Grapevine Flowering Research Articles

Will Roe Deer Persist in a Warmer World?

Will Roe Deer Persist in a Warmer World?

DWARFING AND FLORAL INDUCTION IN VITIS VINIFERA

As grapevine flowering has a major impact on the yield of vines there has been much interest in understanding the biology behind this important developmental process. The study of flowering in grapevine provides some unique challenges due to the unusual shoot architecture of the plant and the extension of the process over two growing seasons. However, with the realisation that tendrils were modified inflorescences, researchers began to reveal methods of converting one to the other. These studies with plant growth regulators or their inhibitors, had suggested a link between gibberellins and fruitfulness in grapes. Ultimate proof for this link came from the discovery of a dwarfed mutant grapevine that is insensitive to gibberellins. Understanding the various stimuli that promote fruitfulness in grapevines can help modify yield in the vineyard, but also gives us insight into the possible evolutionary strategy employed by this species to ensure reproduction.

Dynamics of water and nitrogen stress along the grapevine cycle as affected by cover cropping

Cover cropping is developing in vineyards as it may induce numerous ecosystem services. However, soil cover also competes with grapevine for soil resources. This work aimed at evaluating both the period and intensity of the resulting water and nitrogen stress experienced by grapevine by comparing treatments with bare soil, permanent and non-permanent soil cover. The adopted stress indices were the Fraction of Transpirable Soil Water (FTSW) and the Nitrogen Nutrition Index (NNI).Cover cropping improved winter soil water refilling, but the grass transpiration during spring later led to similar water stress of grapevine among treatments. In dry years, summer water stress was not higher with non-permanent cover than with bare soil. The building of a critical nitrogen content curve for grapevine enabled to diagnose an early nitrogen stress, from budbreak to flowering, in cover cropped treatments. NNI dropped then in dry years, particularly in cover cropped treatments.The early growth limitation of grapevine observed in cover cropped treatments was the consequence of mild early nitrogen stress, which suggests that perennial nitrogen reserves were reduced because of an earlier competition with cover crop. After grapevine flowering, water appeared to be the most limiting factor for both grapevine growth and nitrogen availability.In water limited environment, nitrogen stress is highly dependant on water constraints. However, this work reveals the partial uncoupling of the dynamics of water and nitrogen stress during the grapevine cycle in water-limited cropping systems, which highlights the relevance of a co-ordinated management of water and nitrogen.

General phenological model to characterise the timing of flowering and veraison of Vitis vinifera L.

Background and Aims: Phenological models, which are based on responses of the plant to temperature, are useful tools to predict grapevine (Vitis vinifera L.) phenology in various climate conditions. This study aimed to develop a single process-based phenological model at the species level to predict two important stages of development for V. vinifera L.: flowering and veraison. Methods and Results: Three different phenological models were tested and the model that gave the best results was optimised for its parameters. The chosen model Spring Warming was found optimal with regard to the trade-off between parsimony of input parameters and efficiency. The base temperature (Tb) of 0°C calculated from the 60th day (t0) of the year (for the Northern hemisphere) was found to be the most optimal parameter set tested. This model henceforth referred to as the Grapevine Flowering Veraison model (GFV) was successfully validated at the varietal level using an independent dataset. Conclusions: A general phenological model, GFV, has been successfully developed to characterise the timing of flowering and veraison for the grapevine. Significance of the Study: The model is simple for the user, can be successfully applied to many varieties and can be used as an easy predictor of phenology for different varieties under climate change scenarios.

A molecular genetic perspective of reproductive development in grapevine

The grapevine reproductive cycle has a number of unique features. Inflorescences develop from lateral meristems (anlagen) in latent buds during spring and summer and enter a dormant state at a very immature stage before completing development and producing flowers and berries the following spring. Lateral meristems are unique structures derived from the shoot apical meristem and can either develop into an inflorescence or a tendril. How the grapevine plant controls these processes at the molecular level is not understood, but some progress has been made by isolating and studying the expression of flowering genes in wild-type and mutant grapevine plants. Interestingly, a number of flowering genes are also expressed during berry development. This paper reviews the current understanding of the genetic control of grapevine flowering and the impact of viticulture management treatments and environmental variables on yield. While the availability of the draft genome sequence of grapevine will greatly assist future molecular genetic studies, a number of issues are identified that need to be addressed--particularly rapid methods for confirming gene function and linking genes to biological processes and traits. Understanding the key interactions between environmental factors and genetic mechanisms controlling the induction and development of inflorescences, flowers, and berries is also an important area that requires increased emphasis, especially given the large seasonal fluctuations in yield experienced by the crop and the increasing concern about the effect of climate change on existing wine-producing regions.

Sugars and flowering in the grapevine (Vitis vinifera L.)

