8th international scientific/professional conference SECTION II Izvorni znanstveni rad / original scientific paper Allelopathic effect of invasive species giant goldenrod (Solidago gigantea Ait.) on wheat and scentless mayweed Marija Ravlić1, Renata Baličević1, Ana Peharda2 1Faculty of Agriculture, Josip Juraj Strossmayer University of Osijek, Kralja Petra Svačića 1d, Osijek, Croatia, e-mail: [email protected] 2Student, Faculty of Agriculture, Osijek, Croatia Abstract The aim of the research was to determine allelopathic potential of invasive species giant gol- denrod (Solidago giganetea Ait.) on germination and initial growth of wheat and weed species scentless mayweed (Tripleurospermum inodorum (L.) C.H. Schultz). Experiments were conducted under laboratory conditions to determine effect of water extracts in petri dish bioassay and in pots with soil. Water extracts from dry aboveground biomass of S. gigantea in concentrations of 1, 5 and 10 % (10, 50 and 100 g/l) were investigated. In petri dish bioassay, germination of wheat was slightly reduced, while all extract concentration inhibited wheat growth. T. inodorum germination and seedling growth was affected with higher extract concentration. Application of extract to pots had no effect on wheat emergence and growth, with the exception of 10 % extract which reduced root length. Emergence of T. inodorum was significantly decreased with 5 and 10 % extract for 38.5 and 49.0 %, respectively. Key words: allelopathy, Solidago gigantea Ait., crops, scentless mayweed, water extracts Introduction Excessive use of herbicides in most weed management systems is a major concern since it causes serious threats to the environment, public health and increases costs of crop production. The degree of weed seed germination inhibition and growth suppression which can be attributed to crop allelopathy is highly important and can be considered as a possible alternative weed management strategy (Asghari and Tewari, 2007., Macias, 1995.). Allelopathy is defined as any direct or indirect harmful or beneficial effect of one plant, fungus or microorganism on the other through production of allelochemicals that escape into the environment (Rice, 1984.). Allelopat- hically active crops can be utilized in different ways as i.e. water extracts and soil incorporated green manure (Đikić, 2005., Dhima et al., 2009.). Likewise, certain weed species also have the potential to be used in control of other weeds (Qasem and Foy, 2001.). Giant goldenrod (Solidago gigantea Ait.), belonging to the family Asteraceae, is a perennial herb native to North America and introduced in Europe as an ornamental plant (Weber and Jakobs, 2005.). S. gigantea is an invasive species which prefers ruderal habitats, riversides, forests, roadsides, and it is rarely found on agricultural fields (Knežević, 2006.). Allelopathic potential of goldenrod on crops was reported previously (Sekutowski et al., 2012., Bortniak et al., 2011., Beres and Kazinczi, 2000.). Since the harmful effect of allelopathic plants must be targeted on weeds, while at the same time the crop must be unaffected or tolerant, the aim of the study was to determine allelopathic po- tential of giant goldenrod (S. gigantea) water extracts on wheat and its associated weed species scentless mayweed (T. inodorum). 186 BIOSUSTAINABILITY agriculture in nature and environment protection Materials and methods Experiments were conducted in 2014 in the Laboratory of Phytopharmacy at the Faculty of Ag- riculture in Osijek. The plants of giant goldenrod (S. gigantea) were collected in late summer of 2014 at the flowering stage (Hess et al., 1997.) from ruderal habitats (edges of farm fields). The aboveground fresh biomass was oven dried, cut into small pieces and ground with electronic grinder into fine powder.Water extract was prepared according to Norsworthy (2003.) by mixing 100 grams of dry goldenrod biomass with 1000 ml of distilled water. The mixture was kept for 24 h at room temperature and filtered through muslin cloth and filter paper. The obtained extract was diluted with distilled water to give final concentrations of 1, 5 and 10 % (10, 50 and 100 g/l). Winter wheat (cv. Lucija) was acquired from Agricultural Institute Osijek, while weed seeds of scentless mayweed were collected during 2014 from agricultural fields in Osijek-Baranja County. All seeds were surface-sterilized for 20 min with 1 % NaOCl then rinsed with distilled water (Sid- diqui et al., 2009.). Two sets of experiments were conducted: 1) petri dish bioassay with filter paper and 2) pot cul- ture with soil. In the experiments with petri dishes the effect of three concentrations of extract (1, 5 and 10 %) was