EXTRACT VISCOSITY OF WINTER RYE - VARIATION WITH TEMPERATURE AND PRECIPITATION

Winter rye (Secale cereale L.) is well adapted to the Canadian prairie s and rye grain with low extract viscosity (EV) may become an importan t 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 grow n in thirteen environments on the Canadian prairies. The grain was stu died to determine the effects of precipitation and growing degree-days on EV. The amount of precipitation that plants received 5 wk immediat ely after heading (P-5wk) was closely associated with EV (r = -0.62 to -0.76). Growing degree-days accumulated in 5 wk after heading (GDD(5w k)) 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 d uring the periods from planting to heading or the whole growing season . For all genotypes tested, EV decreased rapidly with increase of P-5w k when P-5wk was below 140 mm. When P-5wk was greater than 140 mm, the response of EV to P-5wk was reduced. Genotypes were significantly dif ferent in the response of EV to P-5wk; the rate of change in EV with P -5wk was greater for some genotypes than for others as indicated by re gression slopes. For example, the genotype RT-150 had a regression slo pe five times greater than that of the genotype G-66S. Our study indic ated 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 re lative viscosity level for rye grown in different environments.