Analysis of Chronological Variation in Pedigree and Agronomic Traits of 325 Korean Rice Varieties

Rice (Oryza sativa L.) is a staple crop in Korea, which is cultivated over 700,000 ha and produces a half million tons of rice every year. Rice research and varietal improvement have been dynamic, changing in line with public demands and needs. Since the 1970s, plant architecture has been improved to increase yield components. In the 2000s, a new emphasis was placed on grain quality and biotic and abiotic stress resistance, and the rice varieties became more diversified according to reduced consumption and increased demands of processing industries. As a result of extensive research, 232 (71.4%) were categorized as good quality for eating in rice bowls, 27 (8.3%) were high yielding, and 21 varieties (6.5%) were for waxy rice among 325 varieties. The culm length was continuously reduced for lodging resistance, and panicle length and number of seeds per panicle increased. Finally, milled rice yields increased by 13% from 491 kg/10a in the 1980s to 555 kg/10a in the 2010s. One of the potential risks in Korean rice breeding is the narrow pool of genetic diversity. The parental origins of 325 Korean varieties show that 66% of the varieties originate from two Korean-bred stocks and 26% of the varieties have at least one parent from Japanese stocks. The limited genetic diversity has a negative influence on hybrid vigor and may lead to potential problems for Korean rice breeding in the future.