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CROP BREEDING, GENETICS & CYTOLOGY

Inheritance of Seed Dormancy in Weedy Rice

^a Plant Sci. Dep., North Dakota State Univ., Fargo, ND 58105 USA
^b Agricultural College, Yangzhou Univ., Yangzhou, 225008 China
^c USDA-ARS, Biosciences Research Lab., Fargo, ND 58105-5674, USA

^* Corresponding author (foleym{at}fargo.ars.usda.gov)

Seed dormancy contributes to the adaptability of plants in nature and is of considerable importance in agriculture. The weedy rice (Oryza sativa L.) strains LD, SS18-2, and TKN12-2 and cultivar ‘N22’ were selected to investigate the inheritance of dormancy in controlled conditions. Initial investigations using intact seeds, caryopses, caryopses with pericarp/testa removed, and excised embryos demonstrated that seed dormancy was imposed by the hull in SS18-2 and TKN12-2, and by the hull and pericarp/testa in LD and N22. Seed dormancy at 0 d after harvest (DAH) was dominant with average degree of dominance (ADD) > 0.8 in the crosses with weedy strains. Dominance for duration of seed dormancy was incomplete when judged by days to 50% germination. Broad-sense heritability (h²_b) for seed germination was lower at 0 DAH and highest at 20 DAH in all the crosses. The weedy strain-derived F₂ populations maintained a higher h²_b during afterripening. The effects of three and two major genes on seed germination at 20 DAH were detected in the SS18-2- and N22-derived F₂ populations, respectively. A positive ADD, a high h²_b, and major gene effect for caryopsis germination at 0 DAH were detected only in the cross with LD. Seed or caryopsis dormancy was correlated with the characteristics awn and black hull or red pericarp colors in the SS18-2- or LD-derived F₂ populations. This research demonstrates that weedy rice provides ideal gene resources to elucidate mechanisms of dormancy and to improve resistance to preharvest sprouting.

Abbreviations: ADD, average degree of dominance • DAH, days after harvest • DAI, days after imbibition • h²_b, broad-sense heritability • RH, relative humidity

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