NV Desamero, FJB Garcia, TA Sigari, MAA Orbase
A successful breeding program for abiotic stress tolerance requires effective and efficient screening facilities and protocols. Centralized mass screens for salt and drought tolerance at seedling stage, drought tolerance at reproductive stage, and submergence tolerance at vegetative stage were established. The test genotypes with tolerance to abiotic stresses were identified for use in the breeding activities.
Findings/Highlights:
• For drought stress screen at seedling stage, selection was based on % plant recovery and biomass production in comparison with the check varieties and progenitor, 10 days after release from stress. The test of means with Dunnett’s identified 17 (5.1%) and 6 (1.8%) genotypes superior to the susceptible check IR64 and tolerant check PSB Rc14, respectively. The response to drought stress of the 332 test genotypes is presented in Table 9.
• For salt tolerance screen, FL478 and IR29 were used as the tolerant and susceptible check, respectively, adopting the one (highly tolerant) to nine (highly susceptible) score system on the basis of visual shoot response to salt stress. The response to salt stress of the 543 test genotypes is presented in Table 10. The frequency distribution of the response was as follows: five (0.9%) highly tolerant; six (1.1%) tolerant; 44 (8.1%) moderately tolerant; 124 (22.8%) susceptible; and 364 (67.0%) highly susceptible.
• The F2 population consisting of 350 seedlings from each of the four crosses with combined salinity and submergence tolerance were evaluated for seedling saline tolerance. The most number of tolerant plants was obtained from the cross between FL478 and PSB Rc160,
with 313/327 (95%) tolerant plants (highly tolerant, tolerant, and moderately tolerant).
• Screening for submergence tolerance was carried out in a concrete tank in 2011 DS, with 18 days old seedlings of 17 IRRI lines, 14 PSB Rc82-Sub 1 lines, 54 NSIC Rc9 seed mutation-derived lines, NSIC Rc9 (progenitor), and 1500 F1 plants from IR64-Sub1 x NSIC Rc160, including FR13A and IR64-Sub 1 as tolerant checks and IR42 as susceptible check.
• Of the 17 IRRI-developed lines, nine were highly susceptible, six susceptible, one moderately tolerant, and one tolerant to submergence. A total of 164 F1 plants from IR64-Sub 1/NSIC Rc160 survived and were genotyped for backcrossing to the recurrent parent. The number of surviving plants from PSB Rc82-Sub 1 lines ranged from zero to nine as compared to 14 surviving plants of the tolerant check FR13A. Plant survival ranged from 0.0% to 62.0%
when compared with the 84.4% survival for PSB Rc18-Sub 1.
• Genotypic variation in plant survival after submergence stress among NSIC Rc9 mutant lines was not significant. Test of means with Dunnett’s identified four lines, with 42.9% to 71.4% plant survival, performing as good as the tolerant check FR13A, with 84.4% survival.
The susceptible check IR42 had 9.4% survival, while the progenitor NSIC Rc9 had 21.9% survival.
• Submergence screening was done on M2 putative variants generated from seed mutation, comprising of 188 families derived from PR34358- 4-Pokkali/AC-37-M5R-14 (DrS 92), 77 families from Salumpikit, 39 families from Nerica 2, 136 families from NSIC Rc222, and 266 families from BPI 76. Each family consisted of 32 seedlings. Surviving M2 plants totaled to 59/6016 (1.0%) for DrS 92, 5/1248 (0.4%) for Nerica 2, 102/4352 (2.3%) for NSIC Rc222, and 370/8512 (4.3%) for BPI 76. Surviving plants were seed increased in the screenhouse to comprise the M3 mutant lines and will be subjected to multi-trait evaluation in 2012.
• In 2011 WS, 64 PSB Rc68 inflorescence culture-derived lines, PSB Rc68, FR13A, and IR42 were subjected to complete submergence for 12 days with two replications. Plant survival ranged from 0.0% to 56.8%. The tolerant check FR13A had 50.4% survival, the susceptible check IR42 had 0%, while the progenitor PSB Rc68 had 56.6%
survival. The frequency distribution of the response to submergence stress on the basis of comparative % survival with FR13A was as follows: 2 (3.1%) highly tolerant; 10 (15.6%) moderately tolerant; 11 (17.2%) susceptible; and 41 (64.1%) highly susceptible.
