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Article

Effects of Gibberellic Acid Application after Anthesis on Seed Vigor of Indica Hybrid Rice (Oryza sativa L.)

by
Xiaomin Wang
,
Huabin Zheng
,
Qiyuan Tang
*,
Wenwei Mo
and
Junjie Ma
College of agronomy, Hunan Agricultural University, Changsha 410128, China
*
Author to whom correspondence should be addressed.
Agronomy 2019, 9(12), 861; https://doi.org/10.3390/agronomy9120861
Submission received: 5 November 2019 / Revised: 3 December 2019 / Accepted: 6 December 2019 / Published: 9 December 2019
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Abstract

:
Gibberellic acid (GA3) application after anthesis is an important practice in hybrid rice seed production, and it plays diverse roles in seed quality and seed yield. The main objective of this study was to determine (1) the effects of GA3 application after anthesis on seed vigor and (2) the optimal GA3 dosage applied to Indica hybrid rice seed production. Field experiments of different GA3 dosages (15 g hm−2 and 30 g hm−2, respectively) after anthesis were conducted in 2016 and 2017, and seed vigor parameters, stigma vigor index, and seed yield were determined. We found that significant differences in seed vigor parameters by a standard germination test and a cool germination test were observed among different GA3 dosages after anthesis. Compared with the water spraying treatment, the germination percentage (GP) increased by 2.5–6.3%, and the vigor index (VI) increased by 8.9–19.8% from GA3 application after anthesis, respectively. Moreover, the stigma vigor index of the female parent was enhanced with an increasing GA3 dosage, and there were significant increases (7.5–16.0%) between the water spraying treatment and GA3 spraying treatments. There were positive significant relationships between the VI and stigma vigor index. Additionally, the seed yield of the GA3 application with 30 g hm−2 was 3.9% higher on average than that of the water spraying treatment. Therefore, our study suggests that seed vigor can be increased by GA3 application after anthesis, and GA3 application should be applied at a rate of 30 g hm−2 to improve seed vigor and maintain seed yield in Indica hybrid rice seed production.

1. Introduction

Seed vigor, which is one of the key components of seed quality and refers to the potential of a seed to germinate rapidly and uniformly under a wide range of field conditions, has been regarded as the essential requirement for agricultural production [1,2]. Hybrid rice seeds with high seed vigor are characterized by a fast germination speed, high germination percentage, and uniform seedling growth, which are beneficial for increasing yield and profits for farmers [2,3]. Recently, numerous studies have reported that the application of diverse chemical hormones to crop seeds by foliar spraying can improve seed quality [4,5,6,7]. Moreover, a number of reviews discuss the regulation of plant hormones on seed quality in detail [8,9,10,11]. These results indicate that seed vigor of Indica hybrid rice may be affected by exogenous chemical hormone application.
Gibberellic acid (GA3), a class of tetracyclic diterpenoid hormones, plays diverse roles in the stimulation and synchronization of flowering, seed development, and seed weight, and is widely used in the agricultural field [12,13,14,15,16,17]. Moreover, many studies have shown that GA3 plays an important role in seed quality [18,19,20]. Jagadeeswari et al. [21] and Parihar et al. [22] found that GA3 application resulted in a better seed set for seed production of a cytoplasmic male sterile line of hybrid rice. Salman et al. [6] found that GA3 application at the time of flowering in the onion cultivar produced seeds with a higher seedling vigor index. Additionally, it has been documented that GA3 stimulates the synthesis and production of hydrolases, resulting in the germination of seeds [11]. Therefore, GA3 application may affect seed vigor during Indica hybrid rice seed production.
Hybrid rice seed production technology has increased rice yield potential by 15–20% and has helped ensure food security in China over the past 30 years [23,24,25]. During hybrid rice seed production, the foliar application of GA3 at the start of panicle emergence has been widely adopted as an essential technology for improving panicle exsertion of male sterile lines. Moreover, many investigations were conducted in southern China, and we find that farmers still spray GA3 at low concentrations (15 g hm−2 or 30 g hm−2) for several days because GA3 application after anthesis can affect stigma properties, including stigma vigor [26,27], which ultimately influence the out-crossing rate and seed yield potential. Previous studies have reported the effect of GA3 application on seed yield during hybrid rice seed production [21,22,28]. However, knowledge is limited about the effect of GA3 application after anthesis on the seed vigor of hybrid rice. We hypothesized that a low concentration of GA3 application after anthesis can enhance stigma vigor and correspondingly improve seed vigor in Indica hybrid rice seed production. Therefore, the main objective of this study was to determine (1) the effects of GA3 application after anthesis on seed vigor, and (2) the optimal GA3 dosage applied to Indica hybrid rice seed production.

