Microspore culture was performed as previously described by Lu et al. (2008). Briefly, the collected spikes were subjected to cold pretreatment at 4 ?C for 2 weeks, and the microspores were collected by crushing the anthers from the sterilized spikes. The collected microspores were isolated by filtration and centrifugation, and finally cultured on the induction medium (N6 basal medium supplemented with 2.0 lM 2.4-D, 2.3 lM KT, and 0.25 M maltose) for embryogenic callus induction. The isolated microspores cultured on the induction medium were used as control group (Control group), and those cultured in the medium containing 500 mg L -1 NaCl were designed as salt-treated group (Salt group). Four biological replicates were prepared for each groups. The microspores in each biological replcate were isolated from at least 20 donor plants, and equally divided into two parts used for two groups. After 21 days of culturing, the formed embryogenic calli in each dish (one
replicate) were separated from liquid culture medium and
measured to calculate the callus yield per dish. Small
amount (*30 mg) of embryogenic calli were collected into
tubes by snap frozen in liquid nitrogen and then stored at
-80 ?C for RNA isolation. The remaining embryogenic
calli were weighed again and transferred to differentiation
medium(MS basal medium supplemented with 2.2 lM
6-BA,7.0 lM KT, 0.25 lM NAA and 83.3 mM maltose) as
described by Lu et al. (2008) for plant regeneration (without
salt treatment). The numbers of green plants per dish were
counted after 1 month of culturing