Table Of ContentCOMPONENTS OF RESISTANCE TO LATE LEAFSPOT OF PEANUT
AND STUDIES ON HEALTHY LEAF AREA DURATION
By
VERMANDO MASINSIN AQUINO
A DISSERTATION PRESENTED TO THE GRADUATE SCHOOL
OF THE UNIVERSITY OF FLORIDA IN PARTIAL FULFILLMENT
OF THE REQUIREMENTS FOR THE DEGREE OF
DOCTOR OF PHILOSOPHY
UNIVERSITY OF FLORIDA
1991
ACKNOWLEDGEMENTS
I would like to express my sincere appreciation to my
adviser and major professor, Dr. Fred M. Shokes, for his
advice, encouragement and support throughout my studies at the
University of Florida.
I would like to thank Dr. Richard D. Berger, cochairman
of my committee, for his support and guidance during the
course of my studies.
Dr. Daniel W. Gorbet provided valuable assistance in the
conduct of field experiments. His support and guidance are
greatly appreciated.
Thanks are also expressed to Dr. Kenneth J. Boote and Dr.
Thomas A. Kucharek for their guidance as members of my
committee.
Thanks are also due to Don Berger and Dale Weeks for
their valuable assistance, and to the staff of NFREC, Quincy
and AREC, Marianna, Florida.
Finally, I would like to thank my friends and my family
for their support and encouragement.
ii
TABLE OF CONTENTS
Rage
ACKNOWLEDGEMENTS ii
LIST OF TABLES V
LIST OF FIGURES vii
ABSTRACT ix
CHAPTERS
1 INTRODUCTION 1
Partial Resistance to Late Leafspot 2
Disease-induced Yield Loss and Healthy Leaf Area
Duration 4
2 EFFECT OF COMPONENTS OF RESISTANCE ON PROGRESS OF
LATE LEAFSPOT 7
Introduction 7
Materials and Methods 9
Peanut Genotypes 9
Field Experiments 11
Components of Partial Resistance 11
Disease Assessments 14
Results 16
Components of Partial Resistance 16
Disease Progression and Pod Yield 21
Discussion 25
3 RELATIONSHIPS AMONG SEVERITY OF LATE LEAFSPOT,
RADIOMETRIC MEASUREMENTS, HEALTHY LEAF AREA
DURATION, AND POD YIELD IN TWO PEANUT
CULTIVARS 28
Introduction 28
Materials and Methods 30
Field Experiments 30
Disease Assessments 33
Radiometric Measurements 34
iii
Leaf Area Index (LAI) and Healthy Leaf Area
Duration (HAD) 34
Results 35
Disease Progression 35
Leaf Area Index 39
Green Leaf Area and Percent Reflectance ... 43
Healthy leaf Area Duration (HAD) and Pod
Yield 50
Discussion 50
4 SUMMARY 55
APPENDICES
A WEATHER DATA 57
B LEAF AREA INDEX DATA 66
C CANOPY REFLECTANCE DATA 69
D TOTAL DISEASE SEVERITY DATA 73
LITERATURE CITED 75
BIOGRAPHICAL SKETCH 81
IV
LIST OF TABLES
Table page
2-1 Peanut genotypes evaluated for components of
resistance in 1988 and 1989 9
2-2 C19o8m8parison of 12 selected genotypes based on
various components of resistance 10
2-3 Mean values of components of resistance to late
leafspot estimated under field conditions during
17
2-4 Mean values of components of resistance to late
leafspot estimated under field conditions during
1989 18
2-5 Mean areas under disease progress curve, rates of
disease progress, and pod yield from field tests in
1988 and 1989 22
2-6 Pearson correlation coefficients relating
components of resistance to AUDPC and rate. . . . 24
A-l Weather data during summer 1988 at AREC, Marianna,
Florida 57
A-2 Weather data during summer 1989 at AREC, Marianna,
Florida 61
A-3 Daily rainfall during summer 1988 at Dozier Boy's
School, Marianna, Florida 64
A-4 Daily rainfall during summer 1989 at Dozier Boy's
School, Marianna, Florida 65
B-l Leaf area index data collected on Florunner in 1988
at AREC, Marianna, Florida 66
B-2 Mean leaf area index for Florunner and Southern
Runner in 1989 at AREC, Marianna, Florida .... 68
C-l Percent reflectance at 800 nm for Florunner in 1988
at AREC, Marianna, Florida 69
v
C-2 Percent reflectance at 800 nm for Florunner in 1989
at AREC, Marianna, Florida 71
C-3 Percent reflectance at 800 nm for Southern Runner
in 1989 at AREC, Marianna, Florida 72
D-l Total disease severity (%) data for Florunner in
1988 at AREC, Marianna, Florida 73
D-2 Total disease severity (%) data for Florunner and
Southern Runner in 1989 at AREC, Marianna,
Florida 74
vi
2-
LIST OF FIGURES
3-
Figure page
1 Weekly accumulation of rain at the Dozier Boy's
School, Marianna, FL during summers of 1988 and
1989 12
1 Weekly accumulation of rain at the AREC, Marianna,
FL during summers of 1988 and 1989. Irrigation is
included in 1989 31
3-2 Progression of late leafspot in Florunner in 1988
under different fungicide treatments (an unsprayed
control, four spray rates initiated at 1% incidence
where x = 1.75 L/ha, and GS or growers schedule
initiated at 35 DAP) 36
3-3 Progression of late leafspot in Florunner in 1989
under different fungicide treatments (an unsprayed
control, three spray rates initiated at 0.5%
incidence where x = 1.75 L/ha, and GS or growers
schedule initiated at 35 DAP) 37
3-4 Progression of late leafspot in Southern Runner in
1989 under different fungicide treatments (an
unsprayed control, three spray rates initiated at
