Generation of transgenic citrus plants with the tolerance-to-salinity gene HAL2 from yeast

Soil salinity significantly limits citrus production in many areas worldwide. Carrizo citrange, considered an excellent citrus rootstock, is very sensitive to salt stress, which restricts its use in salty soils. We have successfully transformed plants of Carrizo citrange via Agrobacterium tumefaciens with the halotolerance gene HAL2, originally isolated from yeast and implicated in salt-tolerance mechanisms. Final selection of HAL2 transgenic plants was made on the basis of PCR data for the detection of HAL2 gene, instead of GUS expression assays, since integration of truncated portions of pB1121. HAL2 T-DNA fragment, where the left border (uidA cassette region) was lost, was probed to be very frequent. Ten regenerated plants, positive for HAL2 by PCR, were selected. The transgenic nature of these plants was confirmed by Southern and Northern analyses. This is the first time that a gene from yeast has been stably integrated and expressed in citrus plants.