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本頁は“Plant Prod.Sci.1:296-297,1998”に掲載したものです.図表一部省略.

Difference with Rice Cultivars in the Rate of Root Regeneration from Embryo Callus and Its Relationship with the Genetic Background

Tomohiko Yoshida1) and Kumi F. Oosato2)
(1)Faculty of Agriculture, Kyushu University, Fukuoka, 812-8581 Japan; 2)Fukuoka Agricultural Research Center, Chikushino 818-8549 Japan)
Key words; Callus induction, Coefficient of parentage, Pedigree analysis, Regeneration, Rice.

The efficiency of tissue culture depends on the genotype of the crops used. In a rice cultivar Koshihikari, well known as a highly palatable cultivar, the percentage of callus induction from both embryo and anther, and that of plant regeneration from the callus are low (Niizeki et al., 1968, Abe et al., 1986, Abe, 1992), although Koshihikari and related cultivars are important cross parents for developing highly palatable breeding materials (Oosato et al., 1996).
Here, the differences among rice cultivars in both callus formation from embryo and root regeneration from the callus were examined, and their relationships with genetic kinship to specific cultivars were estimated to clarify the relationship quantitatively. Coefficients of parentage were computed to show the genetic kinship.

Materials and Method
Sixteen rice breeding lines developed in Fukuoka Agr. Res. Center and 13 check cultivars were used. These cultivars are shown in the legend to Fig. 1. Following Yokoi et al.(1996), dry-stored seeds were dehulled, surface-sterilized and placed in 20 mL N6 medium containing 2,4-D (2 mg L-1) and ABA (1 mgL-1) in a petri-dish in Nov., 1996. Twenty seeds were placed in a petri-dish and incubated at 25℃in the dark with 3-4 replications. After one month, a callus from an embryo was excised, transferred to the regeneration medium containing 1 mgL-1 each of NAA, ABA and Kinetin in N6 medium, and incubated at 25℃ under a 16 hour-photoperiod of 400μmol m-2s-1. In case of germinated seeds, the shoot directly developed on the embryo was removed and only the induced callus was transferred. After 2 months on the regeneration medium, the number of calluses with roots was counted. Some calli developed shoots but the rate was low. Therefore, root development was used as the criterion of plant regeneration in this study.
For genetic background study, coefficients of parentage of each cultivar to Koshihikari and other major cultivars were computed by the method of Mizuta et al.(1996).

Results and Discussion
The rate of callus induction in each genotype varied from 35.1 to 83.4%. Analysis of variance showed that the difference was significant at the 1% level (Table 1). The rate of root induction varied widely from 0 to 51.3% with the genotype (Fig. 1), although the difference was significant at the 10% level but not 5% level (Table 1).
Fig. 1 shows the relationship between root induction rate and the coefficient of parentage to Koshihikari of each cultivar. The correlation coefficient was -0.509 and significant at the 1% level, suggesting that the genotypes with a low root induction rate were genetically closely related with Koshihikari. The correlation coefficient between callus induction rate and the coefficient of parentage to Koshihikari was -0.032, and not significant.
Abe (1992) reported that Koshihikari showed poor callus formation in anther culture and that this trait might have been derived from one of the ancestors, Moritawase. Table 2 shows the correlation between the root induction rate and the coefficient of parentage to several cultivars including Moritawase. Kinuhikari is closely related to Koshihikari. The correlation between the root induction rate and the coefficient of parentage to Kinuhikari was -0.535. In Nipponbare, the correlation was not significant. Nishihomare and Toyotama showed a significant positive correlation with a coefficient of 0.587 and 0.390, respectively. Nishihomare and Toyotama were previously widely grown cultivars with a high yield, high tolerance to diseases and insects and wide adaptability in the Northern Kyushu area, although they had lower palatability. For breeding programs using tissue culture, their high regeneration ability should be utilized along with their good agronomic performance. Norin 22 and Norin 1 are the cross parents of Koshihikari. No significant correlation was found in Norin 22. Norin 1 and ancestors of Norin 1 showed a significant negative correlation with a coefficient of -0.552** in Norin 1, -0.551** in Moritawase and -0.534** in Rikuu 132, confirming the findings of Abe(1992).
In conclusion, the root induction rate in embryo callus differed with the genotype examined. Genotypes genetically related to Koshihikari tended to have a low root induction rate. The cultivars which had a high root induction rate may be useful for tissue culture breeding in rice.

References
Abe K. 1992. Japan. J. Breed. 42:403-413.*
Abe T. et al. 1986. Theor. Appl. Genet. 72:3-10.
Mizuta K. et al. 1996. Agric. Inf. Res. 5:19-28.*
Niizeki H. et al.1968. Proc. Jpn. Acad. 44:554-557.
Oosato K. et al. 1996. Japan. J. Breed. 46:295-301.*
Yokoi S. et al. 1996. Plant Tissue Cult. Lett. 13:85-86.**

* In Japanese with English abstract.
** In Japanese.

