A new strategy for improving resistance level in present day cultivars of sorghum to shootfly, Atherigona soccata Rond. and stem borer, Chilo partellus (Swinhoe)

The value of a cultivar meant for adoption by farmers is determined not only by its grain yield but also by the quality of the fodder it produces and insect resistance it imparts to key pests. The released varieties and hybrids developed from Temperate x Tropical crosses, despite having high yield potential and other agronomic traits failed to express in full due to the attack of key pests of sorghum, viz., the shootfly, Atherigona soccata Rondani and stem borer, Chilo partellus (Swinhoe); midge, Contarinia sorghicola Coquillet and earhead bug, Calocoris angustatus Lethiery. This single cross approach to develop desirable cultivars met with some early success but low levels of resistance and lack of persistence or stability of resistance circumvented the expected performance of most released varieties and hybrids. A new strategy was adopted to overcome ensuring problems by crossing intermediate derivative with intermediate derivative, and resistant with intermediate derivative. New sources of resistance viz., P-217, P-297, P-500 were, thus, identified and stem borer resistant variety P-311 and multiple pest resistant variety SPV 1015 (PGS-1) were developed by following this strategy:Already released hybrids, viz., CSH 9 and CSH 12R, are also based on this approach. This new strategy further led to develop variety PC 121 and hybrid PCH 106 endowed with desirable agronomic and multiple pest resistance traits.