Genetic analysis of vegetative branching in sorghum

Key message

We identified quantitative trait loci influencing plant architecture that may be valuable in breeding of optimized genotypes for sustainable food and/or cellulosic biomass production, and advancing resilience to changing climates.

Abstract

We describe a 3-year study to identify quantitative trait loci (QTLs) for vegetative branching of sorghum in a recombinant inbred line population of 161 genotypes derived from two morphologically distinct parents, S. bicolor × S. propinquum. We quantify vegetative branching based on morphological position and physiological status. Different sets of QTLs for different levels of branching were identified. QTLs discovered on chromosomes 1, 3, 7 and 8 affect multiple vegetative branching variables, suggesting that these regions may contain genes that control general axillary meristem initiation. Other regions that only influence one vegetative branching trait could contain genes that influence developmental processes contributing to divergent patterns of plant architecture. We investigate the relationship between vegetative branching patterns and dry biomass, and conclude that tillers with mature panicles and immature secondary branches each show consistent positive correlation with dry biomass. Among 19 branching-related genes from rice, eight sorghum homologs of seven rice genes are in syntenic blocks within branching-related QTL likelihood intervals. Five of these eight genes are within 700 kb of SNPs significantly associated with differences in branching in genome-wide association study of a diversity panel of 377 sorghum accessions, and three contain striking allelic variations between S. bicolor and S. propinquum that are likely to impact gene functions. Unraveling genetic determinants for vegetative branching may contribute to deterministic breeding of optimized genotypes for sustainable food and cellulosic biomass production in both optimal and marginal conditions, which are resilient to future climates that are more volatile and more stressful.     

Vegetative Propagule Pressure and Water Depth Affect Biomass and Evenness of Submerged Macrophyte Communities

Vegetative propagule pressure may affect the establishment and structure of aquatic plant communities that are commonly dominated by plants capable of clonal growth. We experimentally constructed aquatic communities consisting of four submerged macrophytes (Hydrilla verticillata, Ceratophyllum demersum, Elodea nuttallii and Myriophyllum spicatum) with three levels of vegetative propagule pressure (4, 8 and 16 shoot fragments for communities in each pot) and two levels of water depth (30 cm and 70 cm). Increasing vegetative propagule pressure and decreasing water level significantly increased the growth of the submerged macrophyte communities, suggesting that propagule pressure and water depth should be considered when utilizing vegetative propagules to re-establish submerged macrophyte communities in degraded aquatic ecosystems. However, increasing vegetative propagule pressure and decreasing water level significantly decreased evenness of the submerged macrophyte communities because they markedly increased the dominance of H. verticillata and E. nuttallii, but had little impact on that of C. demersum and M. spicatum. Thus, effects of vegetative propagule pressure and water depth are species-specific and increasing vegetative propagule pressure under lower water level can facilitate the establishment success of submerged macrophyte communities.     

The PSI family of nuclear proteins is required for growth in arabidopsis

PSI1 was identified as a gene that is co-expressed with the phytosulfokine (PSK) receptor genes PSKR1 and PSKR2 in Arabidopsis thaliana. It represents a plant-specific protein family of unknown function with six members in two clades. Clade 1 members PSI1, PSI2 and PSI3 were characterized in this study. All three are nuclear localized. A predicted N-terminal myristoylation site was functionally analyzed. psi1-1 seedlings have shorter roots and hypocotyls. This growth-retarded phenotype was restored by expression of either wildtype PSI1 or PSI1 _G2A with a mutated myristate attachment site in the psi1-1 background suggesting that myristate attachment was not essential for PSI1 function. psi2-1 and psi3-1 seedlings have a wildtype phenotype but overexpression of PSI1 or PSI2 promoted seedling growth. PSI2 activity appears to be linked to PSK signaling as psi2-1 and psi2-1 psi3-1 roots are unresponsive to PSK. PSI3 functions in vegetative plant growth synergistic with PSI2. psi3-1 and particularly psi2-1 psi3-1 rosettes are small. Overexpression of PSI3 promoted plant growth indicating that PSI3 is limiting at the vegetative stage. Severe dwarfism of psi2-1 psi3-1 plants results from reduced cell growth and proliferation and premature leaf growth arrest. Plants further display reduced fertility and premature senescence revealing a crucial function of PSI proteins in vegetative growth and reproduction. Psi single and double knock-out plants have less and PSI3ox plants have more starch compared to wt and growth retardation is partially rescued by sucrose. Our studies reveal a crucial function of the nuclear-localized PSI proteins in growth possibly through metabolic control.     

