Elite Sorghum Research Articles

Genotype by environment interaction, AMMI, GGE biplot, and mega environment analysis of elite Sorghum bicolor (L.) Moench genotypes in humid lowland areas of Ethiopia

This study aimed to evaluate high-yielding, stable sorghum genotypes and determine the ideal (representative and discriminating) testing environments for genotypes in the humid lowlands of Ethiopia. A total of forty-two sorghum genotypes were used for a field trial conducted in six different environments using a randomized complete block design. Yield stability, Additive main effect, multiplicative interaction (AMMI), and genotype and genotype by environment interaction (GGE) were computed. The AMMI analysis explained 62.85% of the G×E variance. The AMMI1 biplot revealed that (G4; Mok079 and (G16; Ba066) genotypes had higher grain yields. AMMI2 biplot suggested that genotypes (G18; Y0470),(G23;100620), (G29; PML981475), and (G11; ETSC300373-4) show higher sensitivity to environmental changes because of their strong genotype-by-environment interactions. The GGE captured 79.46% of the GGE variance, and the GGE biplot identified genotypes (G4; Mok079), (G10; Sl081) and (G16; Ba066) were the most stable genotypes whereas(G39; ETSC120051-3) was the least stable genotypes. The GGE biplot identified Assosa (AS20) as a suitable environment, whereas PW20 and JM20 were the most discriminating and non-representative environments. The GGE biplot was found to identify three main mega-environments for sorghum growing in the humid lowlands of Ethiopia., both the AMMI and GGE biplots revealed (G4; Mok079) had the highest level of adaptability to all tested environments and was approved by the National Variety Release Committee for release in 2022.

Responses of elite sorghum (Sorghum bicolor [L.] Moench) lines developed via gamma-radiation for grain yield, component traits and drought tolerance

Induced plant mutagenesis is a powerful technique to create genetic variation for agronomic traits and drought tolerance selection programs. The objective of this study was to determine the response of elite sorghum (Sorghum bicolor [L.] Moench) lines developed via gamma-radiation for grain yield, component traits, and drought tolerance to select best performing lines for cultivation in water-stressed environments. Ten newly developed mutant lines and four check varieties were evaluated in two growing seasons under drought-stressed (DS) and non-stressed (NS) conditions in Namibia. Mutant lines were evaluated using a factorial experiment laid out in a randomized complete block design with three replications in custom-made rainout-shelter facility. Data on grain yield and yield-related traits were collected and drought tolerance selection indices were computed using mean genotype yield under non-stressed condition and drought-stressed condition. Data were subjected to standard analysis of variance, correlation and principal component analyses. The interaction effect of genotype × drought stress × season was non-significant for most assessed traits suggesting the relatively stable performance of the test lines for selection. Grain yield response of test genotypes varied from 0.55 to 2.27 t/ha under DS and 1.84 to 4.05 t/ha in NS conditions. Grain yield positively and significantly (P < 0.05) correlated with harvest index (r = 0.79), panicle weight (r = 0.75) and panicle length (r = 0.37), and negatively correlated with days to flowering (r = −0.35) under DS condition. Principal component (PC) analysis identified two PCs accounting for 96.35 % of total genotypic variation based on drought tolerance selection indices. Biplot analysis using a combination assessed traits allowed selection of drought tolerant mutant lines designated as ML4, ML10, ML6, and ML5 with mean grain yield of 2.27, 2.05, 1.89 and 1.67 t/ha under DS conditions, in that order. The selected lines are recommended for further multi-environment evaluations for release and large-scale production in Namibia or other related agro-ecologies.

Introgression of Stay Green Quantitative Trait Locus (QTLS) into Elite Sorghum Variety by MABC