Sugars play an important role in grapevine flowering. This complex process from inflorescence initiation to fruit maturity takes two growing seasons. Currently, most of the available data concern the involvement of sugars as energy sources during the formation of reproductive structures from initiation of inflorescences during the summer of the first year, until flower opening during the following spring. Sugars devoted to the development of reproductive structures are supplied either by wood reserves or by photosynthesis in leaves or inflorescences, depending on the stage of development. Female meiosis appears to be a key point in the success of flower formation because (i) flowers are vulnerable at this stage and (ii) it corresponds in the whole plant to the transition between reserve mobilization from perennial organs (roots, trunk, and canes) towards efficient leaf photosynthesis. The perturbation of reserve replenishment during the previous year provokes perturbation in the development of inflorescences, whereas altering the photosynthetic sources affects the formation of flowers during the same year. In particular, a lack of sugar availability in flowers at female meiosis caused by various environmental or physiological fluctuations may lead to drastic flower abortion. Apart from energy, sugars also play roles as regulators of gene expression and as signal molecules that may be involved in stress responses. In the future, these two topics should be further investigated in the grapevine considering the sensitivity of flowers to environmental stresses at meiosis.

VvMADS9, a class B MADS-box gene involved in grapevine flowering, shows different expression patterns in mutants with abnormal petal and stamen structures

VvMADS9, a MADS-box gene, from grapevine (Vitis vinifera L.) cultivar Cabernet Sauvignon has been isolated and its expression pattern studied in wild type Cabernet Sauvignon, Mourvèdre, and Bouchalès cultivars and mutants of the latter two genotypes showing abnormal petal / stamen structures. Sequence analysis showed that VvMADS9 was highly similar to PISTILLATA (PI), the class B gene that specifies the identity of petals and stamens in Arabidopsis. The temporal expression pattern of VvMADS9 studied through real-time PCR revealed that its expression was specific to flower development. The low levels of expression in the Mourvèdre mutant and the skewed expression pattern in the Bouchalès mutant as compared to their wild type counterparts suggested that VvMADS9 is involved in normal formation of petals and stamens. Through in situ hybridisation, expression of VvMADS9 was detected in stamens and weak expression on the basal regions of the petals. This suggested a possible role for VvMADS9 in specifying stamen and petal organ identity in grapevine similar to Class B genes in other species. All evidence thus pointed to the conclusion that VvMADS9 is an orthologue of PISTILLATA in grapevine.

Influence of Defoliation on Overwintering Carbohydrate Reserves, Return Bloom, and Yield of Mature Chardonnay Grapevines

The carbohydrate (CHO) reserve physiology of Chardonnay grapevines growing in the cool climate of New Zealand was examined in relation to subsequent flowering and fruiting using defoliation treatments. Vines were defoliated by removing all but the four basal leaves from shoots at monthly intervals starting at four weeks postbloom. Throughout the following season, CHO reserves in the roots and trunks were measured and detailed assessments of vine flowering and yields were recorded. Previous season’s vine defoliation decreased concentrations of overwintering CHO reserves (mostly starch) in both roots and trunks, with earlier defoliation times resulting in the largest reductions. Roots were most sensitive, with early defoliation reducing starch concentrations at budburst to 1.5% DW compared with 17% DW in non-defoliated vines. Reductions in root and trunk CHO reserves were closely associated with significant decreases in inflorescence number per shoot and flower number per inflorescence (up to 50% less than in control vines). Differences in CHO concentrations in both the root and trunk were maintained to veraison, but at flowering had no effect on the percent fruit set in the first season after defoliation. Therefore, lower yields in the following season were caused by fewer inflorescences per shoot and flowers per inflorescence. Shoot growth and total vine pruning weight were also decreased in vines where CHO reserves were reduced. These findings suggest that restricted CHO reserve accumulation as a consequence of defoliation may have a negative impact on subsequent grapevine flowering and productivity, particularly so in a cool-climate environment where there is no postharvest CHO reserve accumulation period.

New insights into grapevine flowering.

The study of grapevine (Vitis spp.) flowering has unique challenges owing to the unique shoot architecture of the plant and the arrest of the flowering process during winter. The grapevine flowering process: inflorescence number per vine, flower number per inflorescence, fruit set and growth has a major impact on fruitfulness (berries per hectare) and hence yield. This review brings together past research into the biology and physiology of grapevine flowering with recent investigations of genes involved in flowering. Genes involved in floral induction and inhibition by gibberellins (GA insensitive), meristem identity (LEAFY, TERMINAL FLOWER1) and organ identity (MADS-box genes) are discussed. An understanding of the function of key genes controlling the development of uncommitted primordia, floral induction and development, and fruit set in grapevine will provide new opportunities for improving vineyard fruitfulness. Understanding the grapevine floral genetic network will also offer insight into the different evolutionary strategies employed by plants to ensure reproduction.

Tendrils, inflorescences and fruitfulness: A molecular perspective

Tendrils and inflorescences are closely related organs which both derive from the same meristematic structure known as an anlagen or uncommitted primordium. The close relationship between these two structures suggests that there is a control step at the gene level which directs the differentiation of an uncommitted primordium down the tendril or the inflorescence pathway, and that the process is quite plastic. To investigate this process at the molecular level a grapevine flowering model has been developed and will be used as a reference for testing grapevine homologues of Arabidopsis genes known to be involved in flowering. Differences between the flowering of Arabidopsis and grapevine suggest that for some genes, control and even function may differ in the vine. Juvenility and the absence of fruit during the initial years of growth is a feature of many perennial fruit crops, including grapevine. For juvenile grapevines, tendrils develop but inflorescences do not. Genotype-dependent and -independent strategies for overcoming the delay in flowering observed for both juvenile transgenic grapevine plants and progeny from breeding programs are discussed.