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Acta Sci. Pol., Agricultura 9(4) 2010, 69-76 DISCRIMINATORY ANALYSIS OF THE YIELD VARIABILITY OF MAIZE HYBRIDS DEPENDING ON THE DOSES AND TIME OF HERBICIDE APPLICATION Ryszard Weber, Hanna Gołębiowska Institute of Soil Science and Plant Cultivation – National Research Institute in Puławy 1 Abstract. In years 2005-2007, sensitivity assessment of four maize hybrids took place – Gazelle, LG 3225, Lober, and PR 39H32, depending on the time and method of herbicide Mustang 306 SE application. Varietal experiment was established using the method of randomized blocks, in three replications, on soil classified as good wheat complex. Weeding was performed mechanically. Hybrids were sprayed with herbicide Mustang 306 SE at the dose of 0.6 dm3·ha-1 at the 3-4- or 6-7-leaf stage, as well as with a dose limited by 50% at the 3-4- and 6-7-leaf stage. The objects on which the herbicide was applied were compared with the control (no herbicide used). In order to assess the yield variability of the analyzed maize hybrids within the realm defined by four variables (three variants of herbicide application + control), the methods of discriminatory analysis and cluster analysis were used. Gazelle hybrid was characterized by the highest yield variability depending on the date and dose of the applied herbicide in comparison with the control. Significantly higher yield stability was characteristic to hybrids LG 3225 and PR 39H32. Application of herbicide at the 6-7-leaf stage resulted in considerable yield reduction of all the studied maize hybrids (9.09 t·ha-1). Maize hybrid yield on plots sprayed with split Mustang 306 SE herbicide doses at the 3-4-leaf stage (9.83 t·ha-1) and 6-7-leaf stage (10.29 t·ha-1) did not differ, however, from the yield obtained on the control (10.32 t·ha-1). Key words: herbicide application date, maize hybrids, multifactorial analysis INTRODUCTION Maize, in the initial period of development, is a slowly growing species. Its growth is limited the most by weeds that grow in lowland meadow from germination to the 8-10-leaf stage [Evans et al. 2003]. Chemical pest control is based on herbicide selectivity and may be defined as the difference in the response level between species Corresponding author – Adres do korespondencji: doc. dr Ryszard Weber, Institute of Soil Science and Plant Cultivation – National Research Institute in Puławy, Orzechowa 61, 50-540 Wrocław, e-mail: [email protected] 70 R. Weber, H. Gołębiowska after the application of the particular active substance [Carvalho et al. 2009]. In herbicide detoxication process in cultivated plant tissues, three phases may be distinguished. In the first phase – bioactivation – reactive chemical groups are generated in plant cells. Second phase includes herbicide conjugation with endogenous substrate. In phase three – compartmentation – transport of conjugates to vacuoles occurs. Xenobiotics accumulated in the vacuoles undergo further modification under the influence of peroxidase and carboxypeptidase [Kreuz et al. 2006]. This complicated process of herbicide decomposition to a great extent may depend on plant genotype. A significant role is played by interactions between plant protection means and hybrid and environmental conditions [Weber and Gołębiowska 2009]. Therefore, differences in hybrid yield size in the classical analysis of variance without taking into account yield variability assessment may carry a significant error. The aim of the work was the analysis of yield variability of chosen maize hybrids depending on the application time and dose of herbicide Mustang 306 SE. MATERIAL AND METHODS In years 2005-2007, sensitivity assessment of four maize hybrids took place – Gazelle, LG 3225, Lober, and PR 39H32 – to herbicide Mustang 306 SE depending on the time and method of its application. Varietal experiment was established using the method of randomized blocks, in three replications, on soil classified as good wheat complex. In order to determine the response of the particular hybrids to the herbicide, the entire experiment