Hybridization and Pedigree Nursery for Transplanted and Direct-seeded Irrigated lowland rice varieties
B. Rice Varietal Improvement Group
V. Development of Hybrid Rice Varieties
Table 24. Number of PVS sites * by ecosystem coordinated by IRRI and PhilRice and implemented by the RFOs, 2014 WS.
Type ECOSYSTEM REGION/NUMBER OF SITES 1 2 3 4
a 4
b 5 6 7 8 9 10 11 12 1
3 ARMM CAR TOTAL
PVS-RM Irrigated 8 2 4 2 1 4 4 5 1 3 2 2 2 1 41 Submergenc
e 1 2 2 1 1 2 2 11
Salinity 3 2 4 2 2 1 2 2 1 1 2 22
Drought 4 2 5 5 2 1 5 3 1 1 2 2 2 2 2 39
Cool
Elevated 2 5 7
Special
Purpose 2 3 1 2 8
Irrigated -
Hybrid 4 4
TOTAL 1
6 1 2 1
3 6 6 4 1 1 1
6 5 4 6 4 8 6 4 6 128 PVS-FM
** Irrigated 4 4 1
5 5 4 8 1 1 15 30 1 15 103
Saline 4 2
0 1
5 5 2 1 1 1
5 63
Drought 5 2
0 1
5 5 5 1 1 15 30 1
5 1 113
Submergenc
e 2
0 5 2 30 1
5 72
Special Rice 1 30 31
Cool
elevated 15 15
TOTAL 4 0 1 3 6
0 4 5 2
0 1
1 0 8 5 4 30 12 0 4
5 2 30 397 PVS-RM : Participatory Variety Selection Research Managed; FM: Farmer Managed
Development of Hybrid Parent Lines
RA Millas, MSF Ablaza, JM Domingo, KA Garcia, MM Rosario, VP Luciano, JE Carampatana, LV Gramaje, FP Waing, DA Tabanao
One of the challenges in hybrid breeding is the selection,
development and improvement of suitable parental lines that can be used for developing hybrids. In hybrid rice breeding, the cytoplasmic male sterile (CMS) line is considered as the heart in the development of F1 hybrids because failure in purity of this will result to poor hybrid. Therefore, CMS line development is a very essential component in the development of hybrid rice. Because of its great role and importance, diverse CMS lines with good qualitative and quantitative traits must be developed. Introduced CMS lines often are not adapted to local conditions, with very low resistance to biotic stresses and poor grain quality.
Maintainer and restorer lines are very essential components in the development of hybrid rice as well. Without maintainer and restorer lines, multiplication of CMS lines and production of F1 are not possible.
Continuous research on the identification of inbred cultivars that can either maintain the sterility or restore the fertility of CMS lines plays an important role in developing high-yielding germplasm pools. Therefore, there is a need to develop new maintainer and restorer lines and improve existing ones.
The study aimed to: (1) develop new and diverse hybrid parent lines, male sterile lines (A- and S- lines), and pollen parents (R- and P-lines);
(2) improve morpho-agronomic characteristics of parent lines; and (3) convert potential B lines into new A lines and utilize potential R lines to further enhance the restorer line genepool of hybrid breeding program of PhilRice.
Highlights:
• For the development of restorer lines, 1184 (2014DS) and 6035 (2014WS) entries were established and evaluated for phenotypic acceptability and morpho-agronomic traits. Out of these, 1276 consists of 25 F1, 152 F2, 96 F3, 621 F4, 90 F5, 154 F6, and 118 F7 entries were selected and will be advanced in the next generation for 2015 DS evaluation (Table 25 and Figure 16).
• There were 42 (2014DS) and 35 (2014WS) elite lines established in the male parent yield trial (MPYT) nursery for yield evaluation. Table 26 showed the top 16 high yielding restorer advanced elite lines including four checks PSB Rc18, PSB Rc82, Mestiso 26 and Mestiso 48. Two entries (PR42779-HY-1-5-1-2-2 and PR42779-HY-1-5-1-3-1) have
the highest yield of 7.01 and 6.37 t/ha against all the checks.
