Pre-flowering Drought Research Articles

APSIM-based modeling approach to understand sorghum production environments in Mali

Sorghum production system in the semi-arid region of Africa is characterized by low yields which are generally attributed to high rainfall variability, poor soil fertility, and biotic factors. Production constraints must be well understood and quantified to design effective sorghum-system improvements. This study uses the state-of-the-art in silico methods and focuses on characterizing the sorghum production regions in Mali for drought occurrence and its effects on sorghum productivity. For this purpose, we adapted the APSIM-sorghum module to reproduce two cultivated photoperiod-sensitive sorghum types across a latitude of major sorghum production regions in Western Africa. We used the simulation outputs to characterize drought stress scenarios. We identified three main drought scenarios: (i) no-stress; (ii) early pre-flowering drought stress; and (iii) drought stress onset around flowering. The frequency of drought stress scenarios experienced by the two sorghum types across rainfall zones and soil types differed. As expected, the early pre-flowering and flowering drought stress occurred more frequently in isohyets < 600 mm, for the photoperiod-sensitive, late-flowering sorghum type. In isohyets above 600 mm, the frequency of drought stress was very low for both cultivars. We quantified the consequences of these drought scenarios on grain and biomass productivity. The yields of the highly-photoperiod-sensitive sorghum type were quite stable across the higher rainfall zones > 600 mm, but was affected by the drought stress in the lower rainfall zones < 600 mm. Comparatively, the less photoperiod-sensitive cultivar had notable yield gain in the driest regions < 600 mm. The results suggest that, at least for the tested crop types, drought stress might not be the major constraint to sorghum production in isohyets > 600 mm. The findings from this study provide the entry point for further quantitative testing of the Genotype × Environment × Management options required to optimize sorghum production in Mali.

Drought and recovery in barley: key gene networks and retrotransposon response.

During drought, plants close their stomata at a critical soil water content (SWC), together with making diverse physiological, developmental, and biochemical responses. Using precision-phenotyping lysimeters, we imposed pre-flowering drought on four barley varieties (Arvo, Golden Promise, Hankkija 673, and Morex) and followed their physiological responses. For Golden Promise, we carried out RNA-seq on leaf transcripts before and during drought and during recovery, also examining retrotransposon BARE1expression. Transcriptional data were subjected to network analysis. The varieties differed by their critical SWC (ϴcrit), Hankkija 673 responding at the highest and Golden Promise at the lowest. Pathways connected to drought and salinity response were strongly upregulated during drought; pathways connected to growth and development were strongly downregulated. During recovery, growth and development pathways were upregulated; altogether, 117 networked genes involved in ubiquitin-mediated autophagy were downregulated. The differential response to SWC suggests adaptation to distinct rainfall patterns. We identified several strongly differentially expressed genes not earlier associated with drought response in barley. BARE1 transcription is strongly transcriptionally upregulated by drought and downregulated during recovery unequally between the investigated cultivars. The downregulation of networked autophagy genes suggests a role for autophagy in drought response; its importance to resilience should be further investigated.

Exploring drought-responsive crucial genes in Sorghum

Drought severely affects global food production. Sorghum is a typical drought-resistant model crop. Based on RNA-seq data for Sorghum with multiple time points and the gray correlation coefficient, this paper firstly selects candidate genes via mean variance test and constructs weighted gene differential co-expression networks (WGDCNs); then, based on guilt-by-rewiring principle, the WGDCNs and the hidden Markov random field model, drought-responsive crucial genes are identified for five developmental stages respectively. Enrichment and sequence alignment analysis reveal that the screened genes may play critical functional roles in drought responsiveness. A multilayer differential co-expression network for the screened genes reveals that Sorghum is very sensitive to pre-flowering drought. Furthermore, a crucial gene regulatory module is established, which regulates drought responsiveness via plant hormone signal transduction, MAPK cascades, and transcriptional regulations. The proposed method can well excavate crucial genes through RNA-seq data, which have implications in breeding of new varieties with improved drought tolerance.

