other elements, besides P, responded significantly to inoculation, and the impact of AM
symbiosis on the concentration of these ions
was genotype specific, indicating again the relevance of plant genetics.
In the attempt to map the genetic bases of
AM symbiotic variations, also wild relatives
and old varieties are often analyzed since they
represent important genetic resources for
breeding (Singh et al. 2012; Lehmann et al.
2012). It has been hypothesized that the selection of modern varieties, which was likely carried out under highly fertilized conditions, may
have decreased the susceptibility/responsiveness to the AM symbiosis (Zhu et al. 2001;
Lehmann et al. 2012). Depending on the crop
species diverse mycorrhizal response patterns
were observed (Kapulnik & Kushnir 1991; Koltai & Kapulnik 2010; Steinkellner et al. 2012;
Xing et al. 2012; Turrini et al. 2016). A recent
work, through a comparative investigation on
27 crop species and their wild progenitors,
showed that the growth benefits exerted by
the AM symbiosis were dependent on P availability; while wild progenitors positively
responded to the AM symbiosis irrespective of
P availability, in domesticated plants the
growth effect observed at low P became negligible when P availability increased (Martı ´nRobles et al. 2018). In addition, domesticated
plants reduced AM fungal colonization more
strongly than did wild progenitors in response
to increased P availability.
On the whole these studies indicate a strong
fungal genotype X plant genotype interaction
in the mycorrhizal symbiosis. This variation
may have profound impact in natural populations and has to be considered in agricultural
practices where AM fungi are exploited to
improve plant health and productivity.
VI. Conclusions
Genetics and genomics have recently provided
crucial novel information on the biology of
arbuscular mycorrhizas. The genome sequencing of a number of AM fungal species is allowing to identify common features such as the
fatty acid auxotrophy but also dispensable
species-specific components. The detailed characterization of several isolates of R. irregularis
at the level of single nuclei has even opened a
window on the potentials to genetically manipulate AM fungi (Chen et al. 2018).
On the plant perspective, phylogenomics
analyses based on genomes from host and
non-host species are emerging as powerful
tools to identify conserved genes required for
the AM symbiosis (Bravo et al. 2016) and to
trace the evolution of the underlying genetic
network from basal plants to angiosperms
(Delaux et al. 2015). We can also envisage that
the CRISPR/Cas-based genome editing technique will offer an efficient strategy for producing plant genotypes with mutations in genes of
interest. These genes could be selected among
those responsible of the molecular dialogue
between partners (also considering the presymbiotic steps) and among those which regulate AM functionality. In the frame of a more
friendly agriculture, these plant genes could be
the targets for the development of new crop
varieties more susceptible and responsive to
the beneficial AM fungi.
Acknowledgments Research is supported by the Italian
Ministry for University and Research (MIUR - UNITO
Ricerca Locale 2016) and by TOMRES from the European Union’s Horizon 2020 research and innovation
program under grant agreement no. 727929 to L.L.
and by the Italian Ministry for University and Research
(MIUR - UNITO Ricerca Locale 2016) and Fondazione
Cassa di Risparmio di Cuneo (AMforQuality – Bando
Ricerca Scientifica 2015) to A.G.
References
Akiyama K, Hayashi H (2006) Strigolactones: chemical
signals for fungal symbionts and parasitic weeds in
plant roots. Ann Bot 97(6):925–931
Akiyama K, Matsuzaki K, Hayashi H (2005) Plant sesquiterpenes induce hyphal branching in arbuscular mycorrhizal fungi. Nature 435(7043):824–827
Akiyama K, Ogasawara S, Ito S, Hayashi H (2010)
Structural requirements of strigolactones for
hyphal branching in AM fungi. Plant Cell Physiol
51(7):1104–1117
Alvey L, Harberd NP (2005) DELLA proteins: integrators of multiple plant growth regulatory inputs?
