Comparative responses of three subtropical grasses to combined frost and prolonged chilling treatments simulating a New Zealand winter

Abstract

Mature plants of Paspalum dilatation, Cynodon nlemfuensis × C. dactylon selection Cy6-135, and Setaria sphacelata cv. Narok were transferred from outdoors in early winter to controlled environments, and either frosted (−1.5, −3.5°C) for 3 consecutive nights or not frosted. The plants were then either chilled at 13°/5°C (day/night) for 105 days or kept at 25°/20°C. Objectives were to determine if frost and chilling were lethal alone or in combination. Paspalum was not damaged by frost. Frosts of −1.5°C lightly damaged Cy6-135 and ‘Narok’, whereas −3.5°C frosts killed about 50 and 75% of their stem tissues respectively. Under chilling alone, paspalum and Cy6-135 gained dry weight and maintained leaf area; however, ‘Narok’ did not gain weight and leaf area decreased, although most plants survived. ‘Narok’ plants varied widely in chilling sensitivity. Paspalum and Cy6-135 survived all frost/chill combinations including −3.5°C frosts/chill under which Cy6-135 produced new shoots. Most ‘Narok’ plants survived −1.5°frosts/chill, but all died under −3.5°C frosts/chill. However, plants of ‘Narok’ survived the −3.5°C frosts/no chill combination. The poor survival of ‘Narok’ compared with Cy6-135 under −3.5°C frosts/chill was attributed to the relatively low chilling tolerance of ‘Narok’. It was concluded that under winter conditions in the North Island, frost and chilling stress can combine to kill C4 grasses and that high chilling tolerance is important for the survival of frost-sensitive grasses.

Keywords:

• C4 grass
• Paspalum dilatation
• Dallisgrass
• hybrid bermudagrass
• Cynodon nlemfuensis
• Setaria sphacelata
• ‘Narok’
• frost
• chilling
• tolerance
• stress
• survival
• winter killing
• reserves
• temperate climate
• subtropical grasses