EVELOPMENT OF NE SEMIAF SOUCES FO ICE ITH IFFEENT CYTOPLASMS (CV BASMATI70 AN GLOIA) J.E. EUS, E. SUAEZ Instituto de Investigaciones del Arroz, Bauta, Havana, Cuba XA0101026 J.L. FUENTES, A. ALVAEZ, E. PAÓN Centro de Estudios Aplicados al esarrollo Nuclear, Miramar, Playa, Havana, Cuba Abstract In Cuba semidwarf rice varieties grow on 98% of the area. Virtually all carry the same ee-geowon-gen dwarfing gene. Also, most if not all the cultivars have the same cytoplasm. The induced mutations approach was undertaken in order to generate alternative genetic sources of dwarfing with different cytoplasms and to improve the grain quality of Cuban rice. The seeds of two varieties, and, were irradiated with and 00 Gy of 60 Co gamma rays. In several generations of selection, progeny testing and preliminary yield tests 10 mutants (6 from and from ), whose yields exceeded the source cultivars, have been advanced to replicated yield trials. Some of the mutant lines are also resistant to lodging and to blast {Pyricularis grisea). It is concluded the induced mutations can be used successfully to improve plant type and other agronomic traits in rice. The induced mutants will be used also in hybridization programs. 1. INTOUCTION In Cuba, 98% of rice area is cultivated with semidwarf cultivars. Virtually all carry the same semidwarfing gene of II varieties that comes from dwarf Chinese variety ee-geowon-gen (GG) [1,2]. Cuban rice breeders adopted the semidwarf plant type concept, as a breeding objective in the early 70's, and the use of semidwarfs as parents intensified year by year, increasingly crossing semidwarf parents with other semidwarf. Most of these parental varieties employed in the hybridization programs originated from the same maternal parent, implying that the components of their cytoplasm are similar []. This situation highlights the need for alternative sources of dwarfing and for broadening the maternal genetic base in the new cultivars. uring the last 20 years the selection pressure for cooking quality was not so strong. Today the rice cultivars present a good plant type, with a high yield potential, good resistance to the main pests and diseases and they also possesses good milling quality. The cooking quality and the different cytoplasm bases used in the hybridization programs, are not satisfactory. In addition, the gene for semidwarmess is transferred with other genes which reduce the grain quality. Mutation breeding is an important tool to be used for such programs. This research has the following objectives: (a) To identify alternative genetic sources of dwarfing with different cytoplasmic bases by using mutation techniques, (b) To improve the grain quality of the Cuban rice varieties using the high grain quality from India and from Cuba. 2. MATEIALS AN METHOS The experiment was initiated in 199 with the varieties of and (Table I). 7
TABLE I. PINCIPAL AGONOMICAL TAITS OF THE VAIETIES USE Variety Type Tall indica Tall indica Yield potential Low Low Maturity Medium Medium Lodging Highly susceptible Susceptible Aroma Aromatic Standard Character to improve Semidwarf, resistant to lodging Semidwarf, resistant to lodging The breeding scheme is shown in Fig. 1. The seed were exposed to and 00 Gy of 60 Co gamma rays. The irradiated seeds (600 seeds per treatment) were sown in a nursery and transplanted to the field, one plant per hill, spaced 1 * 1 cm apart. The first 2 panicles were harvested from each plant. The progenies from each Mi were raised as the M2 line, each M2 population was transplanted and grown in a pedigree row ( m long), one plant per hill, spaced 2 x 0 cm apart. A total of 2600 M2 plants per treatment in variety and plants per treatment in variety were sown. At maturity the selection was made for following: Semidwarf and intermediate plant type. Earliness. Healthy plants. The M and M generations were sown by direct seeding in m rows. One control row of each of the respective source variety was grown every twenty rows of the mutant lines. The observational yield trials were concluded in the M and Me generations. Small plots with 8 rows m long were utilized. Every ten plots three control varieties were sown, the source varieties Basmati and and the commercial cultivar J-10. They were planted in three locations to evaluate their field performances in different ecological zones.. ESULTS AN ISCUSSION In the M2 generation much variability was found, mainly in plant height. A total of 1 plants, semidwarf and 62 intermediate plant type, were selected. A higher degree of variability was found in the Basmati variety with a radiation doses of Gy (Table II). ifferent types of mutation were identified such as types of grain (bold and medium long grain) and late maturity mutants. On the basis of the data and visual comparison, 71 true breeding lines (8 from Basmati and 1 from ) were selected for further screening and evaluation (Table HI). Many of the M2 selections segregated and did not breed true in the M. 8