Combined use of leaf size and economics traits allows direct comparison of hydrophyte and terrestrial herbaceous adaptive strategies

Background and Aims

Hydrophytes generally exhibit highly acquisitive leaf economics. However, a range of growth forms is evident, from small, free-floating and rapidly growing Lemniden to large, broad-leaved Nymphaeiden, denoting variability in adaptive strategies. Traits used to classify adaptive strategies in terrestrial species, such as canopy height, are not applicable to hydrophytes. We hypothesize that hydrophyte leaf size traits and economics exhibit sufficient overlap with terrestrial species to allow a common classification of plant functional types, sensu Grime''s CSR theory.

Methods

Leaf morpho-functional traits were measured for 61 species from 47 water bodies in lowland continental, sub-alpine and alpine bioclimatic zones in southern Europe and compared against the full leaf economics spectrum and leaf size range of terrestrial herbs, and between hydrophyte growth forms.

Key Results

Hydrophytes differed in the ranges and mean values of traits compared with herbs, but principal components analysis (PCA) demonstrated that both groups shared axes of trait variability: PCA1 encompassed size variation (area and mass), and PCA2 ranged from relatively dense, carbon-rich leaves to nitrogen-rich leaves of high specific leaf area (SLA). Most growth forms exhibited trait syndromes directly equivalent to herbs classified as R adapted, although Nymphaeiden ranged between C and SR adaptation.

Conclusions

Our findings support the hypothesis that hydrophyte adaptive strategy variation reflects fundamental trade-offs in economics and size that govern all plants, and that hydrophyte adaptive strategies can be directly compared with terrestrial species by combining leaf economics and size traits.     

Nitrogen distribution index ofCajanus cajan L. during drought and rehydration

Relative competition among various plant parts for N during water stress,i.e. nitrogen distribution index (NDI) was determined in relation to specific nitrogenase activity (SNA) and nodule and soil nitrogen in both indeterminate (H-77-216) and determinate (ICPL-151) types of pigeonpea (Cajanus cajan L.) under greenhouse conditions. Two levels of water stress,i.e. moderate (soil Ψ_w) -0.77 MPa) and severe (soilΨ_w -1.34 MPa) were created by witholding the irrigation at vegetative (40 DAS) and flowering (70 DAS) stages. At vegetative stage under moderate stress the highest NDI was in nodules of cv. H-77-216 and in leaf of cv. ICPL-151. Under severe stress both the cultivars showed negative values of NDI, with maximum loss of N from root and nodules. Cultivar ICPL-151 behaved differently at flowering and vegetative stages. Very high loss of N from different plant parts was seen at flowering under severe stress. All the plant parts showed gain in N during rehydration. Loss and gain in N at both the stages under stress and rehydration respectively, correlated with available N in soil. Specific nitrogenase activity (SNA) and nodule N were maximum at moderate stress and related with NDI values of leaf and nodules.     

