C-banding analysis of chromosome translocations in doubled haploid wheats

C-banding analysis of plant chromosomes has various applications including construction of karyotypes to identify lines with polymorphic banding patterns, to study structural aberrations and other cytogenetics research. 66 double haploid (DH) lines were produced from crosses of stripe rust susceptible common wheat cultivar ‘Plamiet' (Triticum aestivum, 2n=6x=42; AABBDD) with resistant cultivar ‘Cappelle-Desprez' (CD) characterized with 5B/7B reciprocal chromosome translocations. C-banding analysis was conducted to detect the presences of the 5B/7B translocations among the DH wheat lines. The analysis detected that 35 DH lines were positive and 31 negative for translocations. The differentiated lines will be studied to establish weather previously proposed gene(s) present on the translocated 5B or other chromosome(s) could confer resistance.African Journal of Biotechnology Vol. 4 (6), pp. 541-547, 200

Genetic Variability and Classification of Highland Adapted Quality Protein Maize Inbred Lines Using SSR Markers

Development of improved quality protein maize (QPM) varieties/hybrids would complement strategies for reducing problems of malnutrition in  developing countries such as Ethiopia.The highland maize breeding program in Ethiopia, in collaboration with CIMMYT, has developed QPM inbred lines  adapted to highland sub-humid maize agroecology. However, there is limited information on the genetic variability and interrelationship among the QPM  inbred lines. The present study was, therefore, conducted to assess the genetic variability and thereby classify elite QPM inbred lines developed for  tropical-highlands and highland transition maize agro-ecologies using microsatellite (SSR) markers. A total of 36 white-grained maize inbred lines,  including 30 QPM and six non-QPM were genotyped using 26 simple sequence repeat (SSR) markers. Estimates of the average number of alleles per  locus, gene diversity, and polymorphism information content (PIC) were 3.8, 0.53, and 0.49, respectively. Pairwise Euclidean genetic distances ranged  from 0.11 to 1.10 with mean of 0.74.Three major genetic groups were also identified, which are generally consistent with available pedigree information  except a few discrepancies. Therefore, the genetic classification using the SSR markers could assist in strategic QPM breeding for tropical-highland and  highland transition agro-ecologies. The outputs also form the basis for future studies aimed at confirming heterotic groups and identifying any new  heterotic patterns that can emerge in the highland QPM germplasm.&nbsp

Leaf and stripe rust resistance among Ethiopian grown wheat varieties and lines

Ethiopian grown wheat varieties and lines were studied to identify germplasm sources possessing resistance to leaf rust caused by Puccinia triticina and stripe rust (P. striiformis). Sixty-four lines were included of which 38 were bread wheat (Triticum aestivum, 2n=6x=42, AABBDD) and 26 durum wheat (T. turgidum, 2n=6x=42, AABBDD). Controlled glasshouse studies were conducted by inoculating seedling plants using pathotypes of five P. triticina (UVPrt2, UVPrt3, UVPrt5, UVPrt9 and UVPrt13) and two P. striiformis (6E16A and 6E22A). The result indicated that 20 varieties and lines harbor resistance to the leaf rust and 26 to the stripe rust pathotypes showing infection type

Genetic Variability for Resistance to Leaf Blight and Diversity among Selected Maize Inbred Lines

Maize (Zea mays L.) is an important staple food crop in sub-Saharan Africa (SSA). The productivity of the crop is limited partly by the leaf blight disease caused by Exserohilum turcicum. In breeding for resistance to leaf blight, the germplasm needs to be well-characterized in order to design efficient breeding programs. This study evaluated the (i) genetic variability among maize inbred lines and (ii) diversity of selected medium to late maturity tropical maize inbred lines for hybrid breeding. Plants of 50 maize inbred lines were artificially inoculated in the field during 2011 and 2012. Disease severity and incidence as well as grain yield were measured. A subset of 20 elite maize inbred lines was genotyped using 20 SSR markers. The germplasm showed significant differences in reaction to leaf blight and were classified as either resistant or intermediate or susceptible. Mean disease severity varied from 2.04 to 3.25. Seven inbred lines were identified as potential sources of resistance to leaf blight for the genetic improvement of maize. The genotyping detected 108 alleles and grouped the inbred lines into five clusters consistent with their pedigrees. The genetic grouping in the source population will be useful in the exploitation of tropical maize breeding programs

Application of Microsatellites in Genetic Diversity Analysis and Heterotic Grouping of Sorghum and Maize

