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a USDA-ARS, P.O. Box 1090, Stuttgart, AR 72160
b University of Arkansas, Rice Research and Extension Center, 2900 Hwy 130 East, Stuttgart, AR 72160
* Corresponding author (jnrutger{at}spa.ars.usda.gov)
USDA-ARS and the Arkansas Agricultural Experiment Station released nine indica germplasms of rice (Oryza sativa L.), indica-1, indica-2, indica-3, indica-4, indica-5, indica-6, indica-7, indica-8, and indica-9 (Reg. no. GP-95 to 103, PI 634575 to PI 634583) in 2004. These nine lines are recombinants from indica x indica crossing, which was initiated as a means of base broadening in U.S. rice, where very narrow genetic bases, essentially all in japonicas, have evolved because of the need for adaptation to temperate climates and to specific grain quality requirements. Long-grain cultivars in the USA are tropical japonicas while short- and medium-grain cultivars are temperate japonica (Mackill, 1995). The grain quality requirements for each of these groups are so demanding that infusions of germplasm from non-japonica sources usually has been limited to individual characters such as disease resistance and semidwarfing, followed by backcrossing to the japonica parent to recover satisfactory grain quality. The present nine germplasm lines were selected for early maturity and amylose contents similar to U.S. long-grain cultivars. Although having weak straw compared to japonicas, the indicas generally are competitive in yield, have resistance to blast disease [Pyricularia grisea (Cooke) Sacc.] and kernel smut [Tilletia barclayana (Bref.) Sacc. & Syd. in Sacc.], tolerance to rice water weevil (Lissorhoptrus oryzophilus Kuschel), are less susceptible to rice stalk borer (Chilo plejadellus Zincken), and more susceptible to rice stink bug [Oebalus pugnax (F.)] damage. They should provide useful sources of indica diversity for U.S. rice improvement programs.
The lines were derived by crossing a very early maturing indica cultivar, Zhe 733 (PI 629016) from China (Yan and Cai, 1991), which is about 20 d earlier than U.S. cultivars and has higher amylose, ca 250 g kg–1, than desired for U.S. markets, with the indica cultivar IR64 (IRRI, 1985) and six indica experimentals graciously provided by G.S. Khush of IRRI (personal communication, 20 Dec. 1995). The IRRI materials have amylose contents similar to U.S. long-grain cultivars, 
200 to 230 g kg–1. IR64 is similar in maturity to Arkansas cultivars while the six experimentals generally are 20 d later maturing. Brown rice dimensions of the IRRI materials are similar to the U.S. long-grain cultivars, while Zhe 733 has shorter and heavier grains.
Crosses were made in the greenhouse during the winter of 1997–1998, then materials were advanced in the field in Stuttgart, AR, and the winter nursery in Lajas, PR. Initial selection for early maturity was conducted in the 1999 F2 when only about 10% of the total F2 populations of over 30000 plants was harvested. Subsequent maturity selection in the 2000 F5 population reduced the number to 328 lines. After selection for intermediate amylose content in the 2000 F5 and 2001 F7 generations, the number was reduced to 59 lines. Yield testing was initiated in 2001 with these 59 lines.
The 2001 and 2002 yield tests were conducted in replicated six-row plots, 1.2 m long with 0.3 m row width. Nitrogen fertilizer was applied preflood at the rate of 112 kg ha–1. Zhe 733 was included as an indica check, and LGRU ef (PI 632957, Rutger et al., 2004) was included as a tropical japonica check. In 2002, the weak straw of many indicas became apparent, when severe lodging following 10 cm of rainfall in one week shortly after heading resulted in inconclusive yield data. For the 2003 tests the number of lines was reduced to nine that had performed well in 2001, and the nitrogen rate reduced to 56 kg ha–1. Replicated six-row plots were used in 2002, in rows 5.1 m long and 0.3 m row width. Zhe 733 and the tropical japonica cultivar Francis (Moldenhauer et al., 2002) were included as checks. In all tests, the two center rows were harvested.
