RELATIONSHIPS BETWEEN LEAF CHLOROSIS AND CERTAIN AGRONOMIC TRAITS IN WHEAT, TRITICALE AND WHEAT-TRITICALE LINES INFECTED WITH THE BARLEY YELLOW DWARF VIRUS (BYDV)

To assess the relationships between leaf chlorosis and certain agronom ic traits, eight lines of wheat and triticale and their interspecific crosses were experimentally inoculated with BYDV. BYDV infection cause d a highly significant reduction in tillering, plant height and biomas s in all lines of wheat and triticale irrespective of their degree of tolerance. There was no significant difference between the virus conte nt of the less badly chlorosed and that of the more severely chlorosed plants, indicating that tolerance was the actual mechanism involved i n the triticale lines studied. Generally, all phenotypic and genotypic correlations between the extent of chlorosis and tillering, plant hei ght and biomass were negative and highly significant. This suggests th at agronomic parameters can be used as selection criteria in a breedin g program for resistance to BYDV. through interspecific wheat and trit icale hybridization. The severity of leaf chlorosis is recommended as a selection criterion as it does not require the use of a control popu lation.