EFFECT OF DEVELOPMENTAL STAGE OF WHEAT ON SEED GERMINATION AND DAMAGE BY RHYZOPERTHA DOMINICA F. DURING STORAGE.

The developmental stage of durum wheat (Triticum durum) may affect seed germination and seed damage by lesser grain borer, Rhyzopertha dominica F. (Coleoptera: Bostrichidae), which is considered a major pest damaging the quality of the stored seeds in Jordan. The objective of this experiment was to evaluate the effect of the developmental stage of durum wheat on seed germination and seed damage by R. dominica during storage. Spikes were harvested weekly at six developmental stages: 1) early milk stage (EML); 2) late milk stage (LML); 3) soft-dough stage (SD); 4) hard-dough stage (HD); 5) yellow-spike stage (Y) (physiological maturity); and 6) brown-spike stage (B) (harvest maturity). Seed standard germination and seed damage by R. dominica were evaluated for the air-dried seeds at harvest time and after an 18-month storage period. At harvest time, the standard germination of the seeds harvested at the early and late milk stages (<62%) was lower than the seeds harvested at the SD, HD, Y and B stages (>95%). The seeds harvested at all developmental stages had no damage by R. dominica at harvest time. However, the seeds harvested at the HD and Y stage had the highest seed germination (averaged 90%) after 18-month storage. As the seeds matured from the EML to SD stage, the percentage of normal seedlings in standard germination increased from 18% to 81%, respectively. The seeds harvested at the B stage had 0% germination. Only the seeds harvested at the B stage had 100% seed damage by R. dominica after 18-month storage. These results suggested that harvesting durum wheat at seed physiological maturity (Y stage) preserved seed germination and reduced seed damage by R. dominica after 18-month storage. Early harvest at physiological maturity can be a very useful practice to reduce durum wheat seed infestation by R. dominica. [ABSTRACT FROM AUTHOR]