Figure 2 - uploaded by Hussein Shimelis
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Illustration of the different growth stages of the sweet sorghum head at which the E4FO was applied in Trial 2. A, B, C and D are approximately 0, 3, 6 and 9 days in the head protrusion process. E4FO application time combinations were termed as T1 (A + B + C + D); T2 (B + C + D); T3 (A + B + C); T4 (A + C + D); T5 (B + D) and T6 (Control).
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An effective male sterility system enables targeted crosses between parent plants with desired and complementary characteristics. The use of chemical hybridising agents (CHAs) to induce male sterility is quicker and more efficient than manual emasculation. This study investigated the concentration, stage of application and frequency of application...
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... Detailed information about each genotype is given in Table 1. The chemical hybridising agent (CHA), ethyl 4'fluorooxanilate (E 4 FO), was applied twice at 2000 mg l −1 to induce male sterility in the female genotypes selected for this study (Mangena et al. 2018b). The amount of seed set was minimal only allowing for field evaluation at one location and during one season. ...
Sorghum hybrids can provide enhanced bioethanol yield if genetically complementary parents and progenies are developed using efficient crossing and selection methods. The objective of this study was to determine the combining ability of sweet stem sorghum genotypes, and assess heterosis among F1 hybrids for ethanol production and associated traits. Eight sweet stem sorghum lines and four testers were crossed using a line × tester mating design. The F1 hybrids and parental lines were evaluated for bioethanol yield and related traits. Data were subjected to analysis of variance, combining ability and heterosis analyses. Biomass production of test populations varied from 11.6 to 68 t ha⁻¹, with a mean of 30 t ha⁻¹. Six hybrids were among the top ten biomass producing genotypes. Four hybrids (AS391 × AS246, AS204 × AS251, AS204 × AS79, AS204 × AS74) expressed greater ethanol productivity with positive better-parent heterosis (> 30%). Lines AS253, AS246 and AS 105, and testers AS391 and SS27 had highly positive general combining ability (GCA) effects for almost all the traits in a desirable direction. Due to its consistent, significant and positive GCA effects across the majority of the traits, line AS253 is recommended for utilisation in sweet stem sorghum hybrid programs.
... Lack of consistency of gametocides across seasons has also been reported on rice genotypes (Efisue et al., 2010). These findings are similar to those of Hodnett and Rooney (2018) and Mangena et al., (2019), who reported that male sterility can be induced in sorghum with appropriate timing for application of CHAs. The significant differences among the gametocides in causing male sterility indicated that the chemical hybridizing agents used in this study had variable efficacies. ...
A new generation of chemical hybridization agents (CHAs) or gametocides has shown potential to induce male sterility in predominantly self-fertilizing crops, including sorghum (Sorghum bicolor [L.] Moench). There is a lack of information on the relative efficacy of the various available CHAs for large-scale application in plant breeding programs. Therefore, the objective of the present study was to compare the relative effectiveness of three selected CHAs to induce male sterility in sorghum under a controlled environment for hybridization. Foliar applications of three CHAs and a control (ethrel, trifluoromethanesulfonamide [TFMSA], ethyl 4-fluorooxanilate [E4FO] and distilled water [control]) were tested using three grain sorghum genotypes (ICS-1, ICS-2 and ICS-3) in two seasons. The 24 treatment combinations consisting of 4 levels of CHAs, 3 sorghum varieties and two seasons were laid out using a randomized complete block design with three replications. Data on pollen sterility, pollen diameter, plant height, and panicle height were collected and analyzed. Results showed that the CHAs had significant (p<0.05) differences for efficacy of inducing male sterility in sorghum. Ethrel at a dose of 1 gl-1 induced the highest pollen sterility (98% in both seasons) but was highly phytotoxic with at least 60% mortality in the test population in both seasons, making it unsuitable for practical application. TFMSA (2 mg per plant) and E4FO (1 gl-1) d induced 93% male sterility with minimal phytotoxic effects (20 to 30%). Application of either TFMSA at 2mg per plant after flag leaf emergence or 1gl-1 of E4FO at panicle initiation can be used to successfully induce male sterility in sorghum under greenhouse conditions. Abbreviations: CHA = chemical hybridization agent, CMS = cytoplasmic male sterility, E4FO = ethyl 4-fluorooxanilate, HSD = honestly significant difference, KI-I2 = potassium iodide-iodine, TFMSA = trifluoromethanesulfonamide
... E 4 FO induced 99.5% male sterility at 2 g l −1 in sorghum cultivars used in the study, whereas 97% male sterility was obtained with ethrel at 3 ml −1 . Mangena, Shimelis, and Laing (2019) investigated the concentration, stage of application and frequency of application of E 4 FO for inducing male sterility in sweet sorghum and concluded that applying E 4 FO twice during the heading stage at a rate of 2 g l −1 induced male sterility. ...
