چكيده لاتين :
Introduction: In negative cross-resistance, herbicide-resistant plants being more sensitive to herbicides than
susceptible plants. Negative cross-resistance to other herbicides have been found in triazine-resistant biotypes of
weeds. These biotypes are more sensitive to phenyl urea group of herbicides, as well other herbicides of triazine
group. Also, negative cross-resistance has been reported to bentazone for Brassica napus L, and Amaranthus
retrojlexus L, and to pyridate for B. napus, and Epilobium ci/iatum Raf.. Furthermore, positive cross-resistance
to bentazone has been found in Chenopodium album L., and Solanum nigrum L.. The goal of this study was to
search for herbicides that exert negative cross-resistance at the whole-plant level in order to control atrazineresistant
populations ofjunglerice in sugarcane fields.
Materials and Methods: Suspected resistant and susceptible seeds of junglerice to atrazine were collected
from sugarcane fields and adjacent areas to Karun Agro-lndustry Inc., Shushtar, southwestern of Iran at 2014 -
2015 growing season. These populations were named according to their status and abbreviated as follows: Rl,
R2, R3 and S (susceptible population). All collected seeds (R-and S-populations) were stored at room condition
(25 'C). Herbicides used in this study were tebuthiuron (0, 10, 20, 100, 200, 1000, 2000, 10000 ml ai ha· 1),
linuron (0, 10, I 00, 160, 1000, 1600, I 0000 ml ai ha·' ), diuron (0, I 0, 30, 100, 360, 1000, 3600, I 0000 g ai ha·')
and diuron + hexazinone (0, 10, 24, 100, 240, 1000, 2400, 10000 g ai ha· 1). For the pre-emergence application
treatment, 10 seeds were sown in 500-ml plastic pots containing clay:sand mix. Then, herbicides were applied
using a back pack sprayer with flood nozzle calibrated to deliver 350 lit ha·' to the suspected resistant and
susceptible junglerice populations on one day after sowing. Plants were thinned to four plants per pot. The
aboveground biomass was harvested on 28 days after treatment, dried at 75 'C for 48 h, and weighed. Data were
expressed as a percentage of the untreated control. The experiment was a completely randomized block design
with fQur replications and was repeated. The data were analyzed using nonlinear regression model in R software
(drc packege). Three or four parameters log-logistic equation was fitted to the observed data to describe the
response of populations to herbicides; susceptible population was considered as an index in order to compare the
resistance levels of the populations.
Results and Discussion: The result of screening test showed that three populations were resistant to atrazine.
The results of dose-response analyse for atrazine revealed that resistance factor (RF) for R I, R2 and R3
populations were 12.26, 6.59 and 3.75 based on fresh weight(% of control) and 5.37, 4.22 and 4.71 based on
number of survival plants (% of control), respectively. ED so values of R I, R2 and R3 populations were 36.85,
73.01 and 41.71 ml ai ha· 1 oftebuthiuron compared with 44.42 ml ai ha·' inS-population. RF values in the Rl,
R2 and R3 populations were 0.80, 1.53 and 0.72 oftebuthiuron, respectively. EDso values of the Rl, R2 and R3
populations were 92.76, 107.73 and 106.84 ml ai ha·' of linuron compared with 152.51 ml ai ha·'in S-population.
RF values of the Rl, R2 and R3 populations were I, 1.89 and 3.26 oftebuthiuron, respectively. EDso values of
the Rl, R2 and R3 populations were 74.21, 95.25 and 69.80 g ai ha· 1 ofdiuron compared with 79.03 g ai ha·' in
S-population. l11e RF of the R I, R2 and R3 populations were 0.97, 0.85 and 1.18 of diuron, respectively. The
ED50 values of the Rl, R2 and R3 populations were 62.11, 49.48 and 54.30 g ai ha·' of diuron+hexazinone
compared with 88.72 g ai ha·' inS-population. RF values of the Rl, R2 and R3 populations were 0.62, 0.68 and
0.52 for diuron+hexazinone, respectively. The results showed negative cross resistance to tebuthiuron, linuron,
diuron and diuron + hexazinone in the resistant populations.
Conclusions: In present study, the R2 population was the most sensitive to diuron+hexazinone in
comparison to other populations (RF ~ 0.56).The resistance of other populations treated with this herbicide was
lower than other herbicides. Therefore, this mixture can alone control a wide range of weeds and is more reliable
than herbicides that are used alone. Mixing herbicides both economically and environmentally, will reduce cost
less than each time they are applied individually. Therefore, this mixture is recommended for controlling atrazine
resistant weeds in sugarcane fields. Negative cross resistance may be the major reason that resistance to atrazine
do not evolve where herbicide mixtures were used, when the mixed herbicide (usually a non-PS II inhibiting
acetanilide) also controlled triazine-sensitive weeds.
