Branching Expression Research Articles

Suppression of sorghum axillary bud outgrowth by shade, phyB and defoliation signalling pathways

In recent years, several genetic components of vegetative axillary bud development have been defined in both monocots and eudicots, but our understanding of environmental inputs on branching remains limited. Recent work in sorghum (Sorghum bicolor) has revealed a role for phytochrome B (phyB) in the control of axillary bud outgrowth through the regulation of Teosinte Branched1 (TB1) gene. In maize (Zea mays), TB1 is a dosage-dependent inhibitor of axillary meristem progression, and the expression level of TB1 is a sensitive measure of axillary branch development. To further explore the mechanistic basis of branching, the expression of branching and cell cycle-related genes were examined in phyB-1 and wild-type sorghum axillary buds following treatment with low-red : far-red light and defoliation. Although defoliation inhibited bud outgrowth, it did not influence the expression of sorghum TB1 (SbTB1), whereas changes in SbMAX2 expression, a homolog of the Arabidopsis (Arabidopsis thaliana) branching inhibitor MAX2, were associated with the regulation of bud outgrowth by both light and defoliation. The expression of several cell cycle-related genes was also decreased dramatically in buds repressed by defoliation, but not by phyB deficiency. The data suggest that there are at least two distinct molecular pathways that respond to light and endogenous signals to regulate axillary bud outgrowth.

Genetically controlled branching corms of taro (Colocasia esculenta)

Branching in taro (Colocasia esculenta) corms is a complex, undesired, and rare trait, which is expressed because of proliferation of lateral buds. The evaluation of the Vanuatu national taro germplasm collection showed that the frequency of this trait was significantly high (9.51 % of the accessions were characterised by genetically controlled branching). Such a high frequency can be considered as an indication of close relationships among the majority of the Vanuatu cultivars. The expression of branching depends on the genetic structure, specific environmental conditions, interactions between the genetic structure and the environment, and interactions between various developmental stages of a particular genotype and the environment. The genetic control is complex and involves the interaction of at least two loci. The present study suggests that the existing genetic diversity of taro in Vanuatu (and probably also in other geographically isolated Pacific areas) is insufficient for a successful long‐term breeding programme and should include introductions from other countries, especially from the centres of diversity.

Studies on the inheritance of five qualitative characteristics in clusterbean (Cyamopsis tetragonoloba (L.) Taub)

The inheritance of five characteristics namely branching behaviour, clustering pattern, growth habit, leaf size and hairiness was studied in clusterbean. All the traits were controlled by single pairs of genes except branching behaviour which exhibited digenic inheritance. Complementary gene effects were involved in the expression of branching in the F1 and F2 generations; the F2 showing a ratio of 9:7 for branched to unbranched genotypes in the cross FS 277 × NC 70 where both the parents were single shooted. The alleles governing branching, discontinuous clustering, indeterminate growth habit, small leaf size and hairiness were dominant over the alleles controlling non-branching, continuous clustering, determinate growth habit, broad leaf and glabrous leaf and stem.