Traits In Sorghum Research Articles

Genetic and genomic resources of sorghum to connect genotype with phenotype in contrasting environments.

With the recent development of genomic resources and high-throughput phenotyping platforms, the 21st century is primed for major breakthroughs in the discovery, understanding and utilization of plant genetic variation. Significant advances in agriculture remain at the forefront to increase crop production and quality to satisfy the global food demand in a changing climate all while reducing the environmental impacts of the world's food production. Sorghum, a resilient C4 grain and grass important for food and energy production, is being extensively dissected genetically and phenomically to help connect the relationship between genetic and phenotypic variation. Unlike genetically modified crops such as corn or soybean, sorghum improvement has relied heavily on public research; thus, many of the genetic resources serve a dual purpose for both academic and commercial pursuits. Genetic and genomic resources not only provide the foundation to identify and understand the genes underlying variation, but also serve as novel sources of genetic and phenotypic diversity in plant breeding programs. To better disseminate the collective information of this community, we discuss: (i) the genomic resources of sorghum that are at the disposal of the research community; (ii) the suite of sorghum traits as potential targets for increasing productivity in contrasting environments; and (iii) the prospective approaches and technologies that will help to dissect the genotype-phenotype relationship as well as those that will apply foundational knowledge for sorghum improvement.

Brittle Culm 1 Encodes a COBRA-Like Protein Involved in Secondary Cell Wall Cellulose Biosynthesis in Sorghum.

Plant mechanical strength contributes to lodging resistance and grain yield, making it an agronomically important trait in sorghum (Sorghum bicolor). In this study, we isolated the brittle culm 1 (bc1) mutant and identified SbBC1 through map-based cloning. SbBC1, a homolog of rice OsBC1 and Arabidopsis thaliana AtCOBL4, encodes a COBRA-like protein that exhibits typical structural features of a glycosylphosphatidylinositol-anchored protein. A single-nucleotide mutation in SbBC1 led to reduced mechanical strength, decreased cellulose content, and increased lignin content without obviously altering plant morphology. Transmission electron microscopy revealed reduced cell wall thickness in sclerenchyma cells of the bc1 mutant. SbBC1 is primarily expressed in developing sclerenchyma cells and vascular bundles in sorghum. RNA-seq analysis further suggested a possible mechanism by which SbBC1 mediates cellulose biosynthesis and cell wall remodeling. Our results demonstrate that SbBC1 participates in the biosynthesis of cellulose in the secondary cell wall and affects the mechanical strength of sorghum plants, providing additional genetic evidence for the roles of COBRA-like genes in cellulose biosynthesis in grasses.

Cover Image: NAB1 in tillering control

Tillering is an important agronomic trait in sorghum, contributing to grain yield and plant architecture. In this issue, Chen et al. (938–955) report that a mutation in NAB1 led to activation of axillary buds in sorghum, and NAB1 encodes a carotenoid‐cleavage dioxygenase, homologous to HTD1/D17 in rice and MAX3 in Arabidopsis.

Effect of Nitrogen Fertilizer on some Attributes of SorghumGrown in Saline Soil under Irrigation

The main objective of this study was to investigate the effects of 4 levels of Nitrogen (N) fertilizer (0, 25, 50 and 75 Kg N/fed) on some attributes of Sorghum (Sorghum bicolor L). This study was conducted in the farm of College of Agriculture, University of Bahri-Sudan; during the period 2014-2015. Where the soil is classified as saline with pH ranging from 7.5 -7.8. A randomized completely block designed (RCBD); with 3 replications and four (4) treatments was adopted. All recommended cultural practices were carried out timely. Data; pertaining some plant attributes were collected and analyzed. The result showed that the application of 75KgN/fed has increased both; the average number of leaves as well as the plant height compared to other levels of Nitrogen fertilizer including the control (Figure 1, Figure 2). For the average number of tillers concern, there is non -significant difference between all Nitrogen levels and average number of tillers (Figure 3). The study concluded that the Nitrogen fertilizer has variable effects on the studied agronomic characters, and the application of 75kgN/fed is the optimal level of fertilizer for improving the agronomic traits of Sorghum under Alkadaro conditions.

