Genetic analysis of threshability in grain sorghum [Sorghum bicolor (L.) Moench]

The ease with which seeds are detached from panicles is one of the early domestication traits. Genotypes with sticky panicles are hard to thresh, and whenever threshed, the grain tends to remain attached to the glume which reduces market value and processability. This study was conducted to determine the genetic mechanisms underlying the threshability trait in sorghum. Four seed parents and eleven pollinators differing for threshability were intercrossed in Design II mating scheme and the resulting hybrids and the parents were grown in four environments. Threshability was estimated as the ratio of seed yield to panicle weight (TW) and proportion of seeds without sticky glumes (TG). Variation was significant among the entries, inbreds and hybrids with GCA for TG and TW varying markedly. Mean TG for inbred and hybrids of low threshable genotypes was not markedly different indicating that threshability trait is under the control of additive genes with dominant or partially dominant effects. Segregation analysis indicates that the TG trait may be under the control of few major genes with approximately one to three loci affecting the trait.     

Quantitative-genetic parameters of sorghum growth under striga infestation in Mali and Kenya

To estimate quantitative‐genetic parameters of sorghum for resistance to the hemi‐parasitic weed striga [Striga hermonthica (Del.) Benth.] and for agronomic traits, 36 diallel F₂ populations and their nine parental lines were evaluated under severe striga infestation at two locations each in Mali and Kenya. Location means for grain yield ranged from 132 to 254 g/m². F₂ populations outyielded lines on average by 18%. For striga emergence traits, F₂ heterosis values ranged from ‐36% to 232% among populations. Genetic and genotype x environment interaction variances of lines and F₂s were highly significant for all traits. Broad‐sense heritabilities for areas under striga severity progress curves and grain yield were 0.83 and 0.90 in lines, and 0.81 and 0.89 in F₂s, respectively. General and specific combining ability, and their interaction effects with locations were significant for most traits. F₂ superiority for grain yield under striga infestation demonstrates the potential merit of heterozygous cultivars in the target areas. Significant genotype x environment interaction entails multilocational testing to identify stable resistance. A combination of resistance with striga tolerance is recommended to breeders.     

Mapping of QTLs underlying flowering time in sorghum [Sorghum bicolor (L.) Moench]

Due to its critical importance in crop yield, the photoperiodic regulation of flowering time is considered an important trait in sorghum breeding programs. In this study, quantitative trait loci for flowering time were detected using an F₂ population derived from a cross between Kikuchi Zairai, a late-flowering cultivar originating from Japan and SC112, an early-flowering cultivar originating from Ethiopia. F₂ plants were grown with their parents under a natural day length and a 12 h day length. Two linkage maps were constructed using 213 simple sequence repeats markers. Nine quantitative trait loci controlling flowering time were identified in F₂ plants grown under a natural day length, whereas 7 QTLs were identified under a 12 h day length. Five QTLs controlling flowering time were shared under both of the day length conditions.     

Genetic and Phenotypic Association between Yield Components in Hybrid Sorghum (Sorghum bicolor (L.) Moench) populations

Summary The magnitude of genetic expression and associations among traits are important for the prediction of response to selection in diverse environments and provide the basis for planning and evaluating breeding programs. In this regard, a cross classification mating design was used to produce hybrid sorghum populations, which were evaluated in a randomized completed block design with three replications at four environments in Northern Cameroon. Data on grain yield, days to anthesis, plant height, inflorescence length, threshing percentage and seed mass were collected and subjected to statistical genetic analyses. Significant genotype × environment interaction effects were observed for all traits. Genetic variance was essentially attributed to additive gene effects, with dominance variance for grain yield being negligible. However, the reverse was observed for threshability. Genetic variance components were much higher for plant height and grain yield than for days to anthesis, seed mass and threshability. Heritability estimates for plant height and inflorescence length were high (77 and 54 percent respectively) while the estimates for grain yield and threshability were low (14 and 5 percent respectively). Grain yield had positive genotypic correlation with most of the traits. Days to anthesis were negatively correlated with vegetative and reproductive traits. These results suggest that improvement of days to anthesis, plant height, and inflorescence length should be faster because of higher heritabilities and greater phenotypic variation. However, selection for earliness and reduced plant height would not be possible without hampering grain yield. Selecting for yield primary components namely inflorescence length and seed weight would be effective for increasing production. In addition, optimizing agronomic practices and improved experimental design would increase the selection efficiencies.     

Genetic divergence among a non-restorer collection of sorghum (Sorghum bicolor (L.) Moench) and its relationship with heterosis

Summary A genetic diversity analysis in a collection of 171 non-restorer lines of sorghum (Sorghum bicolor (L.) Moench) using D² technique and canonical variate analysis indicated that considerable variation in grain yield has been added to the collection by the addition of lines derived from random mating populations. The efficiency of D² and canonical variate techniques in distinguishing extremely diverse genotypes was confirmed. However, the two techniques showed weak correspondence in their clusters. The F₁ hybrids of 15 diverse lines exhibited no relationship between heterosis or per se performance of crosses and diversity in their parents. Therefore, traditional plant breeding methods are being advocated.Approved by ICRISAT as Journal Article no. 435.     

