Abstract:
The existence of a partial reproductive isolation in the form of hybrid
inviability and weakness supplemented by hybrid sterility was evident in four
crosses of PTB 7 with PTB 10 and CO 29. F: plants were inviable or weak and
were characterised by stunted growth, less tillering, late flowering and high
spikelet sterility. Selfed progenies of weak Fj plants showed segregation for weak
and inviable and normal plants in definite ratios. However, hybrids between PTB 10
and CO 29 were normal. The lethality and weakness of plants in fl and later
generations were found to be determined by the action of a pair of complementary
dominant lethal genes, one of which was present in PTB 7 and the other present
commonly in both PTB 10 and CO 29.
