Tillers are vegetative branches that develop from axillary buds located in the leaf axils at the base of many grasses. Genetic manipulation of tillering is a major objective in breeding for improved cereal yields and competition with weeds. Despite this, very little is known about the molecular genetic bases of tiller development in important Triticeae crops such as barley (Hordeum vulgare) and wheat (Triticum aestivum). Recessive mutations at the barley Uniculme4 (Cul4) locus cause reduced tillering, deregulation of the number of axillary buds in an axil, and alterations in leaf proximal-distal patterning. We isolated the Cul4 gene by positional cloning and showed that it encodes a BROAD-COMPLEX, TRAMTRACK, BRIC-À-BRAC-ankyrin protein closely related to Arabidopsis (Arabidopsis thaliana) BLADE-ON-PETIOLE1 (BOP1) and BOP2. Morphological, histological, and in situ RNA expression analyses indicate that Cul4 acts at axil and leaf boundary regions to control axillary bud differentiation as well as the development of the ligule, which separates the distal blade and proximal sheath of the leaf. As, to our knowledge, the first functionally characterized BOP gene in monocots, Cul4 suggests the partial conservation of BOP gene function between dicots and monocots, while phylogenetic analyses highlight distinct evolutionary patterns in the two lineages.

Tillering, or the production of lateral branches (i.e., culms), is an important agronomic trait that determines shoot architecture and grain production in grasses. Shoot architecture is based on the actions of the apical and axillary meristems (AXMs). The shoot apical meristem (SAM) produces all aboveground organs, including AXMs, leaves, stems, and inflorescences. In grasses like rice (Oryza sativa L.) and barley (Hordeum vulgare L.), vegetative AXMs form in the leaf axil of lower leaves of the plant and produce tillers (branches). Tiller development is characterized by three stages, including (i) AXM initiation, (ii) bud development, and (iii) outgrowth of the axillary bud into a tiller. Each tiller has the potential to produce a seed-bearing inflorescence and, hence, increase yield. However, a balance between number and vigor of tillers is required, as unproductive tillers consume nutrients and can lead to a decreased grain production. Because of its agronomic and biological importance, tillering has been widely studied, and numerous works demonstrate that the control of AXM initiation, bud development, and tillering in the grasses is via a suite of genes, hormones, and environmental conditions. In this review, we describe the genes and hormones that control tillering in two key cereal crops, rice and barley. In addition, we discuss how the development of new genomics tools and approaches, coupled with the synteny between the rice and barley genomes, are accelerating the isolation of barley genes underlying tillering phenotypes.A t the global level, the most important cereal crops are maize (Zea mays L.), rice, wheat (Triticum aestivum L.) and barley (H. vulgare spp. vulgare), with a total of 2.4 billion tons produced annually at a value of >446 billion

A new podovirus RsPod1EGY Ralstonia phage (GenBank accession no MG711516) with a specific action against R. solanacearum phylotype IIa, sequevar I (race 3, biovar 2) was isolated from Egyptian soil. The potential efficacy of the isolated phage to be used as biocontrol agent was evaluated in vitro and under greenhouse conditions. The podovirus phage produced a plaque size of 3.0-4.0 mm in diameter and completed its infection cycle in 180 min after infection with a burst size of ∼27 virions per infected cell. On the basis of restriction endonuclease analysis, the genome size of the phage was about 41 kb of double-stranded DNA. In vitro studies showed that RsPod1EGY is stable at higher temperatures (up to 60 °C), and at a wide pH range (5-9). SDS-PAGE analysis indicated the major structural protein to be approximately 32 kDa. Bacteriolytic activity of RsPod1EGY against R. solanacearum was detected at different multiplicity of infection (MOI). RsPod1EGY proved to be effective in reduction and prevention of formation of surface polysaccharides of R. solanacearum, during the exponential growth phase of the latter. Interestingly, RsPod1EGY was effective in suppression of R. solanacearum under greenhouse conditions. All Phage-treated tomato plants showed no wilt symptoms or any latent infection during the experimental period, whereas all untreated plants have wilted by 10 days post-infection. The lytic stability of RsPod1EGY phage at higher temperature as well as its effective suppression of wilting symptoms under greenhouse conditions would contribute to biocontrol the bacterial wilt disease in Egypt under field conditions.

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