Morphological, physiological and dormancy responses of three Vitis genotypes to short photoperiod

Dormancy is initiated by decreasing photoperiod or temperature in many woody species. We investigated the effect of photoperiod on the induction of dormancy in Vitis . Three genotypes ( Vitis riparia, Vitis spp. cv. Seyval Blanc and a F₁ hybrid V. riparia ×'Seyval Blanc']) were monitored for morphological and physiological dormancy responses during 6 weeks of short (8 h, SD) and long (15 h, LD) photoperiod treatments. V. riparia became dormant after 4 weeks of SD as indicated by several morphologic changes. Cane elongation ceased, terminal meristems began to abscise, and primary dormant buds failed to grow after pruning and returning to LD. There was also a pronounced decrease in bud water content in response to SD. 'Seyval Blanc', in contrast, maintained actively growing meristems with no terminal abscission throughout SD treatment, and little delay in budbreak after pruning and returning to LD. Moderate decreases in bud water content were observed after 6 weeks of SD treatment in 'Seyval Blanc'. F₁ plants displayed intermediate responses to SD treatment, but more closely paralleled that of the V. riparia parent. Growth cessation, terminal meristem abscission and absence of budbreak occurred in the F₁ after 6 weeks of SD. Ten percent discontinuous SDS-PAGE protein profiles demonstrated SD-induced changes in polypeptide accumulation. A 19-kDa polypeptide increased 2–3-fold in response to SD in all genotypes. A 17-kDa polypeptide appeared at 4 weeks of SD, and represented 2.5–5% of all proteins visualized on the gels by 6 weeks of SD. These increases in polypeptides appear to be a general response to SD. This experimental system with heritable morphological and physiological variations in SD responsiveness will be valuable for studying dormancy initiation and maintenance in Vitis .