Source: CropBiotech Update

Scientists working on improving soybean have faced several obstacles when working on insect resistance for the crop. Resistance to insects in soybean is a quantitatively inherited trait – that is, more than one gene is involved in the insect resistance process, and simple backcrossing will not transfer all insect resistance genes. Genetic engineering could assist in making soybeans resistant to pest, but Bt genes are widely used, raising issues about the evolution of resistance in susceptible insect populations. To engineer insect resistance into soybean, scientists have to not only introduce Bt genes into soybean cells, but to find, characterize, and use native soybean insect resistance genes to manage insect resistance, as well as broaden the resistance of plants with Bt genes.

S. Zhua and colleagues from the University of Georgia, USA undertake the “Fine Mapping of a Major Insect Resistance QTL in Soybean and its Interaction with Minor Resistance QTLs.” Their article, published in a recent issue of Crop Science, mapped a major quantitative trait locus (QTL-M) for insect resistance from soybean, which controls antibiosis (the ability of a crop to excrete one or several metabolites that can harm organisms) and antixenosis (the ability of a plant to keep pests from colonizing it).

The study aimed to fine map QTL-M, as well as to evaluate the effects on and interactions between it and other resistance QTLs using the Benning soybean cultivar, which is susceptible to defoliating insects. These QTLs were introgressed into the Benning cultivar using marker-assisted backcrossing to produce eight near-isogenic lines (NILs). These NILs were then tested for antixenosis and antibiosis.

Scientists found that two minor resistance QTLs provided insect resistance only when QTL-M was also present. This is important, since QTL-M has also been shown to increase the effectiveness of the Bt transgene in soybean, and can thus be used in future resistance engineering efforts.

Subscribers to Crop Science can read the complete article at http://crop.scijournals.org/cgi/content/full/46/3/1094.