Genome-wide association studies identify putative pleiotropic locus mediating drought tolerance in sorghum.

Drought is a key constraint on plant productivity and threat to food security. Sorghum ( Sorghum bicolor L. Moench), a global staple food and forage crop, is among the most drought‐adapted cereal crops, but its adaptation is not yet well understood. This study aims to better understand the genetic basis of preflowering drought in sorghum and identify loci underlying variation in water use and yield components under drought. A panel of 219 diverse sorghum from West Africa was phenotyped for yield components and water use in an outdoor large‐tube lysimeter system under well‐watered (WW) versus a preflowering drought water‐stressed (WS) treatment. The experimental system was validated based on characteristic drought response in international drought tolerant check genotypes and genome‐wide association studies (GWAS) that mapped the major height locus at QHT7.1 and Dw3. GWAS further identified marker trait associations (MTAs) for drought‐related traits (plant height, flowering time, forage biomass, grain weight, water use) that each explained 7–70% of phenotypic variance. Most MTAs for drought‐related traits correspond to loci not previously reported, but some MTA for forage biomass and grain weight under WS co‐localized with staygreen post‐flowering drought tolerance loci (Stg3a and Stg4). A globally common allele at S7_50055849 is associated with several yield components under drought, suggesting that it tags a major pleiotropic variant controlling assimilate partitioning to grain versus vegetative biomass. The GWAS revealed oligogenic variants for drought tolerance in sorghum landraces, which could be used as trait predictive markers for improved drought adaptation.

Distinct Preflowering Drought Tolerance Strategies of Sorghum bicolor Genotype RTx430 Revealed by Subcellular Protein Profiling.

Drought is the largest stress affecting agricultural crops, resulting in substantial reductions in yield. Plant adaptation to water stress is a complex trait involving changes in hormone signaling, physiology, and morphology. Sorghum (Sorghum bicolor (L.) Moench) is a C4 cereal grass; it is an agricultural staple, and it is particularly drought-tolerant. To better understand drought adaptation strategies, we compared the cytosolic- and organelle-enriched protein profiles of leaves from two Sorghum bicolor genotypes, RTx430 and BTx642, with differing preflowering drought tolerances after 8 weeks of growth under water limitation in the field. In agreement with previous findings, we observed significant drought-induced changes in the abundance of multiple heat shock proteins and dehydrins in both genotypes. Interestingly, our data suggest a larger genotype-specific drought response in protein profiles of organelles, while cytosolic responses are largely similar between genotypes. Organelle-enriched proteins whose abundance significantly changed exclusively in the preflowering drought-tolerant genotype RTx430 upon drought stress suggest multiple mechanisms of drought tolerance. These include an RTx430-specific change in proteins associated with ABA metabolism and signal transduction, Rubisco activation, reactive oxygen species scavenging, flowering time regulation, and epicuticular wax production. We discuss the current understanding of these processes in relation to drought tolerance and their potential implications.

Effects of Drought Stress on the Growth, Yield and Physiological Traits of Thai Super Sweet Corn

Growth and yield performances of Thai Super Sweet (TSS) corn cultivar treated with various drought stress levels (25%, 50% and 100% Field Capacity, FC) at various growth stages (vegetative, pre-flowering and flowering) were investigated in an insect-proof net-house of Faculty of Sustainable Agriculture, Universiti Malaysia Sabah, Sandakan Campus. Drought treatments were applied at vegetative (14 to 34 days after sowing (DAS)), pre-flowering (35 to 55 DAS) and flowering (48 to 68 DAS) stages. Parameters measured and statistically analysed were growth, chlorophyll content, proline content and yield. The experiment was conducted as 3 x 3 factorial arrangements of treatments with a completely randomised design with four replications for each treatment. Length of first cob and fresh weight of the first cob showed interaction effects among the drought and growth stage treatments while chlorophyll content, number of cobs, cob girth, number of grains, 100 grains weight and proline content showed significant effects among drought levels treatments and cob girth showed significant effect among growth stages. Shorter flowering time (tasseling at 42 DAS) was found on drought treatment of 25% FC at the pre-flowering stage. It can be concluded that vegetative and flowering stages were sensitive to drought compared to the pre-flowering stage, where the yield components of vegetative and flowering stages were lower compared to the pre-flowering stage. During the pre-flowering drought period, TSS expressed tolerance response through the higher levels of chlorophyll and proline contents and hence able to perform the best overall yield components.

