Relative competitive ability of rice with strawhull and

Jaboticabal
ISSN: 1984-5529
v.44, n.2, p.176–184, 2016
http://dx.doi.org/10.15361/1984-5529.2016v44n2p176-184
Relative competitive ability of rice with strawhull and blackhull
red rice biotypes
Habilidade competitiva relativa de arroz com biótipos de arroz-vermelho
strawhull e blackhull
Marcos André NOHATTO1; Dirceu AGOSTINETTO2; David Robert GEALY3; Luis Antonio de AVILA4;
Bruno Moncks da SILVA5; Nixon da Rosa WESTENDORFF6
“Autor para correspondência” Eng. Agr. Doutor em Fitossanidade, Universidade Federal de Pelotas, Departamento de
Fitossanidade – Campus Universitário Capão do Leão. Caixa Postal 354 -96010-900 – Pelotas-RS,
[email protected]
2 Eng. Agr. Doutor em Fitotecnia. Universidade Federal de Pelotas. [email protected]
3 Dr. Plant Physiologist. USDA-Agricultural Research Service - Dale Bumpers National Rice Research Center.
[email protected]
4 Eng. Agr. Ph.D. em Agronomia. Universidade Federal de Pelotas. [email protected]
5 Eng. Agr. Mestrando em Fitossanidade. Universidade Federal de Pelotas. [email protected]
6 Eng. Agr. Doutorando em Fitossanidade. Universidade Federal de Pelotas. [email protected]
1
Recebido em: 20-08-2015; Aceito em: 27-10-2015
Abstract
The weed interference varies on several factors, especially the composition of the weed community and the
ability to compete with the culture. Thus, this study aimed at evaluating the competitive ability of rice and different
populations of red rice (strawhull or blackhull). The experiments were conducted in greenhouse from January to
August 2013, at United States Department of Agriculture, Dale Bumpers National Rice Research Center
(USDA/DBNRRC) in the city of Stuttgart, Arkansas. The experimental design was completely randomized with
four replications. Treatments consisted of rice or red rice plant ratios (100:0, 75:25, 50:50, 25:75 and 0:100%).
Variables evaluated included: shoot dry weight, leaf area and plant height. Results show that strawhull or
blackhull red rice biotypes have superior competitive ability than rice, CL 142 AR. Overall, the blackhull red rice
biotype has superior competitive ability compared to strawhull one. For rice, the interspecific competition
dominates, while for red rice biotypes the intraspecific competition was more harmful.
Additional keywords: interference; Oryza sativa; replacement series.
Resumo
A interferência de plantas daninhas varia em função de vários fatores, destacando-se a composição da
comunidade infestante e a capacidade dessa de competir com a cultura. Diante disso, o objetivo do trabalho foi
avaliar a habilidade competitiva entre arroz e diferentes populações de arroz-vermelho (strawhull ou blackhull).
Os experimentos foram conduzidos em casa de vegetação, no período de janeiro a agosto de 2013, no
Departamento de Agricultura dos Estados Unidos, Dale Bumpers National Rice Research Center
(USDA/DBNRRC), na cidade de Stuttgart, Arkansas. O delineamento experimental utilizado foi o completamente
casualizado, com quatro repetições. Os tratamentos consistiram nas proporções de plantas de arroz ou arrozvermelho (100:0; 75:25; 50:50; 25:75 e 0:100%). As variáveis avaliadas foram: massa da matéria seca da parte
aérea, área foliar e estatura de planta. Os resultados obtidos evidenciam que os biótipos de arroz-vermelho
strawhull ou blackhull apresentam habilidade competitiva superior ao arroz, cultivar CL 142 AR, enquanto, o
biótipo de arroz-vermelho blackhull, em geral, apresenta superioridade competitiva comparada ao strawhull.
Para o arroz, a competição interespecífica predomina, enquanto para os biótipos de arroz-vermelho a
competição intraespecífica foi mais prejudicial.
Palavras-chave adicionais: interferência; Oryza sativa; série de substituição.