Ten entries (PR42779-HY-1-5-1-2-2, PR42779-HY-1-5-1-3-1, PR42781-HY-1-5-1-1-3, PR42779-HY-1-8-2-1-3,
PR42779-HY-1-10-2-3-3, PR42779-HY-1-8-2-3-3,
PR42779-HY-1-2-2-1-3, PR42779HY-1-2-2-1-1, PR42775- HY-1-10-1-2-2, PR42779-HY-1-5-1-3-2) out-yielded the hybrid check Mestiso 26 (Table 2). These entries will be forwarded to the source nursery for testcrossing with the CMS lines and will be subjected to biotic and abiotic screening in 2015 DS.
• Table 27 showed the line per se performance of male parent lines selected and forwarded to the testcrossing nursery. The male parents NSIC Rc240, NSIC Rc122, NSIC Rc238, NSIC Rc222 and PSB Rc18 had the highest yield of 4779-5860.72 g among lines evaluated. When testcrossed with PRH1A, the line PR46664HY-AC resulted to the highest yield of F1 with 13143g while IR06A150 and PR40803-A014-136 when testcrossed with IR58025A resulted to 10606.5 and 7462g of F1 yield. Most of the top high yielding testcrosses were generated using lines derived from anther culture and lines from upland development study.
• The source nursery of TGMS lines comprised of 47 (2014 DS) and 32 (2014 WS) male pollen parents crossed to five S-lines (PR41917S, PR41918S, PR41919S, TG101S and TG1012S).
The testcrossing generated 154 (DS) and 73 (WS) F1 hybrids evaluated along with their parent lines in the testcross
nursery. From the established 18 F2 entries, 215 sterile plants from 12 cross combinations selected based on phenotypic acceptability were ratooned for seed multiplication in male fertile environment (MFE) in Kayapa, Nueva Vizcaya at Tuba, Benguet. In 2014 WS, 10 F2 entries were established and out of these, 157 fertile plants were selected based on phenotypic acceptability and will be forwarded to pedigree nursery as F3 population.
• For the testcross nursery (TCS) of TGMS lines, 241 (DS) and 72 (WS) F1 plants were established and out of these, seven (DS) and two (WS) entries with good phenotypic acceptability were selected and advanced to seed production observational nursery (SPON) on 2015 DS (Figure 2). For the TGMS pedigree nursery, 663 F2 plants from the male sterile environment (MSE) selected in 2014 DS from 13 cross combinations were seed increased in the MFE. In 2014 WS, from 297 F3 and 170 F4 sterile plants selected from the MSE, only 68 (F3) and 10
(F4) plants were seed increased and observed to have good phenotypic acceptability in the MFE.
• A new RIL’s, G038 F5 (PR34641-2B-19-1-1/Leuang), with 200 lines was also established in replicated yield trial at Philice CES for an initial yield trial evaluation (Figure 3). Phenotypic data such as panicles number per plant, grain yield (harvested from 5 hills) and plant height was gathered. Grain yield data of PR40629-G021 ranged from 1.2 to 7.7t/ha with an average yield of 4.0t/ha. The population will be further evaluated in 2015 DS.
• The selected PR40614-AC, PR40613-AB, PR40615-AD and PR40853 lines were established and further evaluated in replicated yield trials at PhilRice CES in 2014 DS and WS.
Phenotypic data such as panicles number per plant, grain yield and plant height were gathered. Grain yield data of DS ranged from 3.1 to 7.1t/ha with an average yield of 5.5t/ha while 1.2 to 5.2t/ha with an average yield of 3.4t/ha in WS.
The predicted yield data of the top performing PR40614-AC, PR40615-AD and PR40853 lines for two seasons are shown in Table 4. In addition, the 10 promising and consistently top performing lines will be submitted for AYT 2015 DS evaluation.
• The maintainer line nursery was composed of 25 lines for improvement and 53 selected lines with desirable morphological traits. Through hybridization, 38 new BxB crosses were generated. One hundred thirty plants from 13 F2 populations, 41 plants from 35 F3 entries, 43 plants from 121 F4 entries, 95 plants from 41 F5 entries and 222 plants from 129 F6 entries were selected based on good phenotypic acceptability .