Sorghum drought and heat stress patterns across the Argentinean temperate central region

Argentinean current sorghum management is similar across the entire temperate region, and no environmental characterization is assisting breeding and management decisions. Crop growth and development simulation models are a valuable tool for generating this characterization. Our study calibrated and validated APSIM-sorghum for our genetics and production environments, and used it to characterize the main water and heat stress patterns at our temperate central region. The calibration and validation provided accurate phenology, biomass, and yield estimations. Long-term weather records (44–61 years per site) and soil data were used to simulate the seasonal drought patterns at seven representative sites across the region. Clustering analysis identified three major drought environmental types (ENVT): (i) a pre-flowering drought stress, showing large occurrence frequency (39%), (ii) a low terminal drought stress, showing similar frequency (38%), and (iii) a grain-filling drought stress, showing lower frequency (23%). The most frequent ENVT at individual sites agrees with the spatial distribution of annual rainfall. However, most sites evidenced variable frequency of all ENVT. Flowering heat stress (>33 °C) showed an intermediate occurrence frequency (20–50%) only at lower latitudes, and was independent of drought ENVT. Defined ENVT helped explain observed genotype x environment (GxE) interactions for yield in an independent data set, showing they have practical implications for optimizing breeding and management strategies across the region of interest. Grouping sites of similar frequency can help to handle the spatial variability when defining these strategies, but dealing with seasonal variability will be challenging in the context of no predominant ENVT.

Photosynthetic Responses to High Temperature and Strong Light Suggest Potential Post-flowering Drought Tolerance of Sorghum Japanese Landrace Takakibi.

Sorghum [Sorghum bicolor (L.) Moench] is a C4 crop known to be adaptable to harsh environments such as those under high temperature and water deficit. In this study, we focused on a Japanese sorghum landrace Takakibi (NOG) and employed chlorophyll fluorescence measurements to assess its response to environmental stress. Comparison of photosynthetic rate evaluated using two parameters (effective quantum yield and electron transfer rate) indicated that NOG showed less activity than BTx623 in the pre-flowering stage, which was consistent with the higher susceptibility of NOG seedlings to drought than BTx623. The observed differences in photosynthetic activity between the two cultivars were detectable without drought conditions on days with high temperature and strong light. Interestingly, the photosynthetic activity of NOG leaves in stress conditions increased soon after heading, and the trend was similar to that in BTx642, a well-characterized post-flowering drought-tolerant cultivar. In contrast, BTx623 showed a gradual decline in photosynthetic rate. Thus, we inferred that Japanese Takakibi has the potential to show pre-flowering drought susceptibility and post-flowering drought tolerance, through which it adapts to local climates with high temperature and strong light at harvest.

Effect of Pre Flowering Drought on Flowering Behaviour of Yield in Groundnut

The groundnut is one of the important legume crops of tropical and semiarid tropical countries. Drought is the one of the major constraints to groundnut production as it is rainfed crop. Drought at flowering or pod formation can substantially reduce yield of ground but pre-flowering or vegetative stage is not detrimental and actually increases yield. Pot culture study was undertaken to study the effect of pre flowering drought on groundnut yield. Four groundnut genotypes were taken for this study namely CO 7, COGn 4, TMV 7 and TMV 13. Drought was imposed at three stages viz., Pre flowering drought (PFD) between 15- 30 DAS, flowering drought (FD) between 35-50 DAS and post flowering drought between 75-90 DAS (PoFD) by withholding water and control maintained with irrigation to field capacity for comparison. Among four genotypes, CO 7 performed better when compared to other genotypes under pre-flowering drought which produced more flowers (134), pegs (38), pods per plant (26) than control, flowering and post flowering drought. The results revealed that 21.18 per cent of increased pod yield was obtained compared to control under PFD in CO 7. Higher reproductive efficiency of groundnut is higher conversion rates of flowers to pegs, pegs to pods and of total pods to mature pods.

