Variations of seed size and seed number per spikelet and their effects on seed germination in hulled oats

Seed yield components and ear characteristics are critical parameters for seed yield improvement of cereal crops. In this study, 23 hulled oat (Avena sativa) cultivars were planted in four experimental sites during 2018–2020. We determined the ear parameters including the number of four spikelet types, the ear length, the seed weight per ear, and the size of the left and the right seed in the double-seed spikelet. In addition, five oat cultivars with the highest percentage of the triple-seed spikelet were selected to evaluate the germination performance of the left, the middle, and the right seed. The results showed that the double-seed spikelet was present in 73% of the ear, occupying the highest proportion than other spikelet types. The negative correlation showed the trade-off between total seed number per ear and average seed weight. According to the pathway analysis, the number of double-seed spikelet had the significantly highest direct effect on the seed weight per ear with the path coefficient of 0.93. In the double-seed spikelet, the length and the thickness both had significantly positive correlations to the seed weight of the left and the right seeds. The middle seed, which had the smallest seed size, had the lowest germination rate, germination index, vigour index, seedling weight, and length than the right and left seed among three seed positions in the triple-seed spikelet. We conclude that the double-seed spikelet number is a key ear characteristic when breeding high-yielding cultivars.