The Evaluation Of The Allelopathic Characteristic On Weed Suppression And Combinations Performance Of An Allelopathic Male Sterile Line N57S In Rice(Oryza Sativa L.)

In this paper,the allelopathic characteristic on weed suppression and combinations performance of an allelopathic male sterile line N57 S from our research group was studied by using field plot experiment.PI312777,a strong allelopathic rice from the United States,and Allelopathic rice 3,an allelopathic rice released by the Guangdong Crop Variety Approval Committee,were set as controls.Compared with the two controls,the allelopathic characteristics on weed suppression of N57 S and its five hybrid combinations were evaluated.The fertility response to photoperiod and temperature of N57 S and the rice yield and quality trait,and rice blast resistance of the hybrid combinations from N57 S were also evaluated.The main results were as follows:1.N57 S showed good allelopathic characteristics on weed suppression at the six sowing dates in two years.The inhibition effect on the average plant height of the associated barnyard grass of N57 S was significantly stronger than the control Allelopathic rice 3 at the sowing date on July 10,2016,and showed no significant difference compared to the two controls,PI312777 and Allelopathic rice 3,at the six sowing dates.The average inhibition rate of weed suppression at the filling stage,the inhibition rate of weed suppression before crop sealing stage,the inhibition rate of weed suppression from competition and the dry weight per plant of the associated barnyard grass of N57 S also showed no significant difference compared to the two controls at the six sowing dates.The stability of the average plant height and the dry weight per plant of the associated barnyard grass were better than the two controls.The stability of the inhibition rate of weed suppression at the filling stage of N57 S was better than the control Allelopathic rice 3,and its coefficient of variability was only 12.14%,showing the greatest stability among the five kinds of weed suppression traits.2.The five hybrid combinations from N57 S showed strong weed suppression effect at the six sowing dates.Among the five combinations,the five weed suppression traits of the combination N57S/Huahui521 were better than the control PI312777,showing best weed suppression effect.The average over-parent heterosis of the inhibition rate of weed suppression at the filling stage,the inhibition rate of weed suppression before crop sealing stage,the inhibition rate of weed suppression from competition,and the average plant height and dry weight per plant of associated barnyard grass of the hybrid combinations from N57 S were 11.45%,7.51%,74.80%,5.21% and 10.94%,respectively.And the average over-control heterosis of the five weed suppression traits were 1.22%,2.05%,13.21%,1.46% and 1.70%,respectively.All these positive heterosis indicated N57 S could be used for breeding strong allelopathic hybrid rice.3.In Guangzhou,the days from sowing to heading(DSH)of N57 S was about 95 days in early season,and about 76 days in late season.The pollen showed the fertility alternation character from fertility to sterility and then to fertility in a year,and the sterility period lasted for about 160 days,which is a quite long sterile period.Using phytotrons,the examination results of the pollen fertility under different daylength and temperature condition showed that the fertility alteration of N57 S was mainly affected by temperature,showing male sterility under high temperature and male fertility under low temperature.N57 S was belong to temperature-sensitive genetic male sterile(TGMS)line,and the critical temperature for fertility alteration is about 23?,which is safe low and safe for the hybrid seed production.4.Yield comparing tests in four seasons within two successive years showed that the 85.29% hybrid combinations from N57 S were higher yield than the control,and increasing range was between 0.47% and 22.62%.Among these combinations,the yield of N57S/Huahui535 was the highest.The rice quality of the hybrid combinations from N57 S in late season was better than that in early season.Among them,the rice quality of N57S/Huahui55 in late season reached the three-level standard of national rice quality.This indicated that N57 S could be used for breeding hybrid rice with good quality in late season.Besides,the rice chalkness degree and amylose content of some combinations were a bit high,and the insufficiency of N57 S could be remedied by crossbreeding using male parent with low rice chalkness degree and amylose content.The results of rice blast resistance test from Institute of Agricultural Sciences of Yangjiang showed that the hybrid combinations from N57 S were resistant,medium resistant or medium susceptible to rice blast,and the proportion of the resistant and medium resistant combinations were higher.So it was easy to breed hybrid combinations with strong rice blast resistance.In conclusion,N57 S showed good allelopathic characteristics on weed suppression,and its hybrid combinations had allelopathic heterosis.N57 S had long sterile period and stable male sterility.N57 S was easily used to breed hybrid combination with high rice yield,good rice quality and strong rice blast resistance.All these suggest that N57 S is a good allelopathic male sterile line in breeding application,which could be used to breed strong dominance combinations with stronger allelopathic effect,higher yield,better quality and stronger rice blast resistance.