Influence of Pre Flowering Drought on Physiological Parameters and Yield in Groundnut

WGroundnut (Arachis hypogaea L.) is one of the world’s most important legumes. Groundnut provides one of the largest sources of edible oils proteins and also rich source of vitamins, minerals, anti-oxidants, flavonoids and isoflavonoids and commonly called as poor man’s nut. Drought is one of the major factors for groundnut as it is grown in the areas where there is less rainfall. This investigation was conducted to study the physiological parameters in association with groundnut yield under drought with four genotypes namely CO 7, COGn 4, TMV 7, TMVGn 13. Drought was imposed at Pre flowering stage 15-30 DAS by withholding water and control was also maintained with irrigation to field capacity for comparison. Physiological parameters like leaf area, chlorophyll Index, photosynthetic rate, were high in pre-flowering drought recovery plants of CO 7 which contributes to higher pod yield (21.18 %) compared to control plants. In this study the effects of soil moisture deficit on groundnut have been extensively studied and it has been concluded that water stress at pre flowering stage increases the yield.

Agro-morphological characterization of diverse sorghum lines for pre-and post-flowering drought tolerance

The impact of drought stress on sorghum yield does not only depend on the intensity and timing of drought, but as well on the developmental stage of the crop. One of the limitations in breeding for pre-and/or postflowering drought stress resistance in sorghum is the less availability of diverse genetic sources possessing drought tolerant agro-morphological or physiological traits that could be introgressed into elite sorghum lines. This research evaluate a diverse group of 54 introgressed, converted, and commonly used sorghum breeding lines for their tolerance to field drought stress imposed at the pre-flowering and post-anthesis developmental stages in 2015 and 2016 growing seasons. Agro-morphological characteristics such as panicle area, panicle width, and percent green leaf and yield-related characteristics such as total above ground dry biomass and dry panicle weight were identified as significant predictors of grain yield under water stress. The current research identifies other sources that could be use by breeding programs as donor lines for traits related to pre-and postflowering drought tolerance in sorghum. Following statistical distribution and Tukey-Krammer HSD connecting letter tests, lines JB39, SC191, and SC270 and RIL R.11269 were identified as plausible sources for pre-flowering drought tolerance, and JB14, JB15, JB19, JB22, JB24, JB25, JB26, and JB33 as sources for the staygreen trait. While the staygreen is a good selection tool for postflowering drought tolerance, identifying staygreen lines with minimal reductions in grain yield and with earlier flowering dates (JB14, JB22, JB24 and JB25 in this study) than most commonly used staygreen donor lines, will ensure that grain yield is not over sacrificed by the ability of the crop to staygreen under terminal drought conditions.

Mild preflowering drought priming improves stress defences, assimilation and sink strength in rice under severe terminal drought.

Drought stress is a prominent and persisting constraint for sustaining global rice (Oryza sativa L.) production. Priming with mild drought can be effective in reducing the impact of severe terminal drought stress affecting seed set and grain filling in rice. The cultivars N22 (drought tolerant), NSIC Rc222 and IR64 (high yielding, drought sensitive) were tested for short-term mild drought priming before flowering and subsequently exposed to severe drought stress either at the highly sensitive flowering or at the early grain filling stage under greenhouse conditions. Drought stress increased oxidative damage and reduced photosynthesis and sink enzymatic activity, ultimately reducing seed set (20-46%) and grain yield (22-68%) across cultivars. However, priming with mild drought significantly reduced oxidative damage, and increased photosynthesis, stomatal conductance and enzymatic activity, contributing to improved sink strength, thereby significantly reducing seed set (7-18%) and grain yield (12-59%) losses. The higher activity of key enzymes associated with sink strength such as cell wall invertase and sucrose synthase in primed plants probably reduced drought-induced losses at the grain filling stage. The findings support mild drought priming before flowering as a promising strategy for reducing yield penalty by providing partial protection against subsequent severe terminal drought stress. However, application of mild drought priming at the field level would need further investigation.

