Tamás Deák

In this study, the effect of different foliar applications on the grapevine (Vitis vinifera L. cv. Riesling) leaf morphology was investigated. Leaf chlorophyll content was measured with an Apogee MC100 portable chlorophyllmeter, leaf thickness was investigated with a thickness gauge while the light transmittance was evaluated with a smartphone application running on a Xiaomi Redmi Note 9. Results showed that foliar applications have a significant effect on the leaf morphological traits. According to the correlation analysis of pooled samples, there is no significant relation between the monitored parameters. Interestingly if samples are split according to the applied treatments, we found a correlation between the measured traits that highlight the impact of the foliar application on the morphological characteristics. Our present research demonstrates that smartphones can be effectively integrated into agricultural studies and provide data that can complement observations.

Leaf chlorophyll content is a key indicator of plant physiological status in viticulture; therefore, regular evaluation to obtain data for nutrient supply and canopy management is of vital importance. The measurement of pigmentation is most frequently carried out with hand-held instruments, destructive off-site spectrophotometry, or remote sensing. Moreover, smartphone-based applications also ensure a promising way to collect colorimetric information that could correlate with pigmentation. In this study, four grapevine genotypes were investigated using smartphone-based RGB (Red, Green, Blue) and CIE-L*a*b* colorimetry and a portable chlorophyll meter. The objective of this study was to evaluate the correlation between leaf chlorophyll concentration and RGB- or CIE-L*a*b*-based color indices. A further aim was to find an appropriate model for discriminating between the genotypes by leaf coloration. For these purposes, fully developed leaves of ‘Chardonnay’, ‘Sauvignon blanc’, and ‘Pinot noir’ clones 666 and 777 were investigated with the Color Grab smartphone application to obtain RGB and CIE-L*a*b* values. Using these color values, chroma, hue, and a further 31 color indices were calculated. Chlorophyll concentrations were determined using an Apogee MC100 device, and the values were correlated with color values and color indices. The results showed that the chlorophyll concentration and color indices significantly differed between the genotypes. According to the results, certain color indices show a different direction in their relationship with leaf pigmentation for different grapevine genotypes. The same index showed a positive correlation for the leaf chlorophyll concentration for one variety and a negative correlation for another, which raises the possibility that the relationship is genotype-specific and not uniform within species. In light of this result, further study of the species specificity of the commonly used vegetation indices is warranted. Support Vector Machine (SVM) analysis of the samples based on color properties showed a 71.63% classification accuracy, proving that coloration is an important ampelographic feature for the identification and assessment of true-to-typeness.

Grapevine Pinot gris virus (GPGV) is a recently identified trichovirus infecting grapevines. Despite wide distribution, there is limited available information on epidemiology, transmission, and associated symptoms of grapevine leaf mottling and deformation. Occurrence and genetic diversity of GPGV variants were surveyed in an organically cultivated Hungarian vineyard that was planted between 1996 and 2014. Sequence analysis demonstrated the widespread presence and high variability of GPGV, and according to phylogenetic analyses, the Hungarian virus isolates were classified into three groups. Most of the identified variants clustered with the representative asymptomatic isolates, but all isolates from one grapevine cultivar grouped with representative isolates of clade B. Furthermore, one isolate clustered with representative isolates of clade C, and the identified clade C variant had previously undescribed polymorphisms.

As the sensitivity of perennial crops to climate change becomes more pronounced, clonal selection, which is already very time-consuming for grapevine, may take even longer, while its importance is increasing. In the case of indigenous grapevine varieties, the purpose of clonal selection is twofold: to mitigate problems of cultivation and at the same time, to preserve the varietal character. The cultivation technique issue of ‘Kéknyelű’ is the low fertility (functionally female-flowered variety), and as for ‘Juhfark’ it is the significant susceptibility to grey rot. Based on daily meteorological data of 11 years, the years were classified into 3 groups and harvest data were analyzed within each group. Significant difference in yield was found between clone B.2. and the base ‘Kéknyelű’. Both clones of ‘Kéknyelű’ matured with significantly lower pH compared to the base variety. Given the acidic character of ‘Kéknyelű’ wine and the predicted rise in must °Brix and pH as a result of climate change, these differences may be useful in the future. Botrytis infection only showed statistically significant differences between year groups for ‘Juhfark’. It is intriguing that in most years, the rate of grey rot infection was lower in both clones compared to the base variety, especially in year groups 1 and 3 when the overall rate of Botrytis infection was quite low.

