EVALUATION OF NEW CITRUS ROOTSTOCKS FOR 'BEARSS' LIME PRODUCTION IN SOUTHERN FLORIDA.

Authors: CASTLE, WILLIAM - UNIVERSITY OF FLORIDA; Schnell Ii, Raymond; CRANE, JONATHAN - UNIVERSITY OF FLORIDA; GROSSER, JUDE - UNIVERSITY OF FLORIDA; GMITTER, FRED - UNIVERSITY OF FLORIDA; Ayala-Silva, Tomas; Bowman, Kim

Submitted to: Proceedings of Florida State Horticultural Society
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/20/2004
Publication Date: 7/1/2004
Citation: Castle, W.S., Schnell II, R.J., Crane, J.H., Grosser, J.W., Gmitter, F.G., Ayala Silva, T., Bowman, K.D. 2004. Evaluation of new citrus rootstocks for 'Bearss' lime production in southern Florida. Proceedings of Florida State Horticultural Society. 117:174-181.

Interpretive Summary: In the past, Tahiti lime (Citrus latifolia Tan.) production was important to the economy of south Florida. Before Hurricane Andrew destroyed the production area, Florida produced 95.3% of all the limes grown in the USA. The Florida lime industry has always consisted of some mixture of air-layered trees (marcots) and those propagated on a rootstock. From about 1930 through the 1960s the rootstock of choice was Rough Lemon. Rootstock trials were conducted at the University of Florida station in Homestead and they identified C. macrophylla (Alemow) as a replacement for Rough Lemon during the 1960s. These trials were discontinued and C. macrophylla remained the recommended rootstock for lime in south Florida for the next 40 years. The appearance of the brown citrus aphid (BrCA) has renewed interest in rootstocks because C. macrophylla is highly susceptible to citrus tristeza virus (CTV) that is spread very efficiently by the BrCA. CTV is the most important virus disease of citrus in the world. Severe strains of CTV have been reported that cause stem pitting, vein corking, and reduced productivity of limes. When the BrCA invades a new citrus area, such as has happened in south Florida, losses due to CTV increase in the years after the aphid becomes established. To develop new rootstocks two experiments were planted using 52 different rootstocks with a single scion. Unfortunately, both experiments had to be terminated early because of the discovery of Citrus Canker. Despite these early terminations some promising rootstocks were identified and these are listed in the report.

Technical Abstract: Two 'Bearss' lime (Citrus latifolia Tan.) trials were planted in Miami-Dade County to evaluate the performance of new rootstocks specifically selected for their potential on the highly calcareous limerock soils common to the area. The first trial consisted of two replications of 10-tree plots planted in 1997 with a grower-cooperator. There were 20 rootstocks including various sexual and somatic hybrids plus Rangpur (C. limonia Osb.) for comparison. Yield was measured three times over 2 years and the cumulative results ranged from <20 to nearly 160 lb of fruit/tree. The highest yielding trees were those on Volkamer lemon, Rangpur, C. ambylcarpa, HRS-801, and HRS-897. This trial was terminated and removed because of canker. The second trial of 52 sexual and somatic hybrid rootstocks was planted in 2001 at the USDA, Subtropical Horticulture Research Station, Miami, with six replications of single-tree plots. Yield and tree size were measured once in 2004 before further data collection was suspended by the appearance of canker. Most trees were about 6 to 7 ft tall and produced from <1 to about 11 lb of fruit/tree. Among the higher yielding trees were those on the commercial standard for comparison, C. macrophylla, some selections of C. limonia (including Rangpur), several somatic hybrids, and Volkamer lemon. Tree condition and appearance (canopy greenness) were rated as a single variable to express apparent differences in nutritional adaptation to the soil. Trees on macrophylla, HRS-801, HRS-812, HRS-897, several somatic hybrids, the C. limonia selections, Rangpur, rough lemon, and Volkamer lemon were among those with the best ratings.