Physico-chemical characterization of pedigreed sorghum mutant stalks for biofuel production

The successful commercialization of cellulosic biofuels depends on a stable and sustainable supply of high quality biomass at a reasonable cost. The physical property and chemical composition of biomass are the most important indicators of a biomass source’s potential for biofuel application. This study characterized the physical and chemical properties of 148 pedigreed sorghum (Sorghum bicolor L.) mutant stalks for biofuel production in order to accelerate the discovery of genes or gene mutations that underlie significant beneficial traits in sorghum. Large variations of chemical compositions were observed and indicated that breeding progress was achievable for sorghum development with desirable biofuel properties. The extractives are negatively correlated with the cellulose, hemicellulose, and lignin contents with an r of −0.85, −0.87, and −0.94, respectively. However, no relationships between ash and extractives contents were found in this study. Among the tested 148 sorghum mutant stalks, sorghum mutant ARS14 was identified with high sugar contents, high heating values, but less ash contents, which was suitable for the biorefinery industries with both biochemical and thermochemical conversions.

Non-dormant Axillary Bud 1 regulates axillary bud outgrowth in sorghum.

Tillering contributes to grain yield and plant architecture and therefore is an agronomically important trait in sorghum (Sorghum bicolor). Here, we identified and functionally characterized a mutant of the Non-dormant Axillary Bud 1 (NAB1) gene from an ethyl methanesulfonate-mutagenized sorghum population. The nab1 mutants have increased tillering and reduced plant height. Map-based cloning revealed that NAB1 encodes a carotenoid-cleavage dioxygenase 7 (CCD7) orthologous to rice (Oryza sativa) HIGH-TILLERING DWARF1/DWARF17 and Arabidopsis thaliana MORE AXILLARY BRANCHING 3. NAB1 is primarily expressed in axillary nodes and tiller bases and NAB1 localizes to chloroplasts. The nab1 mutation causes outgrowth of basal axillary buds; removing these non-dormant basal axillary buds restored the wild-type phenotype. The tillering of nab1 plants was completely suppressed by exogenous application of the synthetic strigolactone analog GR24. Moreover, the nab1 plants had no detectable strigolactones and displayed stronger polar auxin transport than wild-type plants. Finally, RNA-seq showed that the expression of genes involved in multiple processes, including auxin-related genes, was significantly altered in nab1. These results suggest that NAB1 functions in strigolactone biosynthesis and the regulation of shoot branching via an interaction with auxin transport.

Chemical composition analysis of various genetically modified sorghum traits: Pretreatment process optimization and bioethanol production from hemicellulosic hydrolyzates without detoxification

Compared to other inedible agricultural based feedstocks such as corn stover, rice husk, wheat straw and sugarcane bagasse, sorghum biomass (stalks and leaves) possess elevated credentials towards biofuel production which is highly tolerant against heat and drought conditions. Therefore, a novel sorghum phenotype was generated through genetic mutations called “brown midrib” which possesses low lignin content with enriched palatability. In the present study, the chemical composition of fourteen genetically modified sorghum biomass traits were analyzed which constitute, 52.7–60% of structural carbohydrates (cellulose and hemicellulose) and 11.6–17.7% of lignin. Due to the presence of low lignin content, pretreatment was performed using low energy input system to achieve maximum hemicellulose hydrolysis with minimized levels of sugar decomposition products. As a result, 88–92% of hemicellulose hydrolysis was attained with low amount of furfural (0.34–0.49 g/L) and 5-Hydroxymethylfurfural (0.38–0.56 g/L). Furthermore, fermentation was also performed without detoxification of pretreatment derived hemicellulosic hydrolyzate to evaluate the effect of fermentative inhibitors on ethanol-producing yeast. As a result, 88.8–92.5% ethanol conversion efficiency and 0.45–0.47 (gp/gs) ethanol yield were achieved within 15 h of fermentation time period.