Genotype-by-trait association of sorghum (Sorghum bicolor (L.) Moench) advanced lines grown under arid and semi-arid regions of Zimbabwe

Journal of Crop Science and Biotechnology - Inadequate information is available on trait relations and profiles of sorghum genotypes, yet this information is vital for precise decisions to be...     

Developing new markers and QTL mapping for greenbug resistance in sorghum [Sorghum bicolor (L.) Moench]

Greenbug is a major damaging insect to sorghum production in the United States. Among various virulent greenbug biotypes, biotype I is the most predominant and severe for sorghum. To combat with the damaging pest, greenbug resistant sources were obtained from screening sorghum germplasm collection. This experiment was conducted to identify the genomic regions contributing resistance to greenbug biotype I in a sorghum accession, PI 607900. An F₂ mapping population consisting of 371 individuals developed from a cross of the resistant line with an elite cultivar, BTx623 (susceptible) were tested and scored for their response to greenbug feeding in the greenhouse. Significant differences in resistance were observed between the two parental lines and among their F₂ progeny in response to greenbug feeding at 7, 10, 14 and 21 days after infestation. A linkage map spanning a total length of 729.5 cM across the genome was constructed with 102 polymorphic SSR markers (69 genomic and 33 EST SSRs). Of those microsatellite markers, 48 were newly developed during this study, which are a useful addition for sorghum genotyping and genome mapping. Single marker analysis revealed 29 markers to be significantly associated with the plant response to greenbug feeding damage. The results from interval mapping, composite interval mapping and multiple interval mapping analyses identified four major QTLs for greenbug resistance on chromosome 9. These QTLs collectively accounted for 34–82 % of the phenotypic variance in greenbug resistance. Minor QTLs located on chromosome 3 explained 1 % of the phenotypic variance in greenbug resistance. The major allele for greenbug resistance was on chromosome 9 close to receptor-like kinase Xa21-binding protein 3. These markers are useful to screen more resistant genotypes. Furthermore, the markers tagged to QTL regions can be used to enhance the sorghum breeding program for greenbug resistance through marker-assisted selection and map-based cloning.     

Heritability estimates of variation for NaCl tolerance in Sorghum bicolor (L.) Moench seedlings

Summary Data on root lengths of two-week-old seedlings of 51 Sorghum bicolor (L.) Moench accessions germinated in 50, 100, 150, 175, and 200 mM NaCl solutions were used to estimate broad sense heritabilities of variation for salinity tolerance.Estimates of broad sense heritabilities ranged from 0.38 to 0.73, the highest being in 50 mM NaCl, suggesting that there is potential for improving salinity tolerance in the species through selection and breeding.     

Identification and characterization of RAPD and SCAR markers linked to anthracnose resistance gene in sorghum [Sorghum bicolor (L.) Moench]

Anthracnose, one of the destructive foliar diseases of sorghum growing in warm humid regions, is incited by the fungus Colletotrichum graminicola.The inheritance of anthracnose resistance was studied using the parental cultivars of Sorghum bicolor (L.) Moench, HC 136 (susceptible to anthracnose) and G 73 (anthracnose resistant). The F₁ and F₂ plants were inoculated with the local isolates of C. graminicola cultures. The F₂ plants showed a segregation ratio of 3 (susceptible): 1(resistant) indicating that the locus for resistance to anthracnose in sorghum accession G 73 segregates as a recessive trait in a cross to susceptible cultivar HC 136. RAPD (random amplified polymorphic DNA) marker OPJ 01₁₄₃₇ was identified as marker closely linked to anthracnose resistance gene in sorghum by bulked segregant analysis of HC 136 × G73 derived recombinant inbred lines (RILs) of sorghum. A total of 84 random decamer primers were used to screen polymorphism among the parental genotypes. Among these, only 24 primers were polymorphic. On bulked segregant analysis, primer OPJ 01 amplified a 1437 bp fragment only in resistant parent G 73 and resistant bulk. The marker OPJ 01₁₄₃₇ was cloned and sequenced. The sequence of RAPD marker OPJ 01₁₄₃₇ was used to generate specific markers called sequence characterized amplified regions (SCARs). A pair of SCAR markers SCJ 01-1 and SCJ 01-2 was developed using Mac Vector program. SCAR amplification of resistant and susceptible parents along with their respective bulks and RILs confirmed that SCAR marker SCJ 01 is at the same loci as that of RAPD marker OPJ 01₁₄₃₇ and hence, is linked to anthracnose resistance gene. Resistant parent G 73 and resistant bulk amplified single specific band on PCR amplification using SCAR primer pairs. The RAPD marker OPJ 01₁₄₃₇ was mapped at a distance of 3.26 cM apart from the locus governing anthracnose resistance on the sorghum genetic map by the segregation analysis of the RILs. Using BLAST program, it was found that the marker showed 100 per cent alignment with the contig{_}3966 located on the longer arm of chromosome 8 of sorghum genome. Therefore, these identified RAPD and SCAR markers can be used in the resistance-breeding program of sorghum anthracnose by marker-assisted selection.An erratum to this article can be found at     

