Yield can be increased by breeding and through the addition ofGMtraits. 

Germplasm improvements from traditional breeding have contributed to modest but steady increases in yield. Marker-assisted breeding has nearly doubled the rate of yield gain when compared to traditional breeding alone.

GM traits, such as insect and herbicide tolerance, help to increase yields by protecting the yield that would otherwise be lost due to insects or weeds. The degree to which a farmer enjoys increased yields because of insect and herbicide tolerance traits will in large part be determined by how effective the farmer’s weed and insect control programs were before planting a crop with these traits. If weeds and insects had been controlled well, then the insect and herbicide tolerance traits will not be the primary factor in increasing yield.

In developing countries, where resources to effectively control weeds and insects are often limited, these traits have increased yield substantially. The same is also true for developed countries where there are particular pests that are hard to control--such as the corn rootworm complex or some perennial weeds.

The introduction of GM traits through biotechnology has led to increased yields independent of breeding. Take for example statistics cited by PG Economics, which annually tallies the benefits of GM crops, taking data from numerous studies around the world:

• Mexico - yield increases with herbicide tolerant soybean of 9 percent.
• Romania – yield increases with herbicide tolerant soybeans have averaged 31 percent.
• Philippines – average yield increase of 15 percent with herbicide tolerant corn.
• Philippines – average yield increase of 24 percent with insect resistant corn.
• Hawaii – virus resistant papaya has increased yields by an average of 40 percent.
• India – insect resistant cotton has led to yield increases on average more than 50 percent.

Even where insect and herbicide tolerance are not the primary factors in increasing yield, they provide many other benefits. Analysis by PG Economics also show that GM crops are credited with decreasing pesticide and fuel use, and with facilitating conservation tillage practices that reduce soil erosion, improve carbon retention and lower greenhouse gas emissions. Decreased inputs aren’t just a savings and convenience for farmers; they offer significant environmental benefits for everyone:

• The reduction in greenhouse gas emissions associated with GM crops for 2006 is estimated to be equal to removing more than half a million cars from the road.
• On average, the volume of herbicide used on corn has dropped 20 percent since herbicide tolerant corn was introduced in 1996.

Approximately 95 percent of the soybeans and 75 percent of the corn in the United States are GM. More than 95 percent of the soybeans in Argentina and half the soybeans grown in Brazil are GM. Where given the choice, farmers have consistently adopted GM crops quickly and widely because they see the improvement these products deliver. Whether it is increases in yield, or other benefits, farmers clearly see value in GM crops.

Sandeep,

16 t/ha is close to average yield for potato in Europe, and I guess, in India too.

4 t/ha for is too small and indicate significant problem with plants - severe damage by pests, diseases or lack of fertilization.

Alex

I wan to inform that the insect infestation was 20% in non-counterpart and 0.18% in transgenic. Although the trial was conducted at only one location.

According to some previous research (http://www.sid.ir/fa/VEWSSID/J_pdf/53913930106.pdf),  30% potato leaves infestation cause about 20% of yield loss. Although, I cannot say about time of evaluation of leaves damage. Anyway, 4 t/ha is not normal yield for potato.

Thanx to,

          Raheleh Ahmadzadeh Ghavidel and Alex Ignatov for your openion. I am totally disagree that the insect tolerant any crop can not perform as much as to increase the yield 300% against the non-counterpart.