Introduction
Rice cultivation plays important role in the
world economy and is considered protein and calorie
source for more than half the world's population (FAO,
2015). In Brazil and the United States are produced
annually 11.7 and 8.6 million tons with average
productivity of 5.1 and 8.6 tons per hectare,
respectively. Despite the significant values in
productivity in the United States, it is known that culture
did not reach the productive potential observed in
experimental areas and crops that adopt high
technological level.
Among the main limiting factors for increased
productivity in the culture, there is the competition with
red rice, as this weed has the same demand for the
niche. Botanically, red rice belongs to the same genus
of the cultivated rice, there being different populations
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in the United States that can be mainly classified as
strawhull or blackhull. It is believed that strawhull red
rice came through the crossing between the varieties
of cultivated rice O. sativa L. spp. indica and O.
rufipogon Griff., while blackhull comes from O. sativa
indica var. Aus and O. rufipogon (Londo & Schaal,
2007).
The degree of interference depends on factors
related to the environment (soil, climate and crop
management), culture (cultivar, spacing and seeding
rate), the weed community (species composition,
population and distribution) and the timing and extent
of period in which culture and weed community live in
the same environment (Carvalho, 2011). Therefore,
the study of the competitive dynamics between
different populations of rice and red rice is needed to
understand the losses caused by weeds and
development of management strategies appropriate
for each biotype. Thus, this study aimed at evaluating
the competitive ability of rice and different populations
of red rice (strawhull or blackhull).
Material and methods
The experiments were conducted from
January to August 2013 in greenhouse at the United
States Department of Agriculture, Dale Bumpers
National Rice Research Center (USDA / DBNRRC) in
the city of Stuttgart, Arkansas. A completely randomized design with four replications was used.
Each experimental unit consisted of plastic pot
with four liters capacity filled with soil from rice
ISSN: 1984-5529
cultivation area classified as Neosoil of silty and clayey
texture. It used seeds of CL 142 AR (PI 659515) rice
cultivar, while the red rice biotypes (strawhull or
blackhull) (PI 653422) were from paddy crop of
Stuttgart-AR, stored in the germplasm bank of the
research center.
In the first experiment was carried out
preliminary assessment to rice cultivar and red rice
biotypes in monoculture in order to get the population
to the replacement series experiment, using
populations of 4, 8, 16, 32 and 64 plants per pot
(equivalent to 143, 286, 571, 1,143 and 2,286 plants
m-2). Constant final production of shoot dry weight
(SDW) was obtained with a population of 16 plants per
pot, equivalent to 571 plants m-2 (data not shown).
The other experiments were conducted to
replace series by varying the ratios of rice plants to
strawhull or blackhull red rice per pot of 100: 0, 75:25,
50:50, 25:75 and 0:100 (16:0, 12:4, 8:8, 4:12 and
0:16), maintaining the total plant population
(Experiments II and III). The study also evaluated the
relative competitiveness between the red rice biotypes
(strawhull and blackhull) to determine which one has
more competitive ability (Experiment IV).
The levels of light and temperature were
measured at the top of plants, daily throughout the
experiment, with the aid of ceptometer AccuPAR
Model LP-80 PAR/LAI and local thermometer,
respectively (Figure 1). At 45 days after emergence
(DAE) were evaluated the variables: SDW, leaf area
(LA) and plant height (H).
Light
Temperature
31
1400
30
o
1200
Temperature ( C)
2 -1
Light intensity (mol m s )
1600
1000
29
800
28
600
400
27
200
0
26
0
5
10 15 20 25 30 35 40 45
Days after emergence
Figure 1 - Characterization of light intensity and temperature during the relative competitive experiments
between irrigated rice (CL 142 AR) and red rice (strawhull or blackhull) and, among the weed biotypes.
SDW was quantified by weighing the shoots
after being dried at 60 °C for 96 hours. Quantitation of
LA was performed with the aid of a leaf area meter
(model LI 3000), whereas H was obtained by
measuring the distance from the base to the end of the
last leaf.