evaluated. Twenty five seeds of wheat or thirty seeds of scentless mayweed were placed in sterilized Petri dishes (9 cm in diameter) on top of filter paper. In each Petri dish an equal amount of certain extract was added (5 ml for wheat and 2 ml for weed), while distilled water was used in control. Petri dishes were kept at room temperature (22 °C ± 2) for 8 days. In the experiments with pots the effect of two concentrations of extract (5 and 10 %) was evalua- ted. Twenty five seeds of wheat or thirty weed seeds were sown in pots filled with commercial substrate. Each pot was treated with 75 ml of extract per 100 g of soil, while distilled water was used in control. Thereafter, all treatments were equally watered. Wheat was grown for 10, while scentless mayweed for 14 days under the same conditions. All treatments had four replications and all experiments were conducted twice. Allelopathic effect was evaluated at the end of experiments through number, length of root and shoot (cm) and fresh weight (g/mg) of seedlings. Germination percentage was calculated using the formula: G = (Germinated seed/Total seed) x 100. All emerged seedlings were counted and percentage of emergence was calculated as E= (Emerged seed/Total seed) x 100. The collected data were analysed statistically with ANOVA and differences between treatment means were compared using the LSD-test at probability level of 0.05. Results and discussion S. gigantea water extracts showed allelopathic effect on germination and growth of wheat in petri dish bioassay (Table 1.). Table 1. Effect of S. gigantea water extracts on wheat in petri dishes S. gigantea biomass in Germination (%) Root length (cm) Shoot length (cm) Fresh weight (g) water, g/l 0 99.0 a 14.7 a 8.2 a 0.14 a 10 97.0 ab 8.3 b 7.2 b 0.10 b 50 96.5 ab 3.5 c 4.4 c 0.06 c 100 93.5 b 2.3 d 2.8 d 0.04 d Means followed by the same letter within the column are not significantly different at P<0.05. 187 8th international scientific/professional conference SECTION II Only the highest concentration of extract significantly reduced germination for 5.5 %. With the increase of extract concentration, root and shoot length and fresh weight of seedlings signifi- cantly decreased compared to the control up to 84.4, 65.9 and 71.4 %, respectively. Table 2. Effect of S. gigantea water extracts on T. inodorum in petri dishes S. gigantea biomass in Germination (%) Root length (cm) Shoot length (cm) Fresh weight (mg) water, g/l 0 39.2 a 0.74 a 1.09 a 1.35 a 10 33.8 a 0.82 a 1.06 ab 1.25 a 50 37.1 a 0.41 b 0.96 b 1.29 a 100 20.4 b 0.07 c 0.54 c 0.12 b Means followed by the same letter within the column (lower case letters) or in rows (capital letters) are not signi- ficantly different at P<0.05. Higher concentrations of S. gigantea extract showed allelopathic effect on germination and growth of T. inodorum in petri dish bioassay (Table 2.). Germination and fresh weight were significantly inhibited only with 10 % extract for 47.9 and 91.1 %, respectively. Root and shoot length reduction was up to 90.5 and 50.5 %. The results of pot experiments revealed that extracts had no significant effect on emergence and fresh weight of wheat seedlings (Table 3.). Root length was decreased with higher concen- tration (for 13.1 %), while lower concentration stimulated shoot length. Table 3. Effect of S. gigantea water extracts on wheat in pots with soil S. gigantea biomass in Seedling emergence Root length (cm) Shoot length (cm) Fresh weight (g) water, g/l (%) 0 98.0 a 12.2 a 18.5 b 0.24 a 50 98.0 a 10.9 ab 19.7 a 0.24 a 100 98.0 a 10.6 b 18.6 b 0.23 a Means followed by the same letter within the column (lower case letters) or in rows (capital letters) are not signi- ficantly different at P<0.05. Except for seedlings emergence, extracts had no effect on T. inodorum seedling growth (Table 4.). Both concentrations inhibited germination for 38.5 and 49.0 %, respectively. Table 4. Effect of S. gigantea water extracts on T. inodorum in pots with soil S. gigantea biomass in Seedling emergence Root length (cm) Shoot length (cm) Fresh weight (mg) water, g/l (%) 0 35.1 a 0.73 a 1.02 a 1.02 a 50 21.6 b 0.63 a 0.83 a 0.83 a 100 17.9 b 0.86 a 0.97 a 0.97 a Means followed by the same letter within the column (lower case letters) or in rows (capital letters) are not signi- ficantly different at P<0.05. 188 BIOSUSTAINABILITY agriculture in nature and environment protection The results of the experiment showed that S. gigantea extract possess allelopathic potential to inhibit germination and growth of other plants. According to Sekutowski et al. (2012.) golden- rod fresh biomass extracts reduced germination and root length of buckwheat, while stimula- ted root growth of sunflower.