Physiol Plant 123:153–160
160
L. Lanfranco et al.
symbiosis on the concentration of these ions
was genotype specific, indicating again the relevance of plant genetics.
In the attempt to map the genetic bases of
AM symbiotic variations, also wild relatives
and old varieties are often analyzed since they
represent important genetic resources for
breeding (Singh et al. 2012; Lehmann et al.
2012). It has been hypothesized that the selection of modern varieties, which was likely carried out under highly fertilized conditions, may
have decreased the susceptibility/responsiveness to the AM symbiosis (Zhu et al. 2001;
Lehmann et al. 2012). Depending on the crop
species diverse mycorrhizal response patterns
were observed (Kapulnik & Kushnir 1991; Koltai & Kapulnik 2010; Steinkellner et al. 2012;
Xing et al. 2012; Turrini et al. 2016). A recent
work, through a comparative investigation on
27 crop species and their wild progenitors,
showed that the growth benefits exerted by
the AM symbiosis were dependent on P availability; while wild progenitors positively
responded to the AM symbiosis irrespective of
P availability, in domesticated plants the
growth effect observed at low P became negligible when P availability increased (Martı ´nRobles et al. 2018). In addition, domesticated
plants reduced AM fungal colonization more
strongly than did wild progenitors in response
to increased P availability.
On the whole these studies indicate a strong
fungal genotype X plant genotype interaction
in the mycorrhizal symbiosis. This variation
may have profound impact in natural populations and has to be considered in agricultural
practices where AM fungi are exploited to
improve plant health and productivity.
VI. Conclusions
Genetics and genomics have recently provided
crucial novel information on the biology of
arbuscular mycorrhizas. The genome sequencing of a number of AM fungal species is allowing to identify common features such as the
fatty acid auxotrophy but also dispensable
species-specific components. The detailed characterization of several isolates of R. irregularis
at the level of single nuclei has even opened a
window on the potentials to genetically manipulate AM fungi (Chen et al. 2018).
On the plant perspective, phylogenomics
analyses based on genomes from host and
non-host species are emerging as powerful
tools to identify conserved genes required for
the AM symbiosis (Bravo et al. 2016) and to
trace the evolution of the underlying genetic
network from basal plants to angiosperms
(Delaux et al. 2015). We can also envisage that
the CRISPR/Cas-based genome editing technique will offer an efficient strategy for producing plant genotypes with mutations in genes of
interest. These genes could be selected among
those responsible of the molecular dialogue
between partners (also considering the presymbiotic steps) and among those which regulate AM functionality. In the frame of a more
friendly agriculture, these plant genes could be
the targets for the development of new crop
varieties more susceptible and responsive to
the beneficial AM fungi.
Acknowledgments Research is supported by the Italian
Ministry for University and Research (MIUR - UNITO
Ricerca Locale 2016) and by TOMRES from the European Union’s Horizon 2020 research and innovation
program under grant agreement no. 727929 to L.L.
and by the Italian Ministry for University and Research
(MIUR - UNITO Ricerca Locale 2016) and Fondazione
Cassa di Risparmio di Cuneo (AMforQuality – Bando
Ricerca Scientifica 2015) to A.G.
References
Akiyama K, Hayashi H (2006) Strigolactones: chemical
signals for fungal symbionts and parasitic weeds in
plant roots. Ann Bot 97(6):925–931
Akiyama K, Matsuzaki K, Hayashi H (2005) Plant sesquiterpenes induce hyphal branching in arbuscular mycorrhizal fungi. Nature 435(7043):824–827
Akiyama K, Ogasawara S, Ito S, Hayashi H (2010)
Structural requirements of strigolactones for
hyphal branching in AM fungi. Plant Cell Physiol
51(7):1104–1117
Alvey L, Harberd NP (2005) DELLA proteins: integrators of multiple plant growth regulatory inputs?
Physiol Plant 123:153–160
160
L. Lanfranco et al.