12. Genic interaction between lhs (leafy hull sterile) and some mutant genes related to spikelet formation

T. AIDA1,2, S. NIKURA1,3 and I. TAKAMURE1

1) Faculty of Agriculture, Hokkaido University, Sapporo, 060 Japan
2) Present address: Miyazaki Station of National Livestock Breeding Center, MAFF, Kobayashi,Miyazaki, 886 Japan
3) Present address: Tohoku Seed Co., Utsunomiya, 321-32 Japan

A mutant called 'Leafy hull sterile' is characterized by deformation of lemma and palea showing leafy structures and accompanied by various malformations of floral organs and low seed setting. This mutant is controlled by a single recessive gene, lhs, located on the chromosome 3 (Kinoshita et al. 1977). Based on a comparative observation on floral organs and the peroxidase isozyme reaction, it was supposed that lhs may be related to the developmental modification from glume (hull) to leaf sheath (Niikura et al. 1992). In the present study, the authors examined some genie interaction between lhs and other mutant genes concerned with spikelet formation. 

Double mutants were produced in F2 populations of the crosses between lhs line and eight testers having the genes, Ur1 (Undulate rachis-1), Dn1 (Dense panicle-1), lax (lax panicle), sp (short panicle), Cl (Clustered spikelets), gl (long sterile lemmas-1), mls3 (malformed spikelet-3) and tri (triangular hull), respectively. A regular ratio of 9:3:3:1 was observed in the respective populations showing this is independent of eight genes.

On the other hand, F2 population of the cross between lhs and dp2 (depressed palea-2) lines segregated into the ratio of 9 normal : 3 dp2: 4 lhs (Table 1 ). Thus the expression of dp2 was masked by the action of lhs. Further, lhs mutants lacked a palea and developed two lemmas of the spikelet. Kinoshita et al. ( 1977) reported that fusion, duplication or substitution of the floral organs occurred by the action of lhs even in a single spikelet. Therefore, lhs mutant may have capability to develop more than two florets in a spikelet with two leafy lemmas. In contrast to this, normal allele (Lhs) regularly develops one floret in each spikelet having palea and lemma.

F2 population of the cross between lhs and rp(t) (retarded panicle) lines (Aida et al. 1995) segregated into the ratio of 9 normal : 3 lhs : 3 rp(t) : 1 vegetative shoot (propagule) type (Table 1 and Fig. 1 ). It is obvious that propagule type was the double mutant. These plants have normal empty glumes, vegetative shoots and no floral structures in spikelets (Fig. 2). Usually lhs plants have lemmas showing leaf sheath structure, whereas double mutants have vegetative shoots differentiated into leaf blade and ligule within a spikelet (Fig. 3). It seems that the interaction between lhs and rp(t) inhibits the differentiation of floral organs maintaining the vegetative growth during spikelet formation.

References

Aida, T., I. Takamure and T. Kinoshita, 1995. Inheritance of a physiological mutant showing retarded panicle development. RGN 12:202-203.

Kinoshita, T., Y. Hidano and M. Takahashi, 1977. A mutant 'long hull sterile' found out in the rice variety, 'Sorachi'. -Genetical studies on rice plant, LXVII- Mem. Fac. Agr. Hokkaido Univ. 10(3): 247-268. (in Japanese with English summary)

Niikura, S., I. Takamure and T. Kinoshita. 1992. Character expression of leafy hull sterile (lhs-1) in rice. Japan. J. Plant Breed. 42 (Suppl. 2): 288-289. (in Japanese)


Table 1. Combined segregations of mutant genes in F2 populations
Cross
combination
A:B
F2 segregation

Total

Goodness of fit
AB
Ab
aB
ab
Ratio 
χ2
p
N-135 x H -726

H-726 x N-180

Lhs:dp-2 

lhs:.rp (t)

194

191

56

57

71

60

23

321

331

9:3:4 

9:3:3:1

2.36

0.86

0.3-0.4

0.8-0.9