Resistance Genes and Their Deployment for Control of Leaf Rust of Wheat*

The high yielding, dwarf wheat varieties have become susceptible; hence there is an immediate need for incorporation of resistant genes into commercial varieties. In the present investigation out of the 22 Lr genes, nine genes namely, Lr9, Lrl9, Lr15, Lr10, Lrl, Lr3 (ka), Lrl7, Lr16 and Lr20 have been recognised, which in different combinations confer total resistance to all the races of India. The combinations are (i) Lr9, (ii) Lr19, (iii) Lr10 + Lr15, (iv) Lr1 + Lr10 + Lr16, (v) Lr1 + Lr10 + Lr17, (vi) Lr3 (ka) + Lr10 + Lr17 and (vii) Lr3 (ka) + Lr10 + Lr20. These genes can be identified by using five most virulent and prevalent races viz., 12, 77, 104, 162 and 162A.

For deployment of genes, India could be divided into three regions, (A) central Plains (B) northern Himalyan and (C) southern Niligiri and Palani Hills. Stronger genes Lr9 or Lr19 or Lr10 +Lr15) can be deployed in region A, and other three gene combinations (Lrl + Lr10 + Lr16 or Lr3 ka + Lr10 + Lr17 in region B, and Lr3 ka + Lr10 + Lr20 or Lr1 + Lr10 + Lr17) in region C. When a number of genes are in operation the possibility of build up of a super race is minimised and pathogen will get stabilised. It is suggested that similar line of work with Sr and Yr isogenic lines will help in the release of stable varieties for all the three prevalent rusts of India.