能源甜高粱遗传改良研究进展

甜高粱是最有应用前景的再生能源作物之一,它的能源转换效率取决于植株总生物量和茎秆汁液含糖量的高低。探明决定甜高粱总生物量和茎秆汁液含糖量积累相关过程的生物学机制并开发相应分子标记,是选育生物能专用甜高粱品种的有效途径。本文从甜高粱糖分积累、遗传多样性研究、遗传图谱的构建、含糖量相关性状的定位及遗传工程研究等方面介绍了近年来甜高粱遗传研究进展。     

Combining ability and heterosis as influenced by male-sterility inducing cytoplasms in sorghum [Sorghum bicolor (L.) Moench]

An investigation was carried out to assess the efficiency of A₂ cytoplasmic-nuclear male-sterility (CMS) system in comparison to the widely used A₁ cytoplasm in terms of general combining ability (gca) effects of male-sterile (A-) lines and mean performance, specific combining ability (sca) effects and mid-parent heterosis of hybrids for days to 50% flowering, plant height and grain yield at International Crops Research Institute for the Semi-Arid Tropics, Patancheru, Andhra Pradesh, India in 2001 and 2002 rainy seasons. The material for the study consisted of six pairs of iso-nuclear, allo-plasmic (A₁ and A₂) A-lines and 36 iso-nuclear hybrids produced by crossing these A-lines with three dual restorer (R-) lines. The results revealed that cytoplasm and its first-order interaction with year, R- and A-lines did not appear to contribute to variation in iso-nuclear hybrids for plant height and grain yield. Cytoplasm had limited effect on gca effects of A-lines and on sca effects and mid-parent heterosis of iso-nuclear hybrids for days to 50% flowering, plant height and grain yield. The mean days to 50% flowering, plant height and grain yield of A₂ cytoplasm-based hybrids were comparable with those of widely used A₁ cytoplasm-based hybrids. The relative frequency of the occurrence of the A₁- and A₂-based hybrids with significant sca effects and mid-parent heterosis indicated that A₂ CMS system is as efficient as A₁ with a slight edge over A₁ for commercial exploitation. The implications of these results are discussed in relation to opportunities for broadening not only cytoplasm base but also nuclear genetic base of both the hybrid parents.     

不同类型高粱中胚轴伸长特性的研究

以84份不同类型高粱品种（系）为试验材料,研究高粱中胚轴伸长特性,并筛选不同中胚轴伸长特性种质,为进一步研究高粱出苗能力奠定基础。结果表明,所有参试材料中胚轴平均长度为6.5cm,不育系、保持系、杂交种、恢复系和地方品种中胚轴平均长度分别为4.7、5.1、5.8、7.0和8.4cm。不同类型高粱中胚轴伸长能力不同,其伸长能力表现为地方品种>恢复系>杂交种>不育系、保持系。以中胚轴长度为指标的UPGMA（类平均法）聚类分析结果显示,参试的84份种质可以分为5种类型,即极长中胚轴类型、长中胚轴类型、中胚轴长度中间类型、短中胚轴类型和极短中胚轴类型。杂交种中胚轴伸长的杂种优势属于负向中亲优势。     

A major QTL for plant height is linked with bloom locus in sorghum [Sorghum bicolor (L.) Moench]

Plant height is one of the most important agronomic traits in sorghum with its relevance for biomass, grain yield, fodder and lodging. To understand its genetic basis, the quantitative trait loci (QTL) were identified using a recombinant inbred line (RIL) population consisting of 168 RILs derived from the cross between the two sorghum inbred lines 296B (dwarf) and IS18551 (tall) over six seasons. Two major QTL were identified one each on chromosomes SBI-06 and SBI-07 corresponding to the Dw2 and Dw3 gene loci together accounting 41 % plant height variation. In addition, a morphological bloom trait locus which remained unlinked in the linkage map was found to be significantly linked with plant height in single marker analysis explaining 22 % of the trait variation. By comparing the map positions of Dw1, Dw2 and Dw3, the new locus for plant height linked with bloom is proposed as Dw4 locus. Both SSR and the morphological bloom loci linked with height QTL of the present study can be employed as effective tools in marker-assisted breeding for rapid conversion of selected inbred parent lines either as dwarf seed (male sterile) parents or taller pollinators for hybrid seed industry, or for developing high biomass lines in sweet sorghum for exploitation as high bio-fuel crop.     

