Pre-sowing Treatment for Improving Seed Quality in West African Rice Varieties: I. Seed Germination and Seedling Vigor

Abstract

Ten diverse modem West African rice varieties were exposed to six dry heat temperatures (40° C, 45° C, 50° C, 55° C, 60° C and control (32° C) for 24 hours and thereafter seed germination, speed of germination and seedling vigor were investigated. Dry heat temperatures significantly stimulated seed germination above the control. Temperatures of 40° C, 45° C and 50° C significantly promoted seed germination, seedling vigor and speed of germination of the rice varieties. Although heat intensities at 55° C and 60° C had no adverse effects on both seed germination and speed of germination, 60° C heat treatment specifically failed to increase seedling vigor. Dry heat temperatures generally promoted seed germination of TOx 4004 43-1-2-1 and WITA 12; speed of germination of ITA 230 and seedling vigor of BW348-1, ITA230, SIPI1692033, TOx 4004-43-1-2-1 and WITA 12. There was enhanced seed germination of WITA 12 at all the heat intensities except at 60° C. High dry heat temperatures (50° C, 55° C and 60° C) for 24 hours was suffICient to break seed dormancy that promoted seed germinatation in BW 348-1, WITA 1, CISADANE and WAB 189-B-B-B-Hl. Seed dormancy in ITA 230, WITA 12 and TOx 4004-43-1-2-1 was almost completely broken under natural conditions. BenefiCial carry-over effects beyond seed germination and vigor stages would need further investigations.

Keywords: Heat intensity. seed dormancy, seed quality, seedling vigor index

Tanzania J_Agric-Sc. (2007) Vol. 8 No.2, 149-160