Effect of Cutting Stage on Herbage Yield and Related Traits of Sorghum [Sorghum bicolor (L.) Moench] Plant Grown in Different Locations

Bu çalışma biçim devresinin ve farklı lokasyonların sorgum [Sorghum bicolor (L.) Moench] bitkisinin hasıl verimi ve bazı verim ögelerine etkilerini incelemek amacıyla Antalya’da yürütülmüştür. Tarla denemeleri iki yetişme sezonunda, toprak özellikleri farklı olan Aksu ve Kampüs lokasyonlarında tesadüf blokları deneme desenine uygun şekilde üç tekerrürlü olarak kurulmuştur. Sorgum bitkileri her iki lokasyonda salkım başlangıcı, tam salkım, süt olum, hamur olum ve tam olum dönemi olmak üzere beş farklı devrede biçilmiştir. Çalışmada; bitki boyu, yaprak oranı, salkım oranı, gövde oranı, hasıl verimi, kuru madde oranı ve kuru madde verimi belirlenmiştir. Çalışma sonuçları; biçim devresinin incelenen tüm özellikleri, lokasyonun ise gövde oranı dışında diğer tüm özellikleri istatistiki anlamda önemli derecede etkilediğini ortaya koymuştur. En yüksek hasıl verimleri her iki lokasyonda da hamur olum devresinden elde edilmiştir. Tüm biçim devrelerinde Aksu lokasyonundan elde edilen hasıl verimleri Kampüs lokasyonundan daha yüksek olmuştur. Toplamda elde edilen sonuçlar bu çalışmanın yürütüldüğü koşullarda sorgumun hamur olum devresinde biçilmesinin uygun olduğunu; sorgum üretimi için Aksu lokasyonunun Kampüs lokasyonundan daha elverişli olduğunu göstermektedir. Ayrıca, burada sunulan sonuçlar belirli bir ekolojide sorgumdan yüksek verim elde etmek için arazi seçiminin de çok önemli olduğunu göstermiştir.

The Effect of Foliar Application with Iron and Zinc on the Growth Characteristics of Sorghum Bicolor (L) Moench

A field has been carried out at the experimental station, college of Agriculture, in Abu-Ghralb, University of Baghdad, Iraq, during spring and autumn seasons 2014. The main objective is to find out the effects of iron concentration (0,60,90,120)mg.L-1, znic concentration (0,30,60,90) mg.L-1 and two stages of foliar application (flag leaf emergence and 50% flowering stage on some growth traits of Sorghum cv.Bohooth. 70.Layout of the experiment is R.C.B.D arranged in split-split plots designed with three replications, foliar application stages are assigned as main plots, iron as sub-plots, while zinc concentrations as a sub-sub plots. The results show, there is insignificant effects of foliar application stages on all growth traits. Also, the results show that the addition of iron at a con more than 60 mg.l-1 height, leaf area, percentage of chlorophyll in the leaf and percentage of iron and zinc in leaf. The Highest mean of plant height and leaf area 256 and 267cm is obtained when plants are sprayed with 90 and 120 mg.l-1 in spring and autumn seasons respectively. The Highest mean of 90 mg.l-1. leaf area(6709 and 6788)cm2is obtain when plants sprayed with 120mg.l-1. In addition the percentage of chlorophyll in the leaf and dry matter significantly influenced by iron con with 90mg.L-1 it is 40.6mmg.mg-1 chlorophyll in leaf and 14.465 t.ha-1 dry matter in spring season, while the percentage of chlorophyll and dry matter are 60.5 mmg.mg-1 and 14.429 t.L-1 dry matter in autumn season and are obtained by spraying plants with 120 mg.L-1 iron. Highest mean of iron in leaves in spring and autumn (75and 106) mg. kg leaf weight are obtained when plants sprayed with 120 mg.L-1 in spring and autumn seasons. Foliar application at time of flag leaf emergence give the highest plant height and leaf area, while foliar application at time of 50% flowering give the highest percentage of chlorophyll in leaf. There is no significant effect of time of foliar application on the percentage of chlorophyll, leaf area in autumn season, dry matter and percentage of iron and zinc in the leaf .Also, there is a significant effect of zinc concentration on plant height and leaf area,90 mg.L-1 Zn gives highest mean of high plant and leaf area (254 , 265 cm and 13.65, 13.662 t.h-1) in spring and autumn respectively. The result shows that zinc concentration 60 mg.L-1 give the highest mean of chlorophyll in the leaf in spring season, while 90 mg.L-1 of zinc give the highest mean of chlorophyll in the leaf autumn spring and autumn seasons. The highest mean of plant height and leaf area in spring season and percentage of chlorophyll in spring season is significantly influenced by zinc con in foliar application at time of flag leaf emergence, however, there are no significant effect of the time of foliar application of zinc on dry matter, percentage of iron and zinc in the leaves In terms of interaction between zinc and iron, there is a significant effect between 90 mg.L-1 iron in 90 mg.L-1 zinc and its give the highest mean of plan highest, leaf area and dray matter..