Drought-induced responses of organic osmolytes and proline metabolism during pre-flowering stage in leaves of peanut (Arachis hypogaea L.)

AbstractPeanut (Arachis hypogaea L.), an improtant oil crop, usually encounters drought stress in the process of growth and development, especially at pre-flowering stage. In order to gain insight into the drought tolerance potentials based on osmolyte accumulation and metabolism of proline aspects of peanut, pot experiments were conducted with a split-plot design in Tai'an, Shangdong Province, China in 2013 and 2014. Pre-flowering drought (PFD) stress and optinum irrigation (control, CK) were served as the main plots and the two peanut cultivars Shanhua 11 and Hua 17 served as sub-plots. Shanhua 11 was drought-tolerant cultivar and Hua 17 was drought-sensitive. The content of soluble sugars, soluble protein, free proline and other free amino acids, the activities of enzymes involved in proline metabolism, and malondialdehyde (MDA) content and ion leakage were all investigated in the two cultivars at pre-flowering stage. Results showed that PFD stress significantly increased the levels of soluble protein, free proline and free amino acid, and increased Δ1-pyrroline-5-carboxylate synthetase (P-5-CS, EC 2.7.2.11) activity in the leaves of drought-tolerant and drought-sensitive cultivars. The activity of proline dehydrogenase (proDH) (EC 1.5.99.8) decreased under PFD stress in both cultivars. The leaves of the tolerant cultivar maintained higher increments of osmolyte levels, lower increments of MDA content and ion leakage, as well as a higher increased proportion of P-5-CS activity and higher inhibited proportion of proDH activity under water stress compared with the drought-sensitive cultivar. The study suggests that proline accumulation in peanut leaves under PFD can be explained by the higher enhanced activities of P-5-CS and higher inhibition of proDH. The results will provide useful information for genetic improvement of peanut under drought tolerance.

Physiological and Yield Responses of Groundnut (Arachis hypogaea L.) Genotypes to Drought

Groundnut (Arachis hypogaea L.) is an important oil seed crop mainly grown as rainfed crop. Due to erratic rainfall and frequent drought during the crop growth period, groundnut yields are generally low and unstable under rainfed conditions. Drought during critical crop growth stages is crucial for yield in groundnut varieties. But tolerant genotypes may give better yield due to maintenance of physiological responses that were triggered during drought. The experiment was conducted in the Department of Crop Physiology, Tamil Nadu Agricultural University, Coimbatore during 2015-2016 to study physiological characters responsible for improving yield of different groundnut genotypes viz., CO 7, COGn 4, TMV 7 and TMVGn 13 under water stress at different flowering phases viz., pre flowering drought (PFD) during 15- 30 DAS, flowering drought (FD) during 35-50 DAS and post flowering drought (PoFD) during 75-90 DAS by withholding irrigation and control was also maintained with watering up to field capacity for comparison. Observations on various physiological parameters viz., leaf area, root length, relative water content, osmotic potential and leaf gas exchange parameters including, photosynthetic rate, transpiration rate and stomatal conductance were studied during stress and recovery period. Among the treatments, the plants under PFD performed better in recording higher value of physiological parameters under stress and recovered quickly. The variety, CO7 was found to perform well under all stages of stress followed by TMV 7, TMVGn 13 and COGn 4 with respect to physiological parameters and yield.