For analysis of growth variables, it used the
method of the relative productivity graphical analysis
(Cousens, 1991). This procedure, also known as a
conventional method of substitution experiments,
consists of a diagram based on the relative yield (RY)
and total (RYT) variation. When the result of RY tends
to straight, it means that the skills of the species are
equivalent. If the RY results a concave line, it indicates
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Científica, Jaboticabal, v.44, n.2, p.176-184, 2016
loss in growth of one or both species. On the contrary,
if the RY shows a convex line, there is the advantage
in growth of one or both species. When RYT is equal
to the unity (1) (straight line), there is competition for
the same resources and if it is greater than 1 (convex
line), competition is avoided. If the RYT is less than 1
(concave line) occurs mutual growth impairment
(Cousens, 1991; Radosevich et al., 2007).
The relative competitiveness index (RC),
clustering coefficient (K) and competitiveness coefficient (C) were calculated. RC represents the
comparative growth of cultivated rice (r) in relation to
red rice (rr); K indicates the relative dominance of one
species over another (Kr = rice and Krr = red rice); and
C indicates which of the species is more competitive.
Thus, the RC, K, and C indices indicate which species
is more competitive and their combined interpretation
indicates a safer competitive species (Cousens, 1991).
Rice is more competitive than red rice when RC>1,
Kr>Krr and C>0. On the other hand, red rice is more
competitive than rice when RC<1, Kr<Krr and C<0
(Hoffman & Buhler, 2002). To calculate these rates
proportions of 50:50 of species were used as well as
the following equations: CR = RYr / RYrr; Kr = RYr / (1RYr); Krr = RYrr / (1-RYrr); C = RYr - RYrr.
The statistical analysis for productivity or
relative variation includes the calculation of the
differences in the RY values (DRY) obtained in the
proportions 25, 50 and 75% of the values belonging to
the hypothetical straight in the respective proportions
(Bianchi et al., 2006). The "t" test was used to assess
differences in the indices DRY, RYT, RC, K and C
(Hoffman & Buhler, 2002). The criterion to consider the
RY and RYT curves different from the hypothetical
lines and the existence of differences in
competitiveness for RC, K and C indexes, was the
occurrence of differences by the "t" test at least in two
proportions (Bianchi et al., 2006).
Results obtained for variables, expressed as
average values per plant, were analyzed for normality
by the Shapiro-Wilk test and then were subjected to
analysis of variance (p≤0.05). Afterwards, the
proportions effects in relation to the monoculture
(control) were evaluated by the Dunnett test (p≤0.05)
and between the proportions in the mixture, using the
Tukey test (p≤0.05), separately for each competitor.
Results and discussions
In RY graphical analysis, the combination of
the rice cultivar with strawhull or blackhull red rice, it
was found that the culture was less competitive than
the red rice, with rice RY represented by concave line
and weed RY by convex line (Figure 2). RY deviations
were significant for all variables, except for blackhull
red rice RY for SDW and RY for both weed biotypes
for H (Table 1). This showed an overall benefit for
weed and damage to the crop.
ISSN: 1984-5529
Regarding the RYT, there was no difference
between the expected and estimated values for the
variables studied, except for RYT from the combination
of rice and strawhull in H (Table 1). This demonstrates
that plants interact by the same resources available in
the environment, but the red rice uses resources more
efficiently than rice.
More weed competitiveness has also been
reported in studies on other species such as the wild
radish with soybean (Bianchi et al., 2006) or wheat
(Rigoli et al., 2008), hairy fleabane with soybean
(Silva et al., 2014), besides the red rice competing
with rice (Fleck et al., 2008; Dai et al., 2014).
There was reduction of SDW, LA and H on
rice in competition with strawhull or blackhull red rice
compared to the monoculture, except for 75:25 ratio
competing with blackhull for SDW and H variables
(Table 2). When analyzing the differences between
proportions in the presence of strawhull red rice, it
was observed that a smaller culture proportion
(25:75) showed the lowest SDW, LA and H compared
to 75:25; while in competition with blackhull, none of
the plant proportions with the competitive presence
differed from each other except in SDW, when similar
behavior to rice competing with strawhull.
