Sorghum Bicolor Cultivars Research Articles

Somatic embryogenesis and plant regeneration in Sorghum bicolor (L.) Moench

Callus induction, somatic embryogenesis and plant regeneration were obtained in two cultivars of Sorghum bicolor (L.) Moench. Transverse thin cell layers from roots/epicotyls of 15-day-old seedlings or of regenerated plantlets were used. Callus response depended on the genotype, the size of transverse thin cell layers, the level at which transverse thin cell layers were excised on the epicotyl, the composition of growth substances and the number of in vitro regeneration cycles undergone by the donor plant. Somatic embryos were differentiated under a defined dark/light sequence, from epidermised compact calluses (i.e having already differentiated an epidermis), obtained directly with dicamba or from friable callus initiated with kinetin and 2,4 dichlorophenoxyacetic acid. The importance of kinetin and dicamba on the induction of embryogenic potential is reported.

A cytological study of compatible and incompatible interactions between Sorghum bicolor and Colletotrichum sublineolum

summaryCytological and physiological studies were conducted on the infection process of Colietotrichum sublineolum P. Henn. Kabat et Bub. on susceptible and resistant cultivars of Sorghum bicolor (L.) Moench. Compatible interactions were characterized by an early biotrophic phase lasting c. 24 h, during which intracellular infection vesicles and primary hyphae colonized epidermal cells. Thinner secondary hyphae were first observed branching out from primary hyphae after 66 h. These hyphae proliferated throughout the epidermis and into underlying mesophyll cells. Secondary hyphae were associated with host cell death and the onset of a necrotrophic phase. Pigmented cytoplasmic inclusions, thought to represent the host defence response, were also first observed at 66 h, although there was little apparent effect on subsequent fungal colonization of tissue. By 90 h, secondary hyphae had proliferated throughout the leaf sheath, with production of necrotic lesions and acervuli. In incompatible interactions, infection vesicles formed inside epidermal cells within 42 h of inoculation but there was no evidence for a biotrophic interaction as penetrated cells appeared dead and fungal development was restricted to single epidermal cells. Host defence responses were observed earlier than in compatible interactions: heavily pigmented (dark red) cytoplasmic inclusions were distributed throughout penetrated cells at 42 h. By 66 h, these cytoplasmic inclusions had disintegrated and dark red pigment had spread throughout the cell. Concurrent with the disintegration of the cytoplasmic inclusions was the disruption of the cytoplasm of both the host cell and the fungus. Further fungal development was restricted. These observations are discussed in relation to the importance of the initial biotrophic phase in the successful colonization of S. bicolor by C. sublineolum and the role of the host defence response in preventing colonization.

Effect of Water Stress on Pyruvaté, Pi Dikinase and Phosphoenol Pyruvate Carboxylase Activities in the Leaves of Two Cultivars of Sorghum (Sorghum bicolor L.)

AbstractThe effect of withholding water on the specific activities of pyruvate, orthophosphate dikinase (PPDK EC 2.7.9.1.) and phosphoenol pyruvate carboxylase (PEPC, EC 4.1.1.31) was studied in two cultivars of Sorghum bicolor L. different in their sensitivity to water deficit. The drought sensitive cultivar ICSV 1063 and the more resistant cultivar MIGSOR were subjected to water deficit in controlled conditions. The results showed a decrease in both enzyme specific activities, higher for drought sensitive cultivar ICSV 1063, when leaf water potential (Ψ) was lowered to ‐2.3 MPa. Following rewatering, enzyme specific activities increased in both cultivars, with the increase being more significant in MIGSOR. Relative water content (RWC) decreased significantly for water‐stressed ICSV 1063 cultivar, lower for MIGSOR and returned quickly to that of control plants upon rehydration. Net photosynthesis showed a decrease for water‐stressed plants, higher for ICSV 1063. At minimal Ψ, net photosynthesis was completely inhibited, with the stomata being closed After rehydration, MIGSOR showed a better recovery in photosynthesis but never reached the initial values of day 0. Water stress had a striking effect, both on net photosynthesis by regulation of stomatal aperture and on PPDK and PEPC activities, although the enzymes were still active when photosynthesis ceased. Therefore the level of PPDK and PEPC activities may contribute to the limitation of photosynthetic carbon dioxide fixation.