2. Materials and Methods

2.1. Experimental Sites and Hybrid Combinations

Field experiments were conducted at Guidong (25°08′ N, 113°91′ E), Ningyuan (25°06′ N, 111°95′ E), and Suining (25°59′ N, 110°14′ E), respectively, Hunan Province, China, in 2016 and 2017. Guidong has a moist subtropical monsoon climate with an annual average temperature of 15.4 ℃, an annual average rainfall of 1670.1 mm, and an annual sunshine duration of 1372.4 h. Ningyuan has a moist subtropical monsoon climate with an annual average temperature of 18.4 ℃, an annual average rainfall of 1422.1 mm, and an annual sunshine duration of 1650.7 h. Suining has a moist subtropical monsoon climate with an annual average temperature of 16.7 ℃, an annual average rainfall of 1320.0 mm, and an annual sunshine duration of 1527.8 h. The experimental Indica hybrid combinations used in this study viz. IIyou838 (II-32A as female parent × R838 as male parent; IIY-838), Longliangyou1813 (Longke638S as female parent × R1813 as male parent; LLY-1813), and Yliangyou9918 (Y58S as female parent × R928 as male parent; YLY-9918). IIY-838 and LLY-1813 were collected from Longping Seed Industry Co., Ltd. in Hunan Province, China. YLY-9918 was collected from Hengde Seed Industry Co., Ltd. in Hunan Province, China. IIY-838, LLY-1813, and YLY-9918 have been widely commercialized and planted over wide climatic areas in southern China. IIY-838 has a cumulative planting area of approximately 6.75 million hectares (China Rice Data Center, http://www.ricedata.cn/variety/varis/600751.htm), and YLY-9918 has a cumulative planting area of approximately 0.44 million hectares (China Rice Data Center, http://www.ricedata.cn/variety/varis/605611.htm). The climate of parent seed production sites is moist subtropical monsoon.

2.2. Field Experiments

Treatments were arranged in a randomized block design with three replications, and each plot was 2 × 50 m in size. In 2016 and 2017, there were three treatments including spraying water without gibberellic acid (GA3), GA3 application of 15 g hm−2 and GA3 application of 30 g hm−2. Additionally, spraying water without GA3 was the control treatment (CK). The GA3 applied in the field experiments was purchased from Longping Seed Industry Co., Ltd. in Hunan Province, China. The timing of the beginning of GA3 spraying treatments was the third day after heading, and GA3 spraying continued for three days. Before the practice of treatments, the GA3 application (300 g hm−2, 570 g hm−2 and 1050 g hm−2, respectively) for IIY-838, LLY-1813 and YLY-9918 was performed to change the general structure of hybrid combination populations in hybrid rice seed production.
Parental seedlings were raised on nursery beds and transplanted manually. The sowing and transplanting date are presented in Table 1, and the male parent was sowed twice. The row and plant spacing of the female parent was 133 × 200 mm and 3–4 seeds per plant, respectively. The row and plant spacing of the male parent was 167 × 300 mm and 2–3 seeds per plant, respectively. The parental row ratio was 2:12, and the spacing of the parent was 333 mm. Fertilizer, pesticide and herbicide management followed local practices for hybrid rice seed production.

