Photosynthesis, yield and α-bitter acids content of hop newbreedings and their comparison with other hop cultivars

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1 Genetics, Plant Breeding and Seed Production ORIGINAL SCIENTIFIC PAPER Photosynthesis, yield and α-bitter acids content of hop newbreedings and their comparison with other hop cultivars Jaroslav Pokorný 1, Přemysl Štranc 1, Josef Pulkrábek 1, František Hniliţka 2 1 Department of Plant Production of CULS in Prague, Kamýcká 129, Praha 6 - Suchdol, ĈR (pokornyj@af.czu.cz) 2 Department of Botanics and Plant Physiology of CULS in Prague, Kamýcká 129, Praha 6 - Suchdol, ĈR Abstract In this article we evaluate hop plants of different cultivars regarding photosynthesis rate, yield and alpha - bitter acids (BA). In an experiment we monitored Saaz hop and newly growed, sometimes more effective, hop cultivars and newbreedings, mostly with higher bitter acids content, but with worse composition of compounds important for brewing industry. Cultivars including prospective newbreeding were selected so we could cover all spectrums of cultivars from mild aromatic to high-content. Regarding photosynthesis rate and yield the best was an old Czech cultivar Saaz hop Osvald s clone 72 from root-covered seedling. Prospective newbreeding proved to be newbreeding No regarding yield and alpha - bitter acids content. Keywords: hop, newbreedings, Saaz hop, yield, alpha - bitter acids Introduction In the Czech Republic was cultivated only Saaz hop until half of the nineties. According to valid regulations it was not possible to grow other cultivars or clones in hop areas than those of Saaz hop origin. After new law approval (97/96 of code) it was possible to grow other hop cultivars (Nesvadba, 2000). Hop production and market is oriented on new cultivars production, which suits demanding requirements of brewing industry (Ţepiţka, Dostálek, 2002). New Czech hybrid cultivars of hop, breeded by Hop Institute in Ţatec, are with their performance and economic properties comparable with most of competitive cultivars, whose products are imported from USA and Germany. Czech cultivars are better in their mild bitterness resulting from genetic base, which is aromatic Saaz hop (Vent, Kloub, 1998). Hop yield formation could be characterized as a result of complex effect of different factors, e.g. genetically determined properties of cultivars and weather and soil conditions. Use of production potential is dependent on hierarchical sequence of physiological functions in different levels of plant and stand. Physiology of Saaz hop was studied a lot in the past (Pastyřík, 1973). New Czech hop cultivars introduced to growing practice from half of the nineties often have higher yield potential and different dynamics of matter growth during vegetation. But it is still a question, if they are suitable for hop areas in the CR. Material and Methods Experiment was realized at the experimental station of the Czech University of Life Sciences in Prague with carbonate chernozem on loess. Hop garden is situated 280 meters above sea level with longitude and latitude Average year temperature is around 7.9 C, average year sum of precipitations is approximately 526 mm. 480

2 Genetika, oplemenjivanje bilja i sjemenarstvo In the experiment we monitored four hop cultivars growed in the CR. The first cultivar was Saaz hop (Osvald s clone 72 M) which belongs among mild aromatic hops. Seedling was of two types: (1) naked roots producer: Hop Institute in Ţatec; (2) covered roots producer: Ing. Jaroslav Štranc, CSc. Other cultivars were: Premiant belongs to bitter cultivars, Agnus high content cultivars, but they have properties of bitter cultivars and foreign cultivar Magnum typical high content cultivar. Also four prospective newbreeders were used in experiment: 4788, 4784, 4237, From each cultivar we selected one average plant, in the same growth phase in which were measured physiological processes. We measured photosynthesis rate by commercial portable infrared analyzer LC pro+ (ADC Bio Scientific Ltd.) with leaf chamber, which enables to measure with irradiation density FAR ( nm) in range of µmol.m - 2.s -1 and with temperature range of -5 up to +50 C. We measured on these days: 6. 6., , 3. 7., and Measured values were recorded automatically after chamber conditions stabilization, for minutes in 1 minute interval. Optimum temperature was set to 25 C and irradiation density was 600 nm. Hop plants were monitored and evaluated from emergence to harvest. Alpha - bitter acids content was determined by conductometry. Hop yield is expressed in tons of fresh hop per hectare and in tons of dry hop per hectare (converted to 10% of hop moisture). Hop garden was planted in autumn 2006 ( ) under relatively favourable weather conditions (slightly dry). Manually ditched hollows (35 cm) were filled with compost. After planting and covering of hop seedling we put on surface small layer of mulch for better aeration and moisture collection. From each plant were carried in average two hop shoots to one hop pole. In vegetation period 2007 were except cutting performed usual farming practices. Main growing measures in vegetation period 2007 were: 4.5. hop stringing one hop pole to each plant, weeding of interrow and weeding in rows, hop fixing 2 shoots per one hop pole + SA 300 kg.ha -1, spray against Tetranychus urticae (Nissorun 10 WP 0.05%), weeding of interrow and weeding in rows, weeding of interrow and weeding in rows, reparative hop fixing, spray against Tetranychus urticae (Ortus 5 SC 0.125%), spray against Pseudoperenospora humuli + growth stimulation (Aliette Bordeaux 0,4% + Lexin 0.25 l.ha -1 ), removal of redundant hop shoots, weeding of interrow, weeding in rows + additional fertilization LV 250 kg ha -1, shallow additional ploughing of rows, rolling of diverted heads of fixed hop-vines, spray against Phorodon humuli + growth stimulation (Karate Zeon 5 CS 0,02% + Lexin 0.25 l ha -1 ), spray against Tetranychus urticae (Omite 30 W 0.2%), manual hop harvest. Results and discussion Vegetation monitoring - Hop stand was evaluated as good in the first year of planting. Cultivars Saaz hop: 1 naked-roots seedling and 2 covered-roots seedling, Premiant, Agnus, 4788, 4784, reached top of construction, cultivar Magnum and newbreedings No and 4237 reached only of construction height. Habitus was cylindrical in most cultivars except Saaz hop and 4784, which had cylindrical up to box habitus and these two cultivars had also better growth condition. Hop stand was established in autumn of last year and due to this fact hop cutting was not done. Partially also for this reason the stand was in most cases very unequal. Only Saaz hop had later beginning of lengthening growth (by about 10 days) and its good equability. In plants from this seedling we also found more equal beginning of shooting, cone formation, flowering and technical maturity. Slightly lower, but still good equability was also found in cultivar In Saaz hop from nakedroots seedling we found high percentage of missing (dead) plants, whereas plants died also 45. hrvatski i 5. međunarodni simpozij agronoma 481

