Acta agriculturae Slovenica, 117/3, 1–11, Ljubljana 2021
doi:10.14720/aas.2021.117.3.2114 Original research article / izvirni znanstveni članek
Improvement ability of male parent by gibberellic acid application to 
enhancing the outcrossing of cytoplasmic male sterility rice lines
Hassan HAMAD
 1
, Elsayed GEW AILY
 1
, Adel GHONEIM
 2, 3
, Mohamed SHEHAB
 1
, Neama EL-KHOLLY
 
1
Received February 22, 2021; accepted June 17, 2021.
Delo je prispelo 22. februarja 2021, sprejeto 17. junija 2021
1 Rice Research and Training Center, 33717, Sakha, Kafr Elsheikh, Field Crops Research Institute, Agricultural Research Center, Egypt
2 Agricultural Research Center, Field Crops Research Institute, Giza 12112, Egypt
3 Corresponding author, e-mail: adelrrtc.ghoneim@gmail.com
Improvement ability of male parent by gibberellic acid ap-
plication to enhancing the outcrossing of cytoplasmic male 
sterility rice lines
Abstract: The study quantified the effect of gibberel-
lic acid (GA
3
) as a pre-flowering treatment for male parent 
Giza 178 R and the influence of male to female ratio (2R:10A, 
2R:12A, 2R:14A and 2R:16A) between male (R) to female (A) 
for two Cytoplasmic Male Sterility (CMS) lines (‘IR69625’ and 
‘G46’) on hybrid rice seed production. The main plots were 
occupied by CMS lines while; GA3 application for male par -
ent Giza 178R were arranged in the sub plots and male to 
female ratio was arranged in the sub-sub plots. The results 
indicated that, the, duration of floret opening, angle of floret 
opening, filaments exsertion, filaments length, anther length, 
plant height and number of tiller hill
-1 
of male parent Giza 
178R were significantly at 300 g GA
3
 ha
-1
 concentration. Plant 
height, panicle exsertion, panicle length, flag leaf angle and 
1000-grain mass of CMS were not significantly affected by 
the GA
3
 application for male parent and male to female ratio, 
while, number of fertile panicles hill
-1
, panicle mass, seed set, 
seed yield and harvest index of CMS lines were highly signifi-
cantly affected. The highest seed yield (2.880 and 2.950 t ha
-1
) 
was obtained by CMS line IR69625A using 300 g GA
3
 ha
-1
 of 
male parent Giza 178R with male to female ratio of 2R:14A 
during both seasons.
Key words: hybrid rice production; cytoplasmic male 
sterile lines; gibberellic acid (GA
3
); male to female ratio; pan-
icle exsertion
Izboljševanje sposobnosti moških staršev z giberilinsko ki-
slino za pospeševanje navskrižnega križanja citoplazmatsko 
moško sterilnih linij riža
Izvleček: Preučevan je bil učinek dodajanja giberilinske 
kisline (GA
3
) kot obravnavanja pred cvetenjem na moškega 
starša ‘Giza 178’ (R) in vpliv razmerja med moškimi (R) in 
ženskimi rastlinami (A) (2R:10A, 2R:12A, 2R:14A in 2R:16A) 
za dve citoplazmatsko moško sterilni liniji (CMS), ‘IR69625’ 
in ‘G46’ , na pridelek semena hibridnega riža. Raziskava je po-
trdila razlike v lastnostih navzkrižnega križanja in pridelku 
zrnja dveh CMS linij (IR69625A in G46A) pri uporabi šti-
rih koncentracij GA
3, 
uporabljenih dvakrat, pri 15-20  % in 
35-40 % latenju. CMS linije so bile na podploskvah, razmerje 
med moškimi (R) in ženskimi (A) rastlinami pa na njihovih 
podploskvah (2R:10A, 2R:12A, 2R:14A in 2R:16A). Rezultati 
so pokazali, da so se trajanje odpiranja cvetov (min), kot od-
prtega cveta (
0
), odstotek podaljšanih filamentov (%), dolžina 
filamentov (mm), dolžina prašnic (mm), višina rastlin (cm) in 
število poganjkov na sadilno mesto pri moškem staršu ‘Giza 
178’ značilno povečali pri uporabi 300 g GA
3
 ha
-1
.
Ključne besede: pridelovanje hibridnega riža; citoplaz-
matsko sterilne moške linije; giberilinska kislina (GA
3
); raz-
merje moških in ženskih rastlin; latenje

Acta agriculturae Slovenica, 117/3 – 2021 2
H. HAMAD et al .
1 INTRODUCTION
Hybrid rice breeding, which was initiated in Egypt 
has led to great improvement in rice production (Za-
man et al., 2002; Hamad, 2018). Breeding high-yielding 
hybrid rice is one of the promising potential strategies 
in Egypt for increasing rice production. The hybrid rice 
technology exploits the phenomenon of heterosis or 
hybrid vigor. The heterosis can be defined as the su-
periority of F1 when two genetically dissimilar parents 
are crossed (Sindhua and Kumar, 2002). The three-line 
rice breeding system which uses cytoplasmic male ster -
ile (CMS) lines (A), maintainer lines (B) and restorer 
lines (R) has been proven to be the most useful genetic 
tool in producing F1 hybrid in rice. 
The content of endogenous gibberellic acid (GA
3
) 
in male p lines with pollen abortive wild rice cyto-
plasm (wild abortive [WA] type male sterile [MS] line) 
is generally lower than that of fertile plants, therefore, 
resulting in spikelets unavailable for cross-pollination 
and producing lower seed yield (Lu, 1994; Pan et al., 
2013). Exogenous application of GA
3
 was done to cause 
the panicle base of the CMS line to emerge out of the 
leaf sheath (Gaballah, 2004; Gaballah et al., 2021). In 
addition, lower heading characteristics such as small 
spikelet openings, poor panicle layer carriage and poor 
stigma exsertion can severely reduce cross-pollination 
and limit seed yield production. Hence, hybrid rice seed 
production techniques should be improved to increase 
seed yields and reduce the cost of seeds (Virmani, 2002; 
Virmani et al., 2002). 
Egypt is currently using a number of CMS lines 
for the hybrid rice-breeding programs. However, no 
information is available on how these CMS lines will 
respond to GA
3
 application with reference to their 
heading characteristics. Such data are very important 
to generate baseline information whether genotypic 
variations exist among CMS lines in response to GA
3
 
