Effect of Fruit Thinner on Fruit Set and Quality in 'Hongro' and 'Fuji' Apples

Benzyladenine (BA, 99% purity), MaxCel$^{(R)}$ (1.9% BA), Fruitone (3.5% NAA), MaxCel$^{(R)}$ + Fruitone, a nd s imazine were applied postbloom as fruitlet thinning agents to mature 'Hongro' and 'Fuji' apple (Malus domestica Borkh.) trees. BA and MaxCel$^{(R)}$ were applied at $100mg{\cdot}L^{-1}$ a.i. while Fruitone at $0.1mg{\cdot}L^{-1}$ a.i. and simazine at $400mg{\cdot}L^{-1}$ a.i. All PGRs were applied at 8 days after full bloom (DAFB, 6 mm fruit diameter) in both cultivars, while simazine was treated twice at 7 and 14 DAFB. In 'Hongro', the number of total fruit set per flower cluster in terminal buds was 1.67, 1.84, and 1.81 in MaxCel$^{(R)}$ + F ruitone, MaxCel$^{(R)}$, and simazine applications, respectively, when compared with 2.35 of water control. These reductions in fruit set were mainly attributed to the increased ratio of defruited clusters by the thinning agents. In 'Fuji' apple, the number of total fruit set per flower cluster in terminal buds was 1.29, 1.60, and 1.76 in MaxCel$^{(R)}$ + Fruitone, Fruitone, and MaxCel$^{(R)}$, respectively, when compared with 2.56 of water control in 'Fuji' apple. The addition of Fruitone to the MaxCel$^{(R)}$ promoted the thinning efficacy in both cultivars, compared to MaxCel$^{(R)}$ only. The thinning efficacies were similarly observed with lateral flowers in both cultivars. A significant increase of fruit weight by the postbloom thinning treatments was observed only in the BA application in 'Hongro', while the effect was observed in BA and MaxCel$^{(R)}$ in 'Fuji'. While the soluble solids content increased in the BA, MaxCel$^{(R)}$ and MaxCel$^{(R)}$+Fruitone treatments in both cultivars, other fruit quality attributes were not affected by the application of post-bloom thinning agents.

적과제 처리가 '홍로'와 '후지' 사과의 착과 및 과실품질에 미치는 영향

본 연구는 '홍로'와 '후지' 품종에 benzyladenine(BA, 99% purity), MaxCel$^{(R)}$(1.9% BA), Fruitone(3.5% NAA), MaxCel$^{(R)}$ + Fruitone, simazine 등 약제들이 과실의 착과 및 과실품질에 미치는 영향을 조사하였다. BA와 MaxCel$^{(R)}$은 $100mg{\cdot}L^{-1}$ 농도로, Fruitone은 $0.1mg{\cdot}L^{-1}$ 농도로 과실직경이 6mm인 만개 8일 후에, 그리고 simazine은 $400mg{\cdot}L^{-1}$ 농도로 만개 7일후와 14일 후에 2회 처리하였다. 적과제 처리 후 '홍로' 품종의 정화아의 과총당 착과수는 MaxCel$^{(R)}$ + Fruitone, MaxCel$^{(R)}$, simazine 처리구가 각각 1.67, 1.84, 1.81개로 무처리구 2.35개보다 적어 적과효과를 보였고, 특히 무착과 과총 비율이 높아 적과효과가 더 우수하였다. '후지' 품종의 경우 정화아의 과총당 착과수는 MaxCel$^{(R)}$ + Fruitone, Fruitone, MaxCel$^{(R)}$ 처리구가 1.29, 1.60, 1.76개로 무처리구 2.56개보다 적어 우수한 적과효과를 보였다. 또한, 두 품종 모두에서 MaxCel$^{(R)}$ + Fruitone 혼용처리구가 MaxCel$^{(R)}$ 단독처리구에 비하여 적과증진효과를 보였다. 그리고 액화아의 경우도 정화아의 결과와 유사한 결과를 보였다. 과중은 '홍로' 품종의 BA 처리구에서, '후지' 품종에서는 BA와 MaxCel$^{(R)}$ 처리구에서 증가하였다. 그리고 가용성 고형물 함량은 두 품종 모두에서 BA, MaxCel$^{(R)}$, MaxCel$^{(R)}$ + Fruitone 처리 과실들에서 증가하였지만 다른 과실특성들은 차이를 보이지 않았다.