29. Modification of glume characters due to genic interactions and environmental conditions

Itsuro TAKAMURE and Toshiro KINOSHITA

Plant Breeding Institute, Faculty of Agriculture, Hokkaido University, Sapporo, 060 Japan

For malformation of lemma and palea, more than ten genes have already been reported together with the mode of inheritance (Kinoshita and Takahashi


Fig. 1. Variation in long sterile lemmas of various genotypes. From left to right: dominant type (+G-2), super long type (g-1 G-2), normal (+ +), recessive type (9-1,+). 

Table 1. Combined segregation between gel and G-2 in F2 populations
===============================================================================
Cross               F2 segregation             Total           Goodness of fit
combination    ==============================            ======================
                    +G-2  g-1 G-2  + +  g-l+             X2(9: 3: 3: 1)    P
===============================================================================
83N107OxH-82 Obs.    116     30     38  12      196      1.59          0.7-0.6
83N107OXH-138Obs.     50     19     20  10       99      3.05          0.4-0.3
  Total      Obs.    166     49     58  22      295      1.54          0.7-0.6
===============================================================================
1991). There are two kinds of long sterile-lemma mutants expressed as a dominant or a recessive character. We obtained the seeds of a dominant long sterile lemma mutant through the courtesy of Dr. N.E. Jodon and Dr. E.M. Nowick. Both mutants were crossed with each other, and the F1 plants showed a dominant type of long sterile lemmas. Because of the difference in character expression, it was possible to classify the dominant, recessive and new types besides normal depending on the length and feature of the sterile lemmas, as shown in Fig. 1. We tentatively named the new type as "super long sterile lemmas" and assumed that the interaction between g-1 and G-2 caused the new character. Observed numbers fitted the values expected from a ratio of 9:3:3:1 showing an independent relation between g-1 and G-2 (Table 1). A new genotype having g-1 g-1 G-2 G-2 bred true in the progenies of the super long sterile lemmas.

A mutant line, M-1, characterized by various abnormalities of lemma and palea was used for the next experiment. A prominent fluctuation of this character was recognized under different environmental conditions such as green house and paddy field. In F2 populations a single recessive gene named mls-3(t) was respon- 

Table 2.  Segregation of malformed spikelets in F2 populations of the crosses
between Mutant-1 x testers
===============================================================================
Cross                     F2 segregation               Goodness of fit
combination           =====================    Total  ====================  
                       +    mls-3                     X2(3: 1)  P
===============================================================================
H-59xMutant-1   Obs.  138     38                 176  1.09  0.3-0.2
ws-10xMutant-1  Obs.  211     62                 273  0.76  0.4-0.3
Mutant-1xH-79   Obs.  133     47                 180  0.12  0.8-0.7
Mutant-1xH-126  Obs.  213     57                 270  2.18  0.2-0.1
     Total      Obs.  695    204                 899  2.55  0.2-0.1
===============================================================================
Homogeneity: X2=1.71    d.f.=3         p=0.7-0.6

Table 3.  Rate of malformed spikelets (%) in Mutant-1 under two temperature
conditions
===============================================================================
Temperature                   20 deg C    28 deg C
Heading time              Normal Late  Normal  Late
===============================================================================
Malformed palea and lemma   78.3  46.0  17.4  18.8
Malformed palea             14.1  22.8  21.9   8.5
Malformed lemma              0.2   0.5   0.5   0.0
Normal                       7.4  30.7  60.2  72.7
==============================================================================

Fig. 2. Correlation between seed fertility and rate of malformed spikelets in Mutant-1 population grown under two temperature conditions.

sible for this character (Table 2).

To examine the effect of temperature, the M-1 mutant line was grown in a growth cabinet illuminated with natural light, Koitotron S-152A under two different temperatures, 20 deg C and 28 deg C. As shown in Table 3, percentages of abnormal spikelets were significantly higher under the lower temperature, while the later tillerings had lower abnormality. Seed fertilities were also affected remarkably by the low temperature condition (Fig. 2). Thus it was demonstrated that the gene mls-3(t) is low temperature sensitive like genes rcn-1 and d-58(t) which are responsible for culm numbers and dwarfness, respectively (Takamure and Kinoshita 1985, 1992).

References

Kinoshita, T. and M. Takahashi, 1991. The one hundredth report of genetical studies on rice plant. -Linkage studies and future prospects- J. Fac. Agr. Hokkaido Univ. 65: 1-61.

Takamure, I. and T. Kinoshita, 1985. Inheritance and expression of reduced culm number character. Jpn. J. Breed. 35: 17-24.

Takamure, I. and T. Kinoshita, 1992. Inheritance of small grained dwarfness in rice showing temperature sensitivity. Mem. Fac. Agr. Hokkaido Univ. 18: 59-65.