21. Inheritance of a physiological mutant showing retarded panicle development

    Takenobu Aida, Itsuro Takamure and Toshiro Kinoshita
    Plant Breeding Institue, Faculty of Agriculture, Hokkaido University, Sapporo, 060 Japan

     A spontaneous mutant showing retarded panicle formation was found in rice variety Nagayama 77402 at the paddy Field in Kamikawa Agricultural Experiment Station and named N-180 (Retarded panicle development). It is noted that the character expression of the mutant was remarkably affected by temperature conditions when grown in the growth chambers kept at low (20°C) and high (25°C) temperatures during panicle formation (Fig. 1). Under the low temperature, panicles of the mutant remained in ajuvenile stage after floral differentiation (panicle length: l-6cm) and were covered with white and thick bract hairs (Fig. 2). As the elongation of uppermost internode was inhibited, absence of booting and heading stages were recognized under low temperature condition in the growth chamber and paddy field. In contrast, panicle development and heading were normal under high temperature condition. However a reduced length of panicle with deformed spikelets and low seed setting were observed under high temperature. Thus, the development of panicles is inhibited under low temperature but is somewhat restored under high temperature condition.
    The F1 plants of N-180 X normal testers showed normal panicles and the F2 population segregated into 3 normal : 1 retarded panicle (Table 1). Therefore this mutant is governed by a single recessive gene. Although there are many mutants showing deformity of panicles (Kinoshita 1989), this mutant is distinct from other mutants especially for the sensitivity to the low temperature condition. The gene symbol rtp (t) is tentatively assigned to this mutant.
    The gene, rtp (t) is epistatic to and independent of several mutant genes for panicle
 
Table 1. F2segregations of retareded panicle
Cross combination F2 segregation Total Goodness of fit
Normal retarded c2(3:1) P
N-180xA-58 obs. 245 78 323 0.12 0.7-0.8
do. xN-133 do. 186 59 245 0.11 c2 (3:1)
do. xH-79 do. 147 49 196 0.00 >0.95

Table 2. Combined F2 segregations with several marker genes for panicle and spikelets
 

Gross 

combination

 Gene pair 

A:B

 F2 sesegregation Total Goodness of fit
AB Ab a- c2(9:3:4) p
N-180xH-339 rp(t): Cl obs. 168 54 76 298 0.09 >0.95
N-180xMutant-l rp(t): mls-3 obs. 68 21 28 117 0.16 0.9 -0.95
N-180xN-135 rp(t): dp-2 obs. 100 22 29 151 6.10 0.1 -0.2
N-180x83N1070 rp(t): G-2 obs. 109 55 57 221 6.38 0.05-0.1
N-180xC-46 rp(t): eui obs. 108 20 43 171 5.99 0.1 -0.2

 

and spikelets, e.g. Cl, mls-3, dp-2, g-2, eui (Table 2). The mutant can be utilized for the study on morphogenesis of floral organs.

References

Kinoshita, T., 1989. Report of the Committee on Gene Symbolization, Nomenclature and Linkage Groups, IV

List of gene symbols recommended (with linkage group and key literature). RGN 6: 12-29.