A new ponkan cultivar Huagan No. 3 with large fruits and few seeds

Abstract: Huagan No. 3 is a new tetraploid citrus cultivar, derived from the seedlings of Egan No. 1 ponkan. It was first identified in 2007 through the morphological pre-screening and ploidy determination by using the flow cytometry. SSR molecular analysis confirmed its status as an autotetraploid (or doubled diploid) plant resulting from the spontaneous chromosome doubling of the nucellar cell of Egan No. 1 ponkan. Grafted onto Poncirus trifoliate rootstocks in 2008, Huagan No. 3 first blossomed in 2013. Over five consecutive years from 2014 to 2018, fruit quality and fertility of Huagan No. 3 were evaluated in comparison with its diploid parent, Egan No. 1 ponkan. It was found that Huagan No. 3 exhibited larger leaf, flower and fruit size, along with higher total soluble solid and titratable acid contents. However, the seed number in the fruits of Huagan No. 3 was significantly lower than that of Egan No. 1 ponkan. These characteristics of larger fruit and fewer seeds remained consistent across different years, indicating that Huagan No. 3 was a promising new citrus cultivar with good economic value. In 2021, Huagan No. 3 was granted the Plant New Variety Right (CNA20191005407) by the Ministry of Agriculture and Rural Affairs. The tree of Huagan No. 3 is erect and medium vigorous, with an oval and upright shape. The spring and autumn shoots are the main types of fruit- bearing base branches. The leaves are broadly lanceolate, with a deep green color and a gradually pointed tip at the apex. The leaf length and width are 91.3 mm and 39.7 mm, respectively. The flowers are white and bloom once a year. The petals are long, boat- shaped, and the filaments are separate. The anthers are light yellow and the style is upright with a globular stigma. The fruit of Huagan No. 3 is oblate, with a fruit shape index of approximately 0.85, and average transverse and longitudinal diameters of 74.08 mm and 62.63 mm, re-spectively. Huagan No. 3 fruits are larger than those of Egan No. 1 ponkan, with an average fruit weight of 179.94 g. The fruit peel of Huagan No. 3 is thicker than that of Egan No. 1 with an average thickness of 3.45 mm. Similar to other ponkan mandarins, Huagan No. 3 has orange-yellow flesh, crispy and soft texture, sweet and sour taste and strong flavor. The pulp has a total soluble solid content of 14.49% and a titratable acid content of 1.16%, both of which are higher than those of Egan No. 1 ponkan. The average seed number in Huagan No. 3 fruits is significantly lower, with an average of 2.7 seeds per fruit. In the Wuhan area, Huagan No. 3 fruits typically begin to turn yellow in late October, with the mature period extending from the middle to late December. The yield of Huagan No. 3 is moderate, with five-yearold trees planted at a density of 3.0 m × 4.0 m and being capable of producing 1500 kg per 666.7 m² . Huagan No. 3 exhibits wide adaptability and is well-suited for cultivation in most citrus-producing areas in China, particularly in areas suitable for ponkan cultivation (the annual average temperature ≥ 16 ℃; absolute minimum temperature ≥ -5 ℃; effective annual accumulated temperature (≥ 10 ℃) ≥ 5500 ℃; frost-free period ≤ 280 days; and annual precipitation ≥ 1000 mm).