Development of Transgenic Cotton Lines Expressing <i>Allium sativum</i> Agglutinin (ASAL) for Enhanced Resistance against Major Sap-Sucking Pests

<div><p>Mannose-specific <i>Allium sativum</i> leaf agglutinin encoding gene (<i>ASAL</i>) and herbicide tolerance gene (<i>BAR</i>) were introduced into an elite cotton inbred line (NC-601) employing <i>Agrobacterium</i>-mediated genetic transformation. Cotton transformants were produced from the phosphinothricin (PPT)-resistant shoots obtained after co-cultivation of mature embryos with the <i>Agrobacterium</i> strain EHA105 harbouring recombinant binary vector pCAMBIA3300-<i>ASAL</i>-<i>BAR</i>. PCR and Southern blot analysis confirmed the presence and stable integration of <i>ASAL</i> and <i>BAR</i> genes in various transformants of cotton. Basta leaf-dip assay, northern blot, western blot and ELISA analyses disclosed variable expression of <i>BAR</i> and <i>ASAL</i> transgenes in different transformants. Transgenes, <i>ASAL</i> and <i>BAR</i>, were stably inherited and showed co-segregation in T₁ generation in a Mendelian fashion for both PPT tolerance and insect resistance. <i>In planta</i> insect bioassays on T₂ and T₃ homozygous <i>ASAL</i>-transgenic lines revealed potent entomotoxic effects of ASAL on jassid and whitefly insects, as evidenced by significant decreases in the survival, development and fecundity of the insects when compared to the untransformed controls. Furthermore, the transgenic cotton lines conferred higher levels of resistance (1–2 score) with minimal plant damage against these major sucking pests when bioassays were carried out employing standard screening techniques. The developed transgenics could serve as a potential genetic resource in recombination breeding aimed at improving the pest resistance of cotton. This study represents the first report of its kind dealing with the development of transgenic cotton resistant to two major sap-sucking insects.</p>