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Flower bud development of fruit trees plays a key role in their climatic adaptation. It is closely related to dormancy release that determines winter frost susceptibility. Detailed characterisation of flower bud development of 25 almond (Prunus amygdalus L. Batsch) accessions representing wide range of flowering times have been performed by microsporogenesis and pistil growth studies for 3 years. Six developmental stages were distinguished in the process of microsporogenesis, while pistil development could be classified into four phases. The examined cultivars showed significant differences in the length and occurrence of microspore developmental stages and year effect was observed. On the basis of the length of microsporogenesis stages, cultivars were clustered into five main groups. The shortest periods of archesporium and microsporogenesis as a sum were detected in accessions ‘Eriane’, ‘5/15’ and ‘1/7’ (with an average of 20 and 138 days in all three), while the longest ones were determined in ‘Constanti’ and ‘Vairo’ (65 and 160 days in both), respectively. The increment of pistil length was suspended during the dormancy period and after dormancy release, it was accelerated first at a slow rate followed by a few days of rapid growth prior to blooming. In order to determine the date of endodormancy release, these three methods – microsporogenesis, pistil length studies, and forcing of shoots – were analysed. All methods revealed significant differences among accessions. The dormancy release estimated by microsporogenesis studies showed the highest variability among the three methods used.

The ripening time of peach cultivars is genetically determined, but it is greatly influenced by environmental factors. Prediction of ripening time is very useful from a scientific point of view and for practice as well. Generally, the sum of temperature and the days from flowering to ripening are used for prediction. Our work examined the phenological characteristics of 50 peach cultivars for 26 years in our experimental plantations in the central part of Hungary. We found that the number of days from flowering to ripening and the heat units (temperature sum units) vary greatly from year to year, so these values are not suitable for accurate prediction of the ripening time of cultivars. From a practical point of view, using reference cultivars is more effective for growers. The gradual shift towards earlier ripening time is proved during 26 years. Depending on the cultivar, the starting date of ripening of the investigated peach cultivars was 0.28 to 0.36 days earlier each year in our experimental plantations. [ABSTRACT FROM AUTHOR]

Frost hardiness of flower buds of twenty almond genotypes was investigated in five dormancy periods by determining LT50 values after artificial freezing tests. The main aim of our work was modelling the changing of frost hardiness of the observed accessions during dormancy and assessing the potential best frost tolerance of them. The effect of genotype and year had significant impact on frost hardiness of flower buds. The potential frost hardiness of accessions has been characterised by LT50 values of flower buds averaged of the bests of the four years. 'Sóskút 96/5' was the most sensitive with -17.16 °C, and 'Tétényi keményhéjú' was the most frost hardy with -21.08 °C in averaged of years, but both showed lower and higher frost tolerance as well in different years. Flower buds were most frost-tolerant in December and January but did not achieve the same frost resistance every year. From this, we conclude that temperature plays an important role in the hardening process of them. From the aspect of safe yield, frost hardiness of flower buds is an important trait of cultivars, because Hungary is situated at the northern part of economical almond growing area. Our work contributes to facilitating practical considerations in orchard planning. [ABSTRACT FROM AUTHOR]