25. Streptomycin resistance of rice varieties and dwarf lines

Plant Breeding Institute, Faculty of Agriculture, Hokkaido University, Sapporo, 060 Japan

Antiboiotic-resistant mutations may be useful in somatic hybridization as a chloroplast marker and for the selection of fusion products (Galun and Aviv 1983).

Streptomycin sensitivity at plant level was evaluated by the inhibition of chlorophyll formation in seedling bioassay. In this experiment, 103 varieites of Japonica and Indica tyopes and 17 near-isogenic dwarf lines of the cultivar Shiokari were used. About 100 seeds were dipped into 0.2% aqueous solution of streptomycin at 30 degrees C for 24 hours in the dark. At the third leaf stage, seedlings were graded into classes with scores as follows: gree (score 10), striped with a high proportion of green sectors (6), striped with a high proportion of white sectors (4), and albino (0). The streptomycine resistance of a genotype was evaluated by the mean of the scores of seedlings. The germination rate of seeds in the solution can also be used for evaluation.

As shown in Fig. 1, no significant difference was found between the Japonica and Indica groups, although both groups showed a wide range of variation. The near-isogenic lines having different dwarfing genes in the genetic background of Shiokari showed a variation in resistance (Table 1). Two lines, ID-17 and ID-30 had significantly lower scores than that of Shiokari. This suggests that genes d-17 and d-30 confer an increased susceptibility to streptomycin through their pleiotropic effects.

Fig. 1. Variations in resistance score among Japonica and Indica rice varieties.

Table 1. Streptomycin resistance of seedlings in near-isogenic lines of Shiokari with 19 different dwarfing genes

References

Galun, E. and D. Aviv, 1983. Cytoplasmic hybridization: Genetic and breeding applications. In: Evans, D.A., W.R. Sharp, P.V. Ammirato and Y. Yamada (eds.), Handbook of Plant Cell Culture, Vol. 1, p. 358-392. Macmillan, New York.