3 photosynthesis rate (µmol CO2.m-2.s-1) Genetics, Plant Breeding and Seed Production in newbreeders No and Higher percentage of missing plants in naked-roots seedling of Saaz hop was probably caused by worse quality of seedling. Physiological measurements - Photosynthesis rate was measured in 5 terms. Terms were chosen in dependence on phenology phases of hop plants. Photosynthesis rate during vegetation is shown in Graph 1. Average values of photosynthesis rate are shown in Table Saaz-hop Osvald clone 72-2 Saaz-hop Osvald clone 72-1 Premiant Agnus magnum measurement date Graph 1. Average Photosynthesis Rate of Monitored Hop Cultivars During Vegetation Table 1. Photosynthesis Rate in µmol of CO 2.m -2.s -1 Measurement date Average Saaz-hop Saaz-hop Premiant Agnus Magnum Graph 1 and Table 1 show differences in photosynthesis rate between cultivars and terms of measurement. Regarding terms of measurement we can say that the highest photosynthesis rate (except cultivar No. 4784) was measured at the beginning of June. On the highest immediate photosynthesis rate was found in Saaz hop (Osvald s clone 72 naked roots seedling µmol CO 2.m -2.s -1 ). On contrary the lowest immediate photosynthesis rate was found in cultivar No (7.64 µmol CO 2.m -2.s -1 ). In the half of June, probably due to significant short-term drought and above normal temperatures photosynthesis rate decreased nearly in all monitored cultivars. Only cultivar 4784 had very balanced photosynthesis rate during all monitored period until the beginning of August, when it significantly decreased. At the beginning of July photosynthesis rate did not differ from previous period. Similar trend in photosynthesis rate in Saaz hop (Osvald s clone 72 roots covered seedling), Agnus and 4784 was found in the half of July. Cultivars Premiant, Magnum, No and 4237 had photosynthesis increasement in the 482