2.3. Measurements of Seed Germination

2.3.1. Standard Germination Test

The germination tests were conducted after three months from the harvesting of hybrid seeds. A total of 100 healthy seeds with four replications were surface sterilized with 0.6% (6 g/L) sodium hypochlorite solution for 15 min and then rinsed three times with sterile distilled water. The seeds were then placed in a plastic box (12 × 12 × 5 cm) with two sheets of filter paper, and 9 mL of distilled water was added. The seeds were germinated in a growth chamber at (30 ± 1) ℃ for 7 days with a 12-h light/12-h dark photoperiod. Seeds were considered to be germinated when the root length reached the seed length and the shoot length reached half of the seed length [29]. The number of germinated seeds was counted every day for 7 days. At the end of the test period (7 days), the sum of daily counts was referred to as the final germination percentage (GP), and the germination index (GI) was calculated using the method described by the equation
GI = ∑ (Gt/t)
where Gt is the number of germinated seeds on day t. The germination energy (GE) was calculated using the method described by the equation
GE = ∑ (G1 + G2 + G3)/the total number of seeds × 100%
and the vigor index (VI) was calculated using the method described by the equation
VI = DW × GI
where DW is the dry weight of the seedlings of germinated seeds [30].

2.3.2. Cool Germination Test

The cool germination test was performed with four replications of 100 healthy sterilized seeds placed on two sheets of filter papers and moistened with distilled water as mentioned for the standard germination test. Seeds were germinated in a growth chamber at 20 ℃ for 14 days with a 12-h light/12-h dark photoperiod. Seeds were considered to be germinated when their root length reached the seed length and the shoot length was half of the seed length [29]. The number of germinated seeds was counted every 24 h for 14 days. The germination percentage (GP), germination index (GI), and vigor index (VI) were calculated as mentioned in the description of the standard germination test. The germination energy (GE) was calculated using the method described by the equation
GE = ∑ (G1 + G2 + G3 + G4 + G5 + G6)/the total number of seeds × 100%

2.3.3. Measurements of Stigma Vigor Index of Female Parent

At the full-bloom stage, 10 hills were chosen to sign spikelets that opened naturally on that day, and then the unsigned spikelets and bagged signed spikelets were removed in the afternoon. A total of 21 bags were treated, and each bag had 3 panicles. From the first day to the seventh day, 3 bags of spikelets were pollinated fully using pollen of the restore line every day, and then the spikelets were bagged after pollination. The out-crossing of bagged spikelets was recorded after 20 days of pollination. The stigma vigor index was calculated using the method described by equation [26]
stigma vigor index = (the out-crossing of the second day + the out-crossing of the
third day + the out-crossing of fourth day)/the out-crossing of first day

2.3.4. Measurements of Seed Yield and Its Components

At maturity, 10 hills were sampled diagonally from a 5 m2 harvest area to determine the yield components [31]. The panicle number was counted in each hill to determine the panicle number per m2 and was converted to per hm2. Panicles were hand-threshed, and the filled spikelets were separated from the unfilled spikelets by submerging them in tap water. Three subsamples of 30 g of filled spikelets and 3 g of unfilled spikelets were used to count the number of spikelets. The dry weight of the filled spikelets was determined after oven drying at 70 ℃ to a constant weight and conversion to 1000-grain weight. The spikelets per panicle and the out-crossing rate (100 × filled spikelet number/total spikelet number) were calculated. The hybrid rice seed production yield was determined from a 5 m2 area in each plot and assuming a standard moisture content of 0.14 g H2O g−1.

2.4. Data Analysis

Data were analyzed using analysis of variance (ANOVA) in Statistix 8.0 (Analytical software, Tallahassee, FL, USA), and multiple comparisons were explored using Fisher’s protected least-significant difference (LSD) test at the 0.05 probability level. Before analysis, the percentage data were transformed according to y = arcsin x 100 . In linear regression, the adjusted coefficient of determination R2 was used.

