INTRODUCTION Peach [Prunus persica (L.) Batsch] is one of the most important fruits of the Rosaceae family and ranks 3rd after apples and pears. Though most opine that the peach originates in China (Wang, 1985; and Faust and Timon 1995), a few studies suggest that it originated in Persia. Hilly areas of Tibet and southwest China are the primary centers of peach diversity, while Iran is the secondary center (Kumar et al., 2013). Globally, they are grown on a commercial scale in temperate and subtropical regions. Several different varieties of peaches are grown throughout the world, however, the majority of peach production in India is accounted by a relatively small number of varieties (15-20) (Kumar et al., 2013). As a result of high productivity, regular bearing and precocious nature, low chill peach cultivation has gained considerable attention over the past few years. The fruit of these subtropical peaches is harvested nearly two months earlier than those grown in hills, resulting in good economic returns since there are no other major temperate fruit crops in the market during that period (Kumar et al., 2015). However, due to a variety of circumstances, including insufficient cooling and irregular rainfall, the yield and quality of commercial peach cultivars in the sub-tropics of India have dropped in recent years.It could be attributed much to the formation of the blind node in the sub-tropical condition under the current scenario of climate change. Penso et al. (2020) described that the phenological cycle such as dormancy break is most affected under subtropical and tropical conditions, which results in alterations of flowering and effective fruiting, along with branch growth and development (Nava et al., 2009; Couto et al., 2010). There may also be an impact on the formation of buds, especially floral buds, which are not fully developed and form ‘blind nodes’ (Monet et al., 1971; Dennis et al., 2000; Faust, 2000; Williamson et al., 2008). Variability is the basic requirement of any breeding program; therefore, the characterization and evaluation of germplasm are considered to be an indispensable part of crop improvement programs. The germplasm is a valuable source material because it offers scope for the generation of genetic diversity and its evaluation contributes to the identification of cultivars for its direct or indirect use in the breeding work (Sonaniya and Singh 2022). It focuses mainly on morphological, pomological and phenological characteristics (Yilmaz et al., 2009). There are various standards and guidelines developed both at the international (UPOV; International Union for the Protection of New Varieties of Plants, Geneva and IPGRI; International Plant Genetic Resources Institute, Rome) and national levels (PPV & FRA; Protection of Plant Varieties and Farmer’s Rights Authority, New Delhi) for the taxonomic description and identification of cultivars. The micro-morphological features of pollen grains are also an important diagnostic trait that plays a key role in the identification of different plant species. Besides this, the success of fertilization in controlled pollination depends upon the pollen viability of a genetic resource available and therefore knowledge of such attribute is prerequisite for any crop improvement program. MATERIALS AND METHOD Experimental site and experimental materials. The present study was undertaken on twenty years old low chill peach cultivars (12 Nos) maintained at HRC, Patharchatta, of G. B. Pant University of Agriculture and Technology, Pantnagar located in the Tarai belt of the Himalayas at 29.5º North latitude and 79.3º East longitude and an altitude of 243.94 metres above MSL. The climate of the experimental site is humid subtropical with dry and hot summers. Measurements and observations.The morphological characterization of 12 low chill peach cultivars was carried out for two consecutive years from January, 2021 to June, 2022. The trees evaluated were all kept under uniform cultural practices throughout the experimentation. Tree attributes viz., height and spread were measured with the help of calibrated staff and tree volume as per the methodology outlined by Westwood (1993). The PPV&FRA test guidelines were followed to evaluate the peach cultivars for different phenological observations (Anonymous, 2015). While the pollen viability was determined using the acetocarmine (1%) test. Statistical analysis. The experiment was laid out in a randomized block design. All data were subjected to Analyses of Variance (ANOVA). Significant differences among groups were determined using Duncan’s multiple range tests at p<0.05. All computation and statistical analyses were done using IBM SPSS Statistics 19 statistical software (IBM, NY, USA). RESULTS AND DISCUSSION Tree growth characteristics. Data presented in Table 1 indicate the variability among the cultivars for tree vigour and growth habit. Out of 12 peach cultivars, as many as four (Pratap, Early Grand, Florda Prince and Shan-i-Punjab) were found to have strong vigour, seven had (Florda Gold, Florda Red, Pant Peach-1, Red June, Sharbati Late, Sharbati Surkha and Selection-12) medium vigour and only one (Saharanpur Prabhat) exhibited weak vigour. Variation in tree growth habit was found to be spreading in Florda Prince and rest of all cultivars (Saharanpur Prabhat, Pratap, Early Grand, Florda Gold, Florda Red, Pant Peach-1, Red June, Sharbati Late, Sharbati Surkha, Shan-i-Punjab and Selection-12) displayed upright to spreading growth habit (Table 1). All the 12 peach cultivars under study registered considerable variation for tree vigour and growth characteristics. The differential behaviour in tree growth characteristics of the present study confirms the genetic variability of different cultivars. The study by Gradziel and Beres (1993) suggested that trees with upright growth habits may be suitable for high-density planting systems or could be used as a genetic resource to develop short-statured peach scion varieties. Such variation among the cultivars for tree vigour has been reported by Jana (2015), who found that tree vigour varied from semi-vigorous (Pratap and Prabhat) to vigorous (Florida Sun, Shan-i-Punjab and