pre-flowering treatment and whether such responses 
follow similar trends. This will also help in identifying 
CMS lines which are responsive to GA
3
 application to 
maximize their utilization in the development of new 
hybrid rice varieties with higher seed yield potential.
Therefore, the objective of this investigation was 
to study the performance of Giza178R male parents as 
affected by GA
3
 application rates and male to female ra-
tio on the growth characteristics and hybrid seed yield 
production of two CMS lines (IR69625A and G46A).
2 MATERIALS AND METHODS
2.1 EXPERIMENTAL SITE DESCRIPTION AND 
SOIL SAMPLES
The field experiment was conducted during 2019 
and 2020 rice growing seasons in Rice Research and 
Training Center (RRTC) experimental farm, Sakha, 
Kafr El-Sheikh, Egypt. Representative soil sample was 
taken from 0-20 cm depth before the growing season. 
The soil samples were air-dried, ground and passed 
through 2mm sieve. Composite soil samples were taken 
and analyzed for physical and chemical characteristics 
of the soil namely, electrical conductivity (EC,) pH, or -
ganic matter (OM), texture, cations and anions follow-
ing the standard methods as described by (Page et al., 
1982). The physico-chemical characteristics of the soil 
are presented in Table (1). 
2.2 EXPERIMENTAL LAYOUT
The experiment was set up as split split-plot design 
with three replications. The main plots were devoted to 
two CMS lines (IR69625A and G46A) for male parent 
male parent. The GA
3
 application rates (0, 150, 200 and 
300 g GA
3
 ha
-1
) for male parent Giza 178R was allocated 
to subplots and male to female ratio (2R:10A, 2R:12A, 
2R:14A and 2R:16A) between male (R) to female (A) 
was arranged in the sub-sub plots.
2.3 PLANT MATERIALS
They were obtained from international rice re-
search institute (IRRI) and China and contain the wild 
rice with abortive pollen CMS (Table 2).
2.4 CULTURAL PRACTICES
Phosphorus fertilizer was applied @ 36 kg P
2
O
5
 
ha
–1
 as superphosphate (15.5 % P
2
O
5
) as soil basal ap-
plication. Nitrogen fertilizer was applied @ 165 kg ha
–1
 
as urea. Two thirds of the recommended N fertilizer 
were added as soil basal application, and the other one 
third was applied at panicle initiation. Zinc sulphate at 
the rate of 50 kg ha
-1
 was added during soil preparation.
Rice seeds @ 15 kg of  the CMS Lines (IR69625A 
and G46A) and 5 kg for the male parent (Giza 178 R) 
were soaked in fresh water for 24 hours, then incubated 
for 48 hours to hasten early germination. To get a proper 
synchronization of flowering, the CMS line IR69625A 
(as female parent) was sown on May 
1st
 which is six 

Acta agriculturae Slovenica, 117/3 – 2021 3
Improvement ability of male parent by gibberellic acid application to enhancing the outcrossing of cytoplasmic male sterility rice lines
days earlier than the male parent ‘Giza 178 R’ while, the 
CMS line G46A (as female parent) was sown on 16 May. 
Thirty days old seedlings (3-4) per hill of R and A lines 
were transplanted by 3-4 and 2 seedlings per hill, re-
spectively). Row direction was perpendicular to wind 
direction. The row spacing maintained for R-R, R-A 
and A-A lines were 20, 30, and 15 cm, respectively. Hill 
spacing for both R and A lines was maintained at 15 
cm. Isolation space of 100 m was considered for CMS 
seed production. Moreover, the experimental field was 
surrounded by an additional 20 rows of R line to avoid 
any possibility of cross pollination. Every main plot was 
isolated by plastic barrier (2.5 m height) to avoid any 
pollen grain movement from treatment to another.
2.5 GIBBERELLIC ACID PREPARATION AND AP-
PLICATION
Gibberellic Acid (GA
3
) powder with 90.7 % purity 
was used. Since GA
3
 cannot be completely dissolved in 
distilled water. In 100 ml of ethanol alcohol (70 %), was 
used to dissolve the GA
3
 powder before it was mixed 
with water. Application of GA
3
 was done in two splits. 
The first split consisted of 40 % of the total amount of 
GA
3
 applied at 15-20 % heading. The second split in 
which the remaining 60 % of the total amount of GA
3
 
