The effectiveness of cell selection in vitro for development of drought-resistant plants was evaluated. Embryogenic callus was initiated from immature embryos of F1 hybrids Chi31 x Cateto S.G. and Chi31 x Tuxpeno Norteno, which had been produced by Dr. V.S. Shcherbak (Krasnodar Research Institute of Agriculture). The tolerant cell lines were isolated on MS medium supplemented with 25% PEG (6000), and plants were regenerated from the selected calli.

The drought-tolerance of regenerated plants (R0) and their progeny after self-pollination (R1 and R2) were tested using physiological methods. Since resistance to dessication and thermoresistance are the important components of drought resistance, the water retaining ability under drying and the rate of leaf damage under high temperature (50C) were determined. The water-retaining ability had been shown to correlate with drought tolerance (McCaig and Romagosa, Crop Sci., 31:1583,1991).

The R0 regenerants demonstrated less average water loss under drying than the initial plants. Plants with high and average water-retaining ability were prevalent among regenerants, and the most sensitive forms were eliminated (Fig.1). R1 and R2 were tested under drought at the 8 and 10-11 leaf stages, and during tasseling, 20-30 plants from the progeny of every regenerant were analysed. Average thermoresistance of the selected plants exceeded control values in all families of regenerants through all stages of ontogenesis. The water-retaining ability of R1 was increased in comparison with nonselected plants only during tasseling (Fig.2). Three best families analysed in R2 also demonstrated increased water-retaining ability and thermoresistance. Limits of variability of these traits among selected plants differed from controls (Table).
 

Plants	Water loss, %	Time damage appears, minutes
Chi x Cateto	11.8-29.5	5-15
R 2 # 90	13.1-23.1	9-26
R # 91	7.6-16.6	9-25
R # 119	7.3-13.4	4-24

While silking of the initial plants was delayed under drought, shedding and silking of the selected regenerants took place simultaneously.

Our results reveal that tissue culture of maize can be used for selection of drought-resistant plants.

Figure 1. Water loss under drought.

Figure 2. Water retaining ability and thermoresistance of R1 plants at tasseling.

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