Phenological diversity of flowering and fruiting in cassava germplasm

Souza, Leonardo Silva; Alves, Alfredo Augusto Cunha; Oliveira, E. J. de

doi:10.1016/j.scienta.2020.109253

Cited by 21 publications

(17 citation statements)

References 14 publications

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“…There are five bottlenecks with the reproductive development of cassava that challenge breeding. These are: (1) in some genotypes with traits of interest, flowering is late or in some cases there is no flowering at all; (2) premature abortion of inflorescences and flowers before anthesis; (3) disproportionately large number of male flowers and in some cases no female flowers; (4) non-synchronous development of flowers among genotypes; and (5) low probability of fruit development even when flowering and pollination are successful (Ceballos et al, 2004(Ceballos et al, , 2016Halsey et al, 2008;Adeyemo et al, 2017;Hyde et al, 2020;Souza et al, 2020).…”

Section: Introductionmentioning

confidence: 99%

Flower Development in Cassava Is Feminized by Cytokinin, While Proliferation Is Stimulated by Anti-Ethylene and Pruning: Transcriptome Responses

et al. 2021

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Cassava, a tropical storage-root crop, is a major source of food security for millions in the tropics. Cassava breeding, however, is hindered by the poor development of flowers and a low ratio of female flowers to male flowers. To advance the understanding of the mechanistic factors regulating cassava flowering, combinations of plant growth regulators (PGRs) and pruning treatments were examined for their effectiveness in improving flower production and fruit set in field conditions. Pruning the fork-type branches, which arise at the shoot apex immediately below newly formed inflorescences, stimulated inflorescence and floral development. The anti-ethylene PGR silver thiosulfate (STS) also increased flower abundance. Both pruning and STS increased flower numbers while having minimal influence on sex ratios. In contrast, the cytokinin benzyladenine (BA) feminized flowers without increasing flower abundance. Combining pruning and STS treatments led to an additive increase in flower abundance; with the addition of BA, over 80% of flowers were females. This three-way treatment combination of pruning+STS+BA also led to an increase in fruit number. Transcriptomic analysis of gene expression in tissues of the apical region and developing inflorescence revealed that the enhancement of flower development by STS+BA was accompanied by downregulation of several genes associated with repression of flowering, including homologs of TEMPRANILLO1 (TEM1), GA receptor GID1b, and ABA signaling genes ABI1 and PP2CA. We conclude that flower-enhancing treatments with pruning, STS, and BA create widespread changes in the network of hormone signaling and regulatory factors beyond ethylene and cytokinin.

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Section: Introductionmentioning

confidence: 99%

Flower Development in Cassava Is Feminized by Cytokinin, While Proliferation Is Stimulated by Anti-Ethylene and Pruning: Transcriptome Responses

et al. 2021

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“…Koefender et al [24] observed flowering and the presence of fruits in all the plants they evaluated. Flowering is influenced by genetic and environmental factors and varies greatly in germplasm collections [51,56]. In this study flowering was assessed, as a qualitative descriptor (presence-absence); however, more in-depth flowering studies must be conducted in the Ecuadorian collection to be used in formal breeding; although the most common form of propagation and/or multiplication is vegetative reproduction by cuttings.…”

Section: Groupmentioning

confidence: 99%

Morphological and Ecogeographic Study of the Diversity of Cassava (Manihot esculenta Crantz) in Ecuador

et al. 2021

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Cassava (Manihot esculenta Crantz) is a crop of nutritional and economic importance worldwide, cultivated in more than 100 tropical and subtropical countries including Ecuador, where it is traditionally cultivated in the three continental regions: Amazonia, the Coast and in the valleys of the Sierra. The purpose of this study is to characterize 195 accessions from INIAP’s Ecuadorian cassava collection through (1) morphological characterization with qualitative and quantitative descriptors; and (2) ecogeographic characterization to know the climatic, geophysical, and edaphic conditions in which cassava grows and which environments are frequent or marginal for its cultivation. For the morphological characterization, 27 morphological descriptors were used (18 qualitative and nine quantitative), and for the ecogeographic characterization, 55 variables (41 climatic, two geophysical and 12 edaphic). Four morphological groups and three ecogeographic groups were identified. Morphological variability was evidenced mainly in descriptors related to the leaves, stems, and inflorescences. In addition, it was possible to identify accessions that appear capable of growing under extreme conditions of drought and poor soils. These accessions could be used for improvement.

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“…These studies likely underestimate the impact of inbreeding depression, as only measured plants that successfully grew from self-fertilized seed can be measured, missing impacts on seed germination and sexual reproduction traits. Further evidence for poor sexual reproductive ability in cassava comes from high variability in flowering time, low numbers of female flowers, high rates of flower abortion, and low seed set (Ceballos et al, 2004; Silva Souza et al, 2020; Oluwasanya et al, 2021). These limitations in seed production and viability limits breeders’ abilities to make the successful crosses inherently necessary for developing new varieties and making genetic gains.…”

Section: Introductionmentioning

confidence: 99%

Muller’s Ratchet in Action: The Erosion of Sexual Reproduction Genes in Domesticated Cassava (Manihot esculenta)

Long,

Stitzer,

Monier

et al. 2024

Preprint

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Centuries of clonal propagation in cassava (Manihot esculenta) have engaged Muller's Ratchet, leading to the accumulation of deleterious mutations due to the absence of sexual recombination. This has resulted in both inbreeding depression affecting yield and a significant decrease in reproductive performance, creating hurdles for contemporary breeding programs. Cassava is a member of the Euphorbiaceae family, including notable species such as rubber tree (Hevea brasiliensis) and poinsettia (Euphorbia pulcherrima). Expanding upon preliminary draft genomes, we annotated 7 long-read genome assemblies and aligned a total of 52 genomes, to analyze selection across the genome and the phylogeny. Through this comparative genomic approach, we identified 48 genes under relaxed selection in cassava. Notably, we discovered an overrepresentation of floral expressed genes, especially focused at six pollen-related genes. Our results indicate that domestication and a transition to clonal propagation has reduced selection pressures on sexually reproductive functions in cassava leading to an accumulation of mutations in pollen-related genes. This relaxed selection and the genome-wide deleterious mutations responsible for inbreeding depression are potential targets for improving cassava breeding, where the generation of new varieties relies on recombining favorable alleles through sexual reproduction.

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Phenological diversity of flowering and fruiting in cassava germplasm

Cited by 21 publications

References 14 publications

Flower Development in Cassava Is Feminized by Cytokinin, While Proliferation Is Stimulated by Anti-Ethylene and Pruning: Transcriptome Responses

Flower Development in Cassava Is Feminized by Cytokinin, While Proliferation Is Stimulated by Anti-Ethylene and Pruning: Transcriptome Responses

Morphological and Ecogeographic Study of the Diversity of Cassava (Manihot esculenta Crantz) in Ecuador

Muller’s Ratchet in Action: The Erosion of Sexual Reproduction Genes in Domesticated Cassava (Manihot esculenta)

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