Correlation between Stigma Characteristics and Outcrossing Rate of Five Photo-thermo Sensitive Genic Male Sterile(PTGMS) Rice Lines

[Objective] This study aimed to investigate the correlation between stigma characteristics and outcrossing rate of photo-thermo sensitive genic male sterile（PTGMS） rice lines. [Method] The stigma exsertion rate, stigma size and stigma vitality of Chuang 5S, Yun 9S, Peiai 64 S, P88 S and Y58 S were analyzed. Using R608 as a male parent, outcrossing rate of these five PTGMS lines was determined. [Result]There were differences in stigma exsertion rate, stigma size and stigma vitality among five PTGMS lines. P88 S exhibited the best stigma characteristics and relatively strong stigma vitality, with the stigma exsertion rate of 95.94%, stigma vitality coefficient of 2.71, outcrossing rate of 84.02% in the field. Peiai 64 s had the minimum stigma length（2.41 mm） and stigma width（1.10 mm） and the weakest stigma vitality, with the stigma exsertion rate of 93.04%, outcrossing rate of 65.47%. Yun 9S,Y58 S and Chuang 5S displayed medium stigma characteristics, among which Yun9 S exhibited higher outcrossing rate than other two PTGMS lines. Correlation analysis showed that stigma exsertion rate, stigma length, stigma width, stigma area and stigma volume were significantly correlated to outcrossing rate（P〈0.05）, with correlation coefficients of 0.897, 0.934, 0.934, 0.939 and 0.937, respectively. However,there was no significant correlation between stigma vitality coefficient and outcrossing rate. [Conclusion] Based on stigma characteristics of five PTGMS lines, auxiliary pollination measures should be adopted reasonably to save production costs and improve hybrid rice seed yield.

Breeding and Application of Indica PTGMS Line Yan 161S and Its Hybrid Yanliangyou 1618 in Rice

In 2006, the indica photoperiod- and thermo-sensitive genic male sterile （PTGMS） line Yan 161S was successful y bred by crossing the Guangzhan 63S （♀） and the medium indica breeding material Yan 229 （♂）, which was bred by the Institute of Agricultural Sciences in Coastal Region of Jiangsu Province, after years＇ and generations’ selection in different areas. It passed the identification by Jiangsu Provincial Crop Variety Appraisal Committee in 2013. Crossing the Yan 161S with Yanhui 888, a new high-yielding and high-quality two-line hybrid rice combination Yanliangyou 1618 was developed, and it passed the variety identification in 2014. This paper introduced the breeding processes and characteristics of Yan 161S and Yanliangyou 1618 and the cultivation and seed production techniques of Yanliangyou 1618.

Breeding and Application of Indica PTGMS Line Yan 220S in Rice

Yan 220S, which is derived from a natural variant plant discovered among the population of Guangzhan 63S and developed by Jiangsu Agricultural Research Institute for Coastal Regions through pedigree selection over years, is an indica photo- and thermo-sensitive genic male sterile （PTGMS） line in rice. In 2013, it was technically identified by Jiangsu Crop Variety Appraisal Committee. Its hybrid Yan-liangyou 2208 （Yan 220S/Yanhui 888）, a new two-line hybrid rice combination with high yield and good grain quality, was subsequently developed and released for commercial production by the National Crop Variety Appraisal Committee in 2013.

Improving the resistance of the rice PTGMS line Feng39S by pyramiding blast,bacterial blight,and brown planthopper resistance genes

Knowledge of rice(Oryza sativa L.)genes and various DNA markers can be used in genomic breeding programs aimed at developing improved elite rice cultivars.We used an efficient genomic breeding approach to pyramid four resistance genes(Pi2,Xa23,Bph14,and Bph15)in the popular photoperiod-and thermosensitive genic male sterile(PTGMS)rice line Feng39S.We performed foreground selection for the target genes,followed by recombinant selection and background selection.This process reduced the sizes of the genomic segments harboring the target genes(566.8 kb for Pi2,1143.9 kb for Xa23,774.7 kb for Bph14,and 1574.9 kb for Bph15)and accelerated the recovery of the recurrent parent genome to proportions ranging from 98.77%to 99.16%,thus resulting in four near-isogenic lines.To assemble the four resistance genes in Feng39S,we performed a double-way cross combined with foreground and background selection to generate two improved lines of Feng39S(Pi2+Xa23+Bph14+Bph15)with a recurrent parent genome recovery of 98.98%.The two lines showed agronomic performance,grain quality,and fertility–sterility transition characteristics similar to those of the original Feng39S line.The newly developed PTGMS lines and corresponding hybrid combinations were resistant to various field blast isolates and seven representative isolates of bacterial blight.At the seedling stage,the lines also showed resistance against brown planthopper.This study provides an efficient and accurate genomic breeding approach for introducing desirable traits into PTGMS lines.