Metabolic Responses of Two Contrasting Sorghums to Water‐Deficit Stress

ABSTRACTWater‐deficit stress responses in sorghum [Sorghum bicolor (L.) Moench] have been described in the literature as preflowering drought tolerant (postflowering senescent) or postflowering drought tolerant (preflowering drought sensitive). The underlying physiological mechanisms associated with these drought traits remain unclear. It was hypothesized that the preflowering drought sensitivity of stay‐green lines could be related to reported differences in osmotic potential among stay‐green and senescent lines resulting in an inability of the cultivars to either sense or respond the soil drying until the rate of drying is too great for the stay‐green lines to compensate. The objective of this study was to measure stress‐induced changes in relative water content, abscisic acid (ABA), proline, dhurrin, sucrose, and carbon assimilation during the onset of water‐deficit stress in the preflowering drought‐tolerant line SC1211–11E and the postflowering drought‐tolerant line BTx642 to determine if there were differential responses to the onset of soil drying. In both greenhouse and field studies, it was found that SC1211–11E had lower relative water contents and accumulated higher levels of ABA and proline than the BTx642. The SC1211–11E also showed increases in carbon assimilation shortly after the cessation of irrigation that declined with prolonged stress. These results provide new insights into the differential responses of pre and postflowering drought‐tolerant sorghum lines.

English

A study was conducted to evaluate the response of eleven wild type sorghum accessions to pre-flowering moisture stress. The experiment was carried out at Jimma University College of Agriculture and Veterinary Medicine research site under greenhouse condition in 2013/2014 cropping season. A randomized complete blocks design with two replications was used. The experiment was irrigated by a movable tubular irrigation system the whole season. Pre- flowering drought stress was induced by totally withholding irrigation from panicle differentiation to flowering. A total of 11 morphological characters putatively related with crop performance under drought were studied.&nbsp; Significant variation was found for leaf rolling, root length, leaf drying, plant height and flag leaf width; however, the remaining traits showed non-significant difference among treatments due to moisture stress at (p&le;0.05). Based on this finding, accessions TS217 and DA119 collected from Tigray and Amhara region respectively are found to have superior pre-flowering drought tolerance followed by accessionTS211compared with the check B35. Hence; the authors recommend using accession DA119 and TS217 as parent materials during improvement of sorghum for drought tolerance. However, since this result is limited to data collected in one year in one location and does not compare yields, including other locally adapted lines and doing the experiment over locations and seasons is advisable. &nbsp; Key words: Sorghum, drought, accession, pre-flowering, selection.

RESPONSES OF ROOTING TRAITS IN PEANUT GENOTYPES UNDER PRE-FLOWERING DROUGHT STRESS

The root is an important plant part contributing to peanut productivity under water-limited conditions. Root volume, root surface area and root diameter may be characters responding to pre-flowering drought (PFD) in peanut. The objectives of this study were to investigate the responses to PFD for root surface area, root volume and root diameter and to determine the inter-relationships among the response of rooting traits and the response of yield. The experiment was conducted under field conditions in the dry season 2007 and 2009. A split-plot experiment in a randomized complete block design was used. The main plots were field capacity (FC) and PFD and six peanut genotypes as the sub-plots. Root volume, root diameter and root surface were measured by auger method at 25 days after emergence (DAE), first seed (R5) and physiological maturity (R7). Total dry weight and pod yield were measured at harvest. Root surface area of ICGV 98305 with increase in pod yield was greater in deeper soil layers under PFD compared to FC treatment at both stress and recovery periods. Under PFD conditions, the correlations between drought tolerance index (DTI) for root surface area at deeper soil layer and DTI for pod yield in both seasons were positive and significant at stress and recovery periods, but the correlations were not significant for root diameter and root volume. The response of peanut for root surface area at deeper soil layer contributed to pod yield. This finding could be useful for peanut production in these drought conditions.