was applied at 35-40 % heading. Supplementary pol-
lination was done by shaking the pollen parent  (R line) 
with bamboo sticks. This operation was done 3-4 times 
between 9.30 am to 12.30 am for a period of 10 days. 
2.6 TRAIT EV ALUATION
At complete heading, duration of floret opening 
(min), angle of floret opening (
0
), filaments exertion 
(%), filaments length (mm) and anther length (mm) of 
male parent ‘Giza 178’ were recorded. Ten panicles of 
male parent ‘Giza 178’ from each plot were randomly 
collected to estimate the panicle length (cm). Also, five 
hills of male parent ‘Giza 178’ were randomly identified 
from each plot to estimate the plant height (cm) and 
number of tillers hill
-1
. Data was collected for CMS lines 
where it was days to heading 50 %, plant height (cm), 
panicle exsertion (%), flag leaf angle (
0
), 1000-grain 
mass (g), panicle length (cm), number of fertile panicles 
hill
-1
, panicle mass (g), seed set (%), seed yield (t ha
-1
), 
and harvest index (%). After harvesting, rice grain yield 
was estimated in each plot, and grain yield was adjusted 
to 14 % moisture content and converted to tons ha
-1
. 
Panicle exsertion % was estimated according to 
the following equation:
Panicle exsertion % =  
Seed set % was calculated according to the follow-
ing equation:
Seed set % = 
2.7 STATISTICAL ANALYSIS
All data collected were subjected to standard 
statistical analysis of variance following the method 
described by Gomez and Gomez (1984). Different 
means were compared by Duncan’s multiple range test 
(DMRT) with a 5 % probability level.
3 RESULTS AND DISCUSSION
3.1 EFFECT OF GA
3
 APPLICATION RATES ON 
GROWTH TRAITS OF MALE PARENT
The effect of different GA
3
 application rates on male 
parent traits such as duration of floret opening, angle of 
floret opening, filaments exertion, filaments length, an-
Table 1: The physical and chemical characteristics of the soil during 2019 and 2020 growing seasons
Season pH
EC 
(dS m
-1
)
NPK 
(mg kg
-1
)
Clay  
(%)
Silt  
(%)
Sand  
(%)
OM 
(%)
2019 7.84 1.50 339 13.7 329 56.4 28.3 15.3 1.35
2020 7.89 1.59 368 14.7 359 58.6 27.1 14.3 1.40
Table 2: Cytoplasmic male sterile (CMS) lines used for 
evaluation
CMS Lines Cytoplasmic source Origin
IR 69625A 
G46A
Wild abortive (W A) CMS line 
Gambiaca CMS line
IRRI 
China
EC; Electrical conductivity, OM; Organic matter

Acta agriculturae Slovenica, 117/3 – 2021 4
H. HAMAD et al .
ther length, plant height, number of tiller hill
-1
and pani-
cle length, are presented in (Table 3). The results indi-
cated that, GA
3
 applied for male parent up to 300 g GA
3
 
ha
-1
 recorded a significant increase in duration of floret 
opening, angle of floret opening, filaments exertion, 
filaments length, anther length, plant height, number of 
tiller hill
-1
 and panicle length as compared with GA
3 
0 
g ha
-1
 treatment in both seasons. Application of 300 g 
GA
3
 ha
-1
 on male parent gave the highest duration of 
floret opening (130.59 and 129.94 min), the maximum 
angle of floret opening (41.96 and 44.30 
0
), the highest 
values of filaments exertion (80.81 and 90.15 %), fila-
ments length (9.34 and 9.78 mm), anther length (3.35 
and 3.55 mm), the tallest plant (126.49 and 127.36 cm), 
the highest number of tiller hill
-1
 (24.83 and 25.19) and 
longest panicle (25.71 and 25.90), during 2019 and 2020 
seasons, respectively. A significant increase in panicle 
exsertion was observed on GA
3
 application. The highest 
value of panicle exsertion was observed at the rate of 
300 g GA
3
 ha
-1
, regardless of CMS lines used, indicat-
ing that CMS lines were sensitive to exogenous GA
3
 ap-
plication, hence, the problem of the leaf sheath enclos-
ing the panicle could be alleviated by GA
3
 application. 
Panicle exsertion influenced the percentage of exposed 
spikelets available for pollination, as higher panicle ex-
sertion means a greater number of exposed spikelets. It 
also tended to scatter the panicle branches providing 
more space for each spikelet to trap airborne pollen. 
The increase in panicle exsertion was mainly a function 
of the elongating topmost internode in response to GA
3
 
application that consequently pushes the panicle out of 
the flag leaf sheath. Therefore, poor panicle exsertion of 
CMS lines was due to the inability of the topmost inter -
nodes to elongate during heading stage. The lowest val-
ues of above-mentioned traits were obtained with GA
3 
0 g
 