Despite the different crop responses to
competition with red rice biotypes, cultivated rice
remains in disadvantage in the competitive process.
Study on six red rice biotypes and cultivated rice
from China also reported the superiority of the weed
in relation to crop, showing that as it increases the
presence of red rice in the proportion, it decreases
the values of height, tillering, shoot dry weight and
productivity in the crop (Dai et al., 2014). Still, it was
noted for rice cultivation, the interspecific competition was more damaging than the intraspecific one;
it is rather live with the crop than with the weed.
Studies have shown that although rice belonging to
the same genus of red rice, the culture has distinct
morphological and physiological characteristics that
diminish its competitive ability in relation to red rice,
with less ability to tillering (Balbinot Junior et al.,
2003), lower efficiency of CO 2 use (Ziska &
McClung, 2008) and nitrogen (Chauhan & Johnson,
2011). Furthermore, the study demonstrated that
rice plants have fewer roots than red rice (Eberhardt
et al., 1999).
For strawhull or blackhull red rice living with
the culture, there were differences in the proportions
50:50 and 75:25 compared to the control for the SDW
and LA variables (Table 2). It was also observed that
the proportion 25:75 showed lower value of SDW and
LA compared to 75:25 for strawhull. For blackhull,
none of the plant ratios differed for SDW and LA in
the rice presence. In the H analysis for strawhull or
blackhull red rice competing with rice, there was no
differences in plant proportions compared to the
control or to each other.
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Rice
Blackhull
RYT
1.4
1.2
1.2
1.0
1.0
0.8
0.8
0.6
0.6
0.4
0.4
0.2
0.2
0.0
16-0
12-4
8-8
4-12
0.0
0-16
1.2
1.0
1.0
0.8
0.8
0.6
0.6
0.4
0.4
0.2
0.2
0.0
16-0
8-8
4-12
0.0
0-16
Rice
Strawhull
RYT
1.4
1.4
1.2
1.2
1.2
1.2
1.0
1.0
1.0
1.0
0.8
0.8
0.8
0.8
0.6
0.6
0.6
0.6
0.4
0.4
0.4
0.4
0.2
0.2
0.2
0.2
0.0
16-0
12-4
8-8
4-12
0.0
0-16
0.0
16-0
Rice and blackhull proportions
Rice
Blackhull
RYT
12-4
8-8
1.4
4-12
0.0
0-16
Rice and strawhull proportions
Rice
Strawhull
RYT
1.4
1.4
1.2
1.2
1.2
1.2
1.0
1.0
1.0
1.0
0.8
0.8
0.8
0.8
0.6
0.6
0.6
0.6
0.4
0.4
0.4
0.4
0.2
0.2
0.2
0.2
0.0
16-0
12-4
8-8
4-12
Relative plant height
1.4
Relative plant height
12-4
Rice and strawhull proportions
Relative leaf area
Relative leaf area
1.4
1.4
1.2
Rice and blackhull proportions
Rice
Blackhull
RYT
Rice
Strawhull
RYT
1.4
Relative shoot dry weight
Relative shoot dry weight
1.4
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0.0
0-16
0.0
16-0
Rice and blackhull proportions
12-4
8-8
1.4
4-12
0.0
0-16
Rice and strawhull proportions
Figure 2 - Relative yield (RY) and total (RYT) for shoot dry weight, leaf area and plant height to rice (CL 142
AR) and red rice biotypes (strawhull or blackhull). (●) RY of rice, (○) RY of red rice and (▼) RYT. Dashed lines
refer to the hypothetical relative yields, when there is no interference from one species over another.
Overall, growth variables in red rice were
increased when in competition with the cultivated rice,
except for the H variable, i.e., unlike what occurred for
the culture, intraspecific competition proved to be
more damaging to weed plant.
