Tải bản đầy đủ - 0 (trang)
III. Breeding Applications of Early Maturity Mutants

III. Breeding Applications of Early Maturity Mutants

Tải bản đầy đủ - 0trang



Table II

Early Maturing Public Cultivar and Released Germplasm Lines Derived from Spontaneous or

Induced Mutation in California

Cultivar or

germplasm line



Germplasm lines

CI 11037 (D18)

CI 11038 (D31)

CI 11051 (ED7)

CI 11052 (S-6190-57)

CI 11053 (S-8157-82)

CI 11054 (S-6189-21)


of release




Spontaneous mutant from CS-M3

Camahan et al. (1975)







y-Ray induced mutant of Calrose

y-Ray induced mutant of Calrose

Spontaneous mutant of Calrose 76

y-Ray induced mutant of M5

y-Ray induced mutant of S6

y-Ray induced mutant of Terso

Rutger et al. (1979a)

Rutger et al. (1979a)

Rutger et a[. (1982a)

Rutger et al. (1982a)

Rutger et al. (1982a)

Rutger et al. (1982a)

much as 30-40% of the California rice area. The early maturity characteristic of

M5 has also been recombined with the induced mutant semidwarfhg gene sd, to

breed two semidwarf cultivars with early maturity, M-301 and M-302 (Johnson

et al., 1980, 1981) (Fig. 1).

An induced mutant for very early maturity, germplasm line CI 11038 (D31 in

Fig. l), was the source of the very early maturity of the semidwarf cultivar

M-101 (Rutger et al., 1979a,b) (Fig. 1). CI 11038 and M-101 are about 20 days

earlier than the original Calrose parent, so that M-101 is especially well suited

for production in short season areas of California, for late planting in doublecropping situations following barley or wheat, or for delayed plantings resulting

from heavy winter rains as occurred in the 1982 season.

Several other induced mutants for early maturity have been released as

germplasm lines in California. These lines, which otherwise possess the grain

cooking quality and cold tolerance of their parent cultivars, are expected to be

useful germplasm sources for breeding additional cultivars. The early maturing

mutant CI 11037 came from the same 25 kR-treated seed lot that produced

Calrose 76 and CI 11038 (Rutger et al., 1979a) (Table 11). CI 11037 is about 15

days earlier than Calrose but its height and other characteristics are similar. CI

11037 carries a single, weakly dominant gene for early maturity. Its early maturity was independent of the semidwarf gene in Calrose 76 and the glabrous hull

gene in CS-M3 (McKenzie et al., 1978).

A spontaneous mutant for early maturity, CI 11051 (ED7), was also released

as a germplasm line (Table 11). CI 11051 was found in a seed-increase field of the

semidwarf cultivar Calrose 76; it is 15-20 days earlier than its parent and

similarly carries the semidwarfing gene sd,. Except for its earlier maturity, the



phenotype of CI 11051 is nearly identical to that of Calrose 76. Studies on the

inheritance of the early maturity of CI 11051 suggest that its early maturity was

the result of a single nondominant gene (Rutger et al., 1982a). CI 11051 would

have been considered for direct release as a cultivar had its performance and

adaptation not been identical to those of the cultivar M-101. Furthermore, M-101

has the additional merit of having glabrous hulls, which are generally preferred

by U.S. rice growers.

Three other early maturing mutants were selected following ~ C irradiation


of three medium-to-late maturing cultivars (Table II). CI 11052 is about 1 week

earlier than M5 but is otherwise similar to its parents; CI 11053 also is about 1

week earlier than S6 and otherwise similar to its parent; CI 11054 is about 3

weeks earlier than Terso and is otherwise similar to its parent. Inheritance of

early maturity of CI 11052, CI 11053, and CI 11054 has not been studied (Rutger

et al., 1982a).

Other notable examples of early maturity mutants that have been directly

released as cultivars are Nucleoryza in Hungary (Mikaelsen et al., 1971) and

Kashmir Basmati in Pakistan (Awan and Cheema, 1976). Nucleorzya is 3 weeks

earlier than its parent and is thus better adapted to short-season climates. Similarly, Kashmir Basmati is about 20 days earlier and can be grown at higher elevations than its parent. Two mutants released in Bangladesh, IRATOM 24 and

IRATOM 38, required 23 and 36 days less, respectively, from seeding to maturity than did the original cultivar IR8 (Miah et al., 1981). Four additional

mutants were found to be 23-41 days earlier than IR8. One, Mut 1-2, yielded

2884 kg/ha compared to 1825 kg/ha for the best check cultivar in the experiment, BR-3. In the People’s Republic of China, an early maturing rice cultivar

reported to be derived from radiation breeding, Yuanfeng Early, is 40 days

earlier than its parent cultivar, Kazi No. 6. Yuanfeng Early is grown on more

than 600,OOO hectares in the lower Yangtze River region ( M A , 1982), which

undoubtedly signifies that it is the world’s most widely grown mutant cultivar.

Notable efforts at inducing large numbers of early maturing mutants in rice

have been reprted by Kawai and Sat0 (1969) and Ismachin and Mikaelsen

(1976). Kawai and Sat0 (1969) induced 59 significantly earlier heading mutants

in the cultivar Norin 8. These mutants ranged from 1.3 to 18.4 days earlier than

their parents, and grain yields ranged from 53 to 104% of the parent. Changes in

other characters occurred in most mutants. The frequency of mutants that were at

least 3 days earlier and yielded 95% of the parent was less than one per lo00 M,

strains. Ismachin and Michaelsen (1976) induced a large number of mutants

which matured in 110-120 days as compared to 140-150 days for the parent

cultivar Pelita I. In yield trials, 11 mutants equaled or exceeded the parent. In

addition to consideration for direct release, the mutants were put into a crossbreeding program.






