phyllosphere is a dynamic rapidly changing area surrounding the germinating seed. there are two categories of microbes one is positively enhancing and negatively reducing the plant yield
8. Kinds of stresses
1. Seasonal cycle
2. Developmental,
morphological changes
in plant
3. Day and night cycle
4. Limitations of nutrients
5. Physiochemical
constraints (light,
temperature, radiation,
desiccation)
9. How they survive on the leaves?
Tolerance strategy which permits the
inhabitants to tolerate direct exposure
to environmental stresses on the
surface of the leaf mainly UV
radiation and low moisture
conditions
Eg: Saprophytes typically employ
tolerance strategies to survive in the
foliar zone, as they cannot survive
endophytically
Avoidance strategy which allows the
epiphytes to colonize sites that do not
face these stresses (Beattie and
Lindow, 1995)
Eg: Foliar pathogens can utilize both
the strategies to harbour the plants
more efficiently
Avoidance
Nutrient
limitation
10. Hotspots on leafs
Bases of trichomes,
Stomata,
Epidermal cell wall junctions and
Grooves along veins
(Beattie & Lindow, 1999)
11. Introduction
Phyllosphere is the surface and interior of the aerial parts
of vascular plants (Newton et al., 2010)
Most of the phyllosphere colonizing microorganisms live
as commensals on their host plants
About 0.1–8.4 % of the total bacterial population were
cultivable (Rastogi et al., 2010)
The phyllosphere has an area of roughly about one billion
square kilometres (Morris and Kinkel, 2002), in which the
number of bacteria may reach up to 106–107 cells per
square centimetre of leaf area, which is roughly 1026 ells
12. History
1955- The term phyllosphere was first introduced by the
plant pathologist F.T. Last
1956 - “Phyllosphere” term was coined by Ruinen
1987 - Kinkel tested the equilibrium theory of island
biogeography, assuming that individual leaves form discrete
habitat patches for microbes analogous to oceanic islands for
macroorganisms.
2002 – Morris extended the concept to include both the areas
inside and outside the leaf
2012- Berlec considered phyllospheric microflora as “Plant
probiotics”
2015- Doan and Leveau divided the phyllosphere into two
unique niches i.e., Phylloplane (the leaf surface landscape)
and phyllotelma (the leaf surface waterscape)
22. Ecology of phyllosphere microbiota
Actinobacteria
Bacteroidetes
Firmicutes
Proteobacteria
(Bulgarelli et al., 2013)
Pseudomonas
Sphingomonas
Methylobacterium
Bacillus
Massilia
Arthrobacter
Pantoea
Species richness in fungi is one order of magnitude lower than
that of bacteria (Finkel et al., 2011).
23. Core phyllosphere community of crops
Rice
Rhizobium,
Methylobacterium, and
Microbacterium,
Lettuce
Pseudomonas,
Bacillus,
Massilia,
Arthrobacter, and
Pantoea
Soybean, clover,
Arabidopsis
Sphingomonas,
Methylobacterium
26. Major drivers of phyllosphere microbiota
composition
1) Geographical location
Eg: 1 salt excreting desert tree Tamarix
In this plant major determinant of phyllosphere
microbial community structure is geographical
location. It is evidenced by the fact that
different species of Tamarix (T. aphylla, T.
nilotica, T. teragina) grown in same
geographical location supported similar
bacterial community whereas, plants grown in
different locations showed strong correlation
with geographical differences (Finkel et al.,
2012)
Eg: 2 similar results were found in lettuce
crop, increased distance between lettuce
production sites resulted in more diverse
community structure (Rastogi et al., 2012)
27. Unlike plants and
animals, bacteria did
not exhibit an
elevational gradient
in their diversity
(Fierer et al., 2011)
35. 3) Plant genetics
Phyllosphere communities associated with
Pinua ponderosa were fairly similar to each
other irrespective of the geographical
location (Whipps et al., 2008)
A microbial survey of different cultivars of
lettuce grown in the same field showed that
they supported different bacterial
communities on their foliage (Hunter et al.,
2010)
It was suggested that these differences
correlated with plant genetic components
that regulate leaf texture and the leaching of
metabolites to the leaf surface
36. Is it possible to manipulate community
structure?
Yes, we are already doing it…..
44. Production of growth promoting hormones
Production of pigments
Production of volatile organic compounds
Extracellular oligosaccharides
Cross kingdom signals
Quorum sensing
Cycling of elements as saprophytes (Global N and C cycles)
Remediating residual pesticides and atmospheric
hydrocarbon pollutants
Help in plant development and health as biofertilizers,
phytostimulators and biopesticides to protect against
invading pathogens (Lugtenberg et al., 2002; Delmotte et al.,
2009; Zhou et al., 2011; Ali et al., 2012)
Functions
45. Growth hormones
Auxins Eg: IAA
produced by
Sphingomonas
Cytokinins
Brassinosteroids,
Gibberellins,
Abscisic acid,
Ethylene,
Jasmonates and
Strigolactones
50. UV Protection mechanisms
1. Methylobacterium, Sphingomonas, Pseudomonas etc.,
possess pigmentation
2. Special DNA repair mechanisms
3. Up regulation of stress response proteins (Eg: PhaA)
4. Production of extracellular polysaccharides
52. VOC’s
“Volatile organic compounds (VOCs) are a large class of
low-molecular-weight, carbon-containing compounds
characterized by their high volatility, low vapor pressure
(≥0.01 kPa at 20 °C), and low water solubility” (Herrmann,
2010)
To date, a total of 1700 volatile compounds have been
isolated from more than 90 plant families.
Plant volatiles constitute about 1 % of plant secondary
metabolites and are mainly represented by terpenoids,
phenylpropanoids/benzenoids, fatty acid derivatives, and
amino acid derivatives.
Volatile organic compounds (VOC) are organic
chemicals that when released into the atmosphere can react
with sunlight and nitrogen oxides (NOx) to form tropospheric
(ground-level) ozone (Melanie et al., 2010)
56. Why we need to study about phyllosphere?
Improving our understanding about the behaviour of
microorganisms in this habitat will facilitate biotechnological
applications for protecting plants,
Promoting plant growth,
Avoid human pathogenic bacteria in plant food and,
Phytoremediation of volatile pollutants from the air.