No differences occurred for RY in the evaluated variables for the combination of strawhull with
blackhull red rice, except for LA of strawhull and H for
blackhull (Table 1). As for RYT, there were
differences between the values of expected and
observed deviations only for H (Figure 3 and Table 1).
Thus, overall competitors have equal competitive
ability, or compete for the same resources.
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ISSN: 1984-5529
Table 1 - Differences on relative yield (DRY) and total relative yield (RYT) in the rice (CL 142 AR) to red rice
biotypes (strawhull or blackhull) proportions of 75:25, 50:50 and 25:75.
Plant proportion
Variable
75:25
50:50
25:75
SDW
DRYr (rice)
-0.15(±0.03)*
-0.19(±0.03)*
DRYrr (strawhull)
0.19(±0.02)*
0.22(±0.03)*
0.05(±0.03)ns
RYT
1.04(±0.04)ns
1.03(±0.06)ns
0.93(±0.03)ns
-0.11(±0.06)ns
-0.15(±0.01)*
DRYrr (blackhull)
0.10(±0.04)ns
0.20(±0.03)*
0.07(±0.02)ns
RYT
0.99(±0.10)ns
1.05(±0.03)ns
0.96(±0.03)ns
DRYrrs (strawhull)
-0.00(±0.04)ns
-0.07(±0.01)*
-0.02(±0.01)ns
DRYrrb (blackhull)
-0.08(±0.01)*
0.03(±0.01)ns
0.03(±0.03)ns
0.92(±0.04)ns
0.97(±0.02)ns
1.01(±0.03)ns
DRYr (rice)
RYT
-0.13(±0.00)*
-0.11(±0.01)*
LA
DRYr (rice)
-0.26(±0.03)*
-0.23(±0.01)*
-0.14(±0.01)*
DRYrr (strawhull)
0.16(±0.03)*
0.18(±0.05)ns
0.11(±0.02)*
RYT
0.90(±0.04)ns
0.95(±0.06)ns
0.97(±0.02)ns
DRYr (rice)
-0.27(±0.04)*
-0.23(±0.01)*
-0.13(±0.01)*
DRYrr (blackhull)
0.11(±0.03)ns
0.20(±0.03)*
0.14(±0.02)*
RYT
0.84(±0.06)ns
0.97(±0.02)ns
1.01(±0.02)ns
DRYrrs (strawhull)
-0.03(±0.05)ns
DRYrrb (blackhull)
-0.04(±0.02)ns
0.08(±0.03)ns
0.04(±0.07)ns
0.94(±0.07)ns
0.99(±0.03)ns
1.00(±0.07)ns
RYT
-0.09(±0.01)*
-0.05(±0.01)*
H
DRYr (rice)
-0.11(±0.01)*
-0.09(±0.02)*
-0.07(±0.00)*
DRYrr (strawhull)
0.00(±0.00)ns
-0.00(±0.02)ns
0.03(±0.00)*
RYT
0.89(±0.00)*
0.91(±0.04)ns
0.96(±0.00)*
-0.07(±0.02)ns
-0.08(±0.01)*
-0.04(±0.01)*
DRYrr (blackhull)
0.01(±0.01)ns
-0.01(±0.00)ns
0.04(±0.02)ns
RYT
0.94(±0.03)ns
0.91(±0.01)*
0.92(±0.02)ns
DRYrrs (strawhull)
-0.00(±0.03)ns
-0.02(±0.01)ns
-0.01(±0.01)ns
DRYrrb (blackhull)
0.01(±0.00)*
-0.04(±0.01)*
0.07(±0.01)*
RYT
0.99(±0.03)ns
0.95(±0.01)*
0.92(±0.02)*
DRYr (rice)
* Significant difference by t test (p≤0.05). Values in brackets represent the mean's standard error.
