Field resistance to spot blotch is not associated with undesirable physio-morphological traits in three spring wheat populations

Abstract

SUMMARY Spot blotch, caused by Cochliobolus sativus (Ito and Kurbayzshi) Drechsler ex Dastur is a serious constraint to production of wheat (Triticum aestivum L.) in tropical and sub-tropical environments. Previous efforts to develop genotypes with high levels of resistance combined with other desirable agronomic features have been unsuccessful. This failure was assumed to be largely due to the association of undesirable characters with heightened resistance but information on the existence of such associations is limited. Recently, high levels of resistance have been reported in CIMMYT synthetic wheat genotypes. Our study was done on three populations derived from the spot blotch resistant genotypes ‘Milan/Shanghai #7’, ‘Chirya. 3’ and ‘NL 971’ crossed with the susceptible commercial cultivar ‘BL1473’. Fifteen different physio-morphological traits and areas under disease progress curves (AUDPC) were evaluated in F 2 and F 3 generations during 2005-2006 at Rampur (Chitwan, Nepal). The majority of traits showed weak negative significant or non-significant genetic and phenotypic correlation with AUDPC except Area Under SPAD (soil plant analysis development) decline curve (AUSDC) and flag leaf duration Results showed no undesirable genetic association of resistance with physiomorphological characters, and thus independent selection for individual traits is possible. In addition, AUSDC and flag leaf duration have potential application as complementary traits in selecting for high resistance.