For all nine lines, Zhe 733 was the female parent. The male parents of the nine lines, designated indica-1 to indica-9, were: indica-1, IR65629-22-1-3-3-3-1; indica-2, IR65629-67-3-3-1-1-2; indica-3, 4, 5, IR65629-157-3-2-3-2-1; indica-6, IR65450-3-3-2-3-3-2; indica-7, IR53936-60-3-2-3-1; indica-8, IR60864-88-1-1-1-2; and indica-9, IR64. These nine indica germplasms have similar amylose contents to and are similar to or earlier than the Arkansas tropical japonica check cultivar Francis (Table 1). The indica lines, derived from crossing semidwarf parents, are "tall" semidwarfs, inasmuch they are 13 to 27 cm taller than the conventional height cultivar Francis (Table 1). Yields in 2001 ranged from 7410 to 9480 kg ha–1 compared to 6690 and 5020 kg ha–1 for Zhe 733 and LGRU ef, respectively. In 2003, yields ranged from 7480 to 8930 kg ha–1, compared to 8410 and 7240 kg ha–1 for Zhe 733 and Francis, respectively. Brown rice grain dimensions generally meet U.S. long-grain standards, although indica-3 and -5 had relatively heavy grains. Whole grain milling yields of the indicas ranged from 46 to 57% compared to 54% for Francis and 45% for Zhe 733 (Table 1).
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In 2003, the nine germplasms were evaluated in the Rice Entomology Trial at Stuttgart, in nine-row plots, 2.4 m long and rows 18 cm apart, 56 kg ha–1 of nitrogen applied preflood and a similar amount at mid season. Three tropical japonica check cultivars received 118 kg ha–1 of nitrogen preflood and 50 kg ha–1 at midseason (Bernhardt and Rutger, 2004). Severe lodging (not recorded) again occurred in the indicas, and yields ranged from 7020 to 9550 kg ha–1, compared to 7940 to 9670 kg ha–1 for the three checks. In rice water weevil evaluations, larvae were found in all genotypes, including checks, from 22.0 to 38.9 larvae per core sample. However, in insecticide-treated versus untreated plots, only two of the nine indicas, indica-3 and-9 benefited from insecticide treatment while all three japonicas benefited from treatment. The other seven indicas apparently were able to tolerate rice water weevil larvae better than japonicas.
In rice stalk borer evaluations, the indicas ranged from 0.3 whiteheads per plot (resistant) to slightly susceptible levels of 10.3 whiteheads per plot, while the three japonicas ranged from 2.3 to 65.0 whiteheads per plot (Bernhardt and Rutger, 2004). In rice stink bug evaluations, the indicas ranged from 1.17 to 2.38% stained kernels, susceptible, in brown rice, compared to 0.57 to 1.09% in the three japonica checks. None of the indicas was as susceptible to kernel smut as the tropical japonicas Cocodrie (PI 606331, Linscombe et al., 2000) and LaGrue (PI 568891, Moldenhauer et al., 1994). Thus the insect evaluations indicated the indicas as a group, compared to the japonicas, had tolerance to water weevil and were less susceptible to rice stalk borer and more susceptible to rice stink bug.
In 2003, the nine germplasms also were tested in Rice Breeding trials at Stuttgart and Rohwer, AR, in 20-cm row spacings. At a nitrogen level of 168 kg ha–1 at Stuttgart, such complete lodging occurred that the test was not harvested. At Rohwer, nitrogen level 202 kg ha–1, severe lodging again occurred, ranging from 70 to 100% compared to 0% for the Arkansas check cultivar Wells (U.S. patent 6,287,416, Moldenhauer, 2001). In spite of the severe lodging, yields were obtained, ranging from 5340 to 9490 kg ha–1, compared to 10610 kg ha–1 for Wells. Leaf blast disease scores recorded on a 1 to 9 basis (where 1 = resistant, 9 = very susceptible) were obtained by the Rice Breeding program at Pine Tree, AR, a high blast-incidence testing site. Four indica germplasms, indica-1, -4, -6, and -7, had scores of 1; three germplasms, indica-5, -8, and -9, scores of 2; while the two remaining germplasms, indica-2 and -3, and the Wells check had scores of 4.
Germplasm amounts of seed (
5 g) of the above lines may be obtained by writing to J. Neil Rutger, Dale Bumpers National Rice Research Center, USDA-ARS, P.O. Box 1090, Stuttgart, AR. Seed also will be placed in the National Small Grains Collection, USDA-ARS, 1691 South 2700 West, Aberdeen, ID 83210, where it is available for research purposes, including development and commercialization of new cultivars. If this germplasm contributes to the development of new cultivars, it is requested that appropriate recognition be given to the source.
NOTES
Accepted for publication October 31, 2004.
REFERENCES
This article has been cited by other articles:
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  J. N. Rutger, B. A. Beaty, and R. J. Bryant Registration of Four Early Flowering Indica Germplasms of Rice Journal of Plant Registrations, September 1, 2007; 1(2): 154 - 156. [Full Text] [PDF]
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 J.N. Rutger and L.A. Bernhardt Registration of Four Indica Rice Genetic Stock Mutants Crop Sci., February 6, 2007; 47(1): 461 - 462. [Full Text] [PDF]
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