• Established in the maintainer line yield trial were 11 elite lines and two hybrid check varieties; Mestiso 19 and Mestiso 48.
One parent line, PR41870-HY-13-4-1-1, consistently out- yielded the hybrid checks by 56.6% (Mestiso 19) and 97.0%
(Mestiso 48) (Table 30). This will be crossed to various CMS lines to evaluate its maintaining ability.
• For CMS conversion, 17 inbred lines with the desired traits were assembled. These potential maintainer lines were obtained from plant selections from elite breeding materials of the maintainer development nursery. Eight lines were used for re-testcrossing to CMS lines and included in the backcross
nursery to further evaluate their maintaining ability. Boots were collected for pollen sterility evaluation under the microscope before backcrossing. Pollen sterility of the F1 was evaluated in the following season. One plant from 2 BC1F1, 9 plants from 6 BC2F1 entries, 58 plants from 61 BC3F1, and 1 plant from 8 BC4F1 entries were found to be completely sterile and will be further evaluated. Progeny lines are to be repeatedly backcrossed up to the fifth generation. New CMS lines with stable sterility and good agronomic characters will then be declared and used as new testers in the Source Nursery.
• A new CMS line which is a cross between IR68897A and PR35746-HY-6-6-2-1-1-1 was assigned the pedigree number PR46129A, also known as PR27A (Figure 4). Results of the initial characterization of the CMS line and its maintainer line are shown in Figure 20 and 21.
Table 25. Number of lines evaluated and selected for restorer line development.
Table 26. Yield of advanced restorer lines and checks in the male parent yield trial nursery.
Table 27. Per se and testcross performance of entries in the testcross nursery (2014 WS).
Table 28. Predicted yield performance of the top performing PR40614- AC, PR40615-AD, and PR40853 lines evaluated in replicated yield trials at PhilRice Central Experiment Station during 2014 DS and WS.
Figure 16. F6 entries evaluated based on phenotypic acceptability and morpho-agronomic traits for the development of restorer lines.
Figure 17. Evaluation of testcrosses in MSE and multiplication of TGMS lines in MFE.
Figure 18. G038, a newly developed RILs evaluated in PhilRice CES during 2014DS.
Figure 20. Phenotypic characteristics of PR27B.
Flag leaf: 30.96 cm length 1.4 cm width Erect (veg & rep) Leaf blade: 42.16 cm length 1.04 cm width Dark green color Erect
Intermediate pubescence Basal leaf sheath color: Green Auricle color: Yellowish green Ligule: 20.4 mm length 2-cleft Yellowish green Collar color: Light green Culm: Erect
Green underlying node color Light gold underlying internode color Strong lodging resistance
Stigma color: White
Lemma & Palea color: Green-striped white Lemma apiculus color: Straw
Panicle: Upright main axis Semi-erect branches Sparse secondary branching Partly exserted
Low shattering Leaf senescence: Intermediate
Flag leaf: Erect (vegetative & reproductive) Leaf blade: 45.9 cm length
1.18 cm width
Intermediate pubescence Basal leaf sheath color: Green Auricle color: Yellowish green
Shorter than PR27A Ligule: 21.2 mm length
2-cleft Yellowish green Collar color: Light green Culm: Erect
Green underlying node color Light gold underlying internode color Strong lodging resistance
Stigma color: White
Lemma & Palea color: Green-stripped white Lemma apiculus color: White
Panicle: Semi-upright main axis Semi-erect branches Sparse secondary branching Just exserted
Low shattering Leaf senescence: Early
Development of F1 Hybrids
VP Luciano, MM Rosario, MSF Ablaza, JM Domingo, DA Tabanao Hybrid rice technology is a proven technology in developing superior rice genotypes. Hybrid rice varieties have attained relatively higher grain yields in extensive trials, corresponding to yield advantage of ≥15%
over inbreds. Of the known hybrid rice variety development approaches, utilization of cytoplasmic and thermo-sensitive genetic male sterility systems has proven practicability. Both approaches vary in the type of working male sterility system, and seed production techniques especially in multiplying female parents. The success of hybrid rice breeding depends to a great extent on the quality and diversity of parent lines used in making cross combinations. To increase the yielding potential of hybrid rice testcrosses, careful selection of excellent advanced and released inbred lines from Optimum Plant Morphology (OPM), Tropical Japonica (TJ) breeding, and doubled haploid (DH) nurserues as male parents is done.