Effect of calcium on water-stress-induced biochemical changes and yield of field-grown rice

Three different treatments by calcium (10²M), namely seed treatment, foliar spraying and their combination were applied on field-grown rice (Oryza sativa L. cv. Ratna) under both water stressed and non-stressed conditions in the course of plant development. The relative water content and leaf water potential decreased with increase in age of stressed and non-stressed plants. Pretreatment of seeds with Ca improved the water status of the plants most prominently at the vegetative stage but the effect gradually faded away with plant development. The foliar spraying by Ca was more effective in improving the water status of the plants at the reproductive stage. The combined Ca treatment significantly improved water status of the plants both at the vegetative and reproductive stages. The contents of chlorophyll and protein decreased and the activities of protease and RNase increased in the course of plant development in both non-stressed and even more in stressed plants. Ca treatments of seeds or plants or their combination inhibited the decline in chlorophyll and protein contents and the rising trends of protease and RNase activities, the combined treatment being most effective. During plant development free proline content increased significantly more in water stressed plants. In non-stressed plants there was a marked increase in the free proline content at the mature fruit stage. Ca treatment inhibited the rise of free proline in stressed plants. A significant reduction in yield components and yield of the crop in water stressed plants was increased by Ca treatment.     

Isolation of Flower-inducing and Flower-inhibitory Factors from Aphid Honeydew

The aphid Dactynotus ambrosiae Thomas has been allowed to feed on vegetative or flowering plants of the short-day plant Xanthium strumarium L., and the honeydew which they produce is extracted and tested for an effect on flowering using the long-day plant Lemna gibba L., strain G3 for the bioassay. One zone of flower-inducing activity and at least two zones of flower-inhibitory activity are consistently obtained from the honeydew extracts. The levels of flower-inducing and flower-inhibitory activity are not demonstrably different in vegetative and flowering honeydew. The honeydew extracts are inactive on Xanthium but do give some flower induction with the short-day plant Lemna perpusilla Torr., strain 6746. The flower-inducing activity is clearly of plant origin and is present in the phloem since the same active material can be obtained from vegetative or flowering Xanthium by methanol extraction, and honeydew produced by aphids feeding on a chemically defined synthetic diet is completely without flower-inducing activity. This is the first report of successful flower induction in the long-day plant L. gibba G3 by some means other than long-day treatment.     

Bioclimatic perspectives in the distribution of Quercus ithaburensis Decne. subspecies in Turkey and in the Levant

Aim To define the bioclimatic tolerance ranges of the two Tabor oak subspecies. Prior to this definition, and considering the confusion in the literature regarding the Tabor oak subspecies geography, a reassessment of their present distribution is proposed. Location Turkey and the Levant. Methods The bioclimatic tolerance range of each subspecies was characterized by four parameters: (1) the humidity category (Q₂), (2) the winter variant (m) – the two basic variables used in Emberger's method for the definition of Mediterranean bioclimates, (3) the length of the dry season (LDS) and (4) its severity, expressed by the dry season water deficit (DSWD). The reference to the last two variables in the definition of bioclimatic tolerance ranges of Mediterranean species has so far never been considered. The concept of bioclimatic niche, based on the reference to these four parameters, is proposed and discussed. Results The reassessment of the Tabor oak subspecies distribution shows that their extents of occurrence do not overlap and are significantly distant. The comparison between the characteristics of each subspecies bioclimatic niche has highlighted three major differences: (1) The bioclimatic niche of the subspecies macrolepis is characterized by a great heterogeneity as it includes up to 10 distinct bioclimate types, whereas only four types have been found in the bioclimatic niche of the subspecies ithaburensis. (2) A 10 °C gap has been found between the winter variants of both bioclimatic niches. (3) The third major difference relates to the dry season characteristics: the bioclimatic niche of the subspecies ithaburensis is characterized by an LDS 40–75% longer than it is in the bioclimatic niche of the subspecies macrolepis. Moreover, and surprisingly, although the most arid humidity categories are found in the bioclimatic niche of the subspecies macrolepis, the bioclimatic niche of the subspecies ithaburensis is characterized by a significantly more severe dry season as the DSWD is 36–180% greater than in the bioclimatic niche of the subspecies macrolepis. It is suggested that the duration and the severity of the dry season is a major limiting factor in the spatial distribution of the subspecies macrolepis. Main conclusions The reference to the duration (LDS) and severity (DSWS) of the dry season is essential when defining the bioclimatic niche of Mediterranean species.     