Sorghum is a major staple food crop for the people in semi-arid areas of Asia. Post-flowering drought is a global constraint of sorghum production. The study aimed to improve stay-green characteristics of GS-23 sorghum variety by transferring stg3A and stg3B QTL`s respectively from donor genotypes K260 and K359w of ICRISAT by using marker assisted backcrossing. The experimental material comprised of six basic generations P1, P2, F1, F2, BC1 and BC2 developed from crossing GS-23 × K260 and GS-23 × K359 were genotyped using a set of 133 SNPs and 79 SSR markers. Whereas, 53 polymorphic SNPs among parents and backcross F1s for stay green trait at maturity were used to track introgression of stay green trait. Similarly,10 SSR markers were found to be polymorphic were used to track introgression of stay green trait i.e., stay green trait QTL`s stg3A and stg3B from donor parent K260 and K359w respectively in GS-23 background across backcross population and to identify plants that were homozygous for the desired allele. In which 02 SNPs SnpSB0039 and SnpSB0093 were identified as polymorphic for both K260 and K359w. Whereas 17 SNPs identified polymorphic for K260 and 34 SNPs for K359w. These SNPs were validated in both F1 and BC1F1 populations of both the crosses. Similarly, out of 10 SSR markers utilized, 02 SSRs were identified polymorphic to K260 and 02 SSRs were identified for K359w. Whereas 06 SSRs were polymorphic to both the parents K260 and K359w. Prominent 02 SSRs viz., Xtxp 141_Fam and Xgap84_Vic found to be more reliable and polymorphic to both the parents. These SSRs were validated in both F1 and BC1F1 populations of both the crosses. The genotypic analysis revealed the presence of favorable alleles in homozygous conditions at markers loci associated with stg3A and stg3B QTL`s in BC populations, suggesting successful introgression of stay green QTLs from the donor parents to the recurrent parent. Therefore, our study demonstrated the utility of marker-assisted backcrossing for drought tolerance improvement of locally adapted sorghum variety.

Temporal transcriptomic profiling elucidates sorghum defense mechanisms against sugarcane aphids

BackgroundThe sugarcane aphid (SCA; Melanaphis sacchari) has emerged as a key pest on sorghum in the United States that feeds from the phloem tissue, drains nutrients, and inflicts physical damage to plants. Previously, it has been shown that SCA reproduction was low and high on sorghum SC265 and SC1345 plants, respectively, compared to RTx430, an elite sorghum male parental line (reference line). In this study, we focused on identifying the defense-related genes that confer resistance to SCA at early and late time points in sorghum plants with varied levels of SCA resistance.ResultsWe used RNA-sequencing approach to identify the global transcriptomic responses to aphid infestation on RTx430, SC265, and SC1345 plants at early time points 6, 24, and 48 h post infestation (hpi) and after extended period of SCA feeding for 7 days. Aphid feeding on the SCA-resistant line upregulated the expression of 3827 and 2076 genes at early and late time points, respectively, which was relatively higher compared to RTx430 and SC1345 plants. Co-expression network analysis revealed that aphid infestation modulates sorghum defenses by regulating genes corresponding to phenylpropanoid metabolic pathways, secondary metabolic process, oxidoreductase activity, phytohormones, sugar metabolism and cell wall-related genes. There were 187 genes that were highly expressed during the early time of aphid infestation in the SCA-resistant line, including genes encoding leucine-rich repeat (LRR) proteins, ethylene response factors, cell wall-related, pathogenesis-related proteins, and disease resistance-responsive dirigent-like proteins. At 7 days post infestation (dpi), 173 genes had elevated expression levels in the SCA-resistant line and were involved in sucrose metabolism, callose formation, phospholipid metabolism, and proteinase inhibitors.ConclusionsIn summary, our results indicate that the SCA-resistant line is better adapted to activate early defense signaling mechanisms in response to SCA infestation because of the rapid activation of the defense mechanisms by regulating genes involved in monolignol biosynthesis pathway, oxidoreductase activity, biosynthesis of phytohormones, and cell wall composition. This study offers further insights to better understand sorghum defenses against aphid herbivory.

Natural variation further increases resilience of sorghum bred for chronically drought-prone environments.

Drought stress is one of the major constraints for crop production in the Sahel region of Africa. Here, we explore the potential to use natural genetic variation to build on the inherent drought tolerance of an elite sorghum cultivar, Teshale, that has been bred for Ethiopian conditions including chronic drought. We evaluated a backcross nested-association mapping population using 12 diverse founder lines crossed with Teshale under three drought-prone environments in Ethiopia. All 12 populations averaged higher head exsertion and lower leaf senescence than the recurrent parent in the two most stressful environments, reflecting new drought resilience mechanisms from the donors. A total of 154 quantitative trait loci (QTLs) were detected for eight drought-responsive traits, and their validity was supported by the fact that 113 (73.4%) overlapped with QTLs previously detected for the same traits, concentrated in regions previously associated with 'stay-green' traits. Allele effects showed that some favourable alleles are already present in the Ethiopian cultivar; however, the exotic donors offer rich scope for increasing drought resilience. Using model-selected SNPs associated with the eight traits identified in this study and three in a companion study, phenotypic prediction accuracies for grain yield were equivalent to genome-wide SNPs and were significantly better than random SNPs, indicating that the selected traits are predictive of sorghum grain yield.

