A recent study by researchers at Washington State University has revealed promising news for raspberry growers facing the challenges of climate change. By applying biostimulants containing glycine betaine and kelp extract, scientists demonstrated significant improvements in the heat tolerance of red raspberry plants (Rubus idaeus), offering hope for future agricultural resilience.
The research, conducted from June to September 2023 at the Irrigated Agriculture Research and Extension Center in Prosser, Washington, tested three commercial biostimulants: FRUIT ARMOR™, Optysil®, and KelpXpress™. These products were administered to three different raspberry genotypes, including the highly valued ‘Meeker’ cultivar, under controlled high-temperature conditions (Tmax ≥ 35 °C).
Historically, extreme heat has been known to disrupt key physiological processes within plants, including photosynthesis, which is integral to their growth and productivity. The study’s lead researchers sought to explore whether biostimulants could mitigate these adverse effects, as climate models predict rising temperatures and increased occurrences of heat waves by 2100.
The findings were encouraging. The ‘Meeker’ genotype displayed consistent performance, maintaining high chlorophyll fluorescence and photosynthesis levels regardless of treatments. Interestingly, the application of FRUIT ARMOR™, which consists mostly of glycine betaine, showed marked enhancements across the other genotypes, particularly WSU 2188 and ORUS 4715-2. These genotypes also exhibited improved photosynthesis rates and non-structural carbohydrate accumulation stemming from the treatments.
Chlorophyll fluorescence measurements indicated distinct interactions between genotype and biostimulant treatments over the study's 28 days. Notably, ‘Meeker’ plants treated with FRUIT ARMOR™ maintained stable fluorescence ratios, whereas untreated 'ORUS 4715-2' showed significant declines post-exposure to heat stress. The recovery observed with biostimulant treatments marks glycine betaine’s potential role as a protector of the photosynthetic process.
Another biostimulant, KelpXpress™, which is derived from the brown seaweed Ascophyllum nodosum, also demonstrated positive effects. This product led to increases in chlorophyll fluorescence and gas exchange rates, reaffirming the hypothesis around kelp extracts bolstering plant resilience to heat stress. The antioxidants enhanced by kelp extract through photosynthesis-related pathways appear to safeguard plants from the damaging effects of elevated temperatures.
Biochemical assessments revealed significant increases in anthocyanin levels, with plants receiving FRUIT ARMOR™ and KelpXpress™ showing three- to eleven-fold increases compared with control plants. The accumulation of these pigments, beneficial for plant physiology, suggests not only improved growth but also enhanced photoprotection mechanisms, allowing raspberry plants to withstand oxidative stress caused by heat.
The dynamic between the treatments and plant responses led researchers to conclude: “Biostimulants improved WSU 2188 and ORUS 4715-2 thermotolerance by improving PSII, photosynthetic, and antioxidative capacities.” These insights may lead to more effective strategies for maintaining raspberry production as climate conditions worsen.
The economic ramifications are noteworthy; raspberries are among the valuable fruit crops threatened by extreme climatic conditions. With production nearly doubling over the past decade, strategies like utilizing biostimulants become integral for sustainable farming practices. This study positions biostimulants as viable tools for growers, potentially reshaping how raspberries are cultivated against the rigorous backdrop of climate change.
Further investigations are warranted to refine application protocols for biostimulants and assess their long-term effects under field conditions. By establishing cost-benefit analyses, agriculturalists can make informed decisions about integrating such innovative methods to combat the impacts of heat stress effectively.
This research provides encouragement to both farmers and the industry, showing pathways to bolster crop resilience and maintain the viability of raspberry cultivation amid face of rising global temperatures.