ha
-1
 application rate (Table 3). The improved floral 
traits of male parent were due to increased activity of 
cell division, enlargement and elongation. Gibberellins 
are plant hormones that regulate various processes of 
plant growth and development, which are particular -
ly important in cell elongation (Hedden and Phillips, 
2000). Table 3: Floral traits and growth characters of male parent (Giza 178) as affected by GA
3
 application rates during 2019 and 2020 growing seasons
GA
3
 application  
rate (g ha
-1
) 
Duration of  
floret opening 
(min)
Angle of floret  
opening (
0
)
Filaments  
exsertion (%)
Filaments  
length (mm)
Anther  
length (mm)
Plant  
height (cm)
Number of  
tillers hill
-1
Panicle  
length (cm)
2019 2020 2019 2020 2019 2020 2019 2020 2019 2020 2019 2020 2019 2020 2019 2020
0 
150 
200 
300 
46.75d
68.86c
90.37b
130.5a
48.09d
67.91c
90.62b
129.9a
24.30d
31.56c
36.70b
41.96a
25.03d
32.36c
38.40b
44.30a
44.31c
69.54b
80.47a
80.81a
43.52d
70.07c
79.82b
90.15a
4.32d
6.76c
8.02b
9.34a
4.55d
7.19c
8.12b
9.78a
1.35d
2.28c
2.68b
3.35a
1.65d
2.62c
2.97b
3.55a
100.2d
109.6c
120.0b
126.4a
98.93d
110.47c
120.88b
127.36a
16.05d
19.21c
22.17b
24.83a
15.43d
20.32c
22.38b
25.19a
19.55d
21.87c
23.84b
25.71a
19.33d
20.87c
23.82b
25.90a
F- Test ** ** ** ** ** ** ** ** ** ** ** ** ** ** ** **
* = Significant at 0.05 level, ** = Significant at 0.01 level and NS = Not significant. Means in the same column designated by the same letter are not significantly different at 5 % level

Acta agriculturae Slovenica, 117/3 – 2021 5
Improvement ability of male parent by gibberellic acid application to enhancing the outcrossing of cytoplasmic male sterility rice lines
3.2 F
1 
SEEDS OF CMS LINES CHARACTERISTIC 
AS AFFECTED BY GA
3 
APPLICATION FOR 
MALE PARENT AND MALE TO FEMALE RA-
TIO
Days to 50 % heading, plant height, panicle ex-
sertion, flag leaf angle, panicle length and 1000-grain 
mass were not significantly affected by GA
3 
application 
rates for male parent and male to female ratio (Table 
4). The results showed that there were significant differ -
ences between the two CMS lines IR69625A and G46A. 
Where CMS line IR69625A gave the longest duration 
to 50 % heading, produced the tallest plants, the long-
est panicle exsertion, the highest panicle length and the 
increased flag leaf angle during both seasons. On the 
other hand, the CMS line G46A recorded the highest 
1000-grain mass during the both seasons. The variation 
between the CMS lines could be attributed to the dif-
ference in genetic background. The results are in agree-
ment with those reported by (Hamad et al., 2015). They 
founded that, the different doses of GA
3
 showed highly 
significantly influence on panicle length and panicle ex-
sertion when 2:4 row ratio. Similar results agreement 
with those were reported by Ehsan and Robert (2019). 
Results in Table (4) also showed that, the all of interac-
tions were not significantly affected on days to 50 % 
heading, plant height, panicle exsertion, panicle length, 
flag leaf angle and 1000-grain mass in both growing 
seasons. 
Number of fertile panicles hill
-1
, panicle mass, seed 
set %, seed yield and harvest index % of two CMS lines 
as affected by doses of GA
3 
application rates for male 
parent and male to female ratio as well as their interac-
tions are shown in (Table 5). The results indicated that, 
the CMS line IR 69625A recorded the highest values of 
number of fertile panicles hill
-1
, panicle mass, seed set 
%, seed yield and harvest index % in both seasons. On 
the other hand, the CMS line G46A recorded the lowest 
values of number of fertile panicles hill
-1
, panicle mass, 
seed set, seed yield and harvest index % in both seasons 
(Table 5). The variation between the CMS lines could 
be attributed to the difference in genetic background. 
The results are in agreement with those reported by 
Gaballah, (2004). Results in Table (5) also showed that 
application GA
3
 on the male parent had a high signifi-
cant effect on the number of fertile panicles hill
-1
, pan-
icle mass, seed set, seed yield and harvest index %. The 
dose of GA
3
 application at 300 g ha
-1
 for male parent 
recorded the highest values of number of fertile panicle 
hill
-1
, panicle mass, seed set, seed yield and harvest in-
dex % 2019 and 2020 seasons, while the lowest values 
recoded by control (GA
3 
0 g ha
-1
) in both seasons. The 
increase in plant height is due to increased activity of 
cell division, enlargement and elongation. Gibberellins 
are plant hormones that regulate various processes of 
plant growth and development, which are particularly 
important in stem elongation which enhances the cross 
pollination between both parents. The results are in 
agreement with those reported by (Hedden and Phil-
lips, 2000; Sakamoto et al., 2004; Sun, 2004; Tiwari et 
al., 2011).  Male to female ratio significantly influenced 
number of fertile panicle hill
-1
, panicle mass, seed set, 
seed yield and harvest index %. The male to female ra-
tio 2R:14A recorded the highest values number of fer -
tile panicles hill
-1
, panicle mass, seed set, seed yield and 
harvest index% during both seasons. This might be due 
to that the application of GA
3
 for male parent led to 
a noticeable improvement in the characteristics) plant 
height, panicle exsertion, flag leaf angle, panicle length) 
of the male parent, which made it able to pollinate the 
highest number of male lines consequently, increase the 
number of fertile panicle hill
-1
 and seed yield. On the 
other hand, the male to female ratio 2R:10A recorded 
the lowest values of number of fertile panicles hill
-1
, 
panicle mass, seed set, seed yield and harvest index % 
during the both seasons. 
3.3 INTERACTION EFFECT
All types of interactions among CMS lines, doses 
of GA
3
 application rates for male parent and male to 
female ratio had highly significant effect on number of 
fertile panicles hill
-1
, panicle mass, seed set, seed yield 
and harvest index during 2019 and 2020 seasons (Table 
5). 
The results in Table (6) indicated that, the interac-
tion between the CMS lines and GA
3
 different applica-
tion rates for male parent were highly significantly af-
fected on number of fertile panicles hill
-1
, panicle mass, 
seed set, seed yield and harvest index % in both seasons. 
The CMS line IR69625A, with dose of GA
3
 at the rate of 
300 g ha
-1
 for male parent recorded the highest values of 
number of fertile panicles hill
-1
, panicle mass, seed set, 
seed yield and harvest index % in both seasons. On the 
contrary, the CMS line G46A with 0 g GA
3 
ha
-1
 applica-
tion rates for male parent recoded the lowest values of 
number of fertile panicles hill
-1
, panicle mass, seed set, 
seed yield and harvest index % in 2019 and 2020 sea-
sons. The results are in agreement with those reported 
by Sirajul et al. (2005); Gavino et al. (2008).

