MANIFESTATION OF INHERITANCE OF 1000 KERNEL MASS UNDER ARTIFICIAL STEM RUST INOCULATED AND DISEASE-FREE CONDITIONS IN WHEAT

In a half-diallel experiment, 9 varieties differing in response to ste m rust and all their 36 hybrid progenies were planted in stem rust-inf ected and protected environments in the years 1986 and 1987, with four replicates in each year. Entries were separated by stem rust-suscepti ble spreader rows. In the infected section, these spreader rows were a rtificially inoculated in the stem elongation (31) stage with a mixtur e of stem rust races 1, 1 1, 34, 218 and 331. The protected part was s prayed with Bayleton 25 WP at weekly intervals. Griffing diallel analy sis revealed that mostly additive gene effects controlled the recorded characters of stem rust resistance and 1000 kernel mass, but the nona dditive genes also played an appreciable role. As concerns the general combining abilities with regard to the 1000 kernel mass, significant differences were found between the protected and the infected conditio ns. These differences were clearly caused by the resistance level of t he parents. Covariance/variance regression showed that Aurora and GK S agvari carried dominant genes for stem rust under both conditions, whi le GK Mini Mano, in spite of its low 1000 kernel mass, carried many do minant genes for high 1000 kernel mass under infected conditions, due to its resistance to stem rust. The conclusion may be drawn that study of the inheritance of stress-sensitive quantitative characteristics s hould be performed under stress-free conditions.