Herbicide Resistant Crops

Week 9

herbicide resistant crops _____ and forward

1990’s

herbicide resistant weed

weed that has changed to resist that change

this occurred naturally

are herbicide resistant weeds transgenic

no, it is natural we just select for it

susceptible

death or injury to a species following a herbicide application at normal use rates

tolerant

survival of the normal population of a species from a herbicide that controls other species.

example of tolerant

apply clethodim which controls grasses and broadleaves (soybeans) are tolerant

resistance

a plant that survives a herbicide dose which controls the normal population

__________ and _________ occur naturally and have always been there while __________ is a change.

susceptibility, tolerance, resistance

Advantages of Herbicide-Resistant crops

1. allows the use of higher herbicide rates for weed control to improve effectiveness

2. eliminate herbicide carryover concerns to rotational crops

3. allow herbicide use in crops that are normally sensitive (minor use crops)

   1. decrease crop injury

4. broaden the use of less toxic, more environmentally friendly herbicides

5. broaden the use of herbicides with different modes of action in a crop

Disadvantages of herbicide-resistant crops

1. allow use of herbicides with similar modes of action in major crops (corn and soybeans) — no rotation of MOA’s

2. increase crop injury from application errors, confusion

3. increase reliance on chemical weed control

4. resistant gene transfer to weedy relatives

   1. wild mustard/canola

   2. shatercane /grain sorghum

   3. jointed goat grass / wheat —not done yet

5. herbicide resistant crops becoming a volunteer weed

6. market acceptance

7. unchartered ground for legal and environmental ramifications

   1. tech fee

sulfonylurea tolerant soybeans

resistant to certain sulfonylurea herbicidesc

clearfield rice, sunflowers, wheat, corn

resistant to imidazolinones

poast protected corn

resistant to sethoxydim

Cp4 gene

found in bacteria in cooling pond of manufacturing facility

• put into a gene

• over-expressed the gene to have more of the enzyme within the plant (so the herbicide couldn’t inhibit it anymore)

Eoundup ready

altered EPSPS enzyme and overproductionlib

liberty link

metabolism of glufosinate and overproduction of GS enzyme

RR Xtend 

glyphosate - same as RR

dicamba - transgene for rapid metabolism

ENlist E3

2,4-D transgene for rapid metabolism

glufosinate and glyphosate - same as RR and LL crops

herbicide resistant crops why?

• estimated cost was about half as much to develop and discover a novel herbicide for commercilization

• three way herbicide resistant crops is currently available

  • up to five way stacks of herbicide resistance projected in the next couple years

• cost of a bag of soybean seed

  • 1995 - $15 all non gmo

  • 2020 - $65 ($45 for non gmo)

  • we are currently around 70$

we do not need resistant crops to control weeds

we developed because there were opportunities for advantages - now we are just trying to stay ahead of weed resistance