Does the 'high sugar' trait of perennial ryegrass cultivars express under temperate climate conditions?

The objective was to evaluate water-soluble carbohydrate (WSC) and crude protein (CP) concentration of perennial ryegrass (PRG) cultivars with different genetic potential for producing WSC under two contrasting agronomic managements in temperate climate (southern Chile). A 4 x 2 factorial design was randomly allocated to 24 plots (31 m(2) each, three blocks): four PRG cultivars (diploid standard cultivar, '2nSt'; tetraploid standard cultivar, '4nSt'; diploid high sugar cultivar developed in New Zealand, '2nHSNZ'; and tetraploid high sugar cultivar developed in Europe, '4nHSEU') and two agronomic managements ('favourable,' defoliations at three leaves per tiller and nitrogen (N) fertilization rate of 83.3 kg N ha(-1 )year(-1); 'unfavourable,' defoliations at two leaves per tiller and N fertilization rate of 250 kg N ha(-1 )year(-1)). Herbage samples were collected in early spring, spring, summer and autumn. Concentration of WSC did not differ among cultivars in spring and summer, averaging 194 and 251 g/kg DM, respectively. The cultivar 4nHSEU had the greatest WSC concentration in early spring and autumn (187 and 266 g/kg DM, respectively) and the greatest CP concentration across samplings (average 230 g/kg DM). Favourable management improved WSC concentrations in early spring and summer and decreased CP in spring, summer and autumn. Annual DM yield did not vary with cultivar or management, averaging 8.43 t/ha. Within a 12-month study at one site in a temperate environment in southern Chile, PRG cultivars have not shown a consistent expression of the 'high sugar' trait, where a genetic x environment interaction might be operating.

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