Table 1. Analysis of variance of the rate of callus induction from embryo 
and root induction from callus for 29 rice cultivars.
------------------------------------------------
     Factor        df     ms       f      lsd(5%)
------------------------------------------------
Callus induction
     cultivar       28    370.2    3.33**   16.7
     error          64    111.0
Root induction
     cultivar       28    436.3    1.48#    26.1
     error          71    294.6
------------------------------------------------
**, # Significant at 1% and 10% level, respectively. 

Table 2. Correlation between coefficient of parentage to several major 
cultivars and root induction rate.
---------------------------------------
   Cultivar       Range1)   Correlation2)
---------------------------------------
   Kinuhikari    0.09-0.77   -0.535**  
   Nipponbare    0.12-0.61    0.258    
   Nishihomare   0.07-0.36    0.587**  
   Toyotama      0.08-0.62    0.390*   
   Norin 22#     0.26-0.65   -0.204    
   Norin 1#      0.02-0.53   -0.552**  
   Moritawase#   0.00-0.25   -0.551**  
   Rikuu 132#    0.03-0.31   -0.534**  
---------------------------------------
1)Range of coefficient of parentage to each major cultivar.
2)Calculated between the coefficients of parentage to each major 
cultivar and root induction rate among 29 cultivars used in this 
study(refer to Fig.1). *,** Significant at the 5% and 1% level, 
respectively. # Ancestors of Koshihikari.

Fig. 1 Relationship between root induction rate and coefficient of 
parentage to Koshihikari. The number in the figure shows cultivars. 
1;C1, 2;C8, 3;C12, 4;C13, 5;C14, 6;C15, 7;C18, 8;C19, 9;C23, 10; C24, 
11;C25, 12;C26, 13;C27, 14;C28, 15;C29, 16;C30, 17;Koshihikari, 
18;Reiho, 19;Nipponbare, 20;Tukushihomare, 21;Aoinokaze, 
22;Yokahonami, 23;Kinuhikari, 24;Hinohikari, 25;Chubu 68, 
26;Hinokuniotome, 27;Yumehikari, 28;Saikai 190, 29;Yumetukushi. For 
1-16, C is the abbreviation of Chikushi.

root/callus
	対コシ近縁係数	    callus/embryo    root/callus
   soukan        1           -0.032ns       -0.509**
ちくし1号	0.77	    58.2         30.0 
ちくし8号	0.64	    52.7         34.5 
ちくし12号	0.64	    38.5         30.3 
ちくし13号	0.40	    67.4         19.1 
ちくし14号	0.37	    37.2         16.7 
ちくし15号	0.53	     50.9        23.2 
ちくし18号	0.37	     64.8        14.3 
ちくし19号	0.40	     52.5        30.3 
ちくし23号	0.44	     45.5        20.5 
ちくし24号	0.70	     45.2        11.1 
ちくし25号	0.36	     35.7        30.3 
ちくし26号	0.39	     43.7        51.3 
ちくし27号	0.51	     53.5        11.5 
ちくし28号	0.44	     39.8        32.8 
ちくし29号	0.32	     53.1        32.4 
ちくし30号	0.46	     51.9        24.2 
ユメヒカリ	0.78 	     83.4        27.6 
キヌヒカリ	0.53	     60.5        10.4 
ツクシホマレ	0.19 	     52.5        39.5 
ヒノヒカリ	0.61 	     48.4        27.8 
レイホウ	0.14 	     49.6        38.8 
日本晴	    0.25 	     53.7        45.1 
葵の風	    0.15 	     59.4        32.4 
西海190号	0.20         62.9        35.2 
中部68号	0.40 	     49.1        19.5 
ヨカホナミ	0.78 	     67.8        21.3 
コシヒカリ	1.00 	    43.3         5.6  
ヒノクニオトメ	    0.22 	     61.6        17.8 
夢つくし	0.77 	     35.1        0   
平均	    0.48 	     52.3        25.3 
稲の胚由来カルスからの根再分化率の品種間差およびその遺伝的背景との関係
吉田智彦1)・大里久美2)
(1)九州大学・2)福岡県農業総合試験場)
 水稲の16育成品種と13比較品種を用いて,完熟種子の胚を2,4-D を2 mg/LとABA を1 mg/L含むN6培地で25℃暗黒条件下で培養した.1月後胚からのカルスを種子から切り取り,NAA, ABA とKinetinを各々1 mg/L含むN6 再分化培地に移し,25℃,16時間日長条件下で2ヶ月間培養後に根を分化したカルスを数えた.根再分化率の品種間差は0から51.3%であった.対コシヒカリ近縁係数と根再分化率とには-0.509の1%レベルで有意な負の相関があり,コシヒカリと近縁なものはカルスからの根再分化率が低かった.コシヒカリの祖先品種である,農林1号,森田早生,陸羽132号との近縁係数と根再分化率との相関係数も有意な負の値であった.一方,対ニシホマレ近縁係数とは有意な正の相関係数0.587が得られ,ニシホマレと近縁なものの根再分化率は高かった.
以上