Bt brinjal can resist attack of FSB larvae, safe for consumption: ISAAA study

Written by ASHOK B SHARMA | New Delhi | Updated: Mar 3 2009, 02:09am hrs
A study conducted by the global pro-GMO lobby, ISAAA, has claimed that Bt brinjal can resist the attacks of the common enemy fruit shoot borer (FSB) larvae and also be safe for human consumption.

The study, co-authored by Bhagirath Choudhary and Kadambini Gaur, said that Bt brinjal hybrids containing cry 1 Ac gene express Bt protein in all parts of the plant throughout its life cycle. To get activated and exhibit insecticidal property, Bt protein must be ingested by FSB.

When FSB larvae feed on Bt brinjal plants, they ingest Bt protein along with plant tissue. In insect gut, it is solubilised and activated by gut proteases generating a toxic fragment. The activated insecticidal protein then binds to two different receptors in a sequential manner.

Quoting extracts from a paper in the American Academy of Microbiology, the study said that the first contact of the insecticidal protein is with the cadherin receptor, triggering the formation of oligomer structure. The oligomer then has increased affinity to a second receptor, amino-peptidase-N (APN).

The APN facilitates insertion of the oligomer into membrane causing ion pores. These events disrupt digestive processes such as loss of trans-membrane potential, cell lysis, leakage of the mid-gut contents and paralysis that in turn cause the death of FSB.

The 102-page study entitled - The Development and Regulation of Bt brinjal in India - however, said that Bt brinjal does not harm or pose any threat to higher order organisms and non-target organisms, as they lack specific receptors and conditions for activation of Bt protein in their gut and hence is safe for human consumption.

Apart from Cry 1 Ac gene, Bt brinjal contains a selectable marker, nptll gene, which encodes enzyme neomycin phosphotransferase, Cauliflower Mosaic Virus 355 promoter and aad gene, which encodes for bacterial selectable marker enzyme3n(9)-0- aminoglycoside adenyl transferase.

Addressing the concern of a possible genetic contamination of non-Bt brinjal, the study said that the maximum distance travelled by pollen could be between 15 to 20 metres and outcrossing could vary from 1.46% to 2.7%.

The study attempted to resolve the issue of the centre of origin of the crop by saying that reports suggested Central and South America as the centre of origin of the species of genus Solanum to which potato and brinjal belong.

It further said that brinjal probably originated from African wild species S incanum, S melongena and was first domesticated in South-East China and taken to the Mediterranean region during Arab conquest in the 7th century. There are studies, which also report that brinjal originated in the Indo-Burma region.

The ISAAA study however noted that as brinjal appears in ancient Indian literature, India may be a secondary centre of diversity, while Africa may be the primary centre. Noted scientist Vavilov, however, regarded India as the original home of brinjal.

The ISAAA study lauded the regulatory system in India and hoped that India would be able to give to the world the first Bt brinjal.