Inheritance of Amylose Content and Alkali Digestion Pattern of a High-amylose Mutant Rice “Goami 2”

Genetic study on amylose content and alkali digestion (AD) pattern of rice grain was conducted using F₁, BC₁F₁ and F₂ populations of a reciprocal cross between a high-amylose mutant rice cultivar, Goami 2 and its progenitor variety, Ilpumbyeo. F₁ seeds of reciprocal crosses between Goami 2 and Ilpumbyeo revealed slightly lower level of amylose content compared to that of low-amylose parent. It may be due to the effect of higher temperature conditioned during ripening in the greenhouse compared to the field. Also, F₁ seeds showed ‘spreading’ type of AD pattern similar to the original variety. The seeds of all progenies in BC₁F₁ and F₂ populations were distinctly separated into two different grain types, Goami 2 (GA) type (chalky thin, high amylose and swelling AD pattern) and Ilpumbyeo (IP) type (clear thick, low amylose and spreading AD pattern). However, intermediate type of grain appearance and AD pattern was not observed in the progenies of segregating populations. F₃ seeds from Goami 2/Ilpumbyeo F₂ plants of low-amylose (IP type) and segregating (Seg) type plants segregated into 7 : 8 rather than 7 :8 :1 ratio. This segregation ratio also fitted to grain chalkiness and alkali digestion (AD) pattern, spreading or swelling type. The chalky thin grain appearance, swelling AD pattern, and high-amylose content of the mutant ‘Goami 2’ were pleiotropically expressed in the progenies of segregating populations. The significantly less segregation GA type progenies far from the expected ratio in F₂ might be due to the low germination and poor seedling growth characteristics of the GA genotype itself. These results suggest that the mutant endosperm type of ‘Goami 2’ may be controlled by duplicate recessive genes.