0.5% incidence where x = 1.75 L/ha, and GS or
growers schedule initiated at 35 DAP) 38
3-5 Leaf area index over time for Florunner in 1988
under different fungicide treatments (an unsprayed
control, four spray rates initiated at 1% incidence
where x = 1.75 L/ha, and GS or growers schedule
initiated at 35 DAP) 40
3-6 Leaf area index over time for Florunner in 1989
under different fungicide treatments (an unsprayed
control, three spray rates initiated at 0.5%
incidence where x = 1.75 L/ha, and GS or growers
schedule initiated at 35 DAP) 41
vn
3-7 Leaf area index over time for Southern Runner in
1989 under different fungicide treatments (an
unsprayed control, three spray rates initiated at
0.5% incidence where x = 1.75 L/ha, and GS or
growers schedule initiated at 35 DAP) 42
3-8 Percent Reflectance at 800 nm for Florunner in 1989
under different fungicide treatments (an unsprayed
control, four spray rates initiated at 1% incidence
where x = 1.75 L/ha, and GS or growers schedule
initiated at 35 DAP) 44
3-9 Percent reflectance at 800 nm for Florunner in 1989
under different fungicide treatments (an unsprayed
control, three spray rates initiated at 0.5%
incidence where x = 1.75 L/ha, and GS or growers
schedule initiated at 35 DAP) 45
3-10 Percent reflectance at 800 nm for Southern Runner
in 1989 under different fungicide treatments (an
unsprayed control, three spray rates initiated at
0.5% incidence where x = 1.75 L/ha, and GS or
growers schedule initiated at 35 DAP) 46
3-11 Relationship between percent reflectance at 800 nm
and green leaf area (GLA) of Florunner in 1988. . 47
3-12 Relationship between percent reflectance at 800 nm
and green leaf area (GLA) of Florunner in 1989. . 48
3-13 Relationship between percent reflectance at 800 nm
and green leaf area (GLA) of Southern Runner in
1989 49
3-14 Relationships between healthy leaf area duration
(HAD) and pod yield for Florunner in 1988 and 1989
and Southern runner in 1989 51
viii
Abstract of Dissertation Presented to the Graduate School
of the University of Florida in Partial Fulfillment of the
Requirements for the Degree of Doctor of Philosophy
COMPONENTS OF RESISTANCE TO LATE LEAFSPOT OF PEANUT
AND STUDIES ON HEALTHY LEAF AREA DURATION
By
Vermando Masinsin Aquino
May 1991
Chairman: Dr. Frederick M. Shokes
Cochairman: Dr. Richard D. Berger
Major Department: Plant Pathology
Late leafspot, causedbyCercosporidiumpersonatum (Berk,
and Curt.) Deighton, is one of the most economically
significant diseases of peanut (Arachis hypogaea L.) in
Florida. The pathogen frequently causes severe defoliation
and reduction in pod yield. The objectives of this research
were i) to determine the relationship between components of
partial resistance to late leafspot and disease progression,
and ii) to examine the relationships of disease severity,
canopy reflectance, healthy leaf area duration (HAD) and pod
,
yield. Components of partial resistance to late leafspot were
quantified and late leafspot disease progression were
monitored on 14 peanut genotypes in field experiments at
Marianna, Florida, during 1988 and 1989. Inoculated target
leaves were used to determine various components such as,
incubation period, latent period, maximum percentage of
ix
lesions that sporulated (MPLS) lesion size, lesion number,
,
degree of sporulation, and percent necrotic leaf area.
Genotypes included a resistant breeding line, (UF 81206) a
,
moderately resistant cultivar, (Southern Runner) susceptible
,
cultivar, (Florunner) and eleven breeding lines with various
,
levels of resistance. Lowest AUDPC (area under the disease
progress curve) rate of disease progress, and final level of
,
disease were observed on genotypes UF81206, PI 261893, US
29-b3-B, and US 202-b2. Rate of disease progress and AUDPC
were more highly correlated with MPLS and latent period than
with lesion size, degree of sporulation, and percent necrotic
area. MPLS and latent period were the resistance components
that contributed most towards the reduction of disease
progress in the field. Field studies on healthy leaf area
duration (HAD) were conducted in 1988 and 1989 for peanut
cultivars Florunner and Southern Runner. Spray treatments of
chlorothalonil were applied to establish different levels of
disease. Leaf area index (LAI) was measured eight times
during the season and disease progression and percent
reflectance were monitored. Healthy leaf area duration and
green leaf area were calculated from LAI and the total amount
of disease. Linear relationships were obtained between green
leaf area index and percent reflectance at 800 nm for both
cultivars. Pod yields for all treatments increased with HAD.
Results support the concept that HAD can be used to predict
yield and yield loss due to late leafspot disease.
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