High frequency somatic embryogenesis and plant regeneration from immature inflorescence cultures of two Indian cultivars of sorghum (Sorghum bicolor L. Moench)

Somatic embryogenesis and subsequent plant regeneration were obtained from immature inflorescence segments of two cultivars ofSorghum bicolor L. Moench. Callus was induced on Murashige and Skoog’s medium supplemented with 2,4-dichlorophenoxyacetic acid (2 mg/l) and zeatin (0.1 mg/l). Transfer of calli to Murashige and Skoog medium alone or with reduced level of auxins with or without cytokinins resulted in the production of somatic embryos and plantlets. The combination of a cytokinin with Triiodobenzoic acid promoted the highest number of somatic embryoids. The best response was obtained from inflorescences 10–25 mm in length. Regenerated plants were transferred to field for further evaluation.

Plant, Microbial and Soil Factors, Determining Nitrogen Fixation in the Rhizosphere

AbstractA genotype effect on associative (rhizosphere) N2‐fixation was observed with two cultivars of Sorghum bicolor (nutans) with a maximum rate of 8 μmol C2H4 · h−1 · plant−1 in one genotype compared to 0.9 μmol in the other. Characteristics of the high fixing genotype were a reduced transpiration rate, a lower number of stomata and increased root exudate production per gram root dry weight with higher concentration of dicarboxylic acids. The bacterial rhizosphere composition revealed a three times higher number of N2‐fixing bacteria, a tenfold reduction of actinomycetes and a threefold reduction of Arthrobacter associated with the high fixing cultivar compared to the low fixing genotype. From these and other plant rhizospheres two new nitrogen fixing bacteria, Pseudomonas stutzeri and Erwinia herbicola, were characterized. With the N2‐fixing bacteria Azospirillum brasilense and Klebsiella pneumoniae an enhancement of specific nitrogenase activity by aromatic compounds, for example phenolics, the herbicide alachlor and the insecticide carbofuran was demonstrated. An oscillating nitrogenase activity in Azospirillum brasilense under microaerobic conditions was found, resulting from an encystation and deencystation under those conditions. Experiments with wheat roots demonstrated that reduced oxygen tensions, essential for a maximum rhizosphere N2‐fixation, reduced root growth significantly and altered the N‐metabolism of the roots.

Evaluation of Three Sorghums as Potential Alternative Forages for Crawfish Culture 1

AbstractThree cultivars of Sorghum bicolor (L.) Moench (grain sorghum, forage sorghum, and a sorghum sudangrass hybrid) were evaluated as planted forages for crawfish (Procambarus spp.) in two simulated culture systems, double cropping and crawfish monoculture. Based upon ease of culture, biomass production, and biomass degradation characteristics, grain sorghum and sorghum sudangrass exhibited great potential for either system. With the added advantage of grain production, grain sorghum represents the more attractive option and may provide farmers with a viable alternative to rice for double cropping with crawfish. The sorghum sudangrass produced large amounts of vegetative biomass and also represents a worthwhile forage option for the crawfish fanner. Either of these plants is conveniently incorporated into existing farm operations and could provide options as producers strive to integrate crawfish aquaculture with conventional agriculture.

Allelopathic suppression of weed and nitrification by selected cultivars ofSorghum bicolor (L.) moench

Root exudates of 100 cultivars ofSorghum bicolor L. (Moench) were screened for their ability to inhibit seed germination and seedling growth ofAmaranthus retroflexus L. Exudates of some of the test cultivars were found to inhibit significantly seed germination and/or seedling growth ofA. retroflexus, and most of the inhibitory activity was found in neutral and acetone fractions of root exudates. Testing of aqueous extracts and decaying residues of four selectedSorghum cultivars (two toxic and two nontoxic through root exudation) revealed that all four cultivars significantly reducedA. retroflexus growth and nitrification processes with greater inhibition achieved by the toxic cultivars. This study suggests a potential biological control ofAmaranthus and nitrification by someS. bicolor cultivars.

Screening for drought tolerance in Sorghum using cell culture

Callus growth from 10 cultivars ofSorghum bicolor (L.) Moench was measured with increasing levels of polyethylene glycol (PEG) as an osmoticum in the medium to determine whether differences among these cultivars at the cellular level in response to osmotic stress existed. These cellular ratings were compared to field ratings from the 10 tolerant-to-susceptible cultivars when grown under drought conditions to determine whether cellular ratings corresponded to differences in drought tolerance at the plant level. Callus cultures were grown on Murashige and Skoog inorganic salt formulation plus vitamins, 2,4-dichlorophenoxyacetic acid (2,4-D), kinetin and sucrose, supplemented with 0 to 25% (wt/vol) PEG corresponding to −0.2 to −1.62 MPa osmotic potential. Results suggest that PEG-induced osmotic stress on callus cultures can be used to screen sorghum cultivars for potential early field (preflowering) drought tolerance. This implies that at least a component of the early field drought tolerance in sorghum may have a cellular basis.