Plant functional types and climate at the global scale

Abstract. Globally applicable sets of terrestrial plant functional types (PFTs) have been identified as a major need in the development of dynamic global vegetation models for use with global atmospheric models. Global sets of PFTs should represent the world's most important plant types; characterize them through their functional behavior; and provide complete, geographically representative coverage of the world's land areas. Three main schools of thought on PFTs have emerged: (1) a physiological focus on internal function, especially at the level of basic metabolism; (2) an ecological focus on function in relation to plant form and environmental conditions; and (3) a geophysical focus on how plant functions affect the adjacent atmosphere. A structural approach based on pheno-physiognomy permits ready identification of relatively familiar, recognizable plant types. Many of the criteria cited by other approaches also are intimately related to structure and its seasonal changes. An earlier global system of structural-functional PFTs and their climatic relations has been improved, including addition of less well-known plant types, and is briefly described. A more strictly ‘functional’ approach is proposed, in which major aspects of plant function, initially metabolism and water balance, are used to classify functional types and suggest how these are constrained by climate. Such functional considerations, however, are closely linked to structural manifestations - but also require other functional criteria for more completely functional classifications. A recent global model of potential natural vegetation types suggested ca. 15 major plant types as necessary to cover the world's main terrestrial vegetation patterns. These essential types correspond well with a first-cut set of structural types implied by metabolic considerations.     

A functional cutin matrix is required for plant protection against water loss

The plant cuticle, a cutin matrix embedded with and covered by wax, seals the aerial organ''s surface to protect the plant against uncontrolled water loss. The cutin matrix is essential for the cuticle to function as a barrier to water loss. Recently, we identified from wild barley a drought supersensitive mutant, eibi1, which is caused by a defective cutin matrix as the result of the loss of function of HvABCG31, an ABCG full transporter. Here, we report that eibi1 epidermal cells contain lipid-like droplets, which are supposed to consist of cutin monomers that have not been transported out of the cells. The eibi1 cuticle is fragile due to a defective cutin matrix. The rice ortholog of the EIBI1 gene has a similar pattern of expression, young shoot but not flag leaf blade, as the barley gene. The model of the function of Eibi1 is discussed. The HvABCG31 full transporter functions in the export of cutin components and contributed to land plant colonization, hence also to terrestrial life evolution.Key words: ABC transporter, cuticle, cuticular wax, drought resistance, inclusion     

The Essential Oils of the Greek Endemic Satureja horvatii ssp. macrophylla in Relation to Bioclimate

The essential oils of the Greek endemic Satureja horvatii subsp. macrophylla collected from 36 areas (among them, 23 are included in twelve sites of the EU network NATURA 2000) belonging to different bioclimatic types were studied. The total essential‐oil content is negatively related to the altitude. The variation of the essential oil composition follows a geographical pattern, which is related to the bioclimatic belts along the taxon's range. Carvacrol dominates in areas with Mediterranean and Submediterranean bioclimate (mainly in the S and C part of the taxon's distribution), linalool or trans‐sabinene hydrate, and/or borneol in the Submediterranean or Temperate Axeric bioclimates (in the N part of distribution), whereas thymol is found as main oil constituent in all three bioclimates.     

Ecophysiological and bioclimatic foundations for a global plant functional classification

Question: What plant properties might define plant functional types (PFTs) for the analysis of global vegetation responses to climate change, and what aspects of the physical environment might be expected to predict the distributions of PFTs? Methods: We review principles to explain the distribution of key plant traits as a function of bioclimatic variables. We focus on those whole‐plant and leaf traits that are commonly used to define biomes and PFTs in global maps and models. Results: Raunkiær's plant life forms (underlying most later classifications) describe different adaptive strategies for surviving low temperature or drought, while satisfying requirements for reproduction and growth. Simple conceptual models and published observations are used to quantify the adaptive significance of leaf size for temperature regulation, leaf consistency for maintaining transpiration under drought, and phenology for the optimization of annual carbon balance. A new compilation of experimental data supports the functional definition of tropical, warm‐temperate, temperate and boreal phanerophytes based on mechanisms for withstanding low temperature extremes. Chilling requirements are less well quantified, but are a necessary adjunct to cold tolerance. Functional traits generally confer both advantages and restrictions; the existence of trade‐offs contributes to the diversity of plants along bioclimatic gradients. Conclusions: Quantitative analysis of plant trait distributions against bioclimatic variables is becoming possible; this opens up new opportunities for PFT classification. A PFT classification based on bioclimatic responses will need to be enhanced by information on traits related to competition, successional dynamics and disturbance.     