3. Results

3.1. Variation in Seed Vigor with Gibberellic Acid (GA3) Application

Seed vigor was significantly affected by GA3 application after anthesis in 2016 and 2017 (Table 2). Seed vigor, including GP, GE, GI, and VI, were enhanced with the increase in GA3 dosage after anthesis. The GP of GA3 application with 30 g hm−2 was 3.8% and 6.3% higher on average than the GA3 application with 15 g hm−2 and the CK, respectively. Moreover, there was a significant difference in the VI among the different treatments, and the VI of the GA3 spraying treatments (15 g hm−2 and 30 g hm−2) was 8.9% and 19.8% higher, respectively, than that of CK.
Variation in seed vigor was amplified in the cool germination test (Table 3). The GP of the GA3 spraying treatments in YLY-9918 and IIY-838 showed non-significant differences by the standard germination test in 2017. However, the highest GP (82.3% and 68.7%, respectively) obtained in the GA3 application with 30 g hm−2 was significantly higher than that in the GA3 application with 15 g hm−2 by the cool germination test. Moreover, the VI of the GA3 application with 30 g hm−2 was 66.7% and 57.1% higher than that in the CK, respectively. The GI of the GA3 application with 30 g hm−2 in IIY-838 was significantly higher than that of the CK by the cool germination test, while it was not significantly different by the standard germination test.

3.2. Variation in Seed Yield and Its Components with Gibberellic Acid (GA3) Application

Seed yield was affected by GA3 application after anthesis (Table 4). The highest seed yield (1860.6 kg hm−2 and 4781.4 kg hm−2, respectively) was obtained by the GA3 application with 30 g hm−2 and was 6.4% and 1.3% higher than that of the CK, respectively. Moreover, significant differences were found in the 1000-grain weight and out-crossing rate by GA3 application after anthesis, while there was no significant difference in the number of panicles and grains per panicle. The highest 1000-grain weight (21.7 g and 24.8 g, respectively) and the highest out-crossing rate (35.8% and 61.7%, respectively) were recorded by the GA3 application with 30 g hm−2. Consequently, the higher seed yield with GA3 application was mainly ascribed to the significantly higher 1000-grain weight and out-crossing rate.

3.3. Variation in Stigma Vigor Index of Female Parent with Gibberellic Acid (GA3) Application

The stigma vigor index of the female parent was significantly affected by GA3 application after anthesis in 2016 and 2017 (Figure 1). The stigma vigor index was enhanced with increasing GA3 dosage. The stigma vigor index of GA3 application (15 g hm−2 and 30 g hm−2, respectively) was 7.5% and 16.0% higher on average than that of the CK. Moreover, a significant difference was found in the stigma vigor index of different varieties, and the stigma vigor of IIY-838 was remarkably higher than that of LLY-1813 and YLY-9918.

3.4. Linear Regression between Seed Vigor and Stigma Vigor Index

The seed vigor was positively related to the stigma vigor index (Figure 2). Linear regression between the VI and stigma vigor index was significant (R2 = 0.7270** and R2 = 0.6114**, respectively). Linear regression between the GP and stigma vigor index was significant (R2 = 0.5356*) in IIY-838, while it was not significant (R2 = 0.3064) in YLY-1813.

