Short communicationEffect of Zn and NAA co-treatment on the occurrence of creasing fruit and the peel development of 'Shatangju' mandarin

- The creasing of 'Shatangju' mandarin was investigated to developing accurate preventive strategies for creasing fruit.
- It was treated twice with either Zn or Zn + NAA application in the fruit enlargement stage, respectively.
- The Zn and Zn + NAA treatments enhanced the levels of IAA, GA3, and tryptophan, promoted the division of cells, decreased variation of peel hardness.
- They reduced creasing abnormalities in peel tissue and lowered the creasing fruit rate and cumulative abscission rate of 'Shatangju' mandarin.
- The Zn + NAA treatment could be recommended as a cultivation technique to lower the creasing fruit rate of Shatangju mandarin.

'Shatangju' mandarin creasing results is serious economic loss in many 'Shatangju' mandarin orchards. Based on developing accurate preventive strategies for creasing fruit, the creasing of eight-year-old 'Shatangju' (Citrus reticulata Blanco cv. Shatangju) onto Poncirus trifoliate (L.) rootstock was investigated. It was treated twice with either Zn or Zn + NAA application in the fruit enlargement stage (18th and 27th of May, 2011), and Zn + NAA (18th and 28th of May, 2012), respectively. The Zn and Zn + NAA treatments at the fruit enlargement stage of 'Shatangju' significantly enhanced the levels of IAA, GA3, and tryptophan in the early peel development stage, promoted the growth and division of cells, decreased the range of peel hardness variation during fruit development, reduced creasing abnormalities in peel tissue, especially in albedo, postponed the peel thickness transition time of peel development, and significantly lowered the creasing fruit rate and cumulative abscission rate of 'Shatangju' mandarin. Compared with the control and Zn treatment, Zn + NAA treatment could be recommended in the fruit enlargement stage as a cultivation technique to lower the creasing fruit rate of Shatangju mandarin.