Reliable and effective hybridization methods are required in self-pollinating crops for genetic analysis, recurrent selection and large-scale production of hybrid seed. The objective of this review was to document the different methodologies available for hybrid seed production in predominantly self-pollinating crops. Various methods have been used for hybrid seed production, each with its own advantages and limitations. To obtain a limited quantity of hybrid seed, mechanical emasculation combined with hand pollination remain the most widely used technique. However, these methods are labor-intensive and expensive when a continuous supply of large quantities of hybrid seed is required. Genetic male-sterility systems provide opportunities for large-scale hybrid seed production. However, the occurrence of natural male sterility is rare, and when available, it may not always provide compatible combinations with desirable agronomic attributes. Temporal male sterility can be achieved by the application of chemical hybridizing agents (CHAs), which render the pollen non-viable but maintain female fertility. CHAs hold promise for hybrid seed production because they are easy to use, particularly for field crops that are predominantly self-fertilizing. The cost and variable response of different crops and genotypes to various concentrations of CHAs present technical challenges for their widespread adoption. The choice of crossing method in each breeding program is influenced by the amount of seed required, crop species, level of technical expertise required, availability of cytoplasmic male-sterile lines and access to cheap and effective CHAs. This review provides guidance to plant breeders and seed producers in selecting a suitable crossing method for hybrid seed production in self-pollinating crops.
New generation chemical hybridization agents (CHAs) have shown potential as hybridization agents in predominantly self-fertilizing crops, including sorghum (Sorghum bicolor [L.] Moench). There is a lack of information on the relative efficacy of the various available CHAs for large-scale application in plant breeding programs. Therefore, the objective of the present study was to compare the relative effectiveness of three selected CHAs in inducing male sterility in sorghum under a controlled environment for hybridization. Foliar applications of three CHAs (ethrel, trifluoromethanesulfonamide [TFMSA], and ethyl 4-fluorooxanilate [E4FO]) were tested using three grain-sorghum genotypes (ICS-1, ICS-2 and ICS-3) in two seasons with a randomized complete block design with three replications. The dosages of applications were as follows: 2mg per plant for TFMSA and 1 gl-1 for both ethrel and E4FO. Data on pollen sterility, pollen diameter, plant height, and panicle height were collected and analyzed. Results showed that the CHAs had significant (p<0.05) differences in efficacy in inducing male sterility in sorghum. Ethrel at a dose of 1 gl-1 induced the most pollen sterility (<98% in both seasons), but it was highly phytotoxic, killing the test populations at 60% in 2018 and 55% in 2019, making it unsuitable for practical application. TFMSA (2 mg per plant) and E4FO (1 gl-1) caused mean pollen sterility of <93% with minimal phytotoxic effects (20 to 30%). Two applications of either TFMSA at 2mg per plant after flag leaf emergence or 1gl-1 of E4FO at panicle initiation can be used to successfully induce male sterility in sorghum under greenhouse conditions.
