Grapes (Vitis sp.) are commercially important both as a table fruit and a processed fruit for raisins, juice, jams, and wine. Weather patterns around the world are changing and there is a need to breed new adapted cultivars of a variety of traditional crops, including grapes. There are predictions for dramatic reductions in suitable wine grape acreage in the United States—up to 81% by the late 21st century (White et al. 2006).
Grape seeds have physiological dormancy and usually require 3 to 4 months of chilling stratification to relieve dormancy (Baskin and Baskin 2014; Davies et al. 2018; Lin et al. 2009; Schopmeyer 1974). Although 3 to 4 months of stratification is usually successful in promoting high germination percentages (Ellis et al. 1983; Wang et al. 2009), several studies have shown variable and lower germination percentages after stratification in certain grape types (Selim et al. 1981; Singh 1961). Gan et al. (2008) demonstrated that stratification requirements for high germination percentages could be as long as 6 months, depending on genotype.
Seed germination is an important step in traditional breeding programs as well as accelerated crop breeding programs using novel genetic approaches for crop improvement. Extending the time between genetic crosses to seedling production decreases breeding efficiency. One obvious issue is the extended stratification periods required in many woody perennial fruit crops, such as the 3 to 4 months observed in grapes.
There are several surgical methods to bypass seed physiological dormancy in woody perennials, including embryo removal from the seed, or disruption of seed or fruit coat integrity (Geneve 1991). This has been observed in several fruit crops, including strawberry [Fragaria ×ananassa (Miller et al. 1992)], blackberry [Rubus sp. (Ke et al. 1985)], and grape (Wang et al. 2022). Hormones, primarily gibberellic acid (GA), can also substitute for chilling stratification to satisfy dormancy (Baskin and Baskin 2014). There is also significant anecdotal evidence that using fresh seeds that have not gone through the desiccation process show less dormancy compared with dried seeds in several woody perennials, including alder (Alnus sp.), persimmon (Diospyros sp.), and eucalyptus (Eucalyptus sp.) (Schopmeyer 1974).
Systems to bypass the need for chilling stratification to expedite seedling production could reduce breeding cycles and facilitate novel accelerated breeding programs. Therefore, the objective of this study was to investigate the impact of partial seedcoat removal and gibberellin treatment on the germination of freshly harvested and stored grape seeds.
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