Optimization of tissue culture conditions for Sorghum bicolor L. through somatic embryogenesis from immature embryos is important for the genetic manipulation and improvement of this agronomically valuable crop. In an attempt to develop a successfully reproducible in vitro regeneration protocol for a group of diverse sorghum genotypes, 10 sorghum lines including locally adapted and commercially important elite genotypes were assessed for their regeneration potential on different culture media–containing adequate growth regulators combinations. The maximum response of embryogenic callus induction was obtained from explants cultured on Murashige and Skoog (MS) medium supplemented with 1.5 mgL-1 of 2,4-dichlorophenoxyacetic acid (2,4-D) and 0.7 mgL-1 L-proline. The addition of kinetin to the MS-based culture media had a negative effect on the formation of embryogenic calli. The results reveal that embryogenic callus formation and regeneration were highly genotype dependent. The line LG3 revealed the highest mean number of embryogenic callus (47.5 ± 6.0%) across the media tested. On the other hand, SPP462 was the least responsive (13.4 ± 3.3%) to embryogenic callus induction. The regeneration percentage of the different genotypes ranged from zero to 22.1%. The lines LG3, LG4, Dorado, SPGM94021 and SPMD94001 succeeded to form shoots on the three tested regeneration media. Nevertheless, the genotypes LG8 and TX2794 produced shoots on only two out of the three media. Three lines failed to regenerate on any of the tested media. Adding 0.5 mgL-1 naphthalene acetic acid and 0.5 mgL-1 of indole-3-butyric acid (IBA) did not enhance the root induction. Regenerated shoots developed into normal mature plants. Regeneration of sorghum genotypes could be improved through the use of different auxins and cytokinins in callus induction and shoot formation media. The auxin, 2,4-D was critical for the induction of embryogenic calli. However, the addition of the cytokinin (kinetin) adversely affected the formation of embryogenic callus. On the other hand, the shoot induction was more influenced by the addition of indole-3-acetic acid (IAA), 6-benzylaminopurine (BA) and thidiazuron (TDZ). Key words: Sorghum, immature embryos, callus induction, regeneration, auxin, cytokinin.

Morphological, anatomical, and molecular information facilitates the identification and inference of the relatedness of plant species. In this study, the macromorphological, micromorphological, and anatomical characteristics of nine species from the Brachychiton and Sterculia genera belonging to the Malvaceae family were examined by light and a scanning electron microscope. The study recorded 66 macromorphological, micromorphological, and anatomical characteristics, thus revealing important variations between the studied species in leaf morphology and anatomy. This included variations in leaf complexity, leaf arrangement (phyllotaxy), epidermal cell walls, and their sculpture, as well as in the types of glandular and non-glandular trichomes. The studied species were mostly conserved in shedding patterns, being evergreen only in one out of nine studied species. Similarly, eight species were petiolate. Conversely, leaf arrangement and leaf complexity characteristics were highly divergent among the studied species, though only one species, Sterculia foetida, had compound leaves. The differences in the studied features and the chloroplast genes MaturaseK (MatK) and ribulose-1,5-bisphosphate carboxylase/oxygenase large subunit (rbcl) were exploited to deduce the relationship between the studied species. While the morphological and anatomical features demonstrated a close relationship between the studied intrageneric species, the DNA barcoding analysis proved very efficient in distinguishing the two neighboring genera. Collectively, the different clustering analyses suggest a close relatedness between Brachychiton acerifolius and B. australis, while only DNA-based clustering demonstrates cladistic monophyly of the Sterculia species. This study, therefore, provides a detailed description of various morphological and anatomical features important for the systematic studies within the Malvaceae family and highlights the value of incorporating morphological, anatomical, and molecular approaches for inferring the evolutionary relationship between closely related plant species.

Diversification of transcription factors and of their downstream targets can contribute to new organ morphologies. An example is rice lodicule, a small fleshy petal homolog that aids floret opening, thus facilitates pollination and fertility. To understand mechanisms underlying its specification, we investigated the developmental functions of the rice PISTILLATA (PI) paralogs, OsMADS2 and OsMADS4. Null osmads2 mutants reiterated OsMADS2 nonredundant lodicule specification roles and revealed new roles in flowering time and floral organ number and fate. Doubly perturbed osmads2 ^d8/d8 osmads4kd florets had severe abnormalities, were female infertile, yet initiated parthenocarpy. Ubiquitous OsMADS4 overexpression rescued osmads2 abnormalities. Target genes whose regulation can contribute to OsMADS2 functions were discovered by its genome-wide binding analyses and transcriptome profiling. Several targets are implicated in lodicule and stamen development, floral organ number, cell wall, cell shape and osmotic homeostasis processes. Some targets relevant to lodicule development are cell division regulators (Cyclin D6, Cyclin P4-1-like), aquaporin (PIP1A), peptide transporter (PTR2), vascular development regulator (HOX1) and cell wall modulator (GH9B16). Their deregulation underscores the perturbed cell division, tissue differentiation patterns and physiology of the malformed osmads2 and osmads2 ^d8/d8 osmads4kd lodicules. Altogether, we reveal novel roles for the rice PI paralogs in flowering time, panicle exsertion and embryo sac differentiation, divulge gene targets for lodicule development and provide mechanistic insights on the functional diversification of rice PI paralogs. Keywords: OsMADS2; Rice PISTILLATA; lodicule and stamen development

Immature embryos and immature inflorescences represent the best explants for indirect sorghum regeneration. However, obtaining these explants from field or greenhouse-grown plants requires a lengthy cultivation period. Therefore, shoot apices from seedlings offer a great advantage for readily obtaining explants to sustain the demands for gene transformation experiments throughout the year. Here we report a rapid regeneration protocol from seedling shoot apices for two Egyptian sorghum lines; LG1 and LG3. Callus induction media, CIM1 and CIM2, which differ in the concentration of the synthetic auxin 2,4-Dichlorophenoxyacetic acid (2,4-D) and Kinetin (Kin), were indifferent in their capacity to promote callus formation in the two genotypes, however, the response of the two genotypes to callus induction was significantly different. The lowest callus indication percentage and the highest callus induction percentage were 16.60% and 33.65% for LG3 on CIM1 and LG1 on CIM2, respectively. The difference in the regeneration from callus for the two genotypes was non-significant and was as low as 11.29% and as high as 20.15%. Our results show the potential of utilizing these Egyptian sorghum lines in tissue culture for transgenic and gene editing.