4. Discussion

The seed yield results from the panicles per unit area, the number of spikelets, the grain weight and the out-crossing rate in hybrid rice seed production. Cheng et al. [32] found that spraying GA3 at the initial heading stage could increase the 1000-grain weight and seed setting rate of rice. In this study, the results showed that spraying GA3 with 30 g hm−2 after anthesis could significantly increase the 1000-grain weight and out-crossing rate and resulted in the highest seed yield (1860.6 kg hm−2 and 4781.4 kg hm−2, respectively) in YLY-9918 and IIY-838 (Table 4). These results agree with the findings of Dong et al. [33]. Moreover, Dong et al. [33] found that spraying GA3 could effectively delay the plant senescence process for both Indica and Japonica varieties. Zheng et al. [34] reported that GA3 application after anthesis increased the contribution ration of the panicle to yield by 32.3%, and carbon synthesized in the panicle was used for seed filling in hybrid rice seed production. These results indicated that GA3 application after anthesis could prolong the duration of seed filling and enhance the sink capacity, correspondingly improving grain weight and out-crossing, and eventually increasing the seed yield. Consequently, the higher seed yield under the GA3 application with 30 g hm−2 was mainly ascribed to the significantly higher 1000-grain weight and out-crossing rate. However, some studies have indicated that spraying GA3 after anthesis has an adverse effect on the 1000-grain weight and seed setting rate, resulting in yield reduction [35,36]. This result might be caused by different GA3 application times and concentrations. Therefore, more experiments should be performed to determine the effects of GA3 application times and spraying days on seed vigor during seed production.
Seed quality includes readily measurable characteristics such as viability and seed lot purity, but a more essential component is the enigmatic trait of seed vigor [37]. In this study, GA3 application after anthesis had significant positive effects on the GP, GE, GI, and VI in 2016 and 2017 (Table 2 and Table 3). These results agree with the findings of GI et al. [38]. However, GI et al. used GA3 with 400 g hm−2, which was significantly higher than the spraying dosages applied to this study. This may be the reason that the GA3 spraying time is different. Moreover, GA3 application after anthesis had a positive effect on the stigma vigor index of the female parent (Figure 1), and the VI was significantly and positively related to the stigma index (Figure 2). These results indicated that stigma vigor index of the female parent was enhanced through GA3 application after anthesis and resulted in improved seed vigor. Du et al. [39] found that the inferior grain plumpness in rice was enhanced by 5.5% by spraying GA3 after anthesis. Moreover, GA3 application could prolong the duration of seed filling and enhance the sink capacity and eventually increase the grain weight [33,34]. Therefore, we speculated that a higher stigma vigor index had a positive effect on seed development (especially inferior grains) and correspondingly increased grain weight and eventually improved seed vigor. However, in this study, the development of seeds, including inferior grains and superior grains, was not measured. Additionally, the responses of hybrid combinations to GA3 dosage were varied, such as IIY-838 and YLY-9918. Thus, further study is needed to investigate the growth dynamics of inferior grains and superior grains and the physiological and biochemical mechanisms arising from the influence of GA3 application after anthesis.
Poor panicle exsertion of male sterile lines is a major problem in hybrid rice seed production. Hence, the foliar application of GA3 at the start of panicle emergence has been widely adopted as an essential technology for improving plant height and panicle exsertion [21,22]. However, in this study, GA3 application after anthesis could not result in these changes because the organs were not young. Therefore, the results obtained in this study were not influenced by plant height and panicle exsertion of male sterile lines. Moreover, the effects of preharvest applications on postharvest behavior are determinative in terms of product storability. Preharvest GA3 applications are known to increase a number of postharvest fruit properties and have positive effect on the fruit shelf life during storage [40,41]. Therefore, more experiments should be performed to determine the effects of preharvest GA3 application on seed vigor and shelf life of Indica hybrid rice during storage.

5. Conclusions

In hybrid rice seed production, GA3 application after anthesis significantly enhanced the stigma vigor index of the female parent and correspondingly increased the 1000-grain weight and out-crossing rate, thus improving seed vigor and increasing seed yield. Moreover, GA3 application should be applied at a rate of 30 g hm−2 to improve seed vigor and maintain seed yield in Indica hybrid rice seed production.

Author Contributions

Devised the study, X.W., H.Z., and Q.T.; Received the funding, Q.T.; Planned and oversaw the field experiments, and conducted the data analysis, X.W., W.M., and J.M.; Interpreted the results and wrote the manuscript, X.W.

Funding

This research was funded by China Agriculture Research System (CARS-01-26) and the Special Fund for Agro-scientific Research in the Public Interest (201303002).

Acknowledgments

We thank B.L. and X.X. for assisting with field evaluations, and Y.H. and Q.C. for field management.

Conflicts of Interest

The authors declare no conflict of interest.

