Publications - Faculty - Recently Submitted Faculty Publications 2009

Grosser - Proc. Florida State Horticultural Society

Cultivar dependent gene transfer into citrus using Agrobacterium

M. Dutt, V. Orbović and J.W. Grosser

Abstract. Florida’s citrus industry is currently under severe onslaught from two non-indigenous but now endemic pathogens causing the diseases, Huanglongbing (HLB) and Citrus canker. None of the commercial cultivars are resistant to either disease, which results in severe losses to the industry. Genetic transformation of citrus, to incorporate gene(s) for disease resistance not found in citrus, is gaining importance due to the prevalence of these diseases. In an effort to transform a large number of cultivars via Agrobacterium mediated transformation, epicotyl explants of several citrus scion and rootstock cultivars were evaluated for their ability to incorporate transgenes into their genome. It was determined that genetic transformation efficiency depended on cultivar studied and the cultivars were either relatively easy to transform, moderately difficult or recalcitrant to Agrobacterium infection. In general, of the cultivars investigated, Carrizo and ‘Duncan’ had the highest transformation efficiency (over 40%), followed by ‘OLL8’, a Valencia like somaclone and ‘Hamlin’ (20-40%). Poncirus trifoliata, ‘Marsh’ and ‘Flame’ grapefruit and ‘Valencia’ sweet orange were moderately difficult (10 – 20%), while ‘Mexican Lime’, ‘Volkamer Lemon’, Citrus macrophylla and tangerines were recalcitrant (less than 10%). Our results also suggested that the final recovery rate of transgenics were significantly lower since the cultivars also varied in their ability to regenerate after in vitro grafting.