Influence of weather conditions, irrigation and plant age on yield and alpha-acids content of Czech hop (Humulus lupulus L.) cultivars

Abstract

This study quantifies the effects of weather conditions, irrigation, and plant age on yield and alpha-acids content of Czech hop cultivars Saaz, Sládek, Premiant and Agnus in a 25-year long period, i.e., from 1993 to 2018. The yields of Czech hop cultivars were increasing for the first three years of plant age until they stabilized and then started to decline slightly for 15 to 20 years until they reached the optimal time for replanting. The highest alpha-acids content in hop cones was achieved in the first year of cultivation, followed by a logarithmic decline in the upcoming years. Rainfall was the most significant factor that positively influenced the yield of Saaz hops with correlations of r = 0.59 and 0.61 (P < 0.01) for total seasonal rainfall (April–August), 0.65 (P < 0.001) and 0.60 (P < 0.01) for daily rainfall above 3 mm, 0.37 (P < 0.05) and 0.58 (P < 0.01) for rainfall in May and 0.50 (P < 0.01) and 0.32 (P < 0.05) in July in the Saaz region and the Stekník farm, respectively. The yield of cultivars Sládek, Premiant and Agnus was not statistically influenced by the amount of precipitation, but there was a positive effect of irrigation level on yield increase with correlations 0.58 (P < 0.01), 0.55 and 0.49 (P < 0.05), respectively. High air temperatures during summer were the most significant factor that negatively influenced the alpha-acids content with the correlations ranging from –0.56 to –0.83. However, cv. Agnus showed a stable weather-independent alpha-acids content.

Gene expression for secondary metabolite biosynthesis in hop (Humulus lupulus L.) leaf lupulin glands exposed to heat and low-water stress

“…Of the 1869 DE transcripts from comparisons of CT/CW × HT/CW plants, many can be putatively linked to alpha acid and volatile secondary metabolite production. High temperatures have been clearly linked to reductions in alpha acid production in the past 8,10 , and this study found VPS was down-regulated under heat stress. GO terms related to naringenin-chalcone synthase activity (involved in xanthohumol biosynthesis) and terpene synthase activity (involved in volatile secondary metabolite production) were enriched in the list of DE transcripts, and usually significantly down-regulated under HT stress, suggesting that xanthohumol biosynthesis and volatile secondary metabolite or "hop oil" biosynthesis are also compromised during HT stress conditions.…”

“…Expression of the putative VPS transcript 001329F.g74 was much higher than expression of 00239F.g29, but both transcripts declined significantly in all treatments compared to control treatments, more so than the other genes involved in bitter acid metabolism. Given that there are no transcripts of HlPT1L and HlPT2 in our database, we cannot link previously described declines in alpha acid content [8][9][10] due to HT and LW stress exclusively to VPS. However, stress induced lability in this gene and/or its regulatory elements [51][52][53] likely contributes significantly to declines in bitter acid content during periods of heat and lowwater stress.…”

“…A number of studies have correlated reduced cone yield with LW stress 8,10,11 . We found significantly decreased DW, A, g sw , E, C i , and ɸCO 2 under LW stress.…”

Vulnerability of hop‐yields due to compound drought and heat events over European key‐hop regions

“…At the beginning of June, the tallest plants began flowering in spite of the fact that they had not yet finished their vegetative growth. The result was early flowering after pruning, which agrees with other experimental studies (e.g., Donner et al ., 2020). The basic feature of such irregular hop growth and hop cone development during dry‐hot events is faster generative development in comparison with vegetative growth.…”

“…The majority of studies have been developed by addressing individual factors, even though the impacts usually depend on multiple potentially dependent variables (Cerenak et al ., 2010; Mikyška and Jurková, 2011; Gloser et al ., 2013; Krofta et al ., 2013; Srečec et al ., 2013; Čeh, 2014; Kolenka et al, 2016). With regard to our study area, the majority of hop studies have been focused on new trends in hop brewing, beer and the hop market in Germany (e.g., Weihrauchet et al, 2012), Czech Republic (e.g., Hejnák et al ., 2015; Natsume et al ., 2015; Patzak et al ., 2015; Donner et al ., 2020), Great Britain (e.g., Darby, 2006; Darby, 2010; Capper and Darby, 2014), France (e.g., Steyer et al ., 2014), Spain (e.g., (Cameira et al ., 2007; Fandiño et al ., 2015) and Slovenia (e.g., Pavlovič, 2012; Pavlovič et al ., 2012; Pavlovič et al ., 2013; Pavlovič, 2014). In all hop‐growing regions across Europe, extreme CEs limit beer supply, and hop prices are strongly influenced by the weather and by the level of stocks (Colen and Swinnen, 2016).…”