was weeded mechanically, and then (during the particular phases of development), spraying with the herbicide was carried out. At the 3-4- or 6-7-leaf stage, the hybrids were sprayed with herbicide Mustang 306 SE at the dose of 0.6 dm3·ha-1 and at a dose limited by 50% at the 3-4- and 6-7- leaf stage. On the control, no herbicide was applied. In order to assess the yield variability of the analysed maize hybrids in the realm defined by four variables (three variants of herbicide application + control), the method of discriminatory analysis was used, described in the works by Mądry [1993] and Caliński et al. [1979]. Discriminatory function analysis is applied in order to determine which variables make it possible to divide a given set of cases in the best way into groups that occur in a natural way. On this ground, it may be stated to what degree diversified weeding methods affect the yield variability of the analysed maize hybrids. The values of the particular roots – canonical variables – were assessed with the use of the chi-square test. For the interpretation of the meaning of the canonical variables, standardised coefficients and correlation values between the studied analysed hybrids and canonical roots were used. In the subsequent part of the study, Mahalanobis distance was shown, which is a distance measurement between two objects – the control or the applied herbicide dates in the realm defined by three maize hybrids. Mahalanobis distance is similar to the standard Euclidean space; it additionally takes into account, however, correlations between the studied variables. In order to compare the effect of the different variants of the application of herbicide Mustang and the control on the yield variability of maize hybrids, also cluster analysis was carried out using Ward’s method. The presented dendrogram shows Euclidean space between the studied objects in three-dimensional space but it dos not take into account the relations between the Acta Sci. Pol. Discriminatory analysis… 71 studied variables. Therefore, some Mahalanobis distances may not reflect the distance of the particular objects in the Euclidean space. Statistical analysis was carried out with the use of the analytical program Statistica. RESULTS On the basis of Table 1, it can be said that maize hybrids showed a tendency for higher yields in the conditions of herbicide Mustang 306 SE application at doses reduced by 50% at the 3-4- or 6-7-leaf stage. Multidimensional analysis of variance showed significant yield variability of maize hybrids depending on herbicide application date in comparison with the control (Table 2). Wilks’ Lambda value for the total discrimination of the analysed objects was equal to 0.5569. Approximate F test value indicate that the hypothesis on the equality of the centroids of the four studied populations should be rejected at the significance level of P = 0.05. Partial value of Wilks’ Lambda, as well as the F test related to the individual input of a given variable into the discriminatory power of the model indicate that hybrids Gazelle and Lober showed the highest yield variability under the influence of the diversified dates of the application of herbicide and the control. On the other hand, smaller yield variability was characteristic for hybrids LG 3225 and PR 39H32. In order to confirm the presented differences in the yield variability of the analysed maize hybrids, also the analysis of canonical variables should be carried out. Further analysis made it possible to obtain three linear independent functions in the form of characteristic roots, which present multi-trait diversification of the studied maize hybrids in the realm of canonical variables (Table 3). Table 1. Average yield of maize hybrids depending on the weeding method in 2005-2007, t.ha-1 Tabela 1. Średnie plony odmian kukurydzy zależności od sposobu odchwaszczenia w latach 2005-2007, t.ha-1 Hybrid Mieszaniec Gazelle PR 39H32 LG 3225 Lober Mean – Średnia Control Kontrola 9.80 10.54 11.25 9.68 10.32 Mustang T3 and T6 9.46 10.48 11.36 9.87 10.29 Mustang T3 8.74 10.43 10.36 9.78 9.83 