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Científica, Jaboticabal, v.44, n.2, p.176-184, 2016
In the evaluation among competitors, for the
strawhull there were no differences in the proportions
of plants among each other and in relation to the
control, except for SDW when there was a reduction
of the variable of equal and smaller proportion of
strawhull compared to the control (Table 2). As for
blackhull, there was no difference between the
monoculture of weeds and proportions, except for
ISSN: 1984-5529
75:25 in SDW variable and for all proportions in H.
Overall, there was the less influence of
competition among red rice biotypes on variables
analysis, i.e. both have lower phenotypic plasticity
when in competition among weeds. The exception
was the plant height, which was reduced in the red
blackhull red rice compared to monoculture when
there was the presence of strawhull red rice.
Table 2 - Responses of shoot dry weight (SDW), leaf area (LA) and plant height (H) of rice cultivar (CL 142
AR) and red rice biotypes (strawhull or blackhull) in competition.
Experiment II
75:25
50:50
25:75
0:100 (T)
25:75
50:50
75:25
Proportion
100:0 (T)
75:25
50:50
25:75
0:100 (T)
25:75
50:50
75:25
Proportion
100:0 (T)
75:25
50:50
25:75
0:100 (T)
25:75
50:50
75:25
Experiment IV
SDW (g plant-1)
Proportion
100:0 (T)
Experiment III
Rice
Rice
Strawhull
1.26
a 1.02*
b 0.78*
b 0.62*
1.25
a 1.07ns
ab 0.87*
b 0.72*
1.51
a 1.45ns
a 1.30*
a 1.28*
Strawhull
Blackhull
Blackhull
1.51
c 1.62 ns
b 2.17*
a 2.66*
1.70
a 1.86ns
a 2.35*
a 2.36*
1.76
a 1.83ns
a 1.88ns
b 1.21*
LA (cm2 plant-1)
Rice
Rice
Strawhull
149.29
a 95.15*
a 81.26*
a 72.69*
171.56
a 165.69ns
a 141.48ns
a 139.13ns
Strawhull
Blackhull
Blackhull
175.17
b 201.21ns
ab 237.49*
a 285.23*
189.57
a 225.71ns
a 264.98*
a 272.09*
145.03
a 94.94*
ab 78.35*
b 63.12*
183.17
a 193.68ns
a 211.30ns
a 154.90ns
H (cm plant-1)
Rice
Rice
70.86
a 60.5*
ab 58.3*
b 51.8*
68.8
a 62.6ns
a 57.2*
a 56.6*
Strawhull
Blackhull
91.6
a 95.0ns
a 91.5ns
a 91.9ns
86.0
a 81.9ns
a 84.3ns
a 90.6ns
Strawhull
93.1
a 93.4ns
a 90.3ns
a 90.1ns
Blackhull
87.8
a 79.1*
a 81.5*
a 82.8*
* ou mean differs or not from the control (T) in the column by the Dunnett test (p≤0,05). 1 Means preceded by letters in
the same column, in the presence of competitors, do not differ by Tukey test (p≤0.05).
ns
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Científica, Jaboticabal, v.44, n.2, p.176-184, 2016
Strawhull
Blackhull
RYT
Strawhull
Blackhull
RYT
1.4
1.4
1.2
1.2
1.2
1.2
1.0
1.0
1.0
1.0
0.8
0.8
0.8
0.8
0.6
0.6
0.6
0.6
0.4
0.4
0.4
0.4
0.2
0.2
0.2
0.2
0.0
16-0
12-4
8-8
Relative leaf area
Relative shoot dry weight
1.4
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0.0
0-16
4-12
0.0
16-0
Strawhull and blackhull proportions
Strawhull
Blackhull
RYT
4-12
0.0
0-16
1.4
1.2
1.2
1.0
1.0
0.8
0.8
0.6
0.6
0.4
0.4
0.2
0.2
0.0
16-0
8-8
Strawhull and blackhull proportions
1.4
Relative plant height
12-4
1.4
12-4
8-8
4-12
0.0
0-16
Strawhull and blackhull proportions
Figure 3 - Relative yield (RY) and total relative yield (RYT) of shoot dry weight, leaf area and plant height of
strawhull and blackhull red rice biotypes. (●) RY of red rice strawhull, (○) RY of blackhull red rice and (▼) RYT.
