Effect of Spring Frost Damage on Apple Fruit (Malus domestica Borkh.) Inner Quality at Harvest

In the last few years, spring frosts have become more of a rule than an exception. There are several prevention measures available for growers and numerous are being tested; however, fruitlets are often affected to some extent. One of the more common phenomena is the development of frost rings. The aim of our study was to evaluate how the occurrence of frost rings affects sugar, organic acid, and phenol content in the flesh and phenol content in the peel of cv. ‘Gala’ apples. The results show that the frost damage from spring frost affects compounds in the peel, as well as in the flesh of ripe apples. The flesh of fruits with frost rings contained higher content of fructose and in the flesh directly under the rings there was higher sorbitol and malic acid content. Additionally, the hydroxycinnamic acid and dihydrochalcone content in apple flesh was also altered by frost. The frost-affected peel had a completely different ratio of phenolic compounds content in comparison to healthy apples. While there was a significantly higher content of hydroxycinnamic acids and dihydrochalcones in the corky peel in comparison to the unaffected peel, the flavonol and anthocyanin content was considerably lower.

EVALUATION OF ROMANIAN APPLE CULTIVARS IN LATVIA

Commercial apple growing in Latvia feels some lack of climate adapted modern cultivars. Development of fruits and trees is limited by active growth period (temperatures over 10 °C) of 135-150 days and active temperature sum of 1700-2100 °C. Winter hardiness also is essential, as temperatures below −30°C occur each 10 years, and winter thaws are frequent. Annual precipitation 692 mm favours development of fungal diseases. In 2016, a trial of four Romanian apple cultivars resistant to scab - ‘Aura’, ‘Ciprian’, ‘Jonaprim’ and ‘Romus 3’ was established in Latvia. Trees were grafted on dwarfing rootstock B.396 and planted as 1-year old whips in 3 replications with 2-3 trees in each replication, and trained as slender spindle. Commercial cultivars ‘Auksis’ (midseason) and ‘Ligol’ (late) were used as controls. Most trees of all cultivars in the 2nd year (2017) developed a well branched frame, from 37.5% trees of ‘Ciprian’ to 90% trees of ‘Jonaprim’. The first fruits were harvested in 2017, and commercially significant yield was achieved in 2018, except ‘Jonaprim’, which had the slowest yield increase. By the sum of yield in 2017-2021 ‘Aura’ and ‘Jonaprim’ surpassed commercial cultivar ’Auksis’, but were less productive than ‘Ligol’. Only slightly lower summary yield was obtained from ‘Ciprian’, while ‘Romus 3’ showed the lowest productivity and strong premature fruit drop. Very good taste panel results were obtained for ‘Aura’ and ‘Ciprian’, 7 to 8 points in average. Their fruits also kept well, to 5 months in common storage at 2 ±1oC. Fruits of the other two cultivars were too small and had mediocre or poor taste. The weather conditions in the trial years allowed to test susceptibility to spring frosts and drought. All cultivars showed good tree health after over-wintering. ‘Jonaprim’ and ‘Auksis’ in 2019 had the highest spring frost injury, 60-70% of fruits, while least injured were ‘Aura’ (21.5%) and ‘Ciprian’ (27.7%). Extreme drought in summer of 2021 led to low average fruit mass of all cultivars including the normally large fruited ‘Ligol’ (120-130 g), while in other years ‘Aura’ had fruits over 180 g, very attractive yellow with red stripes. Fruits of ‘Ciprian’ also had good size, but in some years too dark over-colour. ‘Aura’ and ‘Ciprian’ showed good adaptation to the climate of Latvia and can be recommended for wider trials at farms.

Introduction of a New Interesting Walnut Cultivar “Leto”

Ιn an effort to create walnut cultivars (Juglans regia) with high productivity, fruit quality and lateral bearing, a new cultivar, named “Leto”, was created by the cross “Gustine” × “Pedro”. Its main phenological and pomological characteristics were assessed according to the criteria of IPGR (1994) and UPOV-TG/125/6 (1999), for 10 consecutive years and compared with its maternal cultivars and “Chandler”. Observations showed that “Leto” has high lateral bearing habit (90%) and presents satisfactory yield at the full production age. The tree size is smaller than that of its parents and “Chandler”, female flowers bloom from 11 to 22 of April and male from 3 to 6 of April. “Leto” nuts are harvested at the end of September, present easy hull dehiscence and high kernel percentage. Other positive nut characteristics of “Leto” are light kernel color, well kernel filling and easy removal of the kernel halves. “Leto” is a mid-early cultivar of great interest due to its high- quality nuts, suitable for dense plantings, in regions where the last spring frosts occur in late March to early April, thus, making it a promising cultivar for Greece, but also for other regions with similar geomorphological and climatic conditions.

Justification of prospective pistachio (pistacia vera l.) varieties and forms while creating plantations in Uzbekistan

This article presents the results of research on the study of the qualitative properties of the fruits of selected promising pistachio forms. When creating pistachio plantations, it is recommended to use varieties with different periods of flowering and fruit ripening. This arrangement reduces the likelihood of damage to the pistachio flowers by spring frosts, increases the chances of pollination and ensures that the harvest is carried out in stages. For the creation of plantations in forestry, promising forms 518-G, 521-G, 527-SH, 528-G, 52-RG, 21-SH and 59-G are recommended as the most productive, large-fruited and resistant to adverse environmental factors, and also pests.