Mustang T6 7.63 9.40 9.84 9.48 9.09 T3 spraying at the 3-4-leaf stage – T3 oprysk w fazie 3-4 liści T6 spraying at the 6-7-leaf stage – T6 oprysk w fazie 6-7 liści Real dimension of the discriminatory space is described by one characteristic root that differs significantly from zero (Table 4). High absolute values of the canonical coefficients and significant correlations between the studied variables and canonical roots indicate that there is a great share of the particular maize hybrids in yield discrimination in the control and diversified doses and dates of herbicide application. Agricultura 9(4) 2010 R. Weber, H. Gołębiowska 72 First canonical variable explains in 96% the distance between the studied objects. Share of the second canonical variable is significantly lower. On the basis of Table 2, it can be assumed that the highest contribution to the creation of the first canonical variable is made by hybrids Lober and Gazelle. However, the analysis of structural coefficients indicates that only hybrid Gazelle shows a high value of the coefficient of correlation with the first root. Therefore, it should be stated that only this hybrid has the greatest effect on the formation of the first discriminatory function. Table 2. Results of discriminatory function analysis Tabela 2. Zestawienie analizy funkcji dyskryminacyjnej Wilks’ Lambda = 0.5569; approximate F = 2.21; p< 0.0307 Lambda Wilksa = 0,5569; przybliżone F = 2,21; p< 0,0307 Variable Zmienna Wilks’ Lambda Lambda Wilksa Gazelle LG 3225 Lober 0.8095 0.5312 0.7462 PR 39H32 0.5727 Partial Wilks’ Lambda Cząstk. Lambda Wilksa Level of p Poziom p F 0.6879 4.53 0.9538 0.4673 0.7463 3.39 Variable outside the model – Zmienna poza modelem 0.9723 0.28 0.0097 0.7072 0.0303 0.8362 Table 3. Standardized coefficients for canonical variables Tabela 3. Współczynniki standaryzowane dla zmiennych kanonicznych Variable – Zmienna Gazelle LG 3225 Lober Eigenvalues Wartości własne Accumulated percent Skumulowany procent Root 1 Pierwiastek 1 Root 2 Pierwiastek 2 Root 3 Pierwiastek 3 -1.7251 -0.0399 1.4038 -1.0916 1.8175 -0.4820 -0.0563 -0.0305 1.0686 0.7432 0.0282 0.0016 0.9612 0.9978 1.0000 Table 4. Chi-square tests of successive roots Tabela 4. Testy chi-kwadrat kolejnych pierwiastków Canonical roots Pierwiastki kanoniczne Eigen value Wartość własna Canonical R Kanoniczne R Wilks’ Lambda Lambda Wilksa Chi-square Chi2 Level of p Poziom p 0 1 2 0.7432 0.0282 0.0016 0.6529 0.1657 0.0411 0.5569 0.9708 0.993 18.43 0.93 0.05 0.0304 0.8174 0.9201 The presented calculation of Tables 3 and 4 are reflected in Table 2, where the results of the discriminatory analysis confirmed the greatest effect of the above hybrid on the variability of the studied maize hybrids. Table 5 contains the squares of Mahalanobis distances. The greater the distances presented in Table 5, the farther from each other the analysed objects are situated and the higher the discriminatory power is possessed by the presented model in the yield variability of the hybrids under the Acta Sci. Pol. Discriminatory analysis… 73 influence of different variants of the applied herbicide and control. Through the analysis of Table 5, it can by stated that the application of herbicide Mustang at the 6-7-leaf stage caused significant differences in the yield of the studied hybrids in comparison with the control. Late spraying with the applied chemical significantly limited the yield of the studied hybrids. However, the application of herbicide Mustang at the doses lowered by 50% at the 3-4- and 6-7-leaf stage contributed to obtaining yields of the studied hybrids at the level of the control. Table 5. Squared Mahalanobis distances Tabela 5. Kwadraty odległości Mahalanobisa Object Obiekt Control – Kontrola Mustang T3 and T6 Mustang T3 Mustang T6 Control Kontrola Mustang T3 and T6 Mustang T3 Mustang T6 0.0 0.31 1.53 5.21** 0.31 0.0 0.78 3.32* 1.53 0.78 0.0 1.21 5.21** 3.32* 1.21 0.0 for explanations, see Table 1 – objaśnienia pod tabelą 1 While analysing the presented dendrogram (Fig. 1), great effect of the herbicide application date may be confirmed on