Inheritance of Thornlessness in Trifoliate Orange[Poncirus trifoliata(L.) Raf.].

The inheritance of a thornless characteristic in trifoliate orange was studied. Ten-month-old seedlings of the progenies that were obtained from selfing and crossing of the trifoliate orange strains, including thornless ones, which were observed for development of thorns, were classified into a thorny or thornless type. Percentage thorny nodes (PTN) was calculated from randomly selected progenies. From the segregation patterns of thorny and thornless seedlings in the progenies, thornless individuals emerged whenever the thornlessness alleles existed homozygously. Many seedlings with lower PTN, in comparison with that of 'Normal thorny' strain, segregated among the thorny seedlings. Thus, the allele for thorniness seemed to be incompletely dominant over the thornless allele.