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Agronomy 09 00861 g001 550
Figure 1. Stigma vigor index of LLY-1813, IIY-838, and YLY-9918 in 2016 and 2017. Vertical bars represent mean values ± SE (n = 3). Different lowercase letters denote significant differences under different treatments of the same variety at the 0.05 probability level according to the LSD test. LLY-1813, IIY-838, and YLY-9918 indicate Longliangyou1813, IIyou838, and Yliangyou9918, respectively. CK indicates spraying water without GA3.
Figure 1. Stigma vigor index of LLY-1813, IIY-838, and YLY-9918 in 2016 and 2017. Vertical bars represent mean values ± SE (n = 3). Different lowercase letters denote significant differences under different treatments of the same variety at the 0.05 probability level according to the LSD test. LLY-1813, IIY-838, and YLY-9918 indicate Longliangyou1813, IIyou838, and Yliangyou9918, respectively. CK indicates spraying water without GA3.
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Figure 2. Linear regression between seed vigor parameters and stigma vigor index in 2017. Data are adjusted coefficients of determination R2 (n = 9). VI and GP indicate vigor index and germination percentage, respectively. * and ** represent significant at the 0.05 probability level and 0.01 probability level, respectively.
Figure 2. Linear regression between seed vigor parameters and stigma vigor index in 2017. Data are adjusted coefficients of determination R2 (n = 9). VI and GP indicate vigor index and germination percentage, respectively. * and ** represent significant at the 0.05 probability level and 0.01 probability level, respectively.
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Table
Table 1. Sowing and transplanting date of Indica hybrid combinations in 2016 and 2017.
Table 1. Sowing and transplanting date of Indica hybrid combinations in 2016 and 2017.
YearSiteIndica Hybrid CombinationFemale/MaleSowing DateTransplanting Date
2016GuidongIIY-838II-32A05−0706−03
R83805−0706−03
05−1206−03
SuiningLLY-1813Longke638S05−1606−14
R181304−1505−25
04−2305−25
2017GuidongIIY-838II-32A05−0606−03
R83805−0606−03
05−1206−03
NingyuanYLY-9918Y58S05−2706−11
R92805−1806−11
05−2506−11
IIY-838, LLY-1813 and YLY-9918 indicate IIyou838, Longliangyou1813 and Yliangyou9918, respectively.
Table
Table 2. Seed vigor of Indica hybrid combinations under standard germination test in 2016 and 2017.
Table 2. Seed vigor of Indica hybrid combinations under standard germination test in 2016 and 2017.
Hybrid CombinationGA3 Dosage (g hm−2)GP (%)GE (%)GIVI
2016LLY-1813CK67.0 ± 1.2b60.3 ± 0.3b26.9 ± 0.1a5.6 ± 0.1c
1572.0 ± 2.5ab65.3 ± 2.0ab27.4 ± 0.9a6.6 ± 0.2b
30 75.7 ± 1.5a68.7 ± 2.3a29.0 ± 0.6a7.1 ± 0.2a
IIY-838CK82.0 ± 0.6b79.7 ± 0.7b38.7 ± 0.5b10.2 ± 0.1b
15 84.7 ± 1.3b81.7 ± 1.3b40.5 ± 0.6ab11.0 ± 0.2b
3090.0 ± 1.5a88.0 ± 1.2a41.7 ± 0.8a12.4 ± 0.3a
2017YLY-9918CK93.3 ± 0.9b69.0 ± 1.2b29.8 ± 0.5c6.7 ± 0.2c
15 94.0 ± 1.2ab72.7 ± 1.2b31.5 ± 0.6b7.3 ± 0.2b
30 97.0 ± 2.1a88.0 ± 0.6a36.0 ± 0.7a8.0 ± 0.3a
IIY-838CK83.3 ± 1.2a80.3 ± 1.7a39.6 ± 0.6a9.0 ± 0.2b
15 85.0 ± 1.0a81.0 ± 0.6a40.5 ± 0.2a9.4 ± 0.1b
3088.0 ± 1.7a85.0 ± 1.7a40.8 ± 0.8a10.2 ± 0.2a