Cyanogenesis in the Sorghum Genus: From Genotype to Phenotype.

Domestication has resulted in a loss of genetic diversity in our major food crops, leading to susceptibility to biotic and abiotic stresses linked with climate change. Crop wild relatives (CWR) may provide a source of novel genes potentially important for re-gaining climate resilience. Sorghum bicolor is an important cereal crop with wild relatives that are endemic to Australia. Sorghum bicolor is cyanogenic, but the cyanogenic status of wild Sorghum species is not well known. In this study, leaves of wild species endemic in Australia are screened for the presence of the cyanogenic glucoside dhurrin. The direct measurement of dhurrin content and the potential for dhurrin-derived HCN release (HCNp) showed that all the tested Australian wild species were essentially phenotypically acyanogenic. The unexpected low dhurrin content may reflect the variable and generally nutrient-poor environments in which they are growing in nature. Genome sequencing of six CWR and PCR amplification of the CYP79A1 gene from additional species showed that a high conservation of key amino acids is required for correct protein function and dhurrin synthesis, pointing to the transcriptional regulation of the cyanogenic phenotype in wild sorghum as previously shown in elite sorghum.

English

Sorghum is an important staple food crop in Kenya, but its yield is low due to many constraints which include diseases, drought, soil fertility, and pests, notably parasitic weed Striga hermonthica. Twenty elite sorghum genotypes and one resistant check were evaluated in three replications in a complete randomized design in Agar Gel (AG) experiment and randomized complete block design on selected Striga hotspot farms at Kadel and Nyahera in western Kenya. Significant differences (p&lt;0.001) were realized both in the fields (plant height, dry shoot biomass yield, grain yield, field Striga count, and Striga damage ratings) and in the AG experiment with respect to maximum germination distance and numbers of induced germinated Striga seeds. Among the sorghum genotypes evaluated under field conditions, T53B, N57, N68, C26, IESV 92036-SH, T30B, and Uyoma 47 White genotypes had stable yields under Striga infestation in the two sites, whereas Nyadundo 1, Nyadundo 2, and Uyoma 8 were susceptible. In the AG experiment, E117B, T30B, Uyoma 8, Uyoma 42 STR, and T53B induced high numbers of germinated Striga seeds with maximum germination distances (MGD). In contrast, Uyoma 47 Brown, IESV 92038/2-SH, and IESV 92036-SH sorghum genotypes secreted low amounts of SLS suggesting resistance. This study has identified and selected four Striga tolerant (T53B, N68, N57, and T 30B) and resistant (C 26, Uyoma 47 Brown, IESV 92038/2-SH, and IESV 92036-SH) sorghum genotypes which can be utilized in further research programs or adopted to improve sorghum productivity in the highly Striga infested regions of western Kenya. Key words: Striga, sorghum genotypes, resistant, susceptible, tolerant, Agar Gel experiment

Genetic interrelationships of elite sorghum (Sorghum bicolor (L.) Moench) genotypes bred for Striga resistance and compatibility with Fusarium oxysporum f. sp. strigae (FOS) revealed by microsatellites

ABSTRACT Genetic diversity is key for breeding population development, hybrid breeding, heterotic grouping and genetic analysis, among others. The objective of this study was to examine genetic interrelationships among elite sorghum genotypes bred for resistance to Striga hermonthica Del. Benth and S. asiatica (L.) Kuntze and compatible with a biological control agent Fusarium oxysporum f. sp. strigae (FOS) against Striga using 22 polymorphic simple sequence repeat (SSR) or microsatellite markers. The number of alleles per locus detected by the markers varied from 2 to 7 with a mean value of 4.23. The polymorphic information content (PIC) of the SSR markers ranged from 0.15 to 0.84 with a mean of 0.57 showing moderate discriminatory power of the primers. The neighbour-joining clustering algorithm classified the genotypes into three main groups, revealing narrow to moderate variations existing among the test genotypes. Overall, the genetic diversity revealed by the study will be useful for designed crosses and pyramiding of broad-based resistance genes to control Striga for sustainable sorghum production.