An induced mutant for waxy (wx) endosperm was directly released as the

cultivar Calmochi-201 in California (Camahan et af., 1979). Calmochi-201 was

one of three waxy mutants found among 2000 X, generation panicles following

W o irradiation of seeds of the widely grown nonwaxy tall cultivar S6. Calmochi-201 closely resembles its parent, but Calmochi-201 has waxy endosperm,

about 11% reduction in kernel weight, and 6% reduction in yield (Carnahan et

af., 1979). Almost immediately, Calmochi-201 was succeeded by Calmochi-202, a semidwarf waxy recombinant from a cross between a line carrying

the sd, gene and Calmochi-201 (Fig. 1). At the time of its release, Calmochi-202

yielded 17% more than either Calmochi-201 or S6. Both Calmochi-201 and

Calmochi-202 are considered unsatisfactory for making mochi cakes but are

acceptable for other glutinous rice markets (Carnahan et af., 1981a).

An induced mutant for waxy endosperm also was released directly as the

cultivar Miyuki-Mochi in Japan (Toda, 1979). Miyuki-Mochi originated from

one of two panicles having waxy grains in the MI generation, following y

irradiation of seeds of the nonwaxy cultivar Toyonishiki. Miyuki-Mochi closely

resembles its parent, but Miyulu-Mochi has waxy endosperm, about 9% reduction in kernel weight, and 8% reduction in yield. When compared to the standard

local waxy cultivar Shinano-Mochi No. 3, the mutant cultivar had a yield advantage of 15%. Toda (1979) also induced waxy mutants in seven additional nonwaxy cultivars to study the action of the waxy gene. Kernel weights were

reduced 3-16%, and grain yields ranged from 2% increase to 23% decrease.

Khambanonda et al. (1982) reported that three cultivars have been produced

by direct release of induced mutants in Thailand, of which two were induced

mutants for waxy endosperm. RD6 arose from irradiation of Khao Dawk Mali

105, and RDlO arose from fast neutron treatment of the semidwarfcultivar RDl.

A major significance of induced mutation for waxy endosperm is that this

technique permits the almost instantaneous development of high-yielding waxy

cultivars. In the United States, for example, waxy rice represents a very small

fraction (perhaps 1%) of the rice market. Consequently, it was not economically

feasible to spend much effort on breeding improved waxy cultivars, and most

existing waxy lines were unadapted or otherwise low in yield. In Japan, Toda

(1979) also noted that breeding progress of waxy rice in Japan is slow because of

limited interest by breeders. Instead of spending years putting the waxy gene into

high-yielding backgrounds through hybridization, the work by Carnahan et af.



(1979) and Toda (1979) demonstrated that it is possible to take a good local

cultivar and convert it to waxy endosperm by irradiation. In California, this

approach followed by hybridization with a semidwarf source led to the rapid

development of a very high-yielding semidwarf waxy cultivar, Calmochi-202.



Induction of disease resistance would be a desirable goal for many breeding

programs, especially where cultivars otherwise satisfactory are being grown.

Induced mutants for disease resistance in rice in several countries have been

reported for blast (Pyricularia oryzae) and bacterial leaf blight (Xanthomonas

oryzae) (Mikaelson, 1980). Many of these reports have been presented in IAEA

publications (1974, 1977) and are also reviewed by Hajra et al. (1980). However, there seem to be no examples in rice of the widespread use of induced mutants

for disease resistance.

Some of the problems associated with use of induced mutants for disease

resistance are evident from the very thorough series of investigations conducted

by Kawai (1974) and Tanaka et al. (1978) on induction of blast-resistant mutants. Frequency of mutants was very low; most mutants did not show greatly

improved resistance and had negative changes in other agronomic traits (Kawai,


Few workers seem to have taken precautions to eliminate pollen contamination

in the mutated populations. Because spontaneous or “field” hybrids resulting

from fertilization of partially sterile M,plants by foreign pollen have been noted

by several workers (Caldecott et al., 1959; Konzak, 1959; Simons et al., 1962)

as the probable source of disease-resistant plants in irradiated populations of

oats, similar outcrossing probably occurs in mutated populations of rice. Kawai

(1974) and Tanaka et al. (1978) prevented outcrossing in the M, generation by

bagging panicles but did not protect plants in subsequent generations. Outcrossing apparently occurred in the later generations, as resistant plants were found

with disease reactions similar to a blast-differential check cultivar growing in the

same nursery. The variants also showed morphological characters different from

the original parent cultivar. Unless the possibility of foreign pollen is eliminated,

a researcher can never be completely certain that resistance arose from induced

mutation. Although from a breeding standpoint it might be argued that the source

of resistance, whether from natural crossing or induced mutation, does not matter, it is important to know whether or not mutations actually are being induced.

If not, then the considerable efforts in attempting to induce mutants can be


Another problem is that recessive mutants occur at higher frequency than

dominant mutants. Because most disease-resistant genes in plants are dominant,

Tài liệu bạn tìm kiếm đã sẵn sàng tải về

III. Breeding Applications of Early Maturity Mutants

Tải bản đầy đủ ngay(0 tr)