Data are mean values ± SE (n = 4). Different lowercase letters denote significant differences under different treatments of the same variety at the 0.05 probability level according to the LSD test. IIY-838, LLY-1813, and YLY-9918 indicate IIyou838, Longliangyou1813, and Yliangyou9918, respectively. GP, GE, GI, and VI indicate germination percentage, germination energy, germination index, and vigor index, respectively. CK indicates spraying water without GA3.
Table
Table 3. Seed vigor of Indica hybrid combinations under cool germination test in 2017.
Table 3. Seed vigor of Indica hybrid combinations under cool germination test in 2017.
Hybrid CombinationGA3 Dosage (g hm−2)GP (%)GE (%)GIVI
YLY-9918CK73.0 ± 1.5b55.0 ± 2.1b11.9 ± 0.2c0.9 ± 0.1b
1576.7 ± 2.2b72.7 ± 1.8a14.2 ± 0.4b1.1 ± 0.1b
3082.3 ± 1.5a76.0 ± 2.0a15.6 ± 0.3a1.5 ± 0.1a
IIY-838CK60.3 ± 2.2b53.0 ± 2.5a10.5 ± 0.4b0.7 ± 0.1b
1563.7 ± 0.9b54.7 ± 0.9a11.0 ± 0.2ab0.8 ± 0.1ab
3068.7 ± 0.9a57.3 ± 0.7a11.8 ± 0.1a1.1 ± 0.1a
Data are mean values ± SE (n = 4). Different lowercase letters denote significant differences under different treatments of the same variety at the 0.05 probability level according to the LSD test. IIY-838 and YLY-9918 indicate IIyou838 and Yliangyou9918, respectively. GP, GE, GI, and VI indicate germination percentage, germination energy, germination index, and vigor index, respectively. CK indicates spraying water without GA3.
Table
Table 4. Seed yield and its components of hybrid combinations in 2017.
Table 4. Seed yield and its components of hybrid combinations in 2017.
Hybrid CombinationGA3 Dosage (g hm−2)No. of Panicles (× 104 hm−2)Spikelets Per Panicle1000-Grain Weight (g)Out-Crossing Rate (%)Actual Yield (kg hm−2)
YLY-9918CK270.2 ± 0.6a128.2 ± 0.8a20.2 ± 0.1b32.0 ± 0.3c1748.7 ± 4.5c
15270.4 ± 0.7a130.1 ± 1.2a20.5 ± 0.4ab34.3 ± 0.3b1818.6 ± 6.1b
30270.6 ± 0.2a129.8 ± 0.3a21.7 ± 0.2a35.8 ± 0.3a1860.6 ± 5.7a
IIY-838CK366.3 ± 0.8a109.0 ± 0.2a23.3 ± 0.2c59.8 ± 0.6b4719.0 ± 6.2b
15365.7 ± 0.6a109.3 ± 0.8a23.9 ± 0.2b59.5 ± 0.2b4723.6 ± 3.0b
30365.8 ± 0.5a109.5 ± 0.5a24.8 ± 0.1a61.7 ± 0.2a4781.4 ± 2.1a
Different lowercase letters denote significant differences under different treatments of the same variety at the 0.05 probability level according to the LSD test. IIY-838 and YLY-9918 indicate IIyou838 and Yliangyou9918, respectively. CK indicates spraying water without GA3.

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Wang, X.; Zheng, H.; Tang, Q.; Mo, W.; Ma, J. Effects of Gibberellic Acid Application after Anthesis on Seed Vigor of Indica Hybrid Rice (Oryza sativa L.). Agronomy 2019, 9, 861. https://doi.org/10.3390/agronomy9120861

AMA Style

Wang X, Zheng H, Tang Q, Mo W, Ma J. Effects of Gibberellic Acid Application after Anthesis on Seed Vigor of Indica Hybrid Rice (Oryza sativa L.). Agronomy. 2019; 9(12):861. https://doi.org/10.3390/agronomy9120861

Chicago/Turabian Style

Wang, Xiaomin, Huabin Zheng, Qiyuan Tang, Wenwei Mo, and Junjie Ma. 2019. "Effects of Gibberellic Acid Application after Anthesis on Seed Vigor of Indica Hybrid Rice (Oryza sativa L.)" Agronomy 9, no. 12: 861. https://doi.org/10.3390/agronomy9120861

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