Habitat distribution modeling of endangered medicinal plant Picrorhiza kurroa (Royle ex Benth) under climate change scenarios in Uttarakhand Himalaya,India

Climate change has been the key factor in changing the alpine vegetation's habitat and causing it to migrate to higher latitudes. The present study aims to model the current and future potential habitat distribution of endangered medicinal plant Picrorhiza kurroa Royle ex Benth in Uttarakhand Himalaya using the maximum entropy (MaxEnt) modeling. We initially select twenty-two environmental variables (bioclimatic + topographic) got from the Fifty-four (54) species occurrence points, which were further reduced to nine variables to prevent multicollinearity. Shared Socioeconomic Pathways (SSP1–2.6 and SSP2–4.5) from the CMIP6 (BCC-CSM2-MR) climate model for the periods 2041–60 and 2061–80 were used to predict the current and future habitat distribution of P. kurroa. Results showed that the precipitation of the driest month (Bio 14; 33.8%), isothermality (Bio 3; 20.2%), mean temperature of warmest quarter (Bio 10; 12.7%), and temperature annual range (Bio 7; 12.2%) were the important bioclimatic variables influencing the habitat of P. kurroa. Overall, there is a decrease in the habitat of P. kurroa under climate change scenarios. The present results may prove insightful for the decision-makers to identify suitable sites in the wild for the further propagation of P. kurroa.     

Bryophytes of Europe Traits (BET) data set: A fundamental tool for ecological studies

Bryophytes are a diverse group of organisms with unique properties, yet they are severely underrepresented in plant trait databases. Building on the recently published European Red List of bryophytes and previous trait compilations, we present the Bryophytes of Europe Traits (BET) data set, including biological traits such as those related to life history, growth habit, sexual and vegetative reproduction; ecological traits such as indicator values, substrate and habitat; and bioclimatic variables based on the species' European range. The data set includes values for 65 traits and 25 bioclimatic variables, containing more than 135,000 trait values with a completeness of 82.7% on average. The data set will enable future studies in bryophyte biology, ecology and conservation, and may help to answer fundamental questions in bryology.     

Assessment of ecological diversity of rhizobacterial communities in vermicompost and analysis of their potential to improve plant growth

Present study was designed to determine the microbial diversity from three distinctive sites (amended with vermicompost) of Gujarat, India. A set of 76 strains were screened from total of 438 strains that exhibit plant growthpromoting (PGP) and antagonistic potential isolated from sites PS1 (Mehsana district), BS2 (Dantiwada district) and VS3 (Gandhinagar district). Their diversity indices were studied for determining the species richness and evenness of screened isolates. Results revealed that site BS2 showed the most significant diversity indices in terms of Shannon (H′ 1.525) and Simpson (1/D 5.120) than other two samples. Principal component analysis showed that bacterial diversity (H′) was correlated with the soil characteristics. Chickpea and groundnut plants inoculated with MBCU1 and MBCU3 isolates showed an increase in the vegetative growth parameters that evaluate plant growth when compared to uninoculated controls. Strains MBCU1 and MBCU3 were identified as Pseudomonas stutzeri and Pseudomonas mosselii, respectively, according to sequence analysis of the 16S rRNA gene. These both isolates belong to site BS2 and they showed specific PGP traits suggesting that these isolates can promote plant growth by more than one mechanism with respect to their higher diversity index.