Abstract
The relationship between resistance to lysine plus threonine equimolar solution (LT) and free amino acid contents in 10 rice varieties was studied. When seeds were germinated and cultured in 5×l0-4M LT for 7 days, difference in the extents of growth inhibition among the varieties was clearly recognized. Free threonine contents in both seeds and 14-day-old seedlings were. also varied amonb" varieties. In particular, free threonine contents in the seedlings of Shirowase and Binicol, which were classlfied as LT resistant varieties, were extremely hlgher than those of the other varieties. Threonine contents of the two varieties were over 17, 000 nmol/g fresh weight, while the contents of the other 8 varieties were below 8, 000 nmol/g fresh weight. Free lysine contents also increase in the seedlinb"s with increased levels of LT resistance, but not as much as free threonine contents. On the other hand, none of the varieties used in this experiment overproduced free threonine and lysine in the seeds. From these results, it is suggested that LT resistance can be used as a parameter for breeding crops with higher threonine contents.
