Current Approaches to Crop Improvement
Arguably, increased yield in conditions of abi-
otic stresses, such as drought and salinity, could
be best achieved by selecting for increased yield
under optimal production conditions: Plants with
higher yields in good conditions are more like-
ly to have higher yields in stressed conditions
(8). Such an approach will also increase yield in
high-yield environments. However, it is becom-
ing increasingly apparent that specific selection
strategies are needed to enhance yield in low-
yield (stressed) environments. Given that aver-
age global yields of wheat are less than 3 metric
tons/ha (Fig. 1) and given there are many areas
with yields as high as 10 metric tons/ha, the ma-
jority of land cropped to wheat delivers yields
below 3 metric tons/ha. Therefore, by virtue of
the much larger areas of low-yielding land glob-
ally, low-yielding environments offer the greatest
opportunity for substantial increases in global food
production. Increasing yield by 1 metric ton/ha in
a low-yielding area delivers a much higher rel-
ative increase than does the same increase inhigh-yielding environments. This increase can
be achieved by tackling major limitations on
yield in poor environments (termed yield stabil-
ity); for example, by protecting plants and yield
from factors such as salinity and heat or drought
periods. The local social benefits of supporting
farmers on low-yielding lands would also be
great.