Acta agriculturae Slovenica, 117/3 – 2021 6
H. HAMAD et al .
Table 4: Genotypic variations in panicle exsertion and other morphological traits between CMS lines in response to GA
3
 pre-flowering treatment
Days to 50 % heading Plant height (cm) Panicle exsertion (%) Panicle length (cm) Flag leaf angle (
0
) 1000-grain mass (g)
2019 2020 2019 2020 2019 2020 2019 2020 2019 2020 2019 2020
CMS lines(L)
IR69625A
G46A
102.60a
85.50b
103.46a
87.36b
117.26a
96.38b
117.97a
97.00b
77.25a
75.41b
78.16a
77.32b
23.31a
22.42b
24.25a
23.25b
38.90a
37.21b
40.29a
39.60b
24.30a
25.77b
24.24a
25.45b
F-test ** ** ** ** ** ** ** ** ** ** ** **
GA
3
 doses for male parent(G)
0
150 
200 
300 
94.15
94.13
94.95
93.72
95.60
95.36
95.45
95.22
106.79
106.87
106.79
106.85
107.47
107.51
107.44
107.49
76.34
76.28
76.40
76.31
78.70
78.59
78.33
78.48
22.76
22.84
22.97
22.88
23.81
23.76
23.77
23.65
37.71
38.18
38.19
38.15
39.35
39.35
39.23
39.62
25.06
25.02
25.00
25.04
24.88
24.85
24.84
24.77
F-test NS NS NS NS NS NS NS NS NS NS NS NS
Male to female ratio (W)
2R:10A
2R:12A
2R:14A
2R:16A
93.99
94.25
93.82
94.14
95.34
95.18
95.41
95.72
106.93
106.84
106.89
106.64
107.52
107.62
107.30
107.46
76.33
76.09
76.38
76.53
78.71
78.52
78.33
78.58
22.95
22.67
22.93
22.91
23.65
23.82
23.75
23.70
38.16
38.71
37.75
38.27
39.25
39.27
39.23
39.24
25.04
25.03
25.01
25.04
24.83
24.87
24.80
24.84
F-test NS NS NS NS NS NS NS NS NS NS NS NS
L × G
L × W
G × W
L × G × W
NS
NS
NS
NS
NS
NS
NS
NS
NS
NS
NS
NS
NS
NS
NS
NS
NS
NS
NS
NS
NS
NS
NS
NS
NS
NS
NS
NS
NS
NS
NS
NS
NS
NS
NS
NS
NS
NS
NS
NS
NS
NS
NS
NS
NS
NS
NS
NS
* = Significant at 0.05 level, ** = Significant at 0.01 level and NS = Not significant. Means in the same column designated by the same letter are not significantly different at 5% level

Acta agriculturae Slovenica, 117/3 – 2021 7
Improvement ability of male parent by gibberellic acid application to enhancing the outcrossing of cytoplasmic male sterility rice lines
Table 5: Effect of CMS lines, doses of GA
3
 application for male parent and male to female ratio as well as their interactions on seed yield and other morphological traits
Number of fertile panicles 
hill
-1
Panicle mass (g) Seed set (%) Seed yield (t ha
1
) Harvest index (%)
2019 2020 2019 2020 2019 2020 2019 2020 2019 2020
CMS lines (L)
IR69625A
G46A
17.80a
15.92b
19.65a
16.94b
2.67a
2.49b
2.71a
2.51b
34.00a
31.14b
34.90a
33.58b
1.90a
1.69b
2.08a
1.84b
19.26a
17.82b
20.05a
18.50b
F-test ** ** ** ** ** ** ** ** ** **
GA
3
 doses for male parent (G)
0
150
200
300 
14.29d
16.16c
17.40d
19.58a
15.39d
17.06c
19.12b
21.62a
1.91d
2.47c
2.83b
3.10a
1.89d
2.51c
2.86b
3.15a
25.60d
31.28c
33.97b
35.41a
26.84d
32.69c
37.91b
39.52a
1.19d
1.58c
2.02b
2.32a
1.36d
1.72c
2.20b
2.56a
16.02d
17.91c
19.30b
20.92a
16.75d
18.27c
20.00b
21.96a
F-test ** ** ** ** ** ** ** ** ** **
Male to female ratio (W)
2R:10A
2R:12A
2R:14A
2R:16A
15.66d
16.93c
17.64a
17.20b
17.16d
18.13c
19.12a
18.78b
2.23c
2.51b
2.84a
2.73ab
2.25d
2.50c
2.96a
2.74b
28.85d
31.49c
33.59a
32.33b
31.87c
33.76b
36.30a
35.03a
1.57d
1.76c
2.03a
1.82b
1.71c
1.90bc
2.19a
2.03ab
17.16d
18.05c
19.88a
19.07b
17.79d
18.90c
20.62a
19.77b
F-test ** ** ** ** ** ** ** ** ** **
L × G
L × W
G × W
L × G × W
**
*
**
**
**
*
**
**
**
**
**
**
**
**
**
**
**
**
**
**
**
**
**
**
**
**
*
**
**
**
*
**
**
**
*
**
**
**
*
**
* = Significant at 0.05 level, ** = Significant at 0.01 level and NS = Not significant. Means in the same column designated by the same letter are not significantly different at 5% level

