Impact of Nitrate and Ammonium Ratios on Flowering and Asexual Reproduction in the Everbearing Strawberry Cultivar Fragaria × ananassa Albion

Ever-bearing (EB) strawberries are long-day cultivars that show perpetual flowering behavior. Compared to June-bearing short-day cultivars, EB cultivars can initiate flowers with less dependency on light and temperature levels. This leads to a more consistent flowering and fruiting pattern, making EB cultivars favorable for areas with long growing seasons. However, this flowering pattern also brings significant challenges to open-field strawberry nurseries. Consistent flower development in EB cultivars frequently leads to increased labor cost for manual flower removal on nursery ground. The alteration of flowering behavior via fertilizer regimes could be a cost-effective tool for strawberry nurseries. However, while it is known that the source of nitrogen (N) impacts strawberry flowering, its effect on strawberry propagation rates needs further investigation. The objective of this study was to investigate the impact of nitrate (NO3−) to ammonium (NH4+) ratio on flower and daughter plant production in the EB strawberry cultivar ‘Albion’ (Fragaria × ananassa c.v. ‘Albion’). Strawberry plants were grown in a completely randomized design under greenhouse conditions (26.6 °C, 16 h photoperiod). Four treatments of NO3−:NH4+ were implemented: (1) 100%:0%; (2) 80%:20%; (3) 60%:40%; (4) 50%:50%. Strawberry plants fertilized with a 60%:40% NO3−:NH4+ ratio produced 17–31% fewer inflorescences than those fertilized with 100%:0% (8.8 ± 1.19) and 80%:20% (10.3 ± 1.85) ratios. The production of daughter plants remained similar in all four treatments. Our results show that increased ratios of ammonium in combination with decreased ratios of nitrate reduce flowering of EB strawberry cultivars, while propagation rates remain consistent. These results could potentially lead to the development of fertilizer regimes for strawberry nurseries to reduce flower production in EB cultivars.

Pircinque: new strawberry cultivar for Brazilian producers

ABSTRACT The strawberry cultivar ‘Pircinque’ was developed by the breeding program of Consiglio per la Ricerca in Agricoltura e l’Analisi dell’Economia Agraria - Centro di Olivicoltura, Frutticoltura e Agrumicoltura (CREA-OFA-FRF), an Italian research entity, and introduced in Brazil in 2013 by the Centro de Ciências Agroveterinárias da Universidade do Estado de Santa Catarina (CAV-UDESC). In the breeding program in which it originated, ‘Pircinque’ was selected for plant rusticity and resistance to soil pathogens. It can be cultivated where soil sterilization techniques are not used. In Brazil, the cultivation of ‘Pircinque’ has shown to be promising in the major strawberry producing regions. The main characteristics that allowed the development of this cultivar among the growers were plant vigor, productivity, rusticity, flavor, pulp firmness, crispness, sweetness and fruit color. When grown with excessive nitrogen fertilization fruit sensitivity to Botrytis cinerea fungal attack has been found, and a high vegetative plant growth. Due to fruits peculiarity, many growers make differentiated sales, adding value to quality product. Also, due to the high post-harvest period, many growers allocate part of the production to more distant locations. These characteristics are determinant for the cultivar Pircinque be distinguishable from other strawberry cultivars already marketed in Brazil. The cultivar was registered at the Ministério da Agricultura, Pecuária e Abastecimento (MAPA) in 2016, and the commercialization of plants started in 2017 with five nurseries accredited to produce and market ‘Pircinque’ plants throughout Brazil.

