Early Harvesting Improves Seed Vigour of Hybrid Rice Seeds.

Maturity stage in harvesting time greatly affects seed vigour. This work aimed to scientific harvesting time of hybrid rice for being high vigour with high & stable seed yield. Field experiments of different harvesting time were conducted in 2013–2014, and germination percentage (GP), vigour index (VI), seed moisture content and 1000-grain weight was determined. Both GP and VI progressively increased to peaks and then began to decline with harvesting time delayed, and the regression coefficients of varieties were ranged from 0.7214 to 0.9066. In addition, difference values between tangent points (ΔX) of GP were higher than that of VI according to the quadratic functions. Based on seed vigour through the divided range from 75% to 125% of peak value, optimum harvesting time of IIY-416, JY-167, Yliangyou-1 (YLY-1) ranged from 17 to 27, 15 to 23 and 17 to 23 days after the completion of artificial pollination (DACAP), respectively. Moreover, when seedlots harvested from 17 to 23 DACAP, no significant difference was found on 1000-grain weight and the seed moisture content was kept relatively low (19–25%). Therefore, it can be concluded that hybrid rice seed can be earlier-harvest based on seed vigour, and 17 to 23 DACAP can be recommended as optimum harvesting time during hybrid rice seed production.