Floral Competence of Primocane-fruiting Blackberries Prime-Jan and Prime-Jim Grown at Three Temperature Regimens

Abstract

<jats:p>We investigated the responses of staminate and pistillate floral components of Prime-Jan and Prime-Jim primocane-fruiting blackberry (<jats:italic>Rubus</jats:italic> L. subgenus <jats:italic>Rubus</jats:italic> Watson) to three different growth chamber temperature regimens, 35.0/23.9 °C (HT), 29.4/18.3 °C (MT), and 23.9/12.8 °C (LT). Temperature was negatively related to flower size, and morphologically abnormal floral structures were evident in 41% and 98% of the MT- and HT-grown plants, respectively. Anthers of LT- and MT-grown plants dehisced. The viability of pollen (as deduced through staining) from Prime-Jan grown at LT or MT exceeded 70%, whereas that of Prime-Jim pollen was significantly reduced (&lt;40%) by the MT regimen. In vitro pollen germinability (typically &lt;50%) was negatively influenced by temperature but was unaffected by cultivar. Pollen useful life was diminished under HT conditions; LT-grown pollen held at 23.9 °C retained 63% of its original germinability over a 32-h period, while the germinability of that held at 35.0 °C for 16 hours decreased by 97%. Virtually all flowers cultured under HT conditions were male sterile, exhibiting structural or sporogenous class abnormalities including petaloidy and malformation of tapetal cells or microspores; HT anthers that were present, failed to dehisce. Stigma receptivity, pistil density, and drupelet set were also negatively influenced by increased temperature; values for these parameters of floral competency among control plants were reduced by 51%, 39%, and 76%, respectively, in flowers cultured under HT conditions. In this study, flowering and fruiting parameters, and presumably the yield potential of Prime-Jan and Prime-Jim, were adversely affected by increased temperature. However, their adaptive response to heat stress under field conditions awaits assessment.</jats:p>

Intercropping Winter Greens between Blackberry Rows for Year-round High Tunnel Production

“…The sides were kept down in the early spring of this study for the kale and spinach season, which may have caused a negative effect on blackberry yield. In other studies with primocane fruiting blackberry, flowers of high tunnel cultivated plants exhibited decreases in pollen competence of up to 75% due to high temperatures (Stanton et al, 2007). The possible temperature-induced low pollen competence may be responsible for the observed low drupelet density of some berries in this study.…”

“…Blackberry has a lethal minimum temperature of 0°F, after which canes will exhibit damage and be less fruitful (Yao, 2018). To be fruitful, blackberry needs a dormancy period with 300 to 900 chilling hours spent in temperatures below 45°F (Stanton et al, 2007). Blackberry canes can live for 15 years and are productive for 9 years, depending on cultivar and cultivation practices (Takeda et al, 2002).…”

High Tunnel versus Open Field: Management of Primocane-fruiting Blackberry Using Pruning and Tipping to Increase Yield and Extend the Fruiting Season

“…4). Furthermore, ovule viability and receptivity to pollen grains has been shown to decline with exposure to high temperatures (29 to 35°C ; Stanton et al, 2007). Drake and Clark (2003) reported that bloom time temperatures of 36°C resulted in small, crumbly fruit from tipped treatments in 'Prime-Jan' and 'Prime-Jim'.…”

Blackberry Production Systems - A Worldwide Perspective

“…Genotypes of annual-fruiting blackberry are being grown in evaluation trials in many production regions. Cultivars that are less sensitive to high temperature effects on fruit set (Stanton et al, 2007), sun damage of fruit, can be manipulated to fruit during high-value market seasons, and are thornless are desired.…”