The Competitive Ability Of Stacked Transgenic Rice And Fitness Of Hybrids Between Stacked Transgenic Rice And Weedy Rice

The commercial release of transgenic rice may lead to the ecological risk of weediness,including the self-weediness of transgenic rice and the weediness caused by pollen-mediated gene flow with weedy rice.Compared to transgenic rice with single trait,stacked transgenic rice was transferred at least two foreign genes,the gene flow of stacked trait may be more complex than that of gene flow of single trait.Therefore,the ecological risk of stacked transgenic crop should be evaluated comprehensively.In this paper,stacked transgenic rice T2A-1 with cry2A*/bar gene and T1c-19 with cry1C*/bar gene and the receptor Minghui 63(MH63)of two transgenic rice were studied as following:(1)the survival competitive ability of T2A-1;(2)the fitness of hybrid F1 between T2A-1 and three kinds of weedy rice(Guangdong Maoming(WRMM),Hunan Yiyang(WRYY)and Jiangsu Taizhou(WRTZ));and(3)the fitness of hybrid F3 between T1c-19 and three kinds of weedy rice(WRMM,WRYY and WRTZ).The purpose of this study will provide a safety evaluation basis for the environmental release of the two transgenic rice,and lay a foundation for the establishment of the ecological risk evaluation criteria of transgenic rice with stacked traits.(1)The survival competitive ability of T2A-1The results showed that the relative competitive ability of T2A-1 was not significantly different from that of MH63 and conventional rice LC,but significantly greater than that of WRTZ in pure planting without weed.The relative competitive ability of T2A-1 was no significantly difference to MH63,but it was significantly greater than that of LC and WRTZ in mixed planting without weed competition.Under 4 sowing stages and 3 density,the relative competitive ability of T2A-1 at high and medium density were significantly greater than MH63;and the relative competitive ability of T2A-1 under medium density was significantly greater than LC.There was no significant difference in seed shattering between T2A-1 and its receptor MH63,but both of them had significantly lower seed shattering than LC and WRTZ.The above results showed that although T2A-1 has strong competitive advantages under certain experimental conditions,the self-weediness risk of T2A-1 was very low according to comprehensive analysis of seed shattering,seed viability and volunteer seedling.(2)The fitness of hybrid F1 between T2A-1 and three weed riceUnder pure planting and low insect pressure,there was no significant difference in composite relative fitness between T2A-1 and MH63,and between F1+and RF1+(with T2A-1 as paternal and maternal plant,respectively)and corresponding F1-and RF1-(with MH63 as paternal and maternal plant,respectively),respectively.Compared to the corresponding weed rice,the composite relative fitness of F1YY,RF1MM and RF1YY were significantly greater than that of the corresponding weedy rice.And there was no significant difference between other F1+or RF1+and the corresponding weedy rice.The seed shattering of F1+ and RF1+was similar to of F1-and RF1-.F1MM+,F1YY+ and RF1YY+ were significantly lower than corresponding weedy rice,and the other F1+ and RF1+ had the similar seed shattering to weedy rice.(3)The fitness of hybrid F3 between T1c-19 and three kinds of weedy riceIn pure planting:the composite relative fitness of T1c-19 was similar to its receptor MH63 under either natural insect pressure or non-insect pressure.Under natural insect pressure,the composite relative fitness of F3YY+and F3TZ+were significantly greater than that of F3YY-and F3TZ-,while the composite relative fitness of other F3+or RF3+(with T1c-19 as paternal and maternal plant,respectively)were similar to that of F3-or RF3-(with MH63 as paternal and maternal plant,respectively).The composite relative fitness of F3TZ+,F3YY+,RF3TZ+and RF3YY+ were significantly greater than that of their weedy rice parents.Under non-insect pressure,there was no significant difference in the composite relative fitness between the F3+or RF3+and the corresponding F3-or RF3-,and the composite relative fitness of F3TZ+and RF3TZ+were significantly greater than that of the corresponding weedy rice,but there was no significant difference between other F3+or RF3+and the corresponding weedy rice.In mixed planting:the composite relative fitness of T1c-19 was similar to its receptor MH63 under either natural insect pressure or non-insect pressure.Under natural insect pressure,and the composite relative fitness of the all F3+or RF3+were significantly greater than that of the corresponding weedy rice.Under non-insect pressure,the composite relative fitness of F3TZ+and RF3TZ+were significantly greater than that of the corresponding weedy rice.But the composite relative fitness of other F3+and RF3+were similar to that of the corresponding weedy rice.The hybrids between T2A-1 or T1c-19 and weedy rice carrying the staked resistance gene may have greater or similar fitness advantage,as well as heterosis compared to weedy rice.Therefore,in the environmental release process of T1c-19 and T2A-1,the gene flow of transgenic rice and weedy rice should be strictly prevented.