Abstract
The number of triploids in natural hybrid seeds of three lemon cultivars ranged from 0.36 to 0.70 triploids/fruit. The percentage of small seeds (weighing between one-fifth to one-third of the weight of large seeds) and extra small seeds (weighing less than one-fifth of the weight of large seeds) found to be triploid was 46.7–59.6% and 37.5–47.6%, respectively. This observation suggested that triploids could be efficiently obtained from crosses between diploids by selecting a smaller seed size in lemon. Although 88.2% of the triploids obtained from natural hybrid seeds formed pollen, the amount of pollen was low, resulting in 80% of the triploids having less than one seed/fruit. ‘Yellow Bell’, a new lemon cultivar, was bred by selecting triploids from the natural hybrid seedlings of ‘Michitani-line Villafranca’. The tree vigor of ‘Yellow Bell’ was strong, the branches were dense, branch lengths were intermediate, and the internode lengths were short. A high percentage of the branches (65.8%) had thorns. Maturation occurred in mid-December, when the relative juice content (weight of juice/total fruit weight) was high. Fruits were spherical to sub-spherical, and the average fruit weight was approximately 214 g. The thin rind (5.1 mm thick) had a relatively smooth texture, and high relative juice content. The scent was medium. The average number of seeds (2.9 seeds/fruit) was low. The acidity was approximately 5.3%, giving the fruits a mild taste. This new cultivar, with its unique characteristics of a low seed number, high relative juice content, and low acidity, will help increase the demand for lemons.