Screening of Selected Sorghum Genotypes for Resistance to Covered Kernel Smut Disease in Western Kenya

Sorghum is an important food security crop for arid and semi-arid tropics but its production is hampered by many biotic and abiotic factors including covered kernel smut disease (CKSD) caused by fungus Sporosorium sorghi in the Ustilaginaceae family. The disease attacks susceptible sorghum genotypes causing yield losses estimated at 43% in Western Kenya. This study determined the response of selected sorghum genotypes to CKSD under field and greenhouse conditions. A total of 15 elite sorghum genotypes were screened under field conditions in Migori and Homa Bay sites and under greenhouse at the University of Eldoret. Data on disease incidence and severity were collected per genotype and analyzed using R-Studio software and means were separated at 1% using Tukey&amp;rsquo;s test. Results showed significant differences among genotypes for disease incidence and severity under fields and greenhouse conditions. Disease incidence varied significantly (p &amp;lt; 0.001) among the genotypes ranging from zero (for T53, T30, IS3092, N4 and N68) to 64% (for Nyadundo2) under field conditions but ranged from 0-69% under greenhouse conditions. Similarly, severity followed the same trend with C26 having the worst attack with a score of 5 while T53 recorded the least (score of 1). This study has identified potential sources of resistance for covered kernel smut disease that can be utilized to manage the disease and significantly improve sorghum yields in the target regions.

Adaptation Responses to Early Drought Stress of West Africa Sorghum Varieties

Sorghum is the fifth most important cereal crop world-wide and feeds millions of people in the Sahel. However, it often faces early-stage water deficit due to false onsets of rainy seasons resulting in production decrease. Therefore, developing early drought tolerant material becomes a necessity but requires a good knowledge of adaptation mechanisms, which remains to be elucidated. The present study aimed at assessing the effects of early drought stress on ten elite sorghum varieties tested over two years (2018–2019) at the National Agronomic Research Centre (CNRA) of Bambey (Senegal, West Africa). Two different water regimes (well-watered and drought stress) were applied during the dry season. Water stress was applied by withholding irrigation 25 days after sowing for one month, followed by optimal irrigation until maturity. Soil moisture measurements were performed and allowed to follow the level of stress (down to a fraction of transpirable soil water (FTSW) of 0.30 at the end of stress). An agro-physio-morphological monitoring was carried out during the experiment. Results showed highly significant effects of early drought stress in sorghum plants growth by decreasing leaf appearance, biomass, height but also yield set up. The combined analysis of variance revealed highly significant differences (p ≤ 0.01) between varieties in the different environments for most characters. Under water deficit, the variability was less strong on leaf appearance and plant height at the end of stress. The adaptation responses were related to the capacity of varieties to grow up fast and complete their cycle rather, increase the dead leaves weight, reduce photosynthesis rate, stomatal conductance, leaf transpiration and increase the roots length density. However, varieties V1, V2, V8 and V9 showed promising behavior under stress and could be suitable for further application in West Africa for sorghum breeding and farming.

English

For sorghum hybrid development, assessment of parental lines is a pre-requisite. However, information on heterotic performance and combing ability of Ethiopian elite sorghum lines is inadequate. ANOVA revealed mean squares had signifying substantial amount of variability amongst genotypes for most traits. Males 72, 81 and 99 were the best performing parents for yield and related traits. Hybrids, 106 x 94, 106 x 90, 106 x 102, 107 x 99 and 107 x 105 were found maximum heterotic hybrids for yield as compare to check. The estimates of variance of combining ability revealed that σ2gca was found inferior to σ2sca for all traits except plant height and number of heads. The σ2gca/σ2sca ratio revealed preponderance of supremacy gene action for most traits. The degree of dominance was found greater than unity for entire traits except plant height. The estimations of parental GCA effects showed that female 106 and males 79, 96, 94 and 81 were good general combiners for yield and related traits. Based on perse performance, heterotic response, combining ability and nature of gene action for yield and related traits, female parent 106 and male parents 94, 102 and 90 were found most performed. Those parental lines were grouped into dualistic heterotic groups based on their SCA and GCA results. Key words: Combining ability, elite line, general combining ability (GCA) and specific combining ability (SCA), heterosis, heterotic group, hybrid, sorghum.

