INFLUENCE OF KERNEL POSITION, MECHANICAL DAMAGE AND CONTROLLED DETERIORATION ON ESTIMATES OF HYBRID MAIZE SEED QUALITY

During hybrid maize seed production, seed quality may be adversely aff ected by mechanical damage and subsequent storage. Two types of mechan ical damage, impact and abrasion, were imposed upon seedlots composed of kernels from apical, middle or basal positions on the cob. Damage t reatments were followed by a one or three week period of controlled de terioration. After deterioration, seed quality estimates of the seedlo ts damaged by impact were reduced compared with the quality estimates of the seeds damaged by abrasion re gardless of kernel position. By co ntrast, evaluation of damage by the Fast green stain test revealed mor e seeds damaged by abrasion in the 'severe' category than seeds damage d by impact. Viability and vigor of large, flat mid-position kernels g enerally exceeded that of small, round apical- or large, round basal-p osition kernels in terms of increased warm germination values, seedlin g dry weights and lower shoot/root ratios at each level of damage and controlled deterioration period. The damage to internal tissues due to impact. although less readily visualized than abrasion of seed coat, resulted in greater reductions in germination particularly following a n extended period of controlled deterioration.