RESISTANCE TO LEAFHOPPER, Amrasca biguttula biguttula (Ishida) IN SUNFLOWER: SCREENING AND IDENTIFICATION OF RESISTANCE MECHANISM
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Date
2021-07-01
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PROFFESSOR JAYASHANKAR TELANGANA STATE AGRICULTURAL UNIVERSITY
Abstract
The present studies were conducted at ICAR-Indian Institute of Oilseeds
Research, Rajendranagar and College of Agriculture, Rajendranagar, Hyderabad to
screen sunflower germplasm accessions, identify the various biophysical and
biochemical factors of resistance and to understand the mechanism of resistance in some
of the identified germplasm sources.
Fifty seven accessions along with commercial hybrid, Syngenta-SB-275 and a
susceptible check, Morden were screened against A. biguttula biguttula in field under
natural infestation.The population of leafhopper and leafhopper injury were recorded
from all the germplasm accessions during Rabi, 2016-17 and 2017-18 and categorized
based on MSI (0: highly resistant; 0.1-1.0: resistant; 1.1-2.5: moderately resistant; 2.6-
3.5: susceptible and 3.6-5.0: highly susceptible). During Rabi 2016-17, out of 57
germplasm accessions screened, twenty two accessions were found resistant with a MSI
ranging from 0.6 to 1.0, while twenty five were found moderately resistant with a MSI
ranging from1.1 to 2.2, ten accessions were found susceptible with a MSI ranging from
2.6 to 2.7. Syngenta-SB-275 and Morden were found susceptible to leafhoppers with a
MSI of 2.6 and 3.2, respectively. During Rabi-2017-18, fifteen germplasm accessions
were found as resistant with a MSI of 0.8 to 1.0; thirty accessions were found as
moderately resistant with a MSI ranging from 1.2 to 2.4 and twelve accessions as
susceptible with a MSI ranging from 2.6 to 3.5. Syngenta-SB-275 andMorden were
found susceptible to leafhoppers with a MSI of 3.0 and 3.4, respectively.
Thus, fifteen accessions were found resistant to leafhopper consistently for two
years, i.e., 2016-17 and 2017-18. Twenty three accessions were recorded moderately
resistant while ten accessions were found susceptible for two consecutive
years.However, the remaining eight accessions were inconsistent in their reaction.
Among the various biophysical and biochemical parameters studied, significant
differences were observed in mean values of trichome density (midrib, lateral vein and
leaf lamina), trichome length (midrib, lateral vein and leaf lamina), MDA, H2O2, SOD,
CAT, POX, APX, total phenols, total free amino acid and total sugars between resistant
and susceptible accessions.
Correlation of leafhopper nymphal population with biophysical parameters
revealed a significant negative correlation with trichome density on midrib (-0.813*),
lateral veins (-0.727*), leaf lamina (-0.837*), trichome length on midrib (-0.706*),
lateral veins (-0.755*) and leaf lamina (-0.692*)total phenols (-0.886*).Other
biophysical factors like plant height, leaf area, petiole length, leaf thickness and
midribthickness didn‟t show any significant effect on leafhopper nymphal population.
Correlation of leafhopper nymphal population with biochemical factors showed
significant positive correlation with malondialdehyde, hydrogen peroxide, total free
amino acids and total sugars (r = 0.842*, 0.807*, 0.886* and 0.863*, respectively).
Whereas, significant negative correlation with total phenol content (r = -0.886*) was
observed.
The mechanismof resistance evaluated in terms of settling preference study also
revealed less number of nymphs settling on resistant accessions (8.3 to 17.3 nymphs per
plant) compared to susceptible check, Morden (47.1 nymphs per plant). The
ovipositional preference by A. biguttula biguttula under choice and no-choice tests
recorded significantly lowest number of nymphs (4.67 to 7.33 nymphs per plant under
choice test and 4.0 to 6.2 nymphs per plant under no-choice test) on resistant accessions,
compared to susceptible check, Morden (34.0 nymphs per plant under choice test and
12.8 nymphs per plant under no-choice test).
Resistant accessions received less number of feeding punctures(24.33 to 37.50
numbers of punctures per leaf) and lower number of honeydew spots (11.83 to 15.83
number of honeydew spots/8 h/10 nymphs) compared to susceptible check, Morden
(195.17 numbers of punctures per leaf and 62.83 number of honeydew spots/8 h/10
nymphs).
Developmental studies revealed extended larval period (10.90 to 11.68 days),
reduced nymphal survival (15.8% to 32.6%) and shortened adult longevity on resistant
accessions (5.40 to 6.16 days) compared to susceptible check, Morden (9.3 days, 64.9%
and 10.23 days, respectively). The resistant accessions took more number of days for
the development of symptoms compared to susceptible check, Morden.
GMU-339, GMU-696 and TSG-401 showed antixenosis and antibiosis
mechanism of resistance and in future it can be used in the resistance breeding
programme against A.biguttula biguttula.