yield variability of maize hybrids. On the basis of this trait, three independent groups may be distinguished. The first group is made of yield obtained from the control and plots sprayed with the herbicide at split doses. On the other hand, a different reaction of the hybrids in regard to yield was found under the influence of the applied chemical at the 3-4- or 6-7-leaf stage. Fig. 1. Rys. 1. Cluster analysis dendrogram Dendrogram analizy skupień DISCUSSION Results of the research showed dissimilar tolerance of maize hybrids to herbicide Mustang 306 SE application method. The use of the studied herbicide at a full dose at Agricultura 9(4) 2010 74 R. Weber, H. Gołębiowska the 6-7-leaf stage caused a significant decrease in the yield of the analysed maize hybrids. Also the research by Gołębiowska [2002] confirmed that the tolerance level of maize hybrids depends on herbicide application date, plant developmental phase, and atmospheric conditions. Adamczyk et al. [2004] underscore, however, that special threats occur in the initial stadium of maize development. Significant yield variability of hybrid Gazelle in comparison with the remaining objects indicates that under the influence of some herbicides, sensitive hybrids may react in the initial period with growth inhibition, which may contribute to a decrease in plant yield [Gołębiowska and Rola 2008a]. Yet, these damages in many cases are only transitory and do not cause reduction in maize yield [Pannacci and Covarelli 2009]. Unsuitable date or dose of the applied herbicide may also cause, in some hybrids, a decrease in yield or grain qualitative traits [Gołębiowska and Rola 2008b]. Diversified reaction of maize hybrids to active substances is proven in numerous publications, both national and foreign [Gołębiowska and Rola 2003, Kreuz et al. 2006]. According to Sulewska and Koziara [2006], herbicide Mustang showed a decreased effectiveness in comparison with other used chemical means. However, research results obtained by Kierzek [2008], confirmed the decisive role of this herbicide application date. The use of Mustang 306 SE at the 8-9-maize-leaf stage also contributed to a decrease in the grain yield of the grown hybrid [Kierzek 2008]. This herbicide additionally caused phytotoxic symptoms of plant injuries in the form of growth inhibition and leaf twisting. CONCLUSIONS 1. Discriminatory analysis showed that hybrid Gazelle was characterised by the highest yield variability depending on the date and dose of the applied herbicide in comparison with the control. Significantly higher yield stability was characteristic for hybrids LG 3225 and PR 39H32. 2. On the basis of Mahalanobis distance and cluster analysis, it may be stated that the application of herbicide Mustang 306 SE at the 6-7-leaf stage caused significant yield limitation in all the studied maize hybrids. Yield size of the hybrids from plots sprayed with split herbicide doses at the 3-4- and 6-7-leaf stage did not differ, however, from the yield obtained on the control. REFERENCES Adamczyk J., Rogacki J., Cygert H., 2004. Czynniki ograniczające plonowanie kukurydzy w okresie wegetacji [Factors that limit maize yield during growth period]. Pam. Puł. 140, 127-136 [in Polish]. Caliński T., Dyczkowski A, Sitek M., 1979. Procedury testów jednoczesnych w wielozmiennej analizie wariancji [Procedures for simultaneous tests in multivariate analysis of variance]. Mat. stosowana 14, 5-31 [in Polish]. Carvalho S.J.P., Nicolai M., Ferreira R.R., Figueira A.V.O., Christoffoleti P.J., 2009. Herbicide Selectivity by differential metabolism: considerations for reducing crop damages. Sci. Agric. 