The gene for gene hypothesis was actually proposed by Henry Harold Flor in the year 1945 while working with the host-pathogen interaction between of Linum usitatissimum and Melampsora lini inciting linseed/flax rust By this hypothesis for each gene controlling resistance in the plants there is a corresponding gene controlling pathogenicity (avirulence) in the pathogen The resistance of the host is governed by the dominant genes(D) The virulence of the pathogen is governed by recessive genes(d)

1. PAT-622
Disease resistance, Epidemiology and
Forecasting of Plant disease (2+1)
⮚ Boom and Bust cycle
⮚ Area Under Disease Progression Curve (AUDPC)
Submitted by:
V. Sathiya Aravindan
2150100007
I-M.Sc.,(Ag) Plant pathology
Department of plant pathology
Annamalai University

2. Gene for gene hypothesis
⮚ Before entering into the Boom and Bust cycle. We should familiarize with the gene
for gene hypothesis
⮚ The gene for gene hypothesis was actually proposed by Henry Harold Flor in the
year 1945 while working with the host-pathogen interaction between of Linum
usitatissimum and Melampsora lini inciting linseed/flax rust
⮚ By this hypothesis for each gene controlling resistance in the plants there is a
corresponding gene controlling pathogenicity (avirulence) in the pathogen
⮚ The resistance of the host is governed by the dominant genes(D)
⮚ The virulence of the pathogen is governed by recessive genes(d)

3. Gene for gene hypothesis
Quadratic check

4. Vertical resistance
⮚ The term vertical and horizontal resistance was proposed by J.E Vanderplanck
in the book Plant disease epidemics and control in the year 1963
⮚ Vertical resistance: Vertical resistance is one in which the plants are developed
by the breeders to exhibit resistance from only one particular race of pathogen
⮚ If a plant is developed by the breeder using the vertical resistance means that
it can exhibit resistance to one particular race
⮚ For eg : If resistant cultivars for Redgram wilt Fusarium udum race1 is
developed by using vertical resistance then the plant exhibits complete or
pronounced resistance against that particular race only but not against the rest
of the race 2 ,3 ,4

5. Horizontal resistance
⮚ Horizontal resistance is one in which the breeder exploits few minor genes and
develop the crop plants which exhibits resistance to several races of the same
pathogen
⮚ For eg : If a breeder developed resistant cultivar of banana against the Panama
wilt of banana using the horizontal resistance concept, then the banana cultivar
exhibits partial and cumulative resistance against all the 4 races of the
pathogens
⮚ In short the banana plant exhibit resistance against the sub-tropical race 1, 2, 3
and also to the tropical race 4

6. Vertifolia effect
⮚ Vertifolia effect was first observed by J.E Vanderplank who is considered
as the father of Epidemiology
⮚ Vertifolia effect is nothing but the absence of horizontal resistance while
breeding a crop plant for vertical resistance
⮚ This Vertifolia effect was first observed by J.E Vanderplank while breeding
the resistant cultivar for late blight of potato incited by Phytophthora
infestans in the vertifolia variety of potato

7. Difference between vertical and horizontal
resistance
Vertical resistance Horizontal resistance
Resistance provided by single gene
(Monogenic resistance)
Resistance provided by many genes
(Oligogenic or polygenic resistance)
More prone to boom and bust cycle Less prone to boom and bust cycle
Highly race specific Non race specific
Quantitative resistance Qualitative resistance
Often effective against biotrophs Often effective against necrotrophs
They are race-specific, major gene
controlled, pathotype specific resistance
They are race non specific, minor genes
resistance and not pathotype specific
resistance
Puccinia recondita causing leaf rust and the
vertical resistance is solely controlled by the
gene Lr-9 , Lr-19 , Lr-24 , and Lr-38
respectively
Redgram wilt is caused by Phytophthora
dreschleri f.sp. cajani causing Phytophthora
blight is controlled by the cumulative effect
of the genes ICP 7065 KPBR 80-1 and KPBR

8. Boom and bust cycle
⮚ Boom and bust cycle was first proposed by Priestly in the year 1970
⮚ The boom and bust cycle is mostly developed on the plants developed with
vertical resistance
⮚ New variety carrying VR resistant to prevalent pathotypes and released for
cultivation in an area.
⮚ These become popular and occupy large area. This period of popularity is called
as boom phase. This will continues until the virulent pathotype develops or
increases its frequency to cause an epidemic.
⮚ When the popular variety is becoming severely affected and causing epidemic
outbreak, they become obsolete cultivars (recently extinct cultivars)
⮚ This phase is called as bust phase

10. Area Under Disease Progression Curve
(AUDPC)
⮚ Area under disease progression curve (AUDPC) the concept was first introduced
for measuring the disease intensity over time
⮚ AUDPC is nothing but the quantitative summary of disease intensity over time
⮚ The quantitative summary is taken in order to compare the existing data across
year or locations are thereby to adopt the prognosis management measures to
reduce the disease severity and intensity

11. ⮚ The set of data can be feed onto the code run by the R-program
⮚ The data set includes the time in years in the X-axis and disease severity
percentage % in the Y-axis
⮚ The corresponding values give the graphical representation through the past
data trends the future disease prognosis and management could also be
obtained

14. References
? https://apsjournals.apsnet.org/doi/abs/10.1094/PHYTO-07-11-0189
? https://apsjournals.apsnet.org/doi/abs/10.1094/PHYTO.1997.87.5.506
? https://www.apsnet.org/edcenter/disimpactmngmnt/topc/PopGenetics/
Pages/InteractionsGeneticStructure.aspx
? Disease resistance in plants - J.E Vanderplanck 1963
? G.N Agrios 5th edition 2005