Table 9. Saline tolerance screening at seedling stage, glasshouse, PhilRice CES, 2011 DS and 2011 WS. MaterialsNo. of Entries
Test Genotype’s Response HTTMTSHSProgenitor’s responseNo.%No.%No.%No.%no.% 2011 DS NSIC Rc9 mutant lines (seed mutation-derived)5400.023.759.31935.22851.9HS NSIC Rc9 mutant lines (in vitro mutation-derived)8200.000.011.256.17692.7HS PSB Rc10 mutant lines (in vitro mutation-derived)2400.000.000.000.024100.0HS PSB Rc82 mutant lines (in vitro mutation-derived)2500.014.028.000.02288.0HS Pokkali mutant lines (seed mutation-derived)32515.626.313.1825.01650.0HT Azucena (Coll. No. 1528) mutant lines (seed mutation-derived)1000.000.000.0220.0880.0HS PSB Rc40 mutant lines (in vitro mutation-derived)500.000.000.000.05100.0HS PSB Rc62 mutant lines (in vitro mutation-derived)1700.000.000.0211.81588.2S PSB Rc68 mutant lines (seed culture-derived)200.000.000.000.02100.0HS RL2011DS_ON entries1900.000.000.0736.81263.2 RL2011DS_PYT entries2100.000.0733.3942.9523.8 RL2011DS_GYT entries500.000.0120.000.0480.0 Released varieties (different ecosystems) for pyramiding1200.000.000.018.31191.7 Rainfed lowland ecosystem elite lines2500.000.014.014.02392.0 Accessions600.000.000.000.06100.0 KDML 105 doubled haploid lines 200.0150.000.000.0150.0 Total34151.561.8185.35415.825875.7
Table 9. (Con’t) MaterialsNo. of Entries
Test Genotype’s Response HTTMTSHSProgenitor’s responseNo.%No.%No.%No.%no.% 2011 WS Br24 mutant lines (seed culture-derived)2000.000.0420.01575.015.0MT TDK-Sub 1 mutant lines (seed culture-derived)200.000.000.0150.0150.0HS KDML 277 mutant lines (seed culture-derived)200.000.000.0150.0150.0S Samba Mahsuri-Sub1mutant lines (seed culture- derived)1200.000.0650.0650.000.0HS PSB Rc42 mutant lines (seed culture-derived)1000.000.000.0110.0990.0HS FL478 (seed culture-derived)500.000.000.0360.0240.0S Budo-Budo mutant lines (seed culture-derived)300.000.0133.3266.700.0HS PSB Rc68 mutant lines (infloresence culture- derived)6200.000.0914.52438.72946.8HS Genebank’s collections/accessions8600.000.067.01719.86373.3 Total20200.000.02612.97034.710652.5 Grand Total54350.961.1448.112422.836467.0 HT(highly tolerant)=normal growth, no leaf symptoms; T(tolerant)=nearly normal growth, but leaf tips or few leaves whitish and rolled; MT(moderately tolerant)=growth severely retarded, most leaves rolled, only a few are elongating; S (susceptible)=complete cessation of growth, most leaves dry, some plants dying; HS (highly susceptible)=almost all plants dead or dying.
Table 10. Drought tolerance screening at seedling stage, glasshouse, PhilRice-CES Nueva Ecija, 2011 DS and WS.
Test genotype (in group)
Total test genotypes
(no.)
No. of tolerant genotypes as compared with check varieties and progenitor
IR64 PSB Rc14 Progenitor
no. % no. % no. %
2011 DS
NSIC Rc9* mutant lines (seed mutation-
derived) 54 5 9.3 2 3.7 4 7.4
NSIC Rc9* mutant lines (in vitro mutation-
derived) 3 0 0.0 0 0.0 0 0.0
PSB Rc68* mutant lines (in vitro mutation-
derived) 8 0 0.0 0 0.0 0 0.0
Y DAM DO* mutant lines (IVC-derived) 12 0 0.0 0 0.0 0 0.0
PSB Rc60* mutant lines (in vitro mutation-
derived) 2 0 0.0 0 0.0 0 0.0
*Progenitors 4 0 0.0 0 0.0 0 0.0
RL2011DS_PYT entries 24 0 0.0 0 0.0 0 0.0
RL2011DS_GYT entries 5 0 0.0 0 0.0 0 0.0
Rained lowland elite lines (Adaptability trial
entries) 57 8 14.0 2 3.5 0 0.0
Total 169 13 7.7 4 2.4 4 2.4
2011 WS
BR24* (seed culture-derived) 28 0 0.0 0 0.0 0 0.0
Jepun* (seed culture-derived) 1 0 0.0 0 0.0 0 0.0
Tanngiling* (seed culture-derived) 13 1 7.7 0 0.0 3 23.1
Budo-Budo* (seed culture-derived) 3 0 0.0 0 0.0 0 0.0
Vandana* (seed culture-derived) 12 0 0.0 0 0.0 0 0.0
FL478* (seed culture-derived) 4 0 0.0 0 0.0 0 0.0
Samba Mahsuri-Sub1* (seed culture-derived) 13 0 0.0 0 0.0 2 15.4
KDML 277* (seed culture-derived) 2 0 0.0 0 0.0 0 0.0
PSB Rc68-(inflorescence culture-derived) 62 0 0.0 0 0.0 0 0.0
Samba Mahsuri-Sub1* (IVC-derived) 16 0 0.0 0 0.0 0 0.0
*Progenitors 9 3 5.6 2 0.0 0 0.0
Total 163 4 2.5 2 1.2 5 3.1
Grand Total 332 17 5.1 6 1.8 9 2.7
Note: Selection was based on % plant recovery and biomass production after drought stress, in comparison with the check varieties and progenitor supported by test of means with Dunnett’s.