Acta agriculturae Slovenica, 117/3 – 2021 8
H. HAMAD et al .
Table 6: Effect of interaction between CMS liens and doses of GA
3
 application for male parent on panicle characteristics and 
yield during 2019 and 2020 seasons
CMS 
Lines  
(L)
GA
3
 doses for 
male parent (G)
Number of fertile 
panicles hill
-1
Panicle mass (g) Seed Set (%)
Seed 
yield (t ha
-1
)
Harvest 
Index (%)
2019 2020 2019 2020 2019 2020 2019 2020 2019 2020
IR6962A 0
150
200
300
15.50d
16.75c
18.36b
20.55a
16.21d
18.14c
20. 5b
23.71a
1.95d
2.50c
2.90ab
3.22a
1.92d
2.62bc
3.03ab
3.27a
25.69f
31.93d
34.5bc
35.82a
27.19f
33.4d
38.7b
40.2a
1.35e
1.72d
2.10bc
2.43a
1.48de
1.85c
2.27b
2.71a
16.48e
18.43c
20.03b
22.11a
17.23de
19.21c
20.68b
22.99a
G46A 0
150
200
300
13.07f
15.57d
16. 4c
18.61b
14.57e
15.98d
17.67c
19.54b
1.87d
2.42c
2.76b
2.88ab
1.87d
2.46c
2.70bc
3.03ab
25.51f
30.64e
33.40c
34.9ab
26.49i
31.9e
37.0c
38.8b
1.14f
1.45e
1.97c
2.21b
1.24e
1.58d
2.12bc
2.41b
15.57e
17.40d
18.58c
19.73b
16.18e
17.54d
19.23c
20.94b
Means in the same column designated by the same letter are not significantly different at 5 % level
The results in Table (7) showed that the interac-
tion between CMS lines and male to female ratio were 
significantly affected number of fertile panicles hill
-
1
, panicle mass, seed set, seed yield and harvest index 
% in both seasons. The male to female ratio of 2R:14A 
with CMS line IR69625A, recorded the highest values 
of number of fertile panicles hill
-1
, panicle mass, seed 
set %, seed yield and harvest index % in both seasons. 
This may be due to the optimum availability of pollen 
that led to the highest effective grain formation. On the 
other hand, the lowest values of number of fertile pani-
cles hill
-1
, panicle mass, seed set %, seed yield and har -
vest index % were obtained by CMS line G46A when 
male to female ratio of 2R:10A during 2019 and 2020 
seasons. The results are in agreement with those report-
ed by Abo-Y oussef (2009). 
The results in Table (8) showed that the interaction 
between doses of GA
3 
application for male parent and 
male to female ratio was significantly affected number 
of fertile panicles hill
-1
, panicle mass, seed set %, seed 
yield and harvest index (%) in both seasons. The male 
to female ratio 2R:14A with applied 300 g GA
3
 ha
-1
 re -
Table 7: Effect of interaction between CMS lines and male to female ratio on panicle characteristics and yield during 2019 and 
2020 seasons
CMS Lines
Male to Fe-
male ratio 
Number of fertile 
panicles hill
-1
Panicle mass (g)
Seed 
Set (%)
Seed 
yield (t ha
-1
)
Harvest  
Index (%)
2019 2020 2019 2020 2019 2020 2019 2020 2019 2020
IR69625A 2R:10A
2R:12A
2R:14A
2R:16A 
16.84c
17.79b
18.60a
17.92b
18.18c
19.70b
20.62a
20.12a
2.31d
2.61bc
2.93a
2.8ab
2.30d
2.59bc
3.11a
2.84ab
29.17d
31.81b
34.17a
32.8ab
32.3cd
34.23b
37.29a
35.69b
1.71cd
1.85bc
2.15a
1.88bc
1.84c
2.03b
2.32a
2.12ab
18.0de
18.8cd
20.57a
19.59b
18.84c
19.67b
21.33a
20.3ab
G46A 2R:10A
2R:12A
2R:14A
2R:16A 
14.47e
16.07d
16.6cd
16.4cd
16.14e
16.5cd
17.6cd
17.4d
2.16d
2.41cd
2.75ab
2.64b
2.20d
2.41cd
2.80ab
2.64bc
28.54d
31.17c
33.02a
31.8bc
31.38d
33.29c
35.3b
34.36b
1.42e
1.66d
1.92b
1.77cd
1.59d
1.76cd
2.07ab
1.9bc
16.29f
17.26e
19.1bc
18.55c
16.74d
18.14c
19.92b
19.1bc
Means in the same column designated by the same letter are not significantly different at 5 % level