Callus formation from protoplasys of Sorghum cell suspension cultures

Cell suspension cultures have been obtained from three cultivars of Sorghum bicolor L. Moench. Protoplasts readily obtained from these cultures underwent sustained cell division and callus formation.

DROUGHT RESISTANCE OF Sorghum bicolor. 4. HORMAL CHANGES IN RELATION TO DROUGHT STRESS IN FIELD-GROWN PLANTS

This study was undertaken to investigate the nature of hormonal changes in relation to drought stress in two cultivars of Sorghum bicolor L. Moench. Two cultivars, M–35 and NK300, were grown in a field plot protected by a rain shelter. Plants in one soil compartment were stressed by withholding water while those in another (controls) were irrigated frequently. Levels of the plant hormones abscisic acid (ABA), phaseic acid (PA) and indole-3-acetic acid (IAA) measured by high-performance liquid chromatography (HPLC) were determined in the youngest leaves of control and stressed plants at intervals throughout the growth cycle. Plant height, senescence, and leaf water status were also determined. Leaf water potential (ψw) and solute potential (ψs) were reduced in both cultivars by drought stress; values for M–35 plants were lower than NK300. Leaf senescence was higher in M–35 plants and was promoted by stress in both cultivars. Cultivar M–35 behaved as a drought-tolerant plant whereas cultivar NK300 behaved more like a drought avoider. ABA levels were higher in M–35 control plants than in corresponding NK300 plants and levels in both cultivars followed seasonal changes in leaf water potential. Under drought stress, ABA levels increased between 1.5 and 2 times in both cultivars with the largest increases occurring during the vegetative stage in M–35 and during the flowering stage for NK300. PA levels in both cultivars were higher in stressed than in control plants. PA levels in M–35 plants were relatively low and constant throughout the life cycle, whereas in NK300, levels were high until shortly before flowering. IAA levels were higher in NK300 than in M–35 plants, particularly during the vegetative stage. Under drought stress, IAA levels were reduced in both cultivars with a more pronounced reduction in NK300. The high level of ABA in the more drought-tolerant cultivar M–35 was associated with low leaf ψw and ψs and high leaf senescence. On the other hand, in the drought avoider, NK300, high levels of IAA and PA were associated with high leaf ψw and ψs. It is concluded that these cultivars, which differ in their response to drought stress, can be distinguished by their leaf hormone levels.

Environmental and biotic factors affecting the phenolic content of different cultivars ofSorghum bicolor

Levels of phenolic acids in healthy plants ofSorghum bicolor differ considerably with cultivar and always decrease as the plant matures. Laboratory- and field-grown plants show significant differences in phenolics. Environmental factors, particularly light intensity, influence the concentration of phenolics in sorghum. Attack by insects and pathogenic fungi also increase the phenolic content of the plants to varying degrees dependent on the cultivar and the stage of growth of the plant.

Intraspecific Physiological Variants of Striga hermonthica

SUMMARYPreliminary evidence is presented in this study for the existence of (1) intraspecific physiological variants of Striga hermonthica, with Gabob population as the most responsive strain to a range of Sorghum bicolor cultivars, and (2) a local Sudanese sorghum cultivar called Tetron with broad-spectrum resistance to striga. Thus Tetron may be recommended as another standard resistant cultivar with reference to Framida of East Africa.

Embryonic Leaf Number in Sorghum1

The number of embryonic leaves in mature embryos of Sorghum was determined for 11 cultivars of Sorghum bicolor (L.) Moench.s, weet sudangrass(S. sudanense(Piper) Stapf.), johnsongrass (S. halepense (L.) eers.), shattercane (a group of weedy‐type sorghums constituting a hybrid swarm). A minimumof 10 embryos of each entry was examined. All cultivars of S. bicolor and shattercane had four embryonic leaves. Johnsongrass and sweet sudangrass had only three embryonic leaves except one embryo of sweet sudangrass had four leaves. To determine the embryonic leaf number in Sorghum it is beneficial to examine both longitudinal and transverse serial sections of the embryos. The data reported establish the constancy of embryonic leaf number among seeds within a cultivar and among cultivars within a species.