Skip to main content
ARS Home » Southeast Area » Byron, Georgia » Fruit and Tree Nut Research » Research » Publications at this Location » Publication #306982
Title: A standard area diagram set to aid estimation of the severity of Asiatic Citrus Canker on ripe sweet orange fruit

Author
item BRAIDO, RICARDO - University Of Maringa
item GONCALVES-ZULIANI, ALINE - University Of Maringa
item NOCCI, PAULA - University Of Maringa
item JANEIRO, VANDERLEY - University Of Maringa
item CARVALHO, SERGIO - Agronomical Institute Of Campinas (IAC)
item BELASQUE, JUNIOR - Universidad De Sao Paulo
item Bock, Clive
item NUNES, WILLIAM - University Of Maringa

Submitted to: European Journal of Plant Pathology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/2/2014
Publication Date: 10/11/2014
Citation: Braido, R., Goncalves-Zuliani, A.M., Nocci, P.T., Janeiro, V., Carvalho, S.A., Belasque, J.J., Bock, C.H., Nunes, W.M. 2014. A standard area diagram set to aid estimation of the severity of Asiatic Citrus Canker on ripe sweet orange fruit. European Journal of Plant Pathology. 141:327-337.

Interpretive Summary: Asiatic citrus canker (ACC) causes serious yield loss in many citrus-growing regions. Research is needed to develop accurate and reliable methods to measure the severity of ACC. The objective was to validate and compare two standard area diagram sets (SADs) as aids for raters to improve the accuracy and reliability of visual estimates of canker severity on ripe fruit of sweet orange (unripe fruit are green, and have slightly different symptoms compared to ripe fruit, warranting different SADs). A 5-diagram SAD set and a 6-diagram SAD set were compared and validated by 15 raters. Both SADs improved the accuracy and reliability of rater estimates. The 5-diagram SADs resulted in significantly more accurate and reliable estimates compared with the 6-diagram set, and is thus recommended for use. The SADs should have application for estimating ACC severity on ripe fruit of other citrus, including grapefruit.

Technical Abstract: Asiatic citrus canker (ACC) is a major disease of citrus in many tropical and subtropical citrus-growing regions. Severe disease can develop on the fruit, making it unmarketable. Research activities need accurate and reliable methods to measure the severity of citrus canker, most often estimated visually by raters. The objective was to validate and compare two standard area diagram sets (SADs) as aids for raters to improve the accuracy and reliability of visual estimates of canker severity on ripe fruit of sweet orange (unripe fruit are green, and have slightly different symptoms compared to ripe fruit, warranting different SADs). A 5-diagram SAD set (0.7, 2.0, 7.0, 21.0 and 39.0%) and a 6-diagram SAD set (0.7, 2.0, 4.0, 10.0, 21.0 and 39.0%) were compared; the 6-diagram set had an additional diagram in the most common severity range. Fifteen raters evaluated 40 images of cankered, unripe fruit. Both the 5- and 6-diagram SADs improved the accuracy and reliability of rater estimates. Agreement, measured by Lin’s concordance correlation coefficient ('c) was 0.735 to 0.906 when not using SADs, 0.931 to 0.985 when using 5-diagram SADs, and 0.879 to 0.979 when using 6-diagram SADs. Mean inter-rater reliability (R2) was 0.638 when not using SADs, 0.889 when using 5-diagram SADs, and 0.834 when using 6-diagram SADs. The 5-diagram SADs resulted in significantly more accurate and reliable estimates compared with the 6-diagram set, and is thus recommended for use. The SADs should have application for estimating ACC severity on ripe fruit of other citrus, including grapefruit.