Extract viscosity of winter rye: Variation with temperature and precipitation

Winter rye (Secale cereale L.) is well adapted to the Canadian prairies and rye grain with low extract viscosity (EV) may become an important component in animal diets. Information on how environmental factors affect EV is needed for facilitating the selection of low EV materials and production of low EV grain. Eleven winter rye genotypes were grown in thirteen environments on the Canadian prairies. The grain was studied to determine the effects of precipitation and growing degree-days on EV. The amount of precipitation that plants received 5 wk immediately after heading (P5wk) was closely associated with EV (r = −0.62 to −0.76). Growing degree-days accumulated in 5 wk after heading (GDD5wk) had a smaller but significant (P < 0.05) association to EV (r = 0.34 to 0.61). EV was not correlated with temperature or precipitation during the periods from planting to heading or the whole growing season. For all genotypes tested, EV decreased rapidly with increase of P5wk when P5wk was below 140 mm. When P5wk was greater than 140 mm, the response of EV to P5wk was reduced. Genotypes were significantly different in the response of EV to P5wk; the rate of change in EV with P5wk was greater for some genotypes than for others as indicated by regression slopes. For example, the genotype RT-150 had a regression slope five times greater than that of the genotype G-66S. Our study indicates that the critical growth stage when EV can be affected was after plant heading and that the amount of precipitation that plants receive during the period of 5 wk after heading can be used to predict the relative viscosity level for rye grown in different environments. Key words: Secale cereale, extract viscosity, pentosans, rainfall, degree-days, regression