Acta agriculturae Slovenica, 117/3 – 2021 9
Improvement ability of male parent by gibberellic acid application to enhancing the outcrossing of cytoplasmic male sterility rice lines
Table 8: Effect of interaction between doses of GA
3
 application for male parent and male to female row ratio on panicle char -
acteristics and yield during 2019 and 2020 seasons
GA
3
 doses for male 
parent  
(g ha
-1)
Male to 
female  
ratio
Number of fertile  
panicles hill
-1
Panicle  
mass (g)
Seed  
set (%)
Seed yield  
(t ha
-1
)
Harvest  
Index (%)
2019 2020 2019 2020 2019 2020 2019 2020 2019 2020
0 2R:10A
2R:12A
2R:14A
2R:16A 
14.15f
14.53f
14.25f
14.22f
14.61h
15.29gh
15.92g
15.74g
1.84d
1.92d
1.94d
1.94d
1.78e
1.88e
1.99e
1.91e
25.50e
25.46e
25.7de
25.6de
26.57d
26.92d
27.11d
26.75d
1.20g
1.29fg
1.25fg
1.24g
1.28g
1.37f
1.46f
1.34f
15.59g
16.0fg
16.2fg
16.2fg
16.51f
16.66f
17.14ef
16.72f
150 2R:10A
2R:12A
2R:14A
2R:16A 
15.57e
16.17de
16.60d
16.30de
16.00g
16.67f
17.91e
17.67e
1.93d
2.27c
2.92b
2.76b
1.98e
2.35d
3.00c
2.86c
28.28d
31.26c
33.60b
32.00c
28.68d
32.01c
36.10b
33.99c
1.39fg
1.55ef
1.78de
1.59de
1.48f
1.57f
1.99d
1.82e
16.6fg
17.51e
19.04c
18.45e
16.67f
18.19e
19.67d
18.98d
200 2R:10A
2R:12A
2R:14A
2R:16A 
16.01de
17.27c
18.48b
17.85c
17.62ef
19.30d
20.00cd
19.56d
2.48c
2.79b
3.11a
2.94b
2.48d
2.74cd
3.36ab
2.88c
29.6cd
34.31b
37.00a
34.97b
34.45c
37.50b
40.40a
39.2ab
1.70de
1.95c
2.33b
2.15c
1.86d
2.09c
2.50b
2.34bc
17.45e
18.62e
21.0bc
20.07c
18.10e
19.61d
21.71b
20.59cd
300 2R:10A
2R:12A
2R:14A
2R:16A 
16.90d
19.77b
21.23a
20.43a
20.43cd
21.27bc
22.65a
22.1ab
2.69b
3.07ab
3.39a
3.27a
2.77c
3.03bc
3.49a
3.31ab
32.03c
34.94b
38.00a
36.67a
37.81b
38.6ab
41.59a
40.09a
1.92c
2.20b
2.78a
2.39b
2.25c
2.57ab
2.83a
2.61a
18.9de
20.0cd
23.16a
21.53b
19.90d
21.17c
23.99a
22.80a
Means in the same column designated by the same letter are not significantly different at 5 % level
corded the highest values of number of fertile panicles 
hill
-1
, panicle mass, seed set (%), seed yield and harvest 
index (%) in both seasons. On the other hand, the male 
to female row ratio 2R:10A without GA
3
 application 
gave the lowest values number of fertile panicles hill
-1
, 
panicle mass, seed set %, seed yield and harvest index % 
in both seasons. The results are in agreement with those 
reported by Rahman et al. (2010) and Abo-Youssef et 
al. (2017). 
The results in Table (9) showed that the interaction 
among CMS lines, doses of GA
3
 application for male 
parent and male to female ratio was significantly affect-
ed number of fertile panicles hill
-1
, panicle mass, seed 
set, seed yield and harvest index in both seasons. The 
highest values of number of fertile panicles hill
-1
, pani-
cle mass, seed set %, seed yield and harvest index (%) 
were obtained with the CMS line IR69625A by 300 g 
GA
3
 ha
-1
 for male parent when male to female ratio was 
2R:14A during both seasons. While the lowest values of 
number of fertile panicles hill 
-1
, panicle mass, seed set, 
seed yield and harvest index (%) produced by CMS line 
G46A when using male to female ratio 2R:10A with-
out GA
3
 application in both seasons. The results are in 
agreement with those reported by Riaz et al. (2019); 
Ghoneim (2020).

Acta agriculturae Slovenica, 117/3 – 2021 10
H. HAMAD et al .
4 CONCLUSION
The study was conducted to assess the optimal GA
3
 
