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This article in CS

  1. Vol. 26 No. 6, p. 1099-1103
    Received: Oct 21, 1985

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Low Ribonuclease I Activity Prior to Cold Acclimation in Freeze Selected Winter Barley1

  1. D. G. Kenefick and
  2. T. K. Blake2



Etiolated 4-day-old shoot tissue of freeze-resistant winter barley (Hordeum vulgare L.) contains low ribonuclease I (EC activity compared to susceptible cultivars, an indigenous distinction found in nonacclimated tissue. The objective of this report was to determine if a shift in plant population caused by freeze selection resulted in changes in ribonuclease activity of leaf tissue. The RNA-degrading activity in tissue extracts was determined spectrophotometrically and by assays using disc polyacrylamide gel electrophoresis (PAGE) of tissue extracts. Increased freeze survival in hybrid lines and reduction of RNA-degrading activity were demonstrated by subjecting F5 plants to freeze selection. Extracts from tissue of the freeze-susceptible (‘Tennessee Winter’) cultivar contained higher total activity than was present in extracts from the freeze-resistant (‘Dicktoo’) cultivar for range of tissue ages. The prominent distinction between the cultivars in 20-day leaf tissue was a slowly migrating ribonuclease band found at the midpoint of gels containing extracts of the susceptible cultivar, which was essentially absent in the resistant cultivar. A consequence of selection for freeze resistance in winter barley was a reduction in variation of enzyme activity among plants within a cultivar and a lowering of activity. These data were consistent with results showing a selective shift from high to lower activity in composite extracts of shoot tissue grown from seed of unselected and freeze selected plants, respectively.

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