Indian Journal of Genetics and Plant Breeding (The)

The inheritance of resistance to gall midge (Pachydiplosis oryzae Wood-Mason) was studied in 18 crosses involving 10 resistant parents and seven susceptible parents. In all crosses between susceptible and resistant parents, susceptibility exhibited dominance. Ratios of 63S: IR, 15S: IR. 27S: 37R, 81S: 175R and 3S: IR were obtained in seven, four, two, one and one combinations respectively. Further, in crosses involving both resistant parents, a 9 resistant: 7 susceptible ratio was also obtained.

Genes controlling resistance thus showed duplicate and complementary types of gene interaction indicating probably two sources of resistance. This inference is also supported by the reported occurrence of biotypes and differential reaction of some of the varieties/strains. Under these circumstances convergent type of breeding would be most useful.

In three crosses, viz., IR. 20 × W. 1263, Vijaya × W. 1263 and CR. 94-MR. 1550 × Mahsuri, linkage was noted between (i) genes controlling gall midge resistance and brown hull colour (C.O. values ranging from 34.5 to 43.8%), (ii) genes controlling brown hull colour and semi dwarf habit (C.O. values ranging from 29.9 to 36.3%) and (iii) genes controlling semi-dwarf habit and purple stigma colour (C.O. value 27.2%) in one combination. It has been tentatively concluded that these genes belong to the fifth linkage group of Japanese workers.

The association between brown hull colour and resistance to gall midge reported in this study could be useful in breeding programmes for the development of gall midge resistant lines combining other desirable characters