Gene Expression Analysis in Cold Stress Conditions Reveals BBX20 and CLO as Potential Biomarkers for Cold Tolerance in Almond

Late spring frosts can become one of the limiting factors for the expansion of cultivation area towards a harsher climate for the almond [Prunus amygdalus Batsch syn P. dulcis (Mill.) D.A. Webb] crop as spring frost can damage up to 90% of the harvest. In order to identify key genes favoring cold tolerance in almonds, branches from three late-blooming genotypes: ‘Guara’, ‘Soleta’ and ‘Belona’ were exposed at −4 °C during 24 h in a constant climate chamber. Phenotype analysis showed that ‘Guara’ and ‘Soleta’ had a greater acclimation capacity to cold than ‘Belona’. The qRT-PCR BioMark System technology was used to monitor the relative expression of 30 candidate genes with a potential relation to cold response, which are either involved in the ICE-CBF-COR pathway or the independent CBF pathway, and also genes not yet characterized or with unknown function in almond genome. Differences in the gene expression profiles were found among the three studied genotypes and the three time-points of cold exposure (0, 2 and 24 h). BBX20 and CLO genes behaved as differentiator genes between tolerant and susceptible genotypes in cold stress response in almond pistils. In addition, the differences of expression among the tolerant genotypes suggested the intervention of different mechanisms responding to cold stress in almonds.

Sensitivity of Some Sweet Cherry (Prunus Avium L.) Genotypes To Late Spring Frosts During Different Phenological Stages Following Bud Burst

Sweet cherry (Prunus avium L.) is one of the economically important fruit crops worldwide. However, late spring frosts occurring in some years can significantly impact sweet cherry productivity through organ and tissue destruction caused by frost damage, and very little is known about frost tolerance or susceptibility of new cultivars. Differential thermal analysis (DTA) was, therefore, used to examine the exothermic characteristics (temperatures at which 50% of the flower buds were killed - mLTE values) of the flower buds belonging to members of the genus Prunus - 6 Prunus avium cultivars ('Noir de Guben', 'Bigarreau Gaucher', 'Merton Late', 'Merton Bigarreau', 'Van' and wild genotype). In the study, mLTE values of flowers of six cherry cultivars were determined at different floral bud developmental stages such as side green, green tip, open cluster, first white and full bloom under laboratory-based freeze assays for consecutive two years. The mLTE values of flower buds changed according to both different floral bud developmental stages and sweet cherry cultivars. In our findings, the mLTE values of flower buds in all cultivars generally occurred at higher temperatures in the open cluster stage, whereas the mLTE values of the flower buds in the first white stage occurred at lower temperatures, and therefore, these results are not only controversial in terms of previous frost tolerance studies, but also the first findings to be reported in literature. Considering the two-year average, the temperatures causing mLTE values for flower buds was -1.58 to -3.74°C at the side green stage, -0.94 to -3.51°C at the green tip stage, -0.41 to -1.96°C at the open cluster stage, -2.30 to -11.52°C at the first white stage and -2.37 to -9.80°C at the full bloom stage in the range of six cultivars. In laboratory-based freezing experiments, the 'Van' cultivar were least affected by low temperatures, followed by 'Bigarreau Gaucher' cultivar and wild genotype. 'Merton Late' cultivar, on the contrary, was the most sensitive cultivar to low temperatures, followed by 'Noir de Guben' and 'Merton Bigarreau'. These results can be valuable in predicting possible frost damage at different developmental stages of the flower buds in sweet cherry.

Resistance of generative organs of sweet cherry to spring frosts after artificial freezing

Aim. The purpose of this research was to study the sustainability of Institute bred sweet cherry cultivars to spring frosts during flowering by the method of artificial freezing and to identify resistant cultivars.Material and Methods. Seven Institute bred sweet cherry cultivars were studied: 'Adelina', "Malysh", "Orlovskaya Rozovaya", "Orlovskaya Feya", "Podarok Orlu", "Siyana" and "Trosnyanskaya". Spring frosts were simulated in an "Espec" PSL-2KPH climate chamber in early May at -1°, -2°, -3° and -4°C. At each temperature regime, 100 pcs of flowers and buds of each cultivar were taken in 3-fold repetition. Temperature was lowered at the rate of 1°C per hour. The duration of exposure to negative temperatures was 3 hours.Results. Damage to the stamens and pistils was assessed by the darkening of the tissues. In buds and blooming flowers after frosts, the pistils were first damaged but the stamens were not. Resistance to spring frosts decreased with the phenological development of the cherry's generative organs. The beginning of damage to the flowers as a result of the artificial freezing was noted at a temperature of -1°C. At the same time, the high stability of cherry buds was noted. Modeling frosts of -2°...-4°C increased the number of dead flowers and buds. The resistance of sweet cherries to spring frosts was found to depend on the genotype and stage of development of reproductive organs. A different sum of active temperatures for the beginning of flowering and ovary formation was noted, indicating the onset of phenological phases in which generative organs are susceptible to spring frosts.Conclusion. The experiment made it possible to distinguish a medium-resistant cultivar "Malysh" which was resistant to spring frosts. Weakly stable genotypes were "Orlovskaya Rozovaya", "Orlovskaya Feya", "Trosnyanskaya" and "Siyana". Unstable cultivars were "Adelina", and "Podarok Orlu". During the formation of the ovary, the greatest potential for resistance to spring frosts was shown by "Podarok Orlu".