvalho, S.A., Nunes, W.M., Belasque, J.J., Machado, M.A., Filho, J.C., Bock, C.H., Abdo, Z. 2015. A comparison of resistance to Asiatic citrus canker among different genotypes of Citrus spp. in a long-term canker-resistance screening experiment in Brazil. Plant Disease. 99:207-218.

Interpretive Summary: Asiatic citrus canker (ACC) is an important disease in Brazil and elsewhere in the world where citrus is grown. A 6-year study in Paraná State, Brazil, was conducted to compare the susceptibility of 186 genotypes of citrus representing sweet orange (C. sinensis (L.) Osb.), mandarin (C. reticulata Blanco), mediterranean mandarin (C. deliciosa Ten.), clementine mandarin (C. clementina hort. ex Tanaka), satsuma mandarin (C. unshiu Marc.), sour orange (C. aurantium L.), lemon (C. limon (L.) Burm), sweet lime (Citrus aurantifolia (Christim.) Swingle), grapefruit (C. paradisi Macfad), and four hybrids (C. reticulata x C. sp., C. reticulata x C. paradisi, C. reticulata x C. sinensis, and C.unshui x C. sinensis). The most resistant species included Satsuma and lemon genotypes, and the most susceptible grapefruit and sweet lime. Genotypes of Mandarin, sour orange, Mediterranean mandarin and sweet orange had intermediate severity. None of the genotypes were immune to ACC. These results of the relative susceptibility of different citrus genotypes can be used in future research, and to assist in varietal selection or for breeding purposes both within Brazil and other locations where ACC is an issue.

Technical Abstract: Asiatic citrus canker (ACC) is caused by Xanthomonas citri subsp. citri. The disease results in yield loss and renders fruit unfit for the fresh market. A 6-year study in Paraná State, Brazil, was conducted to compare the susceptibility of 186 genotypes of citrus representing sweet orange (C. sinensis (L.) Osb.), mandarin (C. reticulata Blanco), mediterranean mandarin (C. deliciosa Ten.), clementine mandarin (C. clementina hort. ex Tanaka), satsuma mandarin (C. unshiu Marc.), sour orange (C. aurantium L.), lemon (C. limon (L.) Burm), sweet lime (Citrus aurantifolia (Christim.) Swingle), grapefruit (C. paradisi Macfad), and four hybrids (C. reticulata x C. sp., C. reticulata x C. paradisi, C. reticulata x C. sinensis, and C.unshui x C. sinensis). Sweet orange (C. sinensis (L.) Osbeck) was represented by the most genotypes (141). The number of lesions per leaf was assessed eighteen times from 2005 to 2010 (up to 4 times per year). The data were analyzed using mixed model analysis of fixed and random effects, which showed a total of six resistance-susceptibility groupings of species and hybrids. The most resistant species grouping included Satsuma and lemon genotypes (mean lesions per leaf of 4.32 and 4.26, respectively), and the most susceptible grapefruit and sweet lime, with 14.84 and 10.96 lesions per leaf, respectively. Genotypes of Mandarin, sour orange, Mediteranean mandarin and sweet orange had intermediate severity (5.48 to 9.56 lesions per leaf). The hybrids also showed a range of ACC severity, but all were in the more resistant groupings (5.26 to 7.35 lesions per leaf). None of the genotypes were immune to ACC. The most resistant genotype was Muscia (C. reticulata), and the most susceptible Valencia Frost (C. sinensis) (1.86 and 14.78 lesions per leaf, respectively). Approximately one-sixth of the genotypes showed a negative relationship of mean lesions per leaf with time, suggesting increasing resistance as they aged, either due to a reduction in new flush or plant size and structure. These results of the relative susceptibility of different citrus genotypes can be used in future research, and to assist in varietal selection or for breeding purposes both within Brazil and other locations where ACC is an issue.