Morpho-Physiological Characterization of Cold-and Pre-flowering Drought Tolerance in Grain Sorghum (Sorghum bicolor L. Moench) Inbreds

Aim: The relationships between early -season cold temperature germination and pre flowering drought stress in eight grain sorghum inbreds were assessed using morpho physiological traits. Study Design: Field was laid out in a randomized complete block design. Place and Duration: The experiment was conducted at Vernon, Texas (34∫ 9'4N 99∞17'26W) during the month of April to August, 2013. Methodology: Lines were sown in the field in early April to deter mine early-season cold temperature germination. At the pre -booting stage, lines were subjected to limited and no irrigation treatments, to establish a correlation between cold temperature germination and pre-flowering drought stress tolerance. Pre -flowering drought tolerance was assessed at five defined phenological phases of the reproductive growth stage, using morpho physiological traits. Results:Final germination percent (FGP) differed among lines (range 30

Quantitative trait locus mapping of the transpiration ratio related to preflowering drought tolerance in sorghum (Sorghum bicolor).

To meet future food needs, grain production must increase despite reduced water availability, so waterproductivity must rise. One way to do this is to raise the ratio of biomass produced to water transpired, which is controlled by the ratio of CO2 assimilation (A) to transpiration (E) (i.e. the transpiration ratio, A : E divided by vapour pressure deficit) or anything affecting stomatal movement.. We describe the genetic variation and basis of A, E and A : E among 70 recombinant inbred lines (RILs) of sorghum (Sorghum bicolor (L.) Moench), using greenhouse experiments. Experiment 1 used 40% and 80% of field capacity (FC) as water regimes; Experiment 2 used 80% FC. Genotype had a significant effect on A, E and A : E. In Experiment 1, mean values for A : E were 1.2-4.4 mmol CO2 mol-1 H2O kPa-1 and 1.6-3.1 mmol CO2 mol-1 H2O kPa-1 under 40% and 80% FC, respectively. In Experiment 2, values were 5.6-9.8 mmol CO2 mol-1 H2O kPa-1. Pooled data for A : E and A : E VPD-1 from Experiment 1 indicate that A : E fell quickly at temperatures >32.3°C. A : E distributions were skewed. Mean heritabilities for A : E were 0.9 (40% FC) and 0.8 (80% FC). Three significant quantitative trait loci (QTLs) associated with A:E, two on SBI-09 and one on SBI-10, accounted for 17-21% of the phenotypic variation. Subsequent experiments identified 38 QTLs controlling variation in height, flowering, biomass, leaf area, greenness and stomatal density. Colocalisation of A : E QTLs with agronomic traits indicated that these QTLs can be used for improving sorghum performance through marker assisted selection (MAS) under preflowering drought stress.

Leaf Dhurrin Content is a Quantitative Measure of the Level of Pre‐ and Postflowering Drought Tolerance in Sorghum

ABSTRACTThe presence of preflowering or postflowering drought tolerance has been described in sorghum [Sorghum bicolor (L.) Moench]. Sorghum lines with preflowering drought tolerance tend to senesce under postflowering drought stress while sorghum lines with postflowering drought tolerance (the stay‐green trait) tend to be sensitive to preflowering drought stress. Assessments of these phenotypes have been dependent on the incidence of drought stress conditions at specific developmental stages to achieve meaningful evaluation. Therefore, field‐based evaluations, most of which are visual, are notoriously difficult to perform and require growing lines in multiple locations across several years to achieve efficient selection for these traits. Here we report and demonstrate a correlation between leaf dhurrin [(S)‐p‐hydroxymandelonitrile‐β‐D‐glucopyranoside] contents and the level of stay‐green based on leaf and plant death ratings during postflowering drought stresses. Postflowering drought‐tolerant stay‐green sorghums had elevated dhurrin contents while preflowering drought‐tolerant sorghum lines exhibited lower dhurrin contents. Lines with intermediate leaf and plant death ratings exhibited intermediate dhurrin levels. Finally, dhurrin levels determined before flowering from sorghum grown under irrigated or dryland conditions were related to the degree of pre‐ or postflowering drought tolerance.