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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
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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.
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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
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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
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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.
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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
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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.