The main goal of the study was to identify superior hybrid cross combinations as well as to determine the combining ability of newly developed parent lines. Specifically, the study aimed to (1) identify potential maintainer lines (B) and restorer lines (R) from the advanced generation breeding lines of irrigated lowland inbred rice breeding project, and (2) to develop hybrids from a cross between cytoplasmic male sterile (CMS) lines, DH, OPM and TJ lines from the inbred rice breeding project.
Highlights:
• Established in the source nursery (SN) were 211 (DS) and 130 (WS) male parent lines composed of doubled haploids (DH), 142 tropical japonica (TJ) and optimized plant morphology (OPM) and multi-environment trial (MET) entries. These entries were crossed with three CMS lines in DS (PR2A, IR68897A, IR58025A) and four CMS lines in WS PR28A, PR29A, PR30A and IR68897A generating 86 (DS) and 60 (WS) F1 (Table 1). In addition, 122 breeding lines were assembled in the source nursery II (SN II). The lines were comprised of A, DSR, NCT, TJ, DH, RYT and IL entries. NCT lines were testcrossed with six CMS lines (PRH1A, PR2A, IR58025A, PR15A, IR73328A and IR72079A) generating 222 testcrosses. Moreover, parent lines from A, DSR, TJ, DH and IL were crossed with eight female parents (TGMS71, PR20A, PRH1A, PR2A, IR58025A, PR15A, IR73328A and IR72079A) producing a general total of 751 testcrosses (DS). Of the 130 lines, 70 were testcrossed with eight female parents namely PR9A, PR20A, PR2A, PR24A, PRH1A, IR58025A, IR73328A and IR72079A generating 387 testcrosses (WS). The generated testcrosses along with their parent lines will be evaluated in
the testcross nursery (85 breeding lines and 447 testcrosses) in 2015 DS.
• For TCN I, the 164 hybrids generated from the cross of three CMS and 89 parent lines were evaluated in 2014 DS.
Prospecting identified 32 parent lines as potential restorers and 8 lines as potential maintainers. The potential restorer lines will undergo re-testcrossing to evaluate their combining ability, while the potential maintainers were endorsed to the B-line development nursery. Among the F1 hybrids, 15 entries (TCN- 252, TCN-1271, TCN-32, TCN-266, TCN-242, TCN-255, TCN-257, TCN-250, TCN-260, TCN-24, TCN-138, TCN-212, TCN-43, TCN-208, and TCN-185) showed 8.6 to 104.8%
yield advantage over the checks.
• In 2014 WS, 141 male parents were crossed to eight female parents (PR15A, IR58025A, PR28A, PR20A, TGMS71, PR2A, PRH1A and IR72079A) generating 808 testcrosses.
Prospecting identified 36 parent lines as potential restorers which were advanced to R line development nursery, and 30 potential maintainers which were endorsed to B line development nursery (Table 30). Among the F1 hybrids, 20 entries (TCN125, TCN322, TCN784, TCN450, TCN112, TCN442, TCN701, TCN116, TCN689, TCN161, TCN120, TCN144, TCN874, TCN853, TCN117, TCN85, TCN147, TCN884, TCN807, and TCN832) showed 6.71 – 204.63%
yield advantage over check varieties (Table 30).