Elite Sorghum (Sorghum bicolor (L.) Moench) Hybrids for Postrainy Season Adaptation

Improving sorghum cultivars for postrainy season adaptation is crucial toensure food security in dry regions of India. Postrainy season sorghum isprimarily used as a food owing to its good grain quality and also the mainsource of fodder quality especially during dry seasons. Hence, the presentinvestigation was carried out with ten elite sorghum hybrids along withthree controls (M 35- 1, Parbhani Moti and CSH 15R) at three locations viz.,International Crops Research Institute for the Semi-Arid Tropics (ICRISAT),Mahatma Phule Krishi Vidyapeeth (MPKV) and Marathwada AgriculturalUniversity (MAU) during the postrainy season, to identify the best performingsorghum hybrids for postrainy season adaptation. The best performinghybrids for grain yield across three locations were ICSA 502 × SPV 422 (2.4t ha-1), 8712 (2.1 t ha-1), ICSA 38 × SPV 422 (2.1 t ha-1), ICSA 84 × SPV 1411(2.1 t ha-1) and XSR401 (2.1 t ha-1)compared to the control CSH 15R (1.8 tha-1), Parbhani Moti (1.5 t ha-1) and M 35-1 (1.5 t ha-1). The selected hybridswere 3 to 4 days earlier than M 35-1 and at par with CSH 15R. Substantialvariability observed for 100 seed size (2.4 to3.5g) and grain luster (score1 to 2) among the hybrids. The tested hybrids had shootfly dead heartspercentage ranging from 53 to 75. Based on the number of nodes infected,infection length and percent soft rot, two hybrids (ICSA 675 x SPV 1411 andICSA 675 x ICSV 700) appeared tolerant to charcoal rot with <1 internodeinfection, length of infection <5 cm and <10% soft rot.

Combining Ability and Heterosis of Sorghum (&amp;lt;i&amp;gt;Sorghum bicolor&amp;lt;/i&amp;gt; L. Moench) Hybrids for Grain and Biomass Yield

This study was carried out to estimate the magnitude of heterosis and combining abilities (general & specific) for forage and over all grain yield performance of sorghum hybrids. Even though, information on heterotic performance and combining ability of Ethiopian elite sorghum lines for biomass, yield, and overall performance is too insufficient, there is ample amount of sorghum elite lines developed through pedigree breeding. The result of ANOVA found out that mean squares had to indicate a considerable amount of variability among the tested genotypes for most traits. Parents and hybrids are drastically unique for all traits besides thousand-grain weight, number of green leaves, and panicle width. This found out that hybrids have a higher yield than Open pollinated types (OPVs) parents. Hybrids, 106 × 94 (123.5%), 106 × 87 (80.4%), 106 × 78 (72.5%), 107 × 92 (74.5%) 107 × 99 (56.9%), and 107 × 104 (60.8%) have been discovered maximum heterotic hybrids for yield in comparison to check. The estimations of parental GCA effects confirmed that female 106 and males 79, 96, 94, and 81 had been excellent general combiners for biomass, yield and associated traits. Primarily based on perse overall performance, heterotic response, and combining ability, female parent 106 and male parents 94, 102, and 90 were observed maximum performed. Those parental lines could be used for hybrid and germplasm improvement.

A Novel QTL for Root-Knot Nematode Resistance is Identified from a South African Sweet Sorghum Line.