4 Genetika, oplemenjivanje bilja i sjemenarstvo range from 1,16 to 3,16 µmol CO 2.m -2.s -1, but in Saaz hop (Osvald s clone 72 naked roots seedling) and No photosynthesis rate decreased. Very different photosynthesis rate was measured in the last term ( ), when in Saaz hop (Osvald s clone 72 naked roots seedling), Premiant, Magnum, 4784 and 4237 photosynthesis rate decreased rapidly. Cultivar Magnum had in this term the lowest value of photosynthesis rate during all monitored period (1.62 µmol CO 2.m -2.s -1 ). On contrary in Saaz hop (Osvald s clone 72 naked roots seedling), Agnus and No photosynthesis rate slightly increased. Obtained results show that the highest average photosynthesis rate in all vegetation period had cultivar Saaz hop (Osvald s clone 72 covered roots seedling, 8.96 µmol CO 2.m -2.s -1 ). We can say that photosynthesis rate in this cultivar did not show any significant variations due to changes in weather conditions during vegetation. Results show good adaptability of photosynthetic apparatus of this cultivar to weather conditions changes. The highest immediate photosynthesis rate was found in cultivar Saaz hop, but in naked roots seedling (12.36 µmol CO 2.m -2.s -1 on ). Hop cultivar from this seedling showed similarly balanced photosynthesis rate as the same cultivar from covered roots seedling. But average value of photosynthesis rate in monitored period was lower than in cultivar from covered roots seedling, because in the last measurement in naked roots seedling photosynthesis rate decreased to value 4.44 µmol CO 2.m -2.s -1. The result was earlier termination of intensive growth of hop plants from naked roots seedling, which proves different vitality of seedling of the same Saaz hop cultivar from two different producers in favour of covered roots seedling. Cultivar Premiant showed the lowest average photosynthesis rate (5,16 µmol CO 2.m -2.s -1 ). In this cultivar we also found large unequality of photosynthesis rate. In cultivars Agnus, Magnum and 4237 average value of photosynthesis rate did not differ very much in monitored period (6,39, 6,37 and 6,25 µmol CO 2.m -2.s -1 ). During last measurement in cultivar Magnum photosynthesis rate value decreased to the lowest obtained value (1,62 µmol CO 2.m -2.s ). Cultivar No had average photosynhtesis rate in monitored period 7,35 µmol CO 2.m -2.s -1, cultivar No ,05 µmol CO 2.m -2.s -1 and cultivar No ,38 µmol CO 2.m -2.s -1. Yield and content of alpha-bitter acids - Yields are shown in Table 2. and alpha-bitter acids (BA) contents in Table 3. Table 2. Yields in t.ha -1 of Dry Hop t.ha -1 hop -dry Saaz hop 2 Saaz hop 1 Premiant Agnus Magnum Table 3. Contents of Alpha-Bitter Acids Saaz hop 2 Saaz hop 1 Premiant Agnus Magnum % BA Regarding yield the best result was reached by cultivar Saaz hop (Osvald s clone 72 covered roots seedling) 1.11 t.ha -1 (of dry hop) with relatively high content of alpha bitter acids 6.2 % (mildly aromatic cultivar). The same cultivar but from naked roots seedling reached higher bitter acids content - 6,85%, but the yield was by about 0,3 t.ha -1 lower in comparison with cultivar from covered roots seedling. Differences in yield and bitter acids 45. hrvatski i 5. međunarodni simpozij agronoma 483

5 Genetics, Plant Breeding and Seed Production content supports above mentioned photosynthesis rate. Very good yield reached also newbreeding 4237 with yield of 1,07 t.ha -1, but with significantly lower content of alphabitter acids (3.25 %). The third best yield had cultivar ,01 t.ha -1. This cultivar had high content of alpha-bitter acids (10.55 %) and belongs to the group of highcontent cultivars. In newbreeders 4788 and 4837 we found low up to very low yield (0,62 and 0,45 t.ha -1 ), whereas cultivar 4788 had content of alpha bitter acids 8,65 % and cultivar 4837 reached 4.90 %, which is the second lowest value. Cultivars Premiant and Agnus did not exceed in our experiments average yield values. Regarding bitter acids content these cultivars belong to bitter varieties (Premiant) up to highcontent varieties (Agnus), whereas cultivar Agnus should reach according to breeder higher bitter acids content. Foreign cultivar (Germany) Magnum, which provided yield 0.63 t.ha -1 and alpha-bitter acids content was 9.65 %, did not meet parameters for highcontent hops. Conclusion Based on obtained results we can say that average photosynthesis rate during monitored vegetation period was the highest in Saaz hop (Osvald s clone 72 covered roots seedling). Saaz hop has in our conditions the best ability to utilize photosynthetic energy during vegetation, which is confirmed by the highest yield of all monitored cultivars - 1,11 t.ha -1, with relatively high content of alpha-bitter acids. Due to this Saaz hop belongs to traditional and the most growed cultivars in the CR. Seedling quality has significant influence on productivity of hop stand. Regarding yield in newbreeders prospective cultivar seems to be cultivar 4237, and also cultivar 4784, whereas cultivar 4784 reaches relatively high conductometry value (10,55 %). Acknowledgement The results presented in the paper are an output from research projects 2007/2007, CIGA The estimation of biological and technological characteristics of new breedings hop plants and their comparison with fine aroma and high volume of alpha acids varieties References Ţepiţka J., Karabín M. (2002). Polyphenolic compounds of beer natural antioxidants. Chemické listy. 96 (2): Nesvadba, V. (2000). Rajonizace hybridních genotypů chmele. Chmelařství. (9-10): Pastyřík, V. (1973). Vliv přírodních podmínek na výkonnost chmelových odrůd. Kandidátská disertaţní práce: 34 Vent, L.- Kloub,V. (1998). Provozní várky s ţeskými odrůdami chmele. Chmelařství. (6):