Fasciation in Strawberry Floral Organs and Possible Implications for Floral Transition

Fasciation in strawberry is characterized by an enlarged and flattened receptacle, clustering of flowers, and altered inflorescence architecture. However, the developmental process of fasciated flowers remains obscure. In this study, the fasciation incidence and developmental process in the primary fruit and inflorescence architecture were evaluated and compared for the non-susceptible cultivars, ‘Nyoho’ and ‘Sagahonoka’ and one of the most susceptible cultivars, ‘Ai-Berry’. The severity and frequency of flower and inflorescence fasciation was clearly greater in the vigorously growing large plants of ‘Ai-Berry’ compared to small plants and large plants of the other two cultivars. In ‘Ai-Berry’, the deformation of the large shoot apical meristem (SAM) into an oval shape was the initial symptom observed before and during floral transition. Such oval-shaped SAMs often differentiated two or more leaf primordia almost at the same time, which then developed into divided multiple vegetative SAMs before floral transition and linearly-fasciated SAMs during floral transition, respectively. The development of fasciation symptoms was observed after downregulation of FaTFL1. Although inflorescence or receptacle fasciation could be controlled when early and rapid floral induction was achieved by intermittent low-temperature treatment, severe fasciation was observed in late-flowered plants which were either not responsive or not subjected to this treatment. These results indicate that fasciation of floral organs may be triggered and develop during floral transition and that temperature fluctuations around boundary values between floral inhibition to induction may cause a half-finished or slowly processed floral transition and finally result in severe fasciation in vigorously growing ‘Ai-Berry’ plants

Effect of boron deficiency on tip burn and malformed fruit incidence in strawberries

Boron (B) is an essential micro element for plants and plays important roles in the synthesis and functions of cell wall. B deficiency has been reported as one of the causes of fruit malformation in strawberries. We investigated the effect of B deficiency on flower and fruit development of forced strawberries for two cropping seasons (2015-2017). In the second season, B was resupplied for B-deficient plants and we investigated changes in fruit development. When B-free nutrient solutions were supplied, tip burn began to occur in newly emerging leaves and calyx 2 to 3 months later, and fruit malformation including seedy or only partly developed fruits with undeveloped achenes occurred frequently. However, these deficient symptoms were quickly disappeared by supplying B containing nutrient solutions. In conclusion, B nutrition is closely related to the occurrence of fruit malformation through fertility of pollen and pistils, and also development of receptacle tissue in strawberries. It should be possible to reduce fruit malformation in strawberries by proper control of B nutrition.　B（ホウ素）は植物にとって必須な微量要素であり，イチゴの受精不良果発生要因の1 つである．そこで2015年度と2016年度の2 回にわたりB 欠乏がイチゴの受精不良果発生に及ぼす影響について調査した．また，2016年度はB 欠乏処理後にB 回復処理を行い，その後のイチゴの果実形態の変化についても調査した．その結果，B欠乏処理を行うと蒸散機能の低い新葉や花芽においてチップバーンが発生し，種浮き果や部分不受精を主とした受精不良果が多発した．しかし，B 回復処理を行うことでこれらの症状が改善することが明らかになった．B は受精不良果発生に関係しており，欠乏条件下で根から吸収させると急速に若い成長中の組織に転流することが示されたことから，B 栄養をコントロールすることでB 不足によるイチゴの受精不良果発生を軽減できる可能性があると考えられる

Effect of boron deficiency on tip burn and malformed fruit incidence in strawberries

Boron (B) is an essential micro element for plants and plays important roles in the synthesis and functions of cell wall. B deficiency has been reported as one of the causes of fruit malformation in strawberries. We investigated the effect of B deficiency on flower and fruit development of forced strawberries for two cropping seasons (2015-2017). In the second season, B was resupplied for B-deficient plants and we investigated changes in fruit development. When B-free nutrient solutions were supplied, tip burn began to occur in newly emerging leaves and calyx 2 to 3 months later, and fruit malformation including seedy or only partly developed fruits with undeveloped achenes occurred frequently. However, these deficient symptoms were quickly disappeared by supplying B containing nutrient solutions. In conclusion, B nutrition is closely related to the occurrence of fruit malformation through fertility of pollen and pistils, and also development of receptacle tissue in strawberries. It should be possible to reduce fruit malformation in strawberries by proper control of B nutrition.　B（ホウ素）は植物にとって必須な微量要素であり，イチゴの受精不良果発生要因の1 つである．そこで2015年度と2016年度の2 回にわたりB 欠乏がイチゴの受精不良果発生に及ぼす影響について調査した．また，2016年度はB 欠乏処理後にB 回復処理を行い，その後のイチゴの果実形態の変化についても調査した．その結果，B欠乏処理を行うと蒸散機能の低い新葉や花芽においてチップバーンが発生し，種浮き果や部分不受精を主とした受精不良果が多発した．しかし，B 回復処理を行うことでこれらの症状が改善することが明らかになった．B は受精不良果発生に関係しており，欠乏条件下で根から吸収させると急速に若い成長中の組織に転流することが示されたことから，B 栄養をコントロールすることでB 不足によるイチゴの受精不良果発生を軽減できる可能性があると考えられる

Fasciation in Strawberry Floral Organs and Possible Implications for Floral Transition

Fasciation in strawberry is characterized by an enlarged and flattened receptacle, clustering of flowers, and altered inflorescence architecture. However, the developmental process of fasciated flowers remains obscure. In this study, the fasciation incidence and developmental process in the primary fruit and inflorescence architecture were evaluated and compared for the non-susceptible cultivars, ‘Nyoho’ and ‘Sagahonoka’ and one of the most susceptible cultivars, ‘Ai-Berry’. The severity and frequency of flower and inflorescence fasciation was clearly greater in the vigorously growing large plants of ‘Ai-Berry’ compared to small plants and large plants of the other two cultivars. In ‘Ai-Berry’, the deformation of the large shoot apical meristem (SAM) into an oval shape was the initial symptom observed before and during floral transition. Such oval-shaped SAMs often differentiated two or more leaf primordia almost at the same time, which then developed into divided multiple vegetative SAMs before floral transition and linearly-fasciated SAMs during floral transition, respectively. The development of fasciation symptoms was observed after downregulation of FaTFL1. Although inflorescence or receptacle fasciation could be controlled when early and rapid floral induction was achieved by intermittent low-temperature treatment, severe fasciation was observed in late-flowered plants which were either not responsive or not subjected to this treatment. These results indicate that fasciation of floral organs may be triggered and develop during floral transition and that temperature fluctuations around boundary values between floral inhibition to induction may cause a half-finished or slowly processed floral transition and finally result in severe fasciation in vigorously growing ‘Ai-Berry’ plants