dose on male parent and row ratio between male to fe-
male for two CMS lines. The results indicated that, the 
foliar application of GA
3
 significantly increased panicle 
exsertion, seed set and seed yield of CMS lines at 300 
g ha
-1
 concentration. Increase in seed yield was highly 
influenced by the increase in of seed set % presumably 
as a result of higher panicle exsertion, wider flag leaf 
angle, higher degree of spikelet openings. The applica-
tion of GA
3
 on male parent Giza 178R led to a notice-
able improvement in its characteristics such as dura-
tion of floret opening, angle of floret opening, filaments 
Table 9: Effect of interaction among CMS lines, doses of GA
3
 application for male parent and male to female ratio on panicle 
characteristics and yield during 2019 and 2020 seasons
CMS  
Lines 
(L)
GA
3
 doses 
for male 
parent  
(G)
Male to  
female  
ratio 
Number of fertile  
panicles hill
-1
Panicle mass 
(g)
Seed set 
(%)
Seed yield 
(t ha
-1
)
Harvest 
Index (%)
2019 2020 2019 2020 2019 2020 2019 2020 2019 2020
IR69625A 0 2R:10A
2R:12A
2R:14A
2R:16A 
15.54ef
15.65ef
15.40ef
15.42ef
15.20e
16.08de
16.87cde
16.67cde
1.87fg
1.98fg
1.96fg
1.98fg
1.79g
1.90efg
2.01efg
1.96efg
25.60h
25.50h
25.86h
25.79h
26.89hi
27.01hi
27.70hi
27.15hi
1.31fg
1.39fg
1.32fg
1.36fg
1.36g
1.49g
1.62fg
1.45g
16.01fg
16.54fg
16.72fg
16.65fg
17.01h
17.20h
17.96gh
17.15h
150 2R:10A
2R:12A
2R:14A
2R:16A 
16.53de
16.70de
17.02cd
16.76d
17.00cde
18.13c
18.91bc
18.53c
1.89fg
2.21f
3.03b
2.87b
2.00efg
2.41ef
3.15bc
2.97bc
28.76g
32.01de
34.40b
32.54d
29.31gh
32.80f
36.80de
34.70ef
1.53f
1.67ef
1.95cde
1.72def
1.64fg
1.78ef
2.12cde
1.85ef
17.42f
18.00ef
19.40de
18.90e
18.04gh
19.10fg
20.03ef
19.65f
200 2R:10A
2R:12A
2R:14A
2R:16A 
16.88d
18.27c
19.66bc
18.68c
18.03cd
21. 00b
21.98ab
21.24b
2.61de
2.90b
3.16b
2.92bc
2.55de
2.92bc
3.62a
3.02bc
30.02ef
34.47cd
37.80a
35.90b
35.40e
38.10cd
41.50a
40.03bc
1.77def
2.02d
2.44bc
2.15cd
1.97ef
2.16de
2.60bc
2.36cd
18.20ef
19.25de
21.87b
20.79bc
19.01fg
20.20ef
22.39c
21.10de
300 2R:10A
2R:12A
2R:14A
2R:16A 
18.50c
20.55a
22.31a
20.83ab
22.50a
23.60a
24.70a
24.02a
2.86c
3.35a
3.57a
3.50a
2.87bcd
3.11b
3.67a
3.42ab
32.29de
35.27b
38.60a
37.13a
37.88de
39.02c
43.15a
40.88ab
2.11cd
2.27bc
2.88a
2.45bc
2.38bc
2.70ab
2.95a
2.81a
20.50bc
21.60bc
24.30a
22.03bc
21.30d
22.19c
24.95a
23.50b
G46A 0 2R:10A
2R:12A
2R:14A
2R:16A 
12.76g
13.40fg
13.10g
13.02g
14.41e
14.50e
14.56e
14.42e
1.80g
1.85g
1.92fg
1.90fg
1.77g
1.86fg
1.97efg
1.86fg
25.40h
25.42h
25.70h
25.55h
26.24i
26.83hi
26.52hi
26.35i
1.08g
1.19fg
1.17fg
1.12fg
1.20g
1.24g
1.30g
1.23g
15.17g
15.55fg
15.73fg
15.81fg
16.00i
16.11hi
16.31hi
16.29hi
150 2R:10A
2R:12A
2R:14A
2R:16A 
14.60ef
15.63e
16.20d
15.84e
15.00e
15.20e
16.90cde
16.80cde
1.96fg
2.32ef
2.80cd
2.65de
1.95ef
2.28ef
2.84bc
2.75cd
27.80gh
30.50ef
32.80de
31.46ef
28.04h
31.21g
35.40ef
33.28f
1.24fg
1.46ef
1.61de
1.47ef
1.31g
1.36g
1.85ef
1.78ef
15.89fg
17.02f
18.67ef
18.00ef
15.29i
17.27h
19.30fg
18.30g
200 2R:10A
2R:12A
2R:14A
2R:16A 
15.22e
16.26d
17.30d
17.02d
17.20cd
17.60cd
18.01c
17.88c
2.35e
2.67cde
3.06b
2.96b
2.40ef
2.56de
3.10b
2.74cd
29.20fg
34.15c
36.20a
34.03cd
33.50f
36.90de
39.30cd
38.51cd
1.62de
1.88d
2.21bc
2.15cd
1.74efg
2.02ef
2.40bc
2.32cde
16.69fg
17.98ef
20.29c
19.35cd
17.18h
19.02fg
21.03de
20.07ef
300 2R:10A
2R:12A
2R:14A
2R:16A 
15.30e
18.98bc
20.14ab
20.02b
18.36c
18.94bc
20.59ab
20.26b
2.51d
2.79cd
3.20b
3.03b
2.66cd
2.95bc
3.30ab
3.20b
31.76e
34.60cd
37.39a
36.20ab
37.73de
38.20cd
40.02bc
39.30cd
1.73de
2.12cd
2.68a
2.32b
2.11cde
2.43bc
2.71ab
2.40bc
17.39ef
18.47e
22.02b
21.02bc
18.50g
20.14ef
23.02b
22.09c
* = Significant at 0.05 level, ** = Significant at 0.01 level and NS = Not significant. Means in the same column designated by the same letter are 
not significantly different at 5 % level
exsertion, filaments length, anther length, plant height, 
number of tillers hill
-1
, panicle length, plant height and 
panicle exsertion. The CMS line IR69625A produced 
the highest seed yield with application of 300 g GA
3
 ha
-1
 
on male parent when male to female ratio was 2R:14A. 
The highest values of seed yield (2.880 and 2.950 t ha
-1
) 
in 2019 and 2020 seasons were obtained by CMS line 
IR69625A with the application rate of 300 g GA
3
 ha
-1
 
on male parent when male to female ratio was 2R:14A.
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