Dashed lines refer to the hypothetical relative yields, when there is no interference from one species over
another.
Study aimed at characterizing phenotypically
the different types of red rice in the State of Arkansas
found that the blackhull showed higher H compared
to strawhull (Shivrain et al., 2010). However, it is
noteworthy that the blackhull has higher genetic
diversity compared to strawhull due to the greater
proximity with wild rice, which has less selection
pressure imposed by man and therefore less
reduction in genetic diversity (Londo & Schaal, 2007),
which could partly explain the lowest H observed for
blackhull plants in the experiment.
Assuming that the rice is more competitive
than red rice when RC>1, Kr>Krr and C>0 (Hoffman
& Buhler, 2002) and the occurrence of differences in
at least two of these indices (Bianchi et al., 2006) it
was observed for all variables that both weed biotypes have more competitiveness than the crop
(Table 3).
Overall, strawhull or blackhull red rice, when
competing with the rice cultivar, showed higher
growth than the later in all variables, as indicated by
RC index (Table 3). There was dominance of competitors on rice cultivar, as indicated by the index K.
Furthermore, it has been found through the index C
that the red rice was more competitive than the
culture.
Based on the combined analysis of the three
competitiveness indices, blackhull was more
competitive than strawhull for SDW and LA variables,
while there was no difference among biotypes for H
(Table 3). These results are possibly related to
greater tiller emission capacity of blackhull as
described by Shivrain et al. (2010). Study showed
that tillering ability is the best predictor of plant competitiveness, including being used for selection of rice
cultivars with greater competitive ability (Ni et al.,
2000), which helps explain the results.
182
Científica, Jaboticabal, v.44, n.2, p.176-184, 2016
ISSN: 1984-5529
Table 3 - Competitiveness indices among red rice biotypes, competing with rice (CL 142 AR) and among
weed biotypes, expressed by relative competitiveness (RC), relative clustering coefficient (K) and competitiveness coefficient (C).
Proportion
RC
Kr
Krr
C
2.64(±0.37)
2.43(±0.40)
1.15(±0.05)
-0.41(±0.00)*
-0.35(±0.04)*
-0.10(±0.01)*
2.23(±0.45)
2.38(±0.32)
1.39(±0.18)
-0.41(±0.04)*
-0.43(±0.04)*
-0.16(±0.03)*
1.00(±0.08)
0.95(±0.01)
0.86(±0.02)
-0.09(±0.00)*
-0.07(±0.01)*
0.02(±0.01)ns
SDW
Rice:Straw
Rice:Black
Straw:Black
0.43(±0.03)*
0.50(±0.04)*
0.81(±0.01)*
0.45(±0.06)*
0.53(±0.03)*
0.76(±0.03)*
Rice:Straw
Rice:Black
Straw:Black
0.40(±0.01)*
0.39(±0.03)*
0.72(±0.04)*
0.37(±0.02)*
0.37(±0.01)*
0.70(±0.01)ns
Rice:Straw
Rice:Black
Straw:Black
0.82(±0.01)*
0.85(±0.02)*
1.05(±0.02)ns
0.70(±0.04)*
0.71(±0.01)*
0.94(±0.03)ns
LA
H
Not significant and * significant by t test (p≤0.05). Values in brackets represent the mean’s standard error. Kr and Krr
are relative clustering coefficients for rice and red rice, respectively.
ns
Conclusions
The intraspecific competition is more harmful
to red rice biotypes, while the interspecific
competition is more pronounced for culture.
The rice cultivar CL 142 AR has lower
competitive ability in relation to the red rice biotypes
from the United States (strawhull or blackhull), while
the blackhull red rice biotype generally has competitive advantage compared to the strawhull.
Acknowledgements
The authors thank the financial support of
DECIT / SCTIE-MS through CNPq and FAPERGS.
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