In the case of indigenous grapevine varieties, the aim of clonal selection is twofold: to improve their technological cultivation problem while preserving the varietal character. As the sensitivity of perennial crops to climate change becomes more pronounced, clonal selection, which is already very time-consuming for perennial woody crops, may take even longer. In Badacsony, clonal selection breeding of the ‘Kéknyelű’ and ‘Juhfark’ varieties was started in the early 2000s. The problem mentioned above in cultivation technology is the poor fertility of ‘Kéknyelű’ (functionally female-flowered variety), while in the case of ‘Juhfark’ the high susceptibility to grey rot (Botrytis). Based on 11 years of data significant difference in yield between clone B.2. and the base variety was found. In this comparison the year clusters also gave different values, as in years belonging to cluster 1 the ’Kéknyelű’ yielded more than in another year. Both clones of ‘Kéknyelű’ matured with significantly lower pH compared to the base variety. ‘Kéknyelű' is renowned for the distinctive variety character of its wine, which is said to be acidic. Given the acidic nature of ‘Kéknyelű’ wine and the expected increase in must degrees and pH due to climate change, these distinctions may be beneficial in the future. Daily meteorological parameters were also recorded in the years under study, and different indexes were calculated for both of varieties for different phenological periods. The years were classified into 3 clusters and the harvest data were analyzed within each cluster. In the case of 'Kéknyelű' our results revealed significant differences in yield between vintage clusters for clone B.2. However, clone B.1 demonstrated distinct KMW and pH values. Both 'Kéknyelű’ clones have produced a substantially higher incidence of Botrytis infection in cluster 2 years than in cluster 3 years. Botrytis infection only showed statistically significant differences between year clusters for ‘Juhfark’. It is intriguing that in most years, the rotting rate was lower in both clones, especially in year clusters 1 and 3 when the overall rate of Botrytis infection was quite low. Our results highlighted the year-round sensitivity of the two varieties studied and the difficulties of clonal selection.

We elucidate grapevine evolution and domestication histories with 3525 cultivated and wild accessions worldwide. In the Pleistocene, harsh climate drove the separation of wild grape ecotypes caused by continuous habitat fragmentation. Then, domestication occurred concurrently about 11,000 years ago in Western Asia and the Caucasus to yield table and wine grapevines. The Western Asia domesticates dispersed into Europe with early farmers, introgressed with ancient wild western ecotypes, and subsequently diversified along human migration trails into muscat and unique western wine grape ancestries by the late Neolithic. Analyses of domestication traits also reveal new insights into selection for berry palatability, hermaphroditism, muscat flavor, and berry skin color. These data demonstrate the role of the grapevines in the early inception of agriculture across Eurasia.

Grape (Vitis spp.) is one of the most important horticultural crops, cultivated worldwide on more than 7.3 million hectares for various purposes such as winemaking, fresh fruit consumption, rootstock, and ornamental plants. Based on the inter- and intraspecific morphological variability, several descriptor lists, manuals and ampelographic studies are available for identification. Among the organs, leaves have the most traits, while the young shoot, bunch and berry are also important in the characterization of the genotypes. Vitis species and cultivars are described by leaf morphological characterization developed in many ways for the identification of genotypes, to clarify synonymies and distinct clones or evaluate the diversity of wild Vitis taxa. Morphometric—also known as ampelometric—evaluation has an extensive background in the literature. However, for some reasons, only a part of the literature is cited, despite its significant scientific value. In this paper, we summarize the efforts of metric characterization of the grapevine leaf with the introduction of the scientific objectives and reviewing the studies showing the innovations in phenotyping during the past 120 years.

The aim of this review is to provide readers with an integrated knowledge on black rot of grapes, based on a critical survey of previous and recent studies of scientific importance. The current state of the art and perspectives of science are presented, not only on the genetic determinants of grapevine resistance to black rot, predictive models of black rot epidemics, but also on the potential of metabolomics to explore black rot-grape interactions and shorten plant breeding processes. Numerous complications of disease management and ambiguities in phenotype-classification are highlighted, and by exploring the limitations and inconsistencies of previous studies, insights into key dilemmas and controversial findings are also provided, suggesting future research directions. Much research has been conducted, but biochemical and molecular studies of the true interactions between grapevine and Guignardia bidwellii are still rarity.

Null alleles are alleles that are recessive to codominant markers without any effect on the phenotype. In SSR assays, there are several reasons for the lack of amplification at a locus: the primer does not bind well, longer fragments do not amplify due to imperfections in the PCR reaction, or the amount of DNA in the sample is insufficient. In microsatellite studies, null alleles are mostly used in pedigree analysis and population genetics calculations such as diversity estimation. Null alleles in pedigree analysis can cause rejection of the true parent; if not recognized while in population genetics they distort the results in underestimating diversity. In this review, the effects caused by null-alleles in viticultural research and its possible solutions were summarized.