Reproductive growth is less sensitive to water deficit than vegetative growth. For this purpose, the main aim of this study is to find out the effects of early water deficits on vegetative and generative development of Merlot/SO4 grapevines. This research was carried out in ECOTRON System, Montpellier - SupAgro/INRA, 03°51’22’’ E and 43°37’04’’ N and 40 m altitude. The stressed period was started in the 17th E-L stage on the second week of May and stopped in 27th E-L stages on the second week of June. Four stress groups were established which were; well watered WS0 as a control (4 L day-1), second was WS1 (3 L day-1) third was WS2 (2 L day-1) and the fourth was WS3 (1 L day-1) respectively. A randomized complete block design was used and treatments were compared using LSD test to determine the significant differences. In water deficit treatments yellowing of the leaves and partial leaf fall at the shoot bases were observed at WS2 and WS3plants. Final measurements of shoot lengths showed about 60 cm differences between control and stressed grapevines. Shoot elongation was suppressed linearly to increase water deficit. When the average cluster weights and yield per vine in the control were compared with WS3 about 50% reduction was found. It can be stated that the most sensitive period was between 17th and 27th Eichhorn and Lorenz phenological stages which negatively affect the yield of Merlot cv.
Key words: Merlot, early water deficit, growth, cluster weight, shoot elongation.
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