Variability, Heritability, Genetic Advance and Interrelationships for Agronomic and Yield Traits of Sorghum B-Lines under Different Environments

Information on heritability and trait association in crops assist breeders to allocate resources necessary to effectively select for desired traits and to achieve maximum genetic gain with little time and resources. The objectives of this investigation were to determine the amount of genetic variability, heritability, genetic advance and strength of association of yield related traits among sorghum lines under different environments in Egypt. Six environments with 25 sorghum B-lines were at two locations in Egypt (Giza and Shandaweel) in two years and two planting dates in one location (Giza). A randomized complete block design was used in each environment with three replications. Significant variation was observed among sorghum lines for all studied traits in all environments. Across environments, grain yield/plant (GYPP) showed positive and significant correlations with number of grains/plant (r = 0.71), days to flowering (r = 0.47), 1000-grain weight (r = 0.16) and plant height (PH) (r = 0.19). In general, the estimates of phenotypic coefficient of variation (PCV) were higher than genotypic coefficient of variation (GCV). Combined across the six environments, the highest PCV and GCV was shown by PH trait (95.14 and 43.57%) followed by GYPP (36.42 and 30.78%), respectively, indicating that selection for high values of these traits of sorghum would be effective. GYPP and PH traits showed high heritability associated with high genetic advance from selection, indicating that there are good opportunities to get success in improvement of these traits via selection procedures. Results concluded that PH is good selection criterion for GYPP and therefore selection for tall sorghum plants would increase grain yield.

Molecular breeding and industrialization of forage sweet sorghum

Sorghum ( Sorghum bicolor (L.) Moench) is the world’s fifth major crop and a C4 model plant. Sweet sorghum is a variant of grain sorghum with implications in biofuel industry and stress biology because of it remarkable traits including high biomass production, high concentration of soluble sugars in its juicy stem, and strong abiotic tolerance. In recent years, there is a new demand to develop sweet sorghum into a forage crop, which requires the tailor-made modification of its major biological characteristics. Compared to silage maize, sweet sorghum possesses higher levels of directly fermentable reducing sugars and the ability to accumulate high biomass under low-input production systems. In addition, it is tolerant to drought and more efficient in utilization of solar radiation and nitrogen-based fertilizers than maize on marginal lands which are not optimal for food production. These traits collectively make sweet sorghum more attractive than silage maize with huge potential as a forage crop. Yet, due to the relatively short history of sweet sorghum breeding, the development of new varieties adapting to various phenological requirements is restricted, and the rapid deployment of sweet sorghum for forage production is limited. Here we summarize the current status of forage sweet sorghum breeding in China. A suit of sweet sorghum traits, such as plant architecture (leave, and stem), flowering time and maturity, leaf senescence and accumulation of juice and sugar as well as drought and salt tolerance are identified, and recent progression in dissecting their genetic basis reviewed. It is suggested that newly developed cutting-edge technologies such as genome editing and whole-genome selection are needed to harness the genetic improvement of sweet sorghum. Feeding experiments with improved varieties showed that sweet sorghum is an important component of the livestock diet for increasing the palatability and nutrient conversion efficiency. The production-scale demonstration project, forming a production pipeline from sweet sorghum hybrid production, cultivation, distillation and feeding of livestock and cycle of manures, showed that forage sweet sorghum based bio-industry sets a model for circular economy in rural areas. Future forage sweet sorghum breeding and approaches to develop its bio-industry are discussed.