Southern root-knot nematodes, Meloidogyne incognita, feed on the underground portions of hundreds of plant species and affect nutrient partitioning and water uptake of the host plants. Sorghum (Sorghum bicolor) is often not significantly damaged by southern root-knot nematodes (RKN) but some sorghum genotypes support greater population densities of RKN than other genotypes. These higher nematode populations increase the risk of damage to subsequently planted susceptible crops. A previous study identified a major quantitative trait locus (QTL) for RKN resistance on sorghum chromosome (chr.) 3. To maintain long-term resistance, multiple resistance genes should be pyramided in a cultivar. In this study, we identified a new source of RKN resistance, created a mapping population, and identified single-nucleotide polymorphism markers using genotyping-by-sequencing of the segregating population. Use of single-marker analysis and composite interval mapping identified a single QTL on chr. 5 that was associated with egg number and egg number per gram of root from the resistant sweet sorghum line PI 144134. This region on chr. 5 and the prior QTL on chr. 3 can be potentially moved from PI 144134 and Honey Drip, respectively, into elite sorghum germplasm via marker-assisted selection for more durable resistance.

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.

Incorporation of stay-green Quantitative Trait Loci (QTL) in elite sorghum (&lt;i&gt;Sorghum bicolor&lt;/i&gt; L. Moench) variety through marker-assisted selection at early generation

Incorporation of stay-green Quantitative Trait Loci (QTL) in elite sorghum (Sorghum bicolor L. Moench) variety through marker-assisted selection at early generation.Objective: The present investigation was undertaken to develop drought tolerant varieties through introgression of stay-green QTLs in order to improve sorghum yield in semi-arid areas of Burkina Faso.Methodology and Result: Marker-assisted selection was carried out to introgress stay-green QTLs into elite sorghum variety. A stay-green donor source, BTx642 (B35), was crossed to the elite variety (Sariaso09) to obtain F1 progenies that were backcrossed to their recurrent parents to obtain the BC1F1 progenies. Seventeen flanking Simple Sequence Repeat (SSRs) polymorphic markers were used for foreground selection and 18 were used for background selection. Eighteen BC1F1 were heterozygous at all target loci for stay-green (stg1, stg2, stg3, stg4 and stgB), 5 progenies (S9B37, S9B43, S9B46 S9B85 and S9B13) had incorporated 3 of these QTLs. 4 plants (S9B34, S9B38, S9B73 and S9B16) incorporated double QTLs (Stg3 and StgB) and three plants (S9B44, S9B48 and S9B20) were heterozygous for Stg1.Conclusions and applications of findings: Among BC1F1 generation, 30 progenies had incorporated at least one stay-green QTL. Two of the introgression lines had high levels of the recurrent parents’ genomes and constitute some promising lines to develop drought tolerant varieties that will ensure sorghum production in semi-arid tropics areas and therefore, contribute to ensure food security in Burkina Faso. Despite the small number of genotypes obtained, the results showed the efficiency of Marker Assisted Back Crossing (MABC) versus the conventional backcross procedure.Keywords: sorghum, stay-green, drought, post-flowering, QTL, MABC

Quantitative Trait Loci Associated with Anthracnose Resistance in Sorghum

Sorghum [Sorghum bicolor (L.) Moench] is highly susceptible to the fungal disease anthracnose, which is a major biotic constraint to forage and grain production. With an aim to develop durable resistance to anthracnose, two unique genetic sources of resistance in sorghum were selected to create genetic mapping populations and identify genomic regions that control anthracnose resistance. A series of quantitative trait loci (QTL) were identified that conferred variable levels of resistance, three of which controlled stable resistance across all environments, while two QTL were environment specific. A major anthracnose‐resistance QTL on chromosome 9 of the SC155‐14E genome was observed in all environments and controlled from 19 to 62% of the phenotypic variance. An additional major QTL on chromosome 5 of the SC414‐12E genome explained from 20 to 39% of the phenotypic variance and was observed in four of the six environments tested. Resequencing of the genomes of resistant cultivars SC155‐14E and SC414‐12E facilitated a preliminary survey of the coding regions of genes annotated as playing a role in host defense. The resequenced genomes of the resistant genotypes and the linkage mapping resources represent information relevant for more detailed molecular characterization of genes conditioning anthracnose resistance in this tropical cereal. The identification of QTL conferring anthracnose resistance and the identification of single‐nucleotide polymorphisms linked to these loci will provide the necessary molecular tools for marker‐assisted introgression of durable anthracnose resistance into elite sorghum inbreds.