高粱与苏丹草杂种优势利用的研究

高粱与苏丹草杂种优势明显,F1单株生物产量性状高于双亲平均值,甚至超过或接近高亲。影响高粱-苏丹草杂交种单株茎叶鲜重的主要因素是主茎粗、叶长;决定单位面积鲜草产量的主要是密度、叶长和单株茎叶鲜重。多年随机区组试验结果表明,杂交种单位面积鲜草产量显著超过苏丹草,并以30万株/hm2为最适种植密度。杂交种营养品     

Variability and Correlations in Grain Sorghum Genotypes (Sorghum bicolor [L.] Moench) Under Drought Conditions at Different Stages of Growth

Twenty-two genotypes of grain sorghum were grown under drought conditions by omitting one irrigation during stages of before flowering period, kernel filling period, and physiological maturity period at Assiut Univ. Farm in 1987 and 1988 seasons. The results obtained revealed that considerable variation existed among genotypes for all the studied traits. The most effective moisture stress treatment in reducing grain yield, panicle weight and plant height was during flowering stage. While 1000-kernel weight was much affected by moisture stress during grain filling period. The genotype x year interaction (σ²_gy) was large compared to genotype x irrigation treatment (σ²_gl) indicated that genotypes responded differently when they were grown from year to year. The genotypic variance (σ²_g) for all traits were large reflecting the importance of genetic variability. Both phenotypic and genotypic correlations among traits showed that plant height and 1000-kernel weight were highly correlated with grain yield, while leaf area index was low associated with plant height.     

Effect of humidity on intergeneric pollinations of iap (Inhibition of Alien Pollen) sorghum [Sorghum bicolor (L.) Moench]

The production of interspecific or intergeneric progeny involving Sorghum spp. is greatly enhanced by the presence of the iap (Inhibition of Alien Pollen) allele in sorghum [Sorghum bicolor (L.) Moench]. Variation in the expressivity of the iap phenotype has been observed in previous studies, leading to the hypothesis that the humidity during pollination is affecting the degree of alien pollen adhesion and pollen tube growth. The objective of this study was to determine the optimum humidity for maximum maize pollen tube growth on sorghum florets homozygous for iap. Growth chambers were used to create environments of 45, 65, and 85 % humidity with reciprocal crosses made between the 65 and 85 % humidity chambers. Maize pollen was dusted onto the stigmas of Tx3361 (iap iap) and ATx623 (Iap Iap). Pollen adhesion and germination were higher for pollinations with Tx3361 at all humidity levels but the greatest adhesion and germination was observed at 45 % humidity for Tx3361. Under this humidity, pollen tube growth to the style and ovary was observed. The results indicate that lower humidity maximizes maize pollen adhesion and germination on the stigmas of Tx3361. Analysis of the differences in adhesion between Tx3361 and ATx623 indicate that Iap affects pollen adhesion at the stigma surface and may be controlling pollen–pistil incompatibility in interspecific crosses in sorghum.     

Sorghum [Sorghum bicolor (L.) Moench] landrace variation and classification in North Shewa and South Welo, Ethiopia

Fourteen phenotypic characters were chosen for the purpose of obtaining taxonomic evidence on the resemblances of 177 accessions of sorghum from North Shewa and South Welo regions of Ethiopia. Canonical Discriminant Analysis (CDA) and Modeclus cluster analysis were conducted to see if the 177 accessions could form clusters based on their morphological characters, and to test the consistency of farmers’ naming of the five most common Sorghum landraces represented by 44 accessions. Multivariate analyses grouped the 177 accessions into three clusters linked by a few phenotypic intermediate landraces. A botanical key was established for easy classification of the Sorghum crop plants grown in the study area. The number of accessions of the five most common landraces named by the farmers formed dissimilar groups, suggesting that farmers’ naming of these Sorghum landraces are consistent. Midrib color, grain color, grain size, glume color, glume hairiness, and grain shape were the leading morphological characters used by the farmers in naming these Sorghum landraces. This revised version was published online in July 2006 with corrections to the Cover Date.     

Molybdenum Uptake and Nitrate Reductase Activity in Sorghum (Sorghum bicolor L. Moench). Evidence for Heterosis

The absorption of Mo by the roots and. transport to the shoot of intact seedlings of a sorghum hybrid and its parent cultivars were measured for 3 h from 10 to 100 μmol ammonium molybdate. The patterns of absorption revealed hybrid vigour and the hybrid followed the patterns of the male- parent 168. Studies on the effects of different amounts of Mo on the nitrate reductase activity also showed the occurrence of hybrid vigour in the- hybrid CSH-7.