Page 3000 - 1970S

tually simultancously. or they leave
space for weeds to grow in the row
where thc culti vali ng machine ca n–
not go.
In short. the pressurctor uniformity is
o rten ovcrwhclming. The result has
bcen that a la rgc pcrcen1age o f the
available acreage of each crop is
planted with a limit ed number of
varieties. For cxamplc, one hundred
percent or all the mille t grown in
North Ame rica is from three varie1ies
of seeds. Ninety-s ix percent orthe pea
crop is pla nt ed with only two pea
typcs. (See accompanying box.)
"Therc is on ly one gene. as far as
1 know. tha l produces stringle sness
in green and wax bcans." says Dr.
J ames Horsfa ll. plant scienti 1a l the
Connecticut Agricultura! Ex peri–
menl Stalion. ew Haven. " Ifa fun–
gus mutalion comes a long that likes
that gene. we'vc had it.
" For a crop-di sease epidemic lo
occur. the wea ther mus t be ri ght. the
crop va riety must be vulnerable.
and a parasite mu. t be present. We
can' l manipulate the weather very
we ll ; we ca n'l manipulate the para–
site." says Horsfa ll. "The only thing
is to manipulate the host [crop].''
"A nd hanging over al/ crops in al!
countries - ' like the sword of Dam–
ocles.' ' ' say Horsfall. " is the danger
tha t reliance on a single genetic vari–
etv or two can /ead to devastating
losses from disease. "
Wilkes agrees. " In adva nced agri–
culture such as ours. the prey is at
ve ry high den ity. and conditions
are ideal for insects, nematodes,
bacteria. viruses, fungi. and ro–
dents.'' wa rns Wilkes. "Thc price for
the maintenance of high yields is an
arsenal of insecticides and fun gi–
cides. along with the need to con–
s tantly changc 1hc gcneti c material
and brced fo r res istance against the
latest problem th at lh reatens the
yield."
A Lesson from History
Forlunately for 1he Unilcd Stales.
lhe e rrect of 1he 1970 corn blighl
was limited to highcr food costs;
there was no larvation in th e
Uniled Stales dueto the blight. But
such a crop fail ure in other coun–
tries such as Guatema la or Kenya.
where 1he pcople obtain half of all
the ir ca lori es from corn directly,
would have becn disastrous.
The PLAIN TRUTH June 1976
THE DISEASE
TRIANGLE
PLANT
DISEASE
PARASITE WEATHEA
Three factors combine lo produce
disease in man 's crops:
• The host - a susceptible plant
• The parasite or other pathogen
• The weather or environment
Man has virtually no control over
the appearance of new parasites
and d1seases, and he has little or
no control over the weather. How–
ever, he does have a considerable
control over the genetic bas1s of
his crops. But the 1ncreasing uni–
formity of man's crops poses a se–
rious threat lo agriculture: 11 crops
all have the same genetic base,
then 11 is only a matter of time be–
fore the " proper" paraSIIe and weath–
er conditlons preclpitate a devas–
tating destruction of a major crop.
1n fa et. his tory te li s us tha t sueh
disas ters have already occurred . In
the 18th century. the p01ato. a new
food plant from South America, was
introduced into lreland . The gene tic
di ve rsity of the species was sma ll.
but i olated from its diseases. the
potato proliferatcd. allowing the
lrish population to increase. Then.
in the 1830s. with the population of
lrela nd having increased threefold
to eight milli o n. a previous ly
unknown disease, ca uscd by a fun–
gus, a ttacked th e potato c rop.
Within ten yea rs. two mi ll ion Irish
emigra ted. two mi llion died. ancl
four million remain ed. many in ab–
j ec t poverty.
The Irish had inadvcn cntly nar–
rowed the geneti c ba e of the crop,
and there remained little or no resis–
tance to the devasta ting fungus.
" At presc nt. ' ' says Gar ri so n
Wi lkes. " there exis ts a n unstable
't ruce' be tween our basic food
plants and thei r pathogens. Genetic
changes. either mutations or new re–
combinations. are cons tantly taking
place in indi vi dual pathogens. and
if a pathogen uddenly grows suc-
cessfully on a prev iously res istan!
plant host. it will be able to spread.
across the entire plant population if
th e la tter is genetica lly unilorm ...
Professor J. R. Ha rla n of the Uni–
vers ity of lllinois. a n emin cnl Amer–
ican plan t eco logis t. is equally
alarmed. "American agricu lture is
an imponed agricul ture." Harlan
told The Plain Truth a t a news con–
ference during the 1976 Amer ican
Associa tion for the Advanccment o f
Science mee ting in Boston. " Every
crop we grow is based on a vulner–
able gene ti c base.··
Harlan a lso points out th at a re–
markablc proport ion of the human
diet i suppli ed by four cerea ls:
wheat. rice. maizc. and sorghum.
" Imagine, if you can." says Ha r–
lan. " the scope of th e di aster if one
of these should fail. if some new and
virulent disease should appear wit h
which we are unable to cope in time.
Surely it is impera ti ve that we know
a ll tha t we possibly can about ALL of
the germ plasm within genet ic reach
in our major food plants."
Genetic Erosion
Yet the poten tia l danger in over–
rel iance on gcne t ica lly uniform
crops does no t stop wit h the specter
of future crop failures. 1ndeed, if the
possibili ty of a n occasional crop fail–
ure we re the only source of concern.
it could logically be a rgued that
such is th e price we must pay for the
vastly improved production of mod–
ern agriculture.
But an even grea ter problem i
that the very success of the new
hybrids has mcant that th ey have
been supplanting na tive va ri eties all
over the world . and in many cases,
the na ti ve crops - a long with their
gene ti c di ve r ity - have simply dis–
appeared lorever.
"There is nothing biologica lly un–
sound abo ut breeding for high
yi elds, and using a narrow geneti c
base is a plant-breeding expediency
necessary to obtain the mos t uni–
form. high-yield ing seed in the
shonest period of time." Wilkes re–
minds u~. "But it i. unthinkable not
to pre erve and maintain the ready
reserves of genetic di versity thar st ill
exis t in narive agriculture for futu re
plant breeding needs.
"Up Lo the prcse nt time. we have
been able to return to a reas of
33