During the first six months of 2018 with only two rains, the
participating Kansas farmers had given up on and plowed over
fields with struggling regular wheat, but not those growing
Indigo Wheat, Goldman says.
In St. Louis, NewLeaf Symbiotics is interested in bacteria
of the genus Methylobacterium. These microbes, found in all
plants, are known as methylotrophs because they eat methane
gas, which plants release as their cells grow. In return for methane,
M-trophs, as NewLeaf calls them, offer plants diverse benefits.
Some deliver molecules that encourage plants to grow; others
make seeds germinate earlier and more consistently, or protect
against problem fungi.
NewLeaf released its first products this year, including
Terrasym 401, a seed treatment for soybeans. Across four
years of field trials, Terrasym 401 raised yields by more than
two bushels per acre, says NewLeaf cofounder and CEO Tom
Laurita. One bushel is worth about $9. On farms with thousands of acres, that adds up.
Farmers are pleased, but NewLeaf’s and Indigo’s work is
hardly done. Plant microbiome companies all face similar
challenges. One is the diverse environments where crops are
grown. Just because Indigo Wheat thrives in Kansas doesn’t
mean it will outgrow standard varieties in, say, North Dakota.
“The big ask for the next-gen ag biotech companies like
AgBiome or Indigo … is whether the products will deliver as
advertised over a range of field conditions,” Dangl says.
Another issue is that crop fields and plants already have
microbiomes. “We’re asking a lot of a microbe, or a mix of
microbes, to invade an already-existing ecosystem and persist there and do their job,” Dangl says. Companies will need
to make sure their preferred microbes take hold.
And while scientists are well aware that diverse microbial
communities cooperate to affect plant health, most companies
are working with one kind of microbe at a time. Indigo isn’t yet
sure how to approach entire microbiomes, Goldman says, but
“we certainly are thinking hard about it.”
Researchers are beginning to address these questions by
studying microbes in communities — such as Christian’s leaf-
litter microbiomes — instead of as individuals. In the lab, Dangl
developed a synthetic community of 188 root microbes. He can
apply them to plants under stress from drought or heat, then
watch how the communities respond and affect the plants.
A major aim is to identify the factors that determine micro-
biome membership. What decides who gets a spot on a given
plant? How does the plant species and its local environment
affect the microbiome? How do plants welcome friendlies and
eject hostiles? “This is a huge area of importance,” Dangl says.
There’s some risk in adding microbes to crops while these
questions are still unanswered, Mejía cautions. Microbes
that are beneficial in one situation could be harmful in
other plants or different environments. It’s not a far-fetched
scenario: There’s a fungal endophyte of a South American
palm tree that staves off beetle infestations when the trees
are in the shade. Under the sun, however, the fungus turns
nasty, spewing hydrogen peroxide that kills plant tissues.
And although C. tropicale benefits cacao, the genus has a
dark side: Many species of Colletotrichum can cause leaf lesions
Indigo Ag’s microbial treatment for cotton seeds results in bigger, bushier
plants under low-water conditions compared with untreated plants.
for toxicosis. The fungus, Epichloë
coenophiala, produces toxins called ergot
alkaloids. Yet E. coenophiala (at left, blue
squiggles inside fescue cells) is also the
reason tall fescue grows so well: The
fungus helps the plant resist stressors
such as drought and flooding.
2000 Pennington Seed, Inc. releases a tall
fescue variety called Jesup MaxQ, which
contains a different fungus that provides
the stress resistance without the toxic
Today While several low-alkaloid
versions of tall fescue seed are
available, farmers have not yet gone to
the effort to replace all their pastures,
and it’s not clear the new versions work
well in all environments. Scientists at
the University of Kentucky, led by
Christopher Schardl, continue to tinker
with the fungus and its genes in the
hopes of eliminating alkaloid production and making grasses that thrive in
environments where the current
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