Pattern of genetic inheritance of morphological and agronomic traits of sorghum associated with resistance to sorghum shoot fly, Atherigona soccata

Sorghum shoot fly, Atherigona soccata is an important pest of sorghum during the seedling stage, which influences both fodder and grain yield. To understand the nature of inheritance of shoot fly resistance in sorghum, we performed generation mean analysis using two crosses IS 18551 × Swarna and M 35-1 × ICSV 700 during the 2013–2014 cropping seasons. The F1, F2, BC1 and BC2 progenies, along with the parental lines were evaluated for agronomic and morphological traits associated with resistance/susceptibility to sorghum shoot fly, A. soccata. The cross IS 18551 × Swarna exhibited significant differences between the parents for shoot fly deadhearts (%) in the postrainy season. The progenies of this cross exhibited lower shoot fly damage, suggesting that at least one of the parents should have genes for resistance to develop shoot fly-resistant hybrids. Leaf glossiness, leafsheath pigmentation and plant vigor score during the seedling stage exhibited non-allelic gene interactions with dominant gene action, whereas 100 seed weight showed both additive and dominant gene interactions. Presence of awns showed recessive nature of the awned gene. Generation mean analysis suggested that both additive and dominance gene effects were important for most of the traits evaluated in this study, but dominance had a more pronounced effect.

Mapping of QTLs Associated with °Brix and Biomass-Related Traits in Sorghum Using SSR Markers

The non-renewability and greenhouse gas emission nature of crude oil led to the use of renewable plant-based biofuels as alternative energy. Sweet sorghum offers one of the best plant-based bioethanol production from its sugary stalk. Identification and mapping of quantitative trait loci associated with sugar-related traits in sorghum is a crucial step toward the improvement of the sugar content of the crop. The present study was carried out to identify and map QTLs associated with °Brix, stalk diameter and plant height using F2:3 segregating mapping populations derived from a cross between grain sorghum (Sorcoll 163) and sweet sorghum (Gambella). Phenotypic evaluation was conducted in two different environments. A genetic map was constructed using 192 F2 populations genotyped using 76 SSR markers. Estimated heritability for °Brix, stem diameter and plant height amounted to 0.88, 0.41 and 0.65, respectively. A total of seven QTLs distributed across five linkage groups that controls °Brix content were detected using Inclusive Composite Interval Mapping. Each QTL contributed 17.2–44.3% of the total phenotypic variation. The two QTLs located on linkage group SBI-05 and SBI-06 repeated in both environments. These QTLs can be the target of the breeding programs in the future due to high heritability as well as stability in two different environments. The number of SSR markers used in present study is relatively fewer and fine mapping of the target regions should be considered in order to further dissecting the region. All the detected QTLs in this study are categorized as major QTLs, and it could be used further in sweet sorghum improvement program.

Genetic variability studies for stay green and different yield attributing traits in Sorghum

The present study was carried to identify the nature and extend of variability present for stay green and other twelve grain yield attributing traits in the F3 populations of five sorghum crosses viz., K8 × IS18551, CO26 × IS18551, CO26 × B35, CO30 × IS18551 and CO30 × B35. The high mean value coupled with moderate variability was observed for stay green trait in cross CO26 × IS18551 and leaf chlorophyll index, flag leaf length, panicle length, panicle weight and single plant yield in cross CO26 × B35. In cross CO 30 × IS18551, high mean value along with high variability was observed for biological yield and moderate variability for stem girth and number of leaves per plant. High heritability with high genetic advance as per cent of mean indicates that the heritability is due to additive gene effects and selection may be effective. This was observed for grain yield and maximum number of yield contributing traits viz., plant height, number of leaves per plant, panicle length, leaf chlorophyll index, stem girth, stay green trait and biological yield in cross CO26 × B35. Hence among the five crosses, CO26 × B35 considered as a best cross for further evaluation.