Florda Prince) and to weak type in No. 22. Thakur (2019) also observed upright to spreading nature of growth habit in Andros, Glohaven and Paradelux and upright in Pratap, Redhaven, Shan-i-Punjab and Suncrest. The observations recorded on tree height and spread are presented in Table 1, which revealed the highest tree height value (5.40 m) being noted for Florda Prince and the lowest (3.22 m) for Saharanpur Prabhat. Tree spread ranged from 3.44 m (Saharanpur Prabhat) to 4.87 m (Florda Prince). The highest tree spread value examined in Florda Prince differs non-significantly from Shan-i-Punjab (4.76 m) and Red June (4.68 m). The different cultivars under evaluation differed significantly for trunk girth and tree volume (Table 1). Pooled analysis of data revealed the highest trunk girth value (82.95 cm) being noted for Florda Prince and minimum (37.90 cm) for Saharanpur Prabhat. Whereas, with regard to tree volume, Florda Prince had the maximum value (84.16 m3) and Saharanpur Prabhat had the minimum (22.89 m3).In the present study, the genotypes differed considerably for different plant growth attributes. Among the 12 peach cultivars, Florda Prince was found promising genotype for tree height, trunk girth, tree spread and tree volume. Yepthomi (2011) described about ten low-chilling peach cultivars and witnessed maximum tree height in Valle Grand (2.73 m) and minimum in Florda Prince (1.83 m).Previous studies also reported a high variability among peach cultivars for these parameters (Sharma et al., 2012; Kumar, 2015). Flowering characters. The glance of data presented in Table 2 demonstrated that the date of bud swell varied considerably among all the cultivars under investigation and extended from 8th January (Florda Gold) to 25th January (Selection-12) in the year 2021. The earliest bud swell stage was registered for Florda Gold followed by Florda Prince (10th January) and Pant Peach-1 (10th January). Similarly, during 2022 Florda Gold showed the earliest bud swell stage (16th January) followed by Florda Prince (18th January) and Pant Peach-1 (20th January), whereas, the delayed bud swell stage was noted in Selection-12 (3rd February).The perusal of data on the density of flower buds is presented in Table 2. During both the years of investigation, the sparse density of the flower buds was observed in Saharanpur Prabhat, Pratap, Early Grand and Florda Prince; medium dense in Florda Red, Pant Peach-1, Sharbati Late, Sharbati Surkha and Selection-12; dense in Red June and Shan-i-Punjab whereas highly dense flower buds were reported in the cultivar Florda Gold. Out of 12 peach cultivars analyzed, only 2 cultivars namely, Pratap and Early were found to have a non-showy type of flower (Table 2), whereas, rest of other displayed showy type of flower. There was a slight difference noticed in the main colours of corollas of different cultivars studied, including very light pink in Saharanpur Prabhat, Florda Prince, Florda Gold, Shan-i-Punjab, light pink in Pratap, Early Grand, Florda Red, Pant Peach-1, Red June, Sharbati Surkha, Selection-12, and medium pink in Sharbati Late (Table 2). It was noted that the shape of petals (Table 2) varied from medium elliptic in Saharanpur Prabhat, Sharbati Surkha and Shan-i-Punjab to narrow elliptic in Pratap, Early Grand, Florda Gold, Sharbati Late and Selection-12 and to medium ovate in Florda Prince, Florda Red, Pant Peach-1 and Red June. While, the number of petals was obtained as five in all the 12 peach cultivars under study. Data pertinent to the flowering shoot thickness (mm) and length of internodes (mm) is presented in Table 3. The flowering shoot thickness was found maximum (4.04 mm) in Early Grand which differ non-significantly from Pratap (4.02 mm), Florda Prince (3.96 mm) and Red June (3.91 m). The minimum shoot thickness was recorded in Selection-12 (2.64 mm). Out of the 12 accessions studied (Table 3), Pratap recorded maximum (27.04 mm) inter-nodal length, which was statistically at par with Early Grand (26.91 mm), Sharbati Surkha (26.27 mm), Shan-i-Punjab (25.24 mm) and Saharanpur Prabhat (24.71 mm). Whereas Florda Gold recorded minimum (20.06 mm) value followed by Selection-12 (21.07 mm), Red June (21.56 mm), Sharbati Late (21.71 mm) and Florda Red (22.54 mm) (Table 3). PPV&FRA guidelines described similar findings with respect to flowering shoot thickness and revealed it to be less than 3 mm in Fertilia, Nimla; 3-4 mm in Cresthaven, Snowcrest and greater than 4 mm in Red Globe (Anonymous, 2015). Inter-nodal length of shoots is considered a good indicator of dwarfness in a genotype. Chauhan (2016) recorded maximum (3.88 cm) inter-nodal length in Paradelux whereas minimum in July Elberta (2.39 cm). Chalak et al. (2006) observed a showy flower type in Beccoque and Helberta and a non-showy type in Redhaven and Elberta. Thakur (2019) identified the morphology of the petal as medium elliptic in Andros, Glohaven, Paradelux and Shan-i-Punjab; narrow elliptic in Pratap and circular in Redhaven and Suncrest. The findings of the present investigation also substantiate the report of Qadri et al. (2017); Ikinci and Bolat (2018). Pollen viability. It is evident from the data presented in Table 3 and also displayed in Plate 1that the cultivar under study differs significantly for pollen viability. The cultivar Florda Prince obtained the highest pollen viability (98.33%) which was statistically at par with Pant Peach-1 (96.33%), Pratap (96.00%) and Saharanpur Prabhat (95.67%), while the Selection-12 witnessed the lowest pollen viability percentage (82.33%). In general, pollen viability has been reported to vary from species to species, cultivars to cultivars and group to group depending on the ploidy level and the degree of the hybridity of the cultivar. Using acetocarmine (1%) and erythrosine B (0.10%), Singh et al. (2015) investigated the pollen viability of low chill peach cultivars and found that the viability percentage ranged from 94.51 to 98.93% with acetocarmine (1%) and 84.19 to 97.70% with erythrosine B (0.10%). Bodh et al. (2019) also determined the pollen’s viability of peach and reported it to vary from 91.35 per cent to 98.47 per cent with acetocarmine and erythrosine B respectively.