Production of Sweet Orange Somaclones

A summary of tissue culture-derived plants of ‘Hamlin’ and ‘Valencia’ sweet oranges from various sources is provided in Table

9.1. Smaller populations of nucellar seedlings of each cultivar were also included in the study as a control and to

adventitious bud induction on DBA3 medium (Deng et al., 1992), and shoots were rooted on RMAN medium (Grosser and Gmitter, 1990). Plants were regenerated from protoplasts isolated from embryogenic callus or suspension cultures, or nucellar seedling leaves from somatic hybridization experiments requiring cybridization (Grosser et al., 1996), according to Grosser and Gmitter (1990). All grafted trees were planted in the fi eld between 1988 and 1990, split among four locations. Some trees began producing fruit during the 1993–94 season, and fruit quality data collection was initiated at this time. All clones were eval- uated by comparing Brix, acid and juice colour data measured by standard methods. Data from small representative fruit sam- ples (6–8 fruit per tree) taken over several years were used to make primary selections for more in-depth evaluation. For the past few years, larger samples (40–60 fruit per tree) from promising clones were run through the state-certifi ed FMC 091B State Test juice extractor located in the Citrus Research and Education Center (CREC) pilot plant to obtain more meaningful data. Pilot plant data from two or more seasons are provided for selected superior clones with consistent performance for altered traits. Recently, sensory analyses have been added as additional screening for clone selection. Properly conducted, this type of analysis can provide quantitative data with

Table 9.1. Summary of ‘Valencia’ and ‘Hamlin’ sweet orange somaclone trees in the fi eld.

provide an assessment of the natural varia-

tion possible in these cultivars. Regenerated sweet orange plants were budded to either Carrizo citrange, Swingle citrumelo or the precocious dwarfing ‘Hamlin’ + Flying Dragon somatic hybrid rootstock (Grosser et al., 1988) to expedite fruiting.

Cultivar

regenerated from secondary embryogenic callus cultures according to the method of Gmitter and Moore (1986). Organogenic- derived plants were regenerated primarily from nucellar seedling internodes via

Rootstocks: Carrizo citrange, Swingle citrumelo and ‘Hamlin’ + Flying Dragon somatic hybrid. Trees planted from 1988 to 1991. Most of the ‘Hamlin’ embryogenic plants were regenerated by

F. G. Gmitter, Jr.

respect to taste preference and acceptance, and introduces objectivity to discussions of flavour (Lawless and Heymann, 1998; Resurreccion, 1998). Clear clonal differ- ences in fl avour have been observed. All clones showing promise have been propa- gated for further evaluation, including col- lection of yield data.