Productivity and Water Use Efficiency of Sorghum [Sorghum bicolor (L.) Moench] Grown under Different Nitrogen Applications in Sudan Savanna Zone, Nigeria

Nitrogen (N) is an essential nutrient for sorghum growth and development but often becomes limiting due to low availability and loss. The effects of N fertilization on water use efficiency (WUE) and physiological and yield traits of sorghum were investigated in two locations over two cropping seasons (2014 and 2015) in the Sudan Savanna zone of Nigeria. Three sorghum varieties were evaluated under six (6) N-levels (0, 20, 40, 60, 80, and 100 kg ha−1) at a constant phosphorus and potassium level of 30 kg ha−1. Results showed that N increased grain yield by 35–64% at the Bayero University Kano (BUK) and 23–78% at Minjibir. The highest mean grain yield in the N-fertilizer treatments (2709 kg ha−1 and 1852 kg ha−1 at BUK and Minjibir, resp.) was recorded at 80 kg N ha−1. ICSV400 produced the highest mean grain yields (2677 kg ha−1 and 1848 kg ha−1 at BUK and Minjibir, resp.). Significant differences were observed among the N-levels as well as among the sorghum varieties for estimated water use efficiency (WUE). The highest mean value coincided with the highest mean grain yield at an optimum application rate of 80 kg ha−1. N-fertilizer treatments increased WUE by 48–55% at BUK and increased WUE by 54–76% at Minjibir over control treatment. Maturity and physiological trait have a significant effect on WUE. The extra early maturing variety (ICSV400) recorded the highest mean WUE while late maturing variety (CSR01) recorded the lowest WUE.

Effect of Striga Trap Crops and Nitrogen Fertilizer Application on Yield and Yield Related Traits of Sorghum [Sorghum bicolor (L.) Moench] at Fedis District, Eastern Ethiopia

Striga causes a serious threat to successful cultivation of sorghum in areas of low and erratic rainfall and poor soil fertility. Therefore, to reduce yield losses and severity of Striga, a field experiment was conducted during the cropping season of 2015 on heavily Striga-infested field in Fedis District, Boko site to determine the effect of trap crops (cowpea, soybean, desmodium, control) and N fertilizer rates (0, 46, 92 and 138 kg N ha﹣1) on management of Striga, yield related traits and yield of sorghum. The experiment was laid out in a factorial arrangement in a randomized complete block design (RCBD) with three replications. Moreover, LAI, plant height, head weight plot﹣1 and aboveground dry biomass yield of sorghum were significantly (P < 0.05) increased by 4%, 9%, 28% and 33%, respectively, by use of cowpea as a trap crop over the control. Likewise use of cowpea as a trap crop significantly (P < 0.01) increased kernel weight head﹣1 by 6% and grain yield by 23% over the control. Similarly, the main effect of nitrogen showed that increased nitrogen rate up to 46 kg ha﹣1 significantly reduced Striga number at sorghum emergence by about 49.8% over control. Days to heading, flowering and maturity on sorghum were significantly (P < 0.01) affected by nitrogen fertilizer rate and the application of 46 kg N ha﹣1resulted in earlier heading by 6% over138 kg N ha﹣1. Application of 138 kg N ha﹣1delayed days to flowering by 6 days over 46 kg N ha﹣1. Plots that received 46 kg N ha﹣1 attained 90% physiological maturity earlier (127.1 days) than other treatments. Application of 46 kg N ha﹣1significantly increased kernel weight head﹣1 by 12% and aboveground dry biomass yield by 33% over the control. LAI and grain yield were significantly (p < 0.01) affected by main effect of N where the highest (2.387) leaf area index and the highest (3116 kg ha﹣1) grain yield were obtained with 46 kg N ha﹣1.

MicroRNAs as targets for engineering biofuel feedstock Sorghum

Sorghum is a highly efficient C4 crop, with enormous potential as a biofuel feedstock. Fermentable sugars that accumulate in sorghum stalks, high biomass, drought tolerance and adaptability to diverse climates are some of the key attributes of sorghum. However, sustainable production of renewable fuels through large scale plantation of sorghum needs targeted research efforts at several fronts. One of the promising areas is manipulating gene expression to engineer traits-of-interest. In the recent past, microRNAs have emerged as important targets for engineering complex agronomical traits, including biomass yields, sugar accumulation, flowering time, drought tolerance, disease resistance, micronutrient homeostasis, etc., in several crop plants. Both homology-based bioinformatics, and experimental approaches viz. miRNA microarrays and small RNA sequencing have been utilised to gain insights into the role of miRNAs in regulating bioenergy-related traits in sorghum. Through this review, we provide a comprehensive overview of the information available till date about the miRNA-related research in sorghum and propose the prospective directions for future endeavours in this area.

