The Variation Characteristics and Blooming Phenophase of Monoecious Pistacia chinensis Bunge

Pistacia chinensis Bunge is a pioneer tree for afforestation, and of high value as an ornament and for timber and medicine. It has also become the preferred biofuel tree in northern China in current years, with a broader development prospect. However, this development is seriously limited due to its dioecious character (separate sexes), because the male (nonfruit) trees are indispensable for pollination, and this leads to a waste of field and low yields. Fortunately, this bottleneck can be broken with the emergence of rare monoecious (having both female and male flowers, and even bisexual flowers) resources in Hebei Province, China. To determine their cultivation characteristics, the variation characteristics and blooming phenophase of local Pistacia were recorded with text, data, and images, by germplasm resources survey, telephone interviews, and field visits. Results showed that 1) 23 monoecious Pistacia were found, with very complex morphological features. 2) The branches of different gender types, ordered by inflorescence length were female > female on monoecious trees > bisexual flowers > inflorescence with male and female > male on monoecious trees > male. Ordered by inflorescence width: female > bisexual flower > female on monoecious trees > inflorescence with male and female > male on monoecious trees > male. Among these, the inflorescence length, inflorescence width, floret diameter, and floret spacing of bisexual flowers were significantly greater than that of male flowers, providing a basis to judge gender type without destructive sampling. 3) Gender types were unstable in successive years—female, male, mixed, or bisexual flowers could convert to another gender within 1 year, except that no female became male, and the overall trend was from male to mixed or bisexual gender in recent years. 4) The blooming phenophase changed a lot among different strains and sex types, which could enlarge the blooming period.