Development of TGMS lines and two-line rice hybrids through a shuttle breeding program between IRRI and China Tongmin Mou, Chunhai Li, and Junying Xu, The National Key Lab for Crop Genetic Improvement, Huazhong Agricultural University (HAU), Wuhan 430070, China; and S.S. Virmani and D.L. Sanchez, IRRI E-mail:
[email protected]
Based on the discovery of photoperiod-sensitive genic male sterile (PGMS) rice mutant Nongken 58S (Shi 1981), rice scientists in China began work on the two-line system of hybrid rice breeding in the early 1980s. Subsequently, some thermosensitive genic male sterile (TGMS) rice mutants, such as Annong S-1 and 5460S, were developed in 1988 through screening of breeding materials and radiation, respectively (Lu et al 1998). The two-line system was established in China by using PGMS and TGMS lines. This method was considered more efficient than the threeline system in exploiting heterosis to increase yield. More than 10 environment-sensitive genic male sterile lines have been used to breed more than 32 commercial two-line hybrids in China. The area planted to two-line hybrids, which gave 5% higher yield than three-line hybrids, was 2 million ha in 2002. In the tropics, TGMS lines may be more useful than PGMS lines because of the significant temperature variation among seasons. A shuttle breeding program between China and IRRI was conducted in the past 5 years to develop and evaluate TGMS lines and two-line rice hybrids. Several useful TGMS lines have so far been developed. 14
Three TGMS lines TM104S and TM105S from HAU and IR73827-23S from IRRIwere evaluated in the IRRI phytotron. IR73827-23S was also evaluated under natural conditions at Wuhan, China. The results (Table 1) showed that IR73827-23S was completely sterile at 24.9 o C (mean) and partially sterile at 23.9 o C or less. This implies that the critical sterility point (CSP) of IR73827-23S was between 24 and 25 oC in the phytotron for 12 d. TM104S was almost sterile at 24.9 o C and partially sterile at 23.9 oC. Its CSP may be at around 25 o C (mean). TM105S was completely sterile under 23.9 o C and 24.9 oC and partially fertile at 22.9 oC or less. The CSP of TM105S may be between 23 and 24 oC (mean) in the phytotron. The pollen fertilities of IR73827-23S and TM105S at 21.9 oC were lower than those at 22.9 oC because their tolerance for lower temperature was less physiologically. The results of field evaluations at Wuhan showed that IR7382723S was completely sterile when the daily mean temperature was higher than 23.5 o C, almost sterile from 22.0 to 23.5 oC for shorter than 3 d in the sensitive stage, and partially fertile at temperatures lower than 23.5 oC for longer than 4 d (see figure). This means that the CSP under
natural conditions was 23.5 oC in 3 d. The stage sensitive to temperature ranged from 11 to 5 d before heading. IR73827-23S was crosstested by more than 50 conventional inbred lines or restorers of three-line hybrid rice. The combinations were evaluated in observed yield trial nurseries (2-m 2 area per plot) in Hainan and Wuhan in 2003. Several heterotic combinations were identified (Table 2). The yields of three combinations reached 11.67 12.26 t ha 1 , surpassing the three-line control by 10.8 16.4% in Hainan. Yields of six combinations were 7.509.33 t ha 1, 8.535.1% over that of the three-line control in Wuhan, Hubei. The yields in Hainan were higher than those in Wuhan because of the higher fertilization level in Hainan. Table 1. Fertility expression of three TGMS lines in the phytotron for 12 d, IRRI, 2002. Temperature (oC)
Time 0500-0800 0800-1100 1100-1500 1500-1900 1900-0100 0100-0500 Mean IR73827-23S TM104S TM105S
21 23 25 23 21 19 21.9
22 23 24 25 26 27 24 25 22 23 20 21 22.9 23.9 Pollen fertility (%) 25.2 57.7 25.7 81.1 66.0 14.2 24.4 48.8 0.0
24 26 28 26 24 22 24.9 0.0 4. 6 0.0
December 2004
Daily mean temperature (oC) 37.0
Pollen sterility (%) 100
33.5 30.0
90
26.5 80
23.0 19.5
70
16.0
Pollen sterility Temperature
60
12.5 9.0
50
2.0
Sept 20
Sept 10
Aug 31
Aug 21
Aug 11
Aug 1
July 22
July 10
June 30
June 20
June 31
May 31
May 21
May 16
May 11
May 6
May 1
40
5.5
Date of flowering The fertility expression of IR73827-23S in a field at Wuhan, China, in 2003.
References
Table 2. Yield trials of some two-line hybrids, China, 2003. Location
Combination
Growth duration (d)a
Yield (t ha1)
Increase over check (%)
Hainan
IR73827-23S/Luhui 6 IR73827-23S/TMQ30349 IR73827-23S/R615 Shanyou 63 (check) IR73827-23S/Mianhiu501 IR73827-23S/Minghui63 IR73827-23S/TMQ30349 IR73827-23S/R524 IR73827-23S/TMQ30506 IR73827-23S/TMQ30525 II-You 725 (check)
134 137 135 141 133 130 130 130 132 128 129
11.80 12.26 11.67 10.53 8.23 7.50 8.33 8.80 9.33 7.73 6.91
12.0 16.4 10.8
Wuhan
Shi MS. 1981. Preliminary report of breeding and utilization of late japonica natural double purpose line. J. Hubei Agric. Sci. 7:1-3. Lu XG, Virmani SS, Yang RC. 1998. Advances in two-line hybrid rice breeding. In: Virmani SS, Siddiq EA, Muralidharan K, editors. Advances in hybrid rice technology. Proceedings of the Third International Symposium on Hybrid Rice, 14-16 Nov 1996, Hyderabad, India. Los Baños (Philippines): International Rice Research Institute. p 89-98.
19.0 8.5 20.6 27.4 35.1 11.9
Days from seeding to maturity.
a
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Response of transgenic rice expressing two Bt genes to nontarget insects K. Bashir, T. Husnain, and S. Riazuddin, National Centre of Excellence in Molecular Biology (CEMB), 87-W, Canal Bank Road, University of the Punjab, Lahore, Pakistan
Different transgenic lines of indica basmati rice (Basmati 370) expressing cry1Ac, cry2A, or cry1Ac + cry2A genes were selected on the basis of molecular analysis and insect bioassays. During the first year (2001), 396 plants of five IRRN 29.2
different lines, along with the untransformed control, were sown following a randomized complete block design at CEMB, while a total of 3,000 plants of four transgenic lines expressing two Bt genes were randomized following a
split-plot design at CEMB and at Rice Research Institute, Kala Shah Kaku, Lahore, during the second year (2002). These lines showed a high level of resistance to yellow stem borer and rice leaffolder throughout the entire growth 15