Relationship between waxy (high amylopectin) and high protein digestibility traits in sorghum and malting quality

This study determined the relationship between waxy (high amylopectin) and high protein digestibility (HD) traits in sorghum and malting quality with the aim of replacing barley malt in arid, tropical regions. Eight sorghum lines with differing endosperm traits: waxy, heterowaxy, waxy-HD, non-waxy-HD and non-waxy-normal digestibility traits were malted at a laboratory scale and their malt quality and modification during malting were studied. Malt from waxy and heterowaxy sorghum lines generally had improved endosperm modification and starch granule degradation. Only non-waxy-HD and one waxy line malts exhibited clear evidence of endosperm protein degradation. Malt α-amylase activity of the sorghum lines varied more than β-amylase activity but neither were evidently affected by the traits. Malt from waxy lines had improved HWE and FAN. Principal component analysis showed that waxy lines were associated with high HWE, FAN, starch and protein loss. The improved malt quality was probably due to the better starch granule swelling property of amylopectin which could have facilitated hydrolysis by amylases and proteases. This study shows that although β-amylase activity is not affected by the waxy trait, white tan-plant waxy sorghum produces higher quality malt than regular sorghum and has potential as a better partial barley malt replacement for brewing.

QTL mapping and loci dissection for leaf epicuticular wax load and canopy temperature depression and their association with QTL for staygreen in Sorghum bicolor under stress

Plant waxes and staygreen are distinct phenotypic traits that have been independently implicated in heat and drought tolerance among grasses. The association between these two traits has not been fully explored, which makes the exploitation of synergy between them difficult. This study assessed the association between QTL regulating the staygreen (Stg) trait in sorghum and those regulating epicuticular wax load (WL) and associated canopy temperature depression (TD). Using a recombinant inbred line (RIL) population derived from Tx642 and Tx7000, phenotypic data were collected in three replicated field trials and one greenhouse trial. High absolute TD generally corresponded to high WL. The r2 of TD against WL was highest under non-stress conditions in the greenhouse while it was much larger in the cooler and irrigated field conditions compared to hotter, drier field trials. The genetic correlations between the two traits also followed this pattern. Composite interval mapping identified a total of 28 QTL, 15 of which had significant overlaps between different traits. Most of the wax QTL were associated with pre-anthesis drought tolerant Tx7000. However, one QTL for WL overlapped with a QTL for staygreen (Stg2) and was represented by a single, isolated marker near the centromeric region on the short arm of SBI-01. The marker is identified by a Cis-acting regulatory module and is part of a 2-kb multifunctional motif-rich region which includes core promoter and enhancer regions and transcription elements, including a drought-responsive MYB binding site. We suggest that this QTL may be pleiotropic for important stress tolerance mechanisms regulating both staygreen and leaf wax in sorghum.

Diversity in root traits of sorghum genotypes in response to Striga hermonthica infestation

SummaryStriga hermonthica is a major biotic constraint to agriculture in the lowland areas of Ethiopia where sorghum is a major stable crop. A pot and a field experiment were conducted in 2011 during the rainy season using 10 sorghum genotypes. Each experiment had infested and non‐infested conditions as the main plots and the 10 genotypes as subplots. The aim of this study was to examine the response of root traits of the sorghum genotypes to S. hermonthica infested conditions and to investigate relationships among S. hermonthica, root and growth traits of sorghum genotypes. Sorghum genotypes were categorized in to three groups, that is, low, moderate and high S. hermonthica count groups. Each group showed a differential response to root traits. Low S. hermonthica count groups had significantly lower root length, root length density, root to shoot ratio and root dry weight compared with susceptible groups. In contrast to low S. hermonthica count groups, moderate S. hermonthica count groups had higher root length, root length density, root to shoot ratio and root dry weight. Highly significant and strong relations were observed among root traits of sorghum, indicating that any of the root traits can be used as indicators for resistance. The result indicates different reactions in root traits in the upper soil layer may be useful for genetic improvement of S. hermonthica resistance and tolerance breeding in sorghum.