• For female parent testcross variance evaluation 44 male parents were crossed to all eight female parents (PR15A, IR58025A, PR28A, PR20A, TGMS71, PR2A, PRH1A and IR72079A). Among all female parents, PRH1A attained the highest testcross variance of 8086481 and 3799.70 for the tester means
• A total of 818 entries were evaluated in TCN II in 2014 WS, of which 591 were experimental testcrosses derived from crossing 227 male parent lines with eight female parents (IR68897A, IR58025A, PR2A, PR9A, PR15A, PR21A, TGMS71, and PR19A) (Table 20). The 42 (18.50%) testcrosses attained 50.2 – 316.8% yield advantage over the four inbred checks PSB Rc18, PSB Rc82, NSIC Rc222, and NSIC Rc240. The best cross combination was PRH1A x PR36641-HY-9-1 with 206.0 to 316.8% yield advantage over the four check varieties. On the other hand, out of 227 parent lines, 21 (9.25%) achieved a yield advantage of 15.1 to 191.1% over the check varieties.
The male parent lines of the selected hybrids from TCN I was advanced to the source nursery II (SN II) for testcrossing to eight female parents (IR68897A, IR58025A, PR2A, PR9A, PR15A, PR21A, TGMS71, and PR19A). The SN II in 2014 DS generated 700 F1 hybrids. The generated hybrids will be evaluated along with their parent lines in the testcross nursery II (TCN II) in the succeeding season. Sixty potential restorer lines were identified and these will be endorsed to R line development nursery, and 16 potential lines were advanced to B line development nursery.
Table 29. Number of breeding lines and testcrosses generated in the source nursery (SN), 2014WS.
DSR= Direct-Seeded Rice, DH= Doubled Haploid, MARS= Marker-aided recurrent selection, IL= Irrigated Lowland, OPM/TJ=Optimum Plant Morphology/Tropical Japonica, RU=Uniform Restorer (F8)
Table 30. Number of entries evaluated in the testcross nursery (TCN), 2014WS.
Table 31. Line per se and testcross performance in the testcross nursery (TCN) 2014.
WS.
Table 32. List of parent lines with their testcross variance.
Figure 21. Hybridization activity and testcross nursery entries (doubled haploid, tropical japonica, irrigated lowland inbreds, direct seeded rice,
optimized plant morphology).
Performance Tests of Experimental Hybrids
MSF Ablaza, LV Gramaje, AE Pocsedio, KAA Garcia, JE Carampatana, DA Tabanao
Development and cultivation of rice hybrids is among the major complementing approaches in negating the growing rice shortage in the country. Under the same input levels, rice hybrids have demonstrated yield advantage by at least 15% compared to conventional varieties in many test results. Hybrid vigor is the phenomenon responsible for the demonstrated superiority that breeders aim to exploit.
Along the hybrid rice development pipeline, gauging the potential performance of experimental hybrids is a primary activity. Data that can be obtained from various segments of performance testing are indicative of whether a promising hybrid is to be released for public commercial
cultivation. Aside from being able to obtain a measure of heterosis levels with the commercially-important trait which is grain yield, characterization for reaction to biotic and abiotic stress and other morpho-agronomic characters can also be accomplished. Different testing levels which differ in terms of scale and duration all include popular and superior cultivars as checks.
Entries are advanced mainly on merits of grain yield potential estimates, along with other closely associated traits.
The objectives of the study were to evaluate the performance of promising hybrids in different nurseries for grain yield, and other important morpho-agronomic traits, to identify hybrids with a wide range of adaptation and stable performance across environments defined by location × season combinations, and to identify location/season specific hybrids.
Highlights:
• A total of 80 experimental hybrids were evaluated for grain yield potential against five check varieties in the observational nursery (ON). Important morpho-agronomic traits were also included in the evaluation. The trials were laid out in augmented design with the test entries assigned randomly without replication into blocks each with complete sets of checks (Figure 22). For phenotypic acceptability evaluation, the hybrids were planted next to each of their male parent.
