Studies on Reproductive Development and Breeding Habit of the Commercially Important Bamboo Bambusa tulda Roxb

Compared to other grasses, flowering in bamboo is quite divergent, yet complex with respect to time to flower, number of individual culms in a population that have been induced at a time (sporadic vs. gregarious), nature of monocarpy, morphology of inflorescences (solitary spikelet vs. pseudospikelet), biology of pollen and nature of genetic compatibility. Wide diversity exists even across species and genotypes. However, due to the rarity of flowering and inaccessibility, few studies have been done to systematically analyse diverse aspects of the reproductive behaviour of bamboo. In this study, four recurrently occurring, sporadic flowering populations of Bambusa tulda have been closely observed over the last seven years. Detailed inflorescence and floral morphology and development of reproductive organs have been studied. Pollen viability was assessed by staining and in vitro germination. Self and cross pollination experiments were performed in a plantation site to assess the genetic nature of pollen-pistil interaction. The study identifies interesting reproductive features, that are not common in other grasses. A few important observations include the early appearance of a solitary spikelet vs. late appearance of a pseudospikelet in the flowering cycle, low rate of pollen germination, protandry, self-incompatibility and higher rate of seed setting by the pseudospikelet as compared to the solitary spikelet. The findings will not only be useful to understand the reproductive behaviour of this non-woody timber plant, but will also be useful for forest management and sustainable use of bamboo bioresources.

The SOC1-like gene BoMADS50 is associated with the flowering of Bambusa oldhamii

Bamboo is known for its edible shoots and beautiful texture and has considerable economic and ornamental value. Unique among traditional flowering plants, many bamboo plants undergo extensive synchronized flowering followed by large-scale death, seriously affecting the productivity and application of bamboo forests. To date, the molecular mechanism of bamboo flowering characteristics has remained unknown. In this study, a SUPPRESSOR OF OVEREXPRESSION OF CONSTANS1 (SOC1)-like gene, BoMADS50, was identified from Bambusa oldhamii. BoMADS50 was highly expressed in mature leaves and the floral primordium formation period during B. oldhamii flowering and overexpression of BoMADS50 caused early flowering in transgenic rice. Moreover, BoMADS50 could interact with APETALA1/FRUITFULL (AP1/FUL)-like proteins (BoMADS14-1/2, BoMADS15-1/2) in vivo, and the expression of BoMADS50 was significantly promoted by BoMADS14-1, further indicating a synergistic effect between BoMADS50 and BoAP1/FUL-like proteins in regulating B. oldhamii flowering. We also identified four additional transcripts of BoMADS50 (BoMADS50-1/2/3/4) with different nucleotide variations. Although the protein-CDS were polymorphic, they had flowering activation functions similar to those of BoMADS50. Yeast one-hybrid and transient expression assays subsequently showed that both BoMADS50 and BoMADS50-1 bind to the promoter fragment of itself and the SHORT VEGETATIVE PHASE (SVP)-like gene BoSVP, but only BoMADS50-1 can positively induce their transcription. Therefore, nucleotide variations likely endow BoMADS50-1 with strong regulatory activity. Thus, BoMADS50 and BoMADS50-1/2/3/4 are probably important positive flowering regulators in B. oldhamii. Moreover, the functional conservatism and specificity of BoMADS50 and BoMADS50-1 might be related to the synchronized and sporadic flowering characteristics of B. oldhamii.

A population genetics study of three native Mexican woody bamboo species of Guadua (Poaceae: Bambusoideae: Bambuseae: Guaduinae) using nuclear microsatellite markers

Background: Sporadic flowering contributes significantly to genetic diversity and connectivity among populations. Woody bamboos present sporadic or gregarious flowering patterns with long flowering cycles. In this study, we analyze the genetic diversity of three Guadua species distributed along the Gulf of Mexico slope that have different patterns of flowering. Questions: (1) Are the three Guadua species genetically differentiated? (2) Does the vulnerable species G. inermis have low levels of genetic diversity? (3) What is the relative contribution of geographic and environmental factors to the genetic structure of G. inermis? Species studied: Guadua inermis, G. amplexifolia and G. tuxtlensis Study site and dates: During 2014 and 2015, we collected samples of G. inermis in Puebla and southeastern Mexico, G. amplexifolia in Veracruz and Oaxaca, and G. tuxtlensis in southern Veracruz. Methods: We successfully amplified five of nine SSR markers, and genotyped a total of 155 samples. Results: The three Guadua species were genetically differentiated. For G. inermis, we found high levels of population genetic diversity, which are relatively higher than those of other monocot species. Genetic differentiation was high and three groups were detected: north, central and south. We found a significant association between genetic distances and the maximum temperature of the warmest month, but not with geographic distance. Conclusions: Our study is the first to analyze levels of genetic diversity in Mexican bamboos and confirms their taxonomic identity. G. inermis has a strong genetic structure, even when populations are geographically close.

Sporadic flowering of Bambusa mizorameana Naithani in Mizoram

Mizoram, one of the states in northeast India, is known for its rich bamboo resources. Mizoram has been unceasingly experiencing flowering of bamboo. Recently, a new species of bamboo, Bambusa mizorameana, was described from Mizoram. It is a less common species, and its distributions within the state are also very limited. Specimens were also collected from Manipur. There has been no previous report of its inflorescence. The sporadic flowering of the species in certain areas within the nearby forest of Aizawl city, observed since 2017 are reported in this paper.

Sporadic flowering of Bambusa tulda in Mizoram: A preliminary report

Bambusa tulda Roxb. is a semi-deciduous caespitose bamboo endemic to Indo-Burma. It is known as ‘rawṭhing’ in Mizoram, India, and its mass gregarious flowering is called ṭhingtâm. ‘Ṭhingtâm’ has a cycle of about 45-50 years. The first ṭhingtâm, recorded in the region was in 1880, which was preceded by mautâm (gregarious flowering of Melocanna baccifera) in 1862; i.e., the ṭhingtâm phenomenon occurred ~20 years after the Mautâm. The last ṭhingtâm was recorded in 1981. However, there has been a localised ṭhingtâm at Zawlnuam, a village at the northwestern Mizoram. The first flowering was recorded in 2015. This unusual phenomenon needs to be investigated.

Effects of Temperature, Photoperiod, and Light Quality on Flowering in Several Herbaceous Perennial Species

The influence of low temperatures on Campanula carpatica `Blue Clips' and Lavandula angustifolia `Munstead' flowering was determined; plants were stored at 5C for several weeks and forced under 9-h photoperiods with a 4-h night interruption (NI). C. carpatica, L. angustifolia, and Asclepias tuberosa were forced under NI at five temperatures (15–27C) and time to flower under each treatment was calculated. Flower number and size were reduced at highest temperatures. The effectiveness of cool-white fluorescent (CWF), high-pressure sodium (HPS), incandescent (I), and metal halide (MH) lights in inducing flowering in C. carpatica and Coreopsis lanceolata `Early Sunrise' was compared. Lighting was delivered as a 7-h daylength extension with PPF ranging from 0.05–2.0 μmol·m–2·s–1. Minimum irradiances above which all C. carpatica flowered were approximately 0.14, 0.12, 0.1, and 0.17 μmol·m–2·s–1, respectively. C. lanceolata under CWF displayed irregular flowering throughout the range of intensities used. Under HPS and MH, minimum irradiances for 100% flowering were 0.37 and 1.0 μmol·m–2·s–1, respectively, with sporadic flowering at lower intensities. Under I light, all C. lanceolata exposed to 0.12 μmol·m–2·s–1 or more flowered.