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Increasing Stress Resistance by in Vitro Selection for Abscisic Acid Insensitivity in Wheat

Dep. od Agronomy, Kansas State Univ., Manhattan, KS 66506

^* Corresponding author.

Abscisic acid (ABA) concentration in wheat (Triticum aestivum L.) plants increases during heat and drought stress and is associated with stomatal closure, low photosynthetic rate, and senescence. This research was conducted to determine if wheat somaclones selected in vitro for ABA insensitivity are resistant to heat and drought stress and to identify traits that contribute to stress resistance as ABA insensitivity is increased. Five ABA-insensitive somadones and their parental line ND7532 were grown in Hoagland's solution until anthesis, then heat and osmotic stresses were applied through maturity. Heat stress was induced by increasing temperature from 25/20 to 35/25 °C, and osmotic stress (–0.05 MPa) was induced by adding 100 g kg^–1 polyethylene glycol-1000 (PEG-1000) to the hydroponic solution. An exceptional somaclone KTC86211 and parent ND7532 were grown in 1:1:1 sand: Reading silt loam (fine, mixed, mesic Typic Argiudoil):peat. Heat stress was applied as in the first experiment, and drought stress (–0.5 MPa) was induced by withholding water after anthesis and soil water potential was monitored with a thermocouple psychrometer. The ABA-insensitive somaclones KTC86211 and KTC86424 had significantly lower stomatal resistance, higher variable leaf chlorophyll fluorescence, longer leaf area duration, and greater kernel wt. and grain yield per plant than the parent in the first experiment. Crop growth rate, grain filling rate, and grain filling duration were higher in the ABA-insensitive somaclone KTC86211 than in ND7532 in the second experiment, indicating that greater grain yield per plant resulted from rapid assimilation and translocation of nutrients and delayed senescence. We concluded that ABA-insensitive genotypes may have high growth rates and long leaf area duration under stress and that selection for ABA insensitivity may be an effective approach to improving heat and drought resistance in wheat.

Received for publication May 16, 1988.

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