Grain yield (yield) data were recorded from 2.4m2 (DS) and 1.92m2 (WS) crop cuts and adjusted to a moisture factor value of 1.0 and expressed as estimates in t/ha. In the DS (Table 33), six three line hybrids from crosses involving four CMS lines and six restorers, and nine two-line hybrids from crosses involving five TGMS lines and eight pollen parents, were tested against four check varieties; two hybrids (Mestiso 19 and Mestiso 29) , and two inbreds (NSIC Rc240 and PSB Rc18). Only four entries, all being TGMS-based hybrids, namely, PR45648H (17.10), PR45646H (16.68), PR45672H (15.86) and PR45647H (15.50) consistently earned positive yield advantage values ranging from 3% to 21% over the two inbred check varieties. Among all test hybrids, only PR45631H fell short of 8 t/ha. All DS test hybrids will be advanced to the preliminary yield trial in 2015 DS. Analysis of variance for grain yield revealed highly significant differences among entries and blocks. Using Dunnett`s t-Test, two entries (PR45648H and PR45646H) yielded significantly higher than the two inbred checks. In the WS, 21 two-line hybrids from crosses involving 2 TGMS lines and 21 pollen parents, and 44 three-line hybrids from crosses involving 9 CMS lines and 39 restorer lines were evaluated against five check varieties- two hybrids (Mestiso 19 and Mestiso 48) and three inbreds (NSIC
Rc240, PSB Rc18 and PSB Rc82). Yield of the checks were 10.73 (Mestiso 19), 10.91 (Mestiso 48), 10.04 (NSIC Rc240), 9.44 (PSB Rc18) and 8.51 (PSB Rc82). Only the top three test hybrids (PR46997H, PR46992H, PR47007H) posted a yield advantage of at least 5% over both hybrid checks. ANOVA for grain yield revealed highly significant differences among genotypes with CV=8.98 and R2=0.99. Dunnett`s t-Test identified entries with significant yield differences relative to the corresponding checks at 5% level of significance (Table 33).
• Evaluation of 59 entries composed of 23 experimental hybrids and 36 restorer lines derived through anther culture against five check varieties was done in the preliminary yield trial. The experiments were laid out in randomized complete blocks with three replications (Figure 23). Grain yield (yield) data were recorded from 7.42m2 (DS) and 7.36m2 (WS) crop cuts and adjusted to a moisture factor value of 1.0 and expressed as estimates in t/ha. In the DS, 36 restorer lines were evaluated against four check varieties (Table 34); two hybrids (Mestiso 19 and Mestiso 29) and two inbreds (PSB Rc18 and PSB Rc82).
Yield of the entries (Table 2) ranged from 2.02 (ACTN-12) to 5.07 (AC RSN-59). Yields recorded for the checks were 4.43 (Mestiso 19), 4.30 (Mestiso 29), 5.41 (PSB Rc18) and 4.34 (PSB Rc82). Of the total number of entries, about 30%
obtained positive yield advantage against PSB Rc82, namely AC RSN-59, AC RSN-67, AC RSN-57, AC RSN-60, AC RSN- 63, AC RSN-62, AC RSN-64, AC RSN-65, ACTN-15, AC RSN- 9 with yields ranging from 4.36 to 5.07, and yield advantage ranging from 1% to 17%. In terms of yield levels, 55%
recorded values of 4.0 t/ha, 42% recorded ≥4.0 t/ha but 5.0 t/
ha, and 3% attained ≥5.0 t/ha. Analysis of variance for grain yield revealed highly significant differences among entries only.
No entries yielded significantly higher than the check varieties at 5% level of significance when subjected to Dunnett`s t-Test.
In the WS, 23 three-line hybrids (Table 35) developed from crosses of 6 CMS lines and 23 restorer lines were evaluated against five check varieties; two hybrids (Mestiso 32 and Mestiso 48) and three inbreds (NSIC Rc240, PSB Rc18 and PSB Rc82). Maturity (DAS) of the entries ranged from 98 (PR45215H) to 128 (PSB Rc18), averaging at 108 while plant height (cm) ranged from 107.47 (PR42661H) to 125.40 (PR45215H), averaging at 116.94. NSIC Rc240 had the lowest tiller number (8) while PSB Rc18 and PR42661H had the highest (14), with an overall mean of 11. The highest yielder (5.04) and the only entry with >5.0 t/ha was PR47014H while