Ice encasement in timothy and cocksfoot - a possible screening method for application in breeding programs

Tronsmo Anne Marte, Svendsen S°lveRannsˇknastofnun landb˙na­arins, B˙na­arfÚlag ═slands, BŠndaskˇlinn ß Hvanneyri, Rannsˇknast÷­ SkˇgrŠktar rÝkisins, Tilraunast÷­ hßskˇlans Ý meinafrŠ­i, Vei­imßlastofnun1989ReykjavÝk


Frß vefstjˇra: Greinina Ý heild sinni er a­ finna Ý pdf-skjalinu hÚr a­ ofan


Methods used for testing ice-encasement tolerance of grasses in Norway are discussed. Results are presented from experiments where grasses are tested by the method described by Andrews and Pomeroy (1975) and others. The differences between cultivars were not significant because of considerable variation between replicates. The best procedure was very time consuming. The method is therefore of limited use in a breeding program for grasses. An improved method is under preparation.

Key words: breeding, cocksfoot, ice encasement, timothy, winter hardiness.


A­fer­ til mŠlinga ß svell■oli vallarfoxgrass og axhno­apunts Ý jurtakynbˇtum

Kynntar eru a­fer­ir til mŠlinga ß svell■oli sem reyndar hafa veri­ Ý Noregi. Lag­ar eru fram ni­urst÷­ur tilrauna ■ar sem svell■ol grasa er mŠlt samkvŠmt a­fer­ Andrews og Pomeroy (1975). Mismunur ß milli stofna var ekki raunhŠfur vegna ■ess hve mikil sveifla var ß milli endurtekninga. A­fer­in reyndist mj÷g tÝmafrek. A­fer­in er ■vÝ talin gagnslÝtil Ý kynbˇtaverkefnum fyrir gr÷s. Unni­ er a­ endurbˇtum ß a­fer­inni.


The main overwintering agricultural crop in Norway is perennial grasses. The mean annual cost of winter injuries in grasses was in 1985 estimated to be 100 millions Norwegian kroner (SNP utredning, 1988). In addition, there are frequent injuries in amenity grasses, but the cost has not been estimated. Resistance to winter injuries is therefore an important goal in our breeding program for grasses.

Artificial tests for resistance to factors causing winter injury can enhance the breeding progress. Norwegian grasses used for breeding are at present tested for resistance to freezing and to snow mould fungi. However, in north-western Norway, ice encasement is one of the most important factors causing winter injury and artificial testing for ice tolerance should be an important supplement.

To be useful in a breeding program for grasses, an artificial screening method has to be fast and simple; i.e. we must be able to handle at least 60 entries (populations, cultivars), each composed of 20 genotypes, in one test. It is obviously a fundamental prerequisite that such a method should be reliable. The main objection against the method applied earlier for testing ice tolerance (Larsen, unpublished), was that the results were not reproducible. As a possible alternative we adapted a method originally published by Andrews and Pomeroy (1975). Plants are hardened prior to testing for resistance to winter stress factors. As a part of the adjustment of this method to our plant material, the duration of the hardening period had to be determined. This report presents an investigation of ice tolerance in two cultivars of cocksfoot and four cultivars of timothy in four replicates at different times. The effect of 2 and 3 weeks hardening prior to ice encasement was compared to non-hardening.