High CO2 Reduces Spoilage Caused by Botrytis cinerea in Strawberry Without Impairing Fruit Quality

High CO₂ (> 20 kPa) conditions are beneficial for suppressing spoilage caused by Botrytis cinerea in strawberry fruit; however, these conditions are often accompanied by discoloration, off-flavors, and faster softening. Stepwise increments of CO₂ concentrations have been proposed to alleviate injuries in fruits caused by high CO₂. In this study, we investigated whether stepwise increments of CO₂, up to 30 kPa and under a reduced O₂ concentration, are beneficial for reducing fungal spoilage without inducing CO₂ injury symptoms in strawberry fruit. Based on recommended settings (5-10 kPa O₂ with 15-20 kPa CO₂), we first selected optimal O₂ and CO₂ concentrations that best-reduced spoilage caused by B. cinerea in red ripe "Sonsation" strawberry fruit. We found that higher O₂ (10 kPa) and CO₂ (20 kPa) concentrations were most beneficial for prolonging strawberry fruit shelf life. Subsequently, we studied the performance of red ripe "Arabella" strawberry fruit stored at 5°C under different controlled atmosphere (CA) conditions (10 kPa O₂ with either 0, 20, or 30 kPa CO₂). The CO₂ concentrations were achieved either within 8 h or in a stepwise manner within the first 4 days of storage. As a control, 21 kPa O₂ and 0 kPa CO₂ were used. Following storage for up to 11 days, the spoilage incidence was assessed at 12°C for 5 days. The application of high CO₂ (20 and 30 kPa) combined with 10 kPa O₂ greatly suppressed fruit spoilage during storage and subsequent shelf life. High CO₂ suppressed respiration as well as maintained a higher pH and firmness in treated fruit. The level of total sugars did not change, but during storage, a substantial part of sucrose was converted into glucose and fructose, especially under high CO₂ conditions. High CO₂ did not affect ascorbic acid and anthocyanin levels. The stepwise increments of CO₂ did not result in beneficial effects compared to the static application of high CO₂. Our results show that "Arabella" strawberry fruit are highly tolerant to elevated CO₂ and can be stored under 30 kPa CO₂ to prolong the shelf life.

Characterization of wall-associated kinase/wall-associated kinase-like (WAK/WAKL) family in rose (Rosa chinensis) reveals the role of RcWAK4 in Botrytis resistance

BACKGROUND

Wall-associated kinase (WAK)/WAK-like (WAKL) is one of the subfamily of receptor like kinases (RLK). Although previous studies reported that WAK/WAKL played an important role in plant cell elongation, response to biotic and abiotic stresses, there are no systematic studies on RcWAK/RcWAKL in rose.

RESULTS

In this study, we identified a total of 68 RcWAK/RcWAKL gene family members within rose (Rosa chinensis) genome. The RcWAKs contained the extracellular galacturonan-binding domain and calcium-binding epidermal growth factor (EGF)-like domain, as well as an intracellular kinase domains. The RcWAKLs are missing either calcium-binding EGF-like domain or the galacturonan-binding domain in their extracellular region. The phylogenetic analysis showed the RcWAK/RcWAKL gene family has been divided into five groups, and these RcWAK/RcWAKL genes were unevenly distributed on the 7 chromosomes of rose. 12 of RcWAK/RcWAKL genes were significantly up-regulated by Botrytis cinerea-inoculated rose petals, where RcWAK4 was the most strongly expressed. Virus induced gene silencing of RcWAK4 increased the rose petal sensitivity to B. cinerea. The results indicated RcWAK4 is involved in the resistance of rose petal against B. cinerea.

CONCLUSION

Our study provides useful information to further investigate the function of the RcWAK/RcWAKL gene family and breeding research for resistance to B. cinerea in rose.