MicroRNA expression profiles in response to drought stress in Sorghum bicolor

The regulatory role of small non-coding RNAs that are 20–24 nucleotides in length has become the foremost area of research for biologists. A major class of small RNAs represented by the microRNAs (miRNAs), has been implicated in various aspects of plant development including leaf pattering, meristem function, root patterning etc. Recent findings support that miRNAs are regulated by drought and other abiotic stresses in various plant species. In this study, were report the expression profiling of 8 known abiotic stress deregulated miRNAs in 11 elite sorghum genotypes, under watered and drought conditions. Significant deregulation was observed with miR396, miR393, miR397-5p, miR166, miR167 and miR168. Among these, the expression levels of sbi-miR396 and sbi-miR398 were the highest in all the genotypes. The expression of sbi-miR396 was maximum in the grain sorghum HSD3226 under well-watered conditions and the profile shifted towards HSD3221 under drought stress. Forage accessions, N98 and Atlas, showed an opposite behavior in expression patterns of miR397-5p in drought physiologies. Such dynamic expression patterns could be indicative of prevailing drought tolerant mechanisms present in these sorghum accessions. This data provides insights into sorghum miRNAs which may have potential use in improving drought tolerance in sorghum and other cereal crops.

English

Considerable effort has been made to improve drought-stress tolerance in sorghum by incorporating the stay-green trait into drought-susceptible elite sorghum varieties. Keeping track of the several genes involved in the expression of this complex trait during the breeding program is an enormous task. In this study, the fidelity of recently identified SSR markers were tested for introgression of stay-green QTLs into elite sorghum lines. Of the 102 SSR loci tested, seventy- eight (78) markers were found to be polymorphic between the donor lines (B35 and E36-1) and the recipient lines (Sekedo and Seredo). In total, 25 polymorphisms were detected in SSR loci flanking key stay-green quantitative trait loci (QTLs) from the B35 donor line, and 6 in E36-1. In B35, 5 SSR markers were linked to the QTL StgA, 6 linked to StgB, 3 linked to Stg1, 2 linked to Stg2, 4 linked to Stg3 and 5 linked to Stg4. In contrast, only 6 polymorphic SSR markers were detected in the vicinity of key QTLs found in E36-1. Two were linked to LGA, 1 to LGJ and 3 to LGG. No markers were found linked to QTL LGD and LGH. Similar SSR polymorphisms were observed for markers needed to recover the recurrent parent genomes (RPG) in the subsequent backcross generations. These findings reveal the limitations of using E36-1 as a donor parent in marker-assisted selection (MAS) programmes for improvement of drought tolerance. Low hybridization efficiency (22.5%) was achieved using the anther dehiscence method. Such low hybridization efficiency requires use of molecular markers to easily identify plants harbouring the required genotypes. Key words: Stay-green, drought tolerance, quantitative trait loci (QTL), simple sequence repeat (SSR) markers, polymorphism.

PHENOTYPIC AND GENOTYPIC VARIANCE AND HERITABILITY OF STAY GREEN CHARACTER AMONG 22 ELITE SORGHUM (Sorghum bicolor (L.) Moench) GENOTYPES

&lt;p&gt;Delaying of leaf senescence (stay green) is an effective strategy for increasing of crop yield, particularly under water-limited conditions. Study of genotypic variance of stay green is very useful for breeding program of stay green character. Replicated field experiment was carried out in Farm Experimental Station, Faculty of Agriculture Padjadjaran University during dry season. The objectives of this study were: i) to estimate genotypic and phenotypic variances of stay green character; ii) to evaluate and investigate stay green performance of the 22 elite sorghum genotypes. High genotypic and phenotypic variances were observed for plant morphology (plant height, stem diameter), leaf morphology (leaf number, leaf width, leaf length and total leaf area) and yield component (panicle length) and were supported by high estimation of heritability value. Corresponding heritability ranged between 0.77 and 0.94. Genotypic variance of stay green characters was narrow and estimation of broad sense heritability was low. Stay green characters in sorghum might be a quantitative character that was controlled by many genes. Unpad 1.3, Unpad 1.1 and 1090 genotype showed good performance for stay green character. These genotypes can be recommended as stay green parental in breeding program.&lt;/p&gt;&lt;p&gt;&lt;br /&gt;&lt;strong&gt;Keywords&lt;/strong&gt;: Genotypic variance, Heritability, Phenotypic variance, Sorghum, Stay green&lt;/p&gt;