66(1), 136-142. Evans S.P., Knezevic S.Z., Lindquist J.L., Shapiro C.A., 2003. Nitrogen application influence the critical period for weed control in corn. Weed Sci. 51, 408-417. Acta Sci. Pol. Discriminatory analysis… 75 Gołębiowska H., 2002. Oddziaływanie herbicydów na wzrost, rozwój i plonowanie mieszańców kukurydzy w zależności od warunków pogodowych [Effect of herbicides on growth, development, and yield of maize hybrids depending on the weather conditions]. Pam. Puł. 130(1), 223-231 [in Polish]. Gołębiowska H., Rola H., 2003. The influence of weather conditions on selectivity of sulfonylourea herbicides to the selected maize varieties. J. Plant Prot. Res. 43, 219-224. Gołębiowska H., Rola H., 2008a. Reakcja odmian kukurydzy na herbicydy w świetle badań prowadzonych w warunkach Dolnego Śląska w latach 1992-2007 [Response of maize hybrids to herbicides in the light of research conducted in Lower Silesia in years 1992-2007]. Prog. Plant Protection/Post. Ochr. Roślin 48, 2, 590-601 [in Polish]. Gołębiowska H., Rola H., 2008b. Wpływ herbicydów sulfonylomocznikowych na zdrowotność i wybrane parametry jakościowe ziarna odmian kukurydzy uprawianej w monokulturze [Effect of sulfonylurea herbicides on heath and chosen qualitative parameters of the grain of maize hybrids grown in monoculture]. Frag. Agron. XXV(1), 145-156 [in Polish]. Kierzek R., 2008. Reakcja kukurydzy na mieszaninę 2,4 D + florasulam (Mustang 306 SE) stosowaną w różnych dawkach i terminach [Maize response to mixture 2.4 D + florasulam (Mustang 306 SE) applied at different doses and dates]. Prog. Plant Protection/Post. Ochr. Roślin 48(1), 272-275 [in Polish]. Kreuz K., Gaudin J., Ebert E., 2006. Effects of safeners CGA 154281 oxabetrinil and fenclorim on uptake and degradation of metolachlor in corn (Zea mays) seedlings. Weed Res. 29(6), 399-405. Mądry W., 1993. Studia statystyczne nad wielowymiarową oceną zróżnicowania cech ilościowych w kolekcjach zasobów genowych zbóż [Statistical studies on the multidimensional assessment of quantitative traits diversification in the collections of cereal gene supplies]. Wyd. SGGW Warszawa [in Polish]. Pannacci E., Covarelli G., 2009. Efficacy of mesotrione used at reduced doses for post-emergence weed control in maize (Zea mays L.). Crop Prot. 28(1), 57-61. Sulewska H., Koziara W., 2006. Skuteczność wybranych herbicydów stosowanych powschodowo w kukurydzy [Effectiveness of chosen herbicides applied on maize after germination]. Prog. Plant Protection/Post. Ochr. Roślin 46(2), 243-245 [in Polish]. Weber R., Gołębiowska H., 2009. Wpływ herbicydu Titus 25 WG na zmienność plonowania odmian kukurydzy na Dolnym Śląsku [Effect of herbicide Titus 25 WG on the yield variability of maize hybrids in Lower Silesia]. Fragm. Agron. 26(4), 181-188 [in Polish]. ANALIZA DYSKRYMINACYJNA ZMIENNOŚCI PLONOWANIA ODMIAN KUKURYDZY W ZALEŻNOŚCI OD WIELKOŚCI DAWEK I TERMINU STOSOWANIA HERBICYDU Streszczenie. W latach 2005-2007 przeprowadzono ocenę wrażliwości mieszańców kukurydzy Gazelle, LG 3225, Lober i PR 39H32 w zależności od terminu i metody aplikacji herbicydu Mustang 306 SE. Doświadczenie odmianowe założono w układzie losowanych bloków w 3 powtórzeniach na glebie zaliczanej do kompleksu pszennego dobrego. Doświadczenie odchwaszczono mechanicznie. Mieszanki były opryskiwane herbicydem Mustang 306 SE w dawce 0,6 dm3·ha-1 w fazie 3-4 liści lub 6-7 liści, jak również dawką ograniczoną o 50% w fazie 3-4 i 6-7 liści. Obiekty ze stosowanym herbicydem porównywano z kontrolnymi (bez herbicydu). W celu oceny zmienności plonów analizowanych odmian kukurydzy w przestrzeni zdefiniowanej przez 4 zmienne (3 warianty stosowania herbicydu + kontrola) zastosowano metodę analizy dyskryminacyjnej i skupień. Odmiana Gazelle odznaczała się największą zmiennością plonów w zależności od terminu i dawki zastosowanego herbicydu w porównaniu z obiektem Agricultura 9(4) 2010 76 R. Weber, H. Gołębiowska kontrolnym. Istotnie większą stabilnością plonowania charakteryzowały się mieszańce LG 3225 i PR 39H32. Zastosowanie herbicydu w fazie 6-7 liści spowodowało znaczne ograniczenie plonowania wszystkich badanych odmian kukurydzy (9,09 t.ha-1). Wysokość plonów mieszańców kukurydzy na poletkach opryskiwanych dawkami dzielonymi herbicydu Mustang 306 SE w fazie 3-4 (9,83 t.ha-1 ) i 6-7 (10,29 t.ha-1) liści nie różniły się natomiast od plonu uzyskanego na obiekcie kontrolnym (10,32 t.ha-1). Słowa kluczowe: analiza wielocechowa, mieszańce kukurydzy, termin stosowania herbicydu Accepted for print – Zaakceptowano do druku: 25.10.2010 Acta Sci. Pol.