Varieties and Irradiation gamma, 199 Harvest, single plants M 2 Basmati 2600 plants/treatment plants/treatment ry season, 199 Selection of semidwarf and intermediate M -M et season, 199 et season, 199 T J Pedigree selection Screening S.O./P.O./grain quality s 6 Observational yield trials Three location T M 7 -M 8 eplicated yield trials Three locations Inheritance studies of semidwarfness FIG. 1. Breeding scheme. TABLE II. NUMBE OF SELECTE M 2 PLANTS AN THEI POPETIES, Y SEASON Variety Gamma dose (Gy) 00 00 Semidwarf 8 2 19 11 Plants selected, number Intermediate 19 62 Early 6 8 2 21 79 0 2 21 17 9
TABLE III. NUMBE OF TUE BEEING M MUTANT LINES SELECTE FO EUCE HEIGHT AN EALINESS Variety Gamma dose (Gy) 00 00 Semidwarf 6 17 7 6 Intermediate height 2 1-6 Early 1 2 12 8 86 TABLE IV. YIELS OF SEMIAF MUTANT LINES SELECTE FOM OBSEVATIONAL YIEL TIALS IN THEE LOCATIONS ( = Y SEASON; = ET SEASON) Mutant lines B 00-10-l--l BJOO--2-1 BMO-1--1 Source Basmati y00gy Basmati-yGy BJOO-10-2-2 B00-IO-I- B2oo-1-2-l Basmati-yGy G00-10-2-1-7 -y00gy G 00-10-2-7- -y00gy G00-10-2- -y00gy G-10-2-1-6 -ygy Control varieties Unknown Unknown J-10 I80--9-/ I90-10-1 7.9 6.6..9...6. 1.9.1 8. I.I.A..6..6.9.7..1.2. 1. 2.2 6.1 S. 6.9.2 7.0. 7.9 6.. 1..0 8.9 Spirits.9 Yield t/ha Jucarito 6.7.0.7...8.7.6 1.2 2.1 6. 7.2.1 6.1..0. 1.7 2.7 8..7.0...1.9.1.0 1.0 1.9 6.2 7.2.6..8..7 1.7 2.9 8.6 Mean.8.8...7.... 1.2 2. 6.2 In the observational yield trials, performed in three different locations, 22 lines from Basmati-70 and 12 from, showed higher yields than the source cultivars (between 2.2 and more than. t/ha). On the basis of their field performance and yield data, ten mutants were selected for further evaluation in replicated yield trials (Table IV). The mutant line B10-1--1 showed the highest yield with good resistance to Pyricularia grisea and lodging. The high frequency of semidwarf mutants in this experiment demonstrated that induced mutations can be successfully used to improve plant type in rice as has been reported previously [,, 6, 7]. Induced mutations generated new semidwarf germplasm with useful agronomic traits. These new lines will be used for hybridization breeding as semidwarf parents with different cytoplasms and genetic background. 0
TABLE V. AGONOMIC ATA FO THE TEN SELECTE SEMIAF MUTANT LINES, MEAN VALUES OF THEE LOCATIONS ( = Y SEASON; = ET SEASON) Material B 00-10-l--l B00-9-2-I B -l --1 B00-10-2-2 B 00-10-l- B -1-2-l G00-I0-2-I-7 G00-10-2-7- G 00-10-2- G 20O -10-2-l-6 Control varieties J-10 Source Basmati y00gy Basmati-yGy Basmati-yGy -y00gy -y00gy -y00gy -ygy Unknown Unknown I80--9-/ I90-10-1 Vigor 2 - Lodging" HS S H Tagosodes c LE Maturity (days) 12 16 1 1 18 1 10 128 16 11 16 12 1 11 11 110 110 11 118 1000 grain wt.(g) 2.9 2.8 2.7 2.1 2.1 2.7 26. 26.8 26.9 2. 1.2 Plant height (cm) 8 9 90 92 100.2 100. 101.2 97. 17 1 9. a a higher score denotes higher vigor. b = resistant, = moderately resistant, H = highly resistant, S = susceptible, HS = highly susceptible. c eaction to Tagosodes onizycoles. Panicle length (cm) 26.2 2 26. 2. 2 26. 2.8 27. 2.2 26.7 2 EFEENCES [1] AQUINO,.C., JENNINGS, P.. Inheritance and significance of semidwarfism in an Indica rice variety. Crop Sci. 6 (1966) 1-. [2] FOSTE, K.., UTGE, J.N. Inheritance of semidwarfism in rice. Genet. 82 (1978) 9-7. [] HAGOVE, T.., COFFMAN,.., CABANILLA, V.I. Ancestry of improved cultivars of Asian rice crop. Crop Sci. 20 (1980) 721-727. [] MACKILL,.J., UTGE J.N. The inheritance of induced mutant semidwarfing genes in rice. J. Hered. 70 (1979) -1. [] MALUSZYNSKI M., VAN ZANTEN, L., ASHI, A., BUNNE, H., AHLOOALIA B., ZAP ATA, F.J., ECK, E. Mutation techniques in plant breeding, Use of Induced Mutation and Molecular Techniques for Crop Improvement, IAEA, Vienna (199) 19-2. [6] UTGE, J.N. Applications of induced and spontaneous mutations in rice breeding and genetics. Adv. Agron. 6 (198) 8-10. [7] SINGH, V.P., ZAMAN, F.U., SAANANA, A.. Induced variation in aromatic rice cultivars. II Newslett. 1 (1989) 1. 1