时间:2019-01-30 作者:英语课 分类:农业与发展


英语课

AGRICULTURE REPORT - Audience Mail: A Maize 1 Mystery for AGRICULTURE REPORT
By Mario Ritter


Broadcast: Tuesday, April 26, 2005


I'm Gwen Out with the VOA Special English Agriculture Report.


 
 
A listener in Vietnam has a question about corn breeding. Ho Lan Phuong has read about "pure-line development" and "broad-line development." She wants to know the difference.


Since ancient times, farmers have chosen the best examples from each crop to provide seed for the next year. This method is called mass selection. It may be what our listener has seen described as broad-line development. Mass selection produces plants with similar genetic 2 qualities over time.


The pure-line method of breeding is similar. But it is more systematic 3. In pure-line breeding, the best plants are chosen from a crop that has many different genetic qualities.


The seeds from these plants are grown. Then the best plants are chosen from the new crop. This process can go on for many years, until the seeds produce plants with measurable similarities and desirable qualities. Seed companies may use this method to produce seed for some crops.


But the pure-line method is not often used with widely traded crops. Today major crops like corn or wheat are developed as hybrids 5.


About one hundred years ago, a scientist in the United States, G.H. Shull, made important discoveries about corn hybrids.


He mated corn with itself. Corn does not normally fertilize 6 itself in nature. If corn is inbred, the seeds will produce a plant that clearly shows the qualities of the parent. But this inbreeding does not produce a strong plant.


Shull found that if he mated two inbred corn plants, they would produce a strong line with the good qualities of the parent plants. This is called crossbreeding.


Researchers soon recognized that they could crossbreed four inbred lines of corn. This "double cross" results in stronger corn with the best qualities of the parent plants. This is the way most hybrid 4 corn is developed.


Modern hybrid corn produces much more grain than its ancestors. But success can create its own problems. For example, there is very little genetic difference in the corn grown across the United States. Experts estimate that current hybrids use less than five percent of the genetic diversity that exists.


There is a project called Germplasm Enhancement of Maize, or GEM 7. It is a cooperative effort to increase the genetic diversity in corn. The project involves the Department of Agriculture, sixteen universities and twenty international companies.


This VOA Special English Agriculture Report was written by Mario Ritter. I'm Gwen Outen.



n.玉米
  • There's a field planted with maize behind the house.房子后面有一块玉米地。
  • We can grow sorghum or maize on this plot.这块地可以种高粱或玉米。
adj.遗传的,遗传学的
  • It's very difficult to treat genetic diseases.遗传性疾病治疗起来很困难。
  • Each daughter cell can receive a full complement of the genetic information.每个子细胞可以收到遗传信息的一个完全补偿物。
adj.有系统的,有计划的,有方法的
  • The way he works isn't very systematic.他的工作不是很有条理。
  • The teacher made a systematic work of teaching.这个教师进行系统的教学工作。
n.(动,植)杂种,混合物
  • That is a hybrid perpetual rose.那是一株杂交的四季开花的蔷薇。
  • The hybrid was tall,handsome,and intelligent.那混血儿高大、英俊、又聪明。
n.杂交生成的生物体( hybrid的名词复数 );杂交植物(或动物);杂种;(不同事物的)混合物
  • All these brightly coloured hybrids are so lovely in the garden. 花园里所有这些色彩鲜艳的杂交花真美丽。 来自辞典例句
  • The notion that interspecific hybrids are rare is ill-founded. 有一种看法认为种间杂种是罕见的,这种看法是无根据的。 来自辞典例句
v.使受精,施肥于,使肥沃
  • Fertilizer is a substance put on land to fertilize it.肥料是施在地里使之肥沃的物质。
  • Reading will fertilize his vocabulary.阅读会丰富他的词汇。
n.宝石,珠宝;受爱戴的人 [同]jewel
  • The gem is beyond my pocket.这颗宝石我可买不起。
  • The little gem is worth two thousand dollars.这块小宝石价值两千美元。
学英语单词
a-homered
acute bacillary dysentery
alentejoes
aPKCs
Auerbach im Vogtland
bakhet
bigrid valve
blackened fish
bottles up
bowet
brymen
carbamidobenzoic acid
ceramic laser
chassidic
combined tap and drill
constant relative risk averse (crra) utility function
continuous cropping
continuous system channel
control instruction counter
converted starch
cycloneuralians
Descargamaria
desulfurizing
deuterophlebiids
dipaths
duns-man
effectiveness of operation
ejector pin
eogyrinids
eponychium
finnerty
foveolae trochlearis
Geltabs
Goha Hills
Haco
Hartia yunnanensis
hearthrug
heavy liquid residuum
houkel
Icterus galbula
Ilirneyskiy Kryazh
infant phenomenon
kinematical seal
knuths
lead(plumbum)monoxide
lufyllin
marine database
Marquess of Queensbery rules
Mazus gracilis
Melodinus morsei
multiple robot
non divisi
normal type
nychthemer
open loop series circuit
operating system theory
orifice spacing
oxide electrode
pampuro
Pembroke
penright
per kilogram
periclimenes
plane component
poststall
procoelous vertebrae
property investment
proton-recoil method
pseudoscutum
pulmonary ascariasis
pump oil can
remote control rack
ricca
RNAnucleotidyl transferase
Rosellen
roughhouses
rubee
rutile nelsonite
salient cue
sand saltation
saturation steam
semi-active
sisfs-s
sodium alkyl-sulfinate
spoofers
starch hyacinth
strain burst
suction overfall
supplementary relay
surely not
swirl skirt
televoter
teretous
tielt (thielt)
time-stretched
tonsillocentesis
travel agencies
underbuys
vasodilatative
wallwood
Wasit
wererats