The Past and Potential of Parson Brown

Abstract

The Parson Brown is an early season sweet orange that was identified in 1875 by J.L. Carney and named as the Carney Parson Brown (CPB). As citrus groves throughout Florida were in serious decline from the effects of Huanglongbing (HLB), growers mentioned about certain rootstock and/or cultivars that seemed to exhibit varying levels of tolerance to HLB. One mentioned often in conversation was the Parson Brown sweet orange. These trees were observed to be productive with normal sized fruit and very little fruit drop even under endemic HLB conditions. We focused our efforts on understanding the mechanism of tolerance and emphasised on the Systemic Acquired Resistance (SAR) process. We identified the upregulation of the PR1 gene in all Parson Brown trees that were evaluated. Many of these trees also had the other SAR marker (PR2) in an enhanced state. These initial results were interesting since it potentially indicated that the Parson Brown trees have some sort of internal mechanism that allows them to better protect the trees against infection when compared to Hamlin, which is very susceptible to HLB.