Cross-pollination affects fruit colour, acidity, firmness and shelf life of self-compatible strawberry

Cross-pollination affects the fruit characteristics of many crops but the effects of cross-pollination on fruit quality of strawberry (Fragaria × ananassa Duch.) are poorly known. This study determined how cross-pollination affects fruit quality of the strawberry cultivar, Redlands Joy, under controlled environment conditions. Plants were allocated to one of four treatments, with all flowers on each plant receiving either: (1) unassisted self-pollination (Autogamy); (2) hand-pollination with Redlands Joy pollen (Self); (3) hand-pollination with cross-pollen from a small-fruited cultivar (Sugarbaby); or (4) hand-pollination with cross-pollen from a large-fruited cultivar (Rubygem). Cross-pollination did not significantly affect plant yield or fruit mass, size, shape, firmness or shelf life. However, cross-pollination affected fruit colour and taste attributes. Cross-pollinated fruit were 3%–5% darker than self-pollinated fruit. They also had 26%–34% lower acidity and 43%–58% higher Brix:acid ratio. Cross-pollination by Sugarbaby increased fruit P, K, Ca, Fe and Mn, but decreased B, Cu and Zn, concentrations. Cross-pollination by Rubygem increased fruit Mn, but decreased K and Na, concentrations and reduced shelf life. Fruit mass, length, diameter and firmness within all treatments increased with increasing numbers of fertilized seeds per fruit. Hand self-pollinated fruit had a higher percentage of fertilized seeds than fruit arising from autogamy and they were also darker, redder, firmer, and had a longer shelf life, higher protein concentration, and lower Al and Na concentrations. The results indicate that strawberry fruit quality can be affected by both the source of pollen and the number of stigmas pollinated.

Characterization of Strawberry Host Plant Resistance to Powdery Mildew caused by Podosphaera aphanis

Host plant resistance is an essential tool in plant disease management worldwide. Evaluations of strawberry cultivar resistance to powdery mildew were done previously in California, but many new cultivars have been released since the last evaluation in 1996 and merit evaluation for today’s growers. Two studies were conducted over the winter and summer of 2020, evaluating ten commonly grown cultivars. Powdery mildew-free plants were established in 3 L pots under high plastic tunnels and after three weeks (four- to five-leaf stage) moved into a powdery mildew-infested greenhouse. Disease incidence and severity ratings were taken weekly beginning at the first sign of disease. Ratings taken at 40 (winter) and 41 (summer) days after transfer to the greenhouse were used to make comparisons among cultivars. Significant differences were found in foliar disease severity among cultivars, but none were totally free of disease. Moderately resistant cultivars were ‘San Andreas’ and ‘Sweet Ann’. Highly susceptible cultivars were ‘BG 3.324’ and ‘Royal Royce’. Two field evaluations of the ten cultivars confirmed the observed relative differences in host resistance under field conditions. This information is valuable to California strawberry growers who select cultivars based in part on their susceptibility to economically important diseases such as powdery mildew.

Influence of irrigation regimes on yield, pomological parameters and population development of Tetranychus cinnabarinus Boisd. (Acari: Tetranychidae) in strawberry

In this study, the effect of full (IR100), 50% (IR50), 75% (IR75) and 125% (IR125) irrigation levels on population development of the carmine spider mite (CSM) as well as on yield and some pomological properties of ‘Fortuna’ strawberry cultivar grown in high tunnels were evaluated in two consecutive growing seasons (2016–2017 and 2017–2018). The numbers of CSM were significantly lower on strawberry leaves which were irrigated by IR50 and IR75 in both growing seasons. Full (IR100) and highest (IR125) irrigation levels were the most favorable for the development of CSM populations. On the other hand, in the CSM thriving period (2017), the fruit weight was generally high in the plots with the highest irrigation (IR125) level. Although there was no interaction with the CSM population, fruit acidity (%) increased in the IR100 and IR125 irrigation levels, possibly due to stress in plants, when CSM population was highest (in March). In the absence of CSM, fruit acidity was significantly high in the plots where water stress was experienced. While no significant interaction was found between the pomological characters and the CSM population, the mites affected the yield significantly in that plants were more productive under IR 75 even when there was a CSM population. This study suggests that the application of IR75 level in Fortuna strawberry is related to lower CSM population growth and significantly higher yields.