Sorghum and maize are major cereal crops worldwide and key food security crops in Sub-Saharan Africa. The difference in the mating systems, maize as predominantly a cross-fertilizer and sorghum as a self-fertilizer is reflected in differences in visible phenotypic and genotypic variations. The reproductive differences dictate the level of genetic variation present in the two crops. Conventionally, a heterotic group assignment is made based on phenotypic values estimated through combining ability and heterosis analyses. However, phenotypic evaluation methods have their limitation due to the influence of the environment and may not reflect the heterotic pattern of the lines accurately. Therefore, more effective and complementary methods have been proposed for heterotic grouping of candidate lines. Estimation of molecular-based genetic distance has proven to be a useful tool to describe existing heterotic groups, to identify new heterotic groups, and to assign inbreds into heterotic groups. Among the molecular markers, microsatellites markers have proved to be a powerful tool for analyzing genetic diversity and for classifying inbred lines into heterotic groups. Therefore, the aim of this chapter was to elucidate the use of microsatellite markers in genetic diversity analysis and heterotic grouping of sorghum and maize

Breeding wheat for drought tolerance: Progress and technologies

AbstractRecurrent drought associated with climate change is among the principal constraints to global productivity of wheat (Triticum aestivum (L.) and T. turgidum (L.)). Numerous efforts to mitigate drought through breeding resilient varieties are underway across the world. Progress is, however, hampered because drought tolerance is a complex trait that is controlled by many genes and its full expression is affected by the environment. Furthermore, wheat has a structurally intricate and large genome. Consequently, breeding for drought tolerance requires the integration of various knowledge systems and methodologies from multiple disciplines in plant sciences. This review summarizes the progress made in dry land wheat improvement, advances in knowledge, complementary methodologies, and perspectives towards breeding for drought tolerance in the crop to create a coherent overview. Phenotypic, biochemical and genomics-assisted selection methodologies are discussed as leading research components used to exploit genetic variation. Advances in phenomic and genomic technologies are highlighted as options to circumvent existing bottlenecks in phenotypic and genomic selection, and gene transfer. The prospects of further integration of these technologies with other omics technologies are also provided

Selection of M5 mutant lines of wheat (Triticum aestivum L.) for agronomic traits and biomass allocation under drought stress and non-stressed conditions

IntroductionIn the face of climate changes and limited water availability for irrigated crop production, enhanced drought tolerance and adaptation is vital to improve wheat productivity. The objective of this study was to determine the responses of newly bred and advanced mutant lines of wheat based on agronomic traits and biomass allocation under drought-stressed and non-stressed environments for production and breeding.MethodsFifty-three mutant lines, including the parental check and six check varieties, were evaluated under non-stressed (NS) and drought stressed (DS) conditions in the field and controlled environments using a 20 x 3 alpha lattice design with two replicates. The following agronomic data were collected: days to 50% heading (DTH), days to maturity (DTM), plant height (PH), number of productive tillers (PTN), shoot biomass (SB), root biomass (RB), total biomass (TB), root: shoot ratio (RSR), spike length (SL), thousand seeds weight (TSW) and grain yield (GY). Data were analyzed and summarized using various statistical procedures and drought tolerance indices were computed based on grain yield under NS and DS conditions.ResultsSignificant (P < 0.05) differences were recorded among the mutant lines for most assessed traits under NS and DS conditions. Grain yield positively and significantly (p < 0.001) correlated with PTN (r = 0.85), RB (r = 0.75), SB (r = 0.80), SL (r =0.73), TB (r = 0.65), and TSW (r = 0.67) under DS condition. Principal component analysis revealed three components contributing to 78.55% and 77.21% of the total variability for the assessed agronomic traits under DS and NS conditions, respectively. The following traits: GY, RB, SB, and PTN explained most of the variation with high loading scores under DS condition. Geometric mean productivity (GMP), mean productivity (MP), harmonic mean (HM), and stress tolerance index (STI) were identified as the best drought tolerance indices for the identification of tolerant lines with positive correlations with GY under NS and DS conditions.DiscussionAmong the advanced lines tested, LMA16, LMA37, LMA47, LMA2, and LMA42 were selected as the superior lines with high performance and drought tolerance. The selected lines are recommended for multi-environment trails and release for production in water-limited environments in South Africa

Fall armyworm infestation and development : screening tropical maize genotypes for resistance in Zambia

DATA AVAILABILITY STATEMENT : All data are provided in the manuscript.SUPPLEMENTARY MATERIAL : TABLE S1: Artificial diet used for laboratory rearing of FAW. TABLE S2: Mean performance and AUPPCs of 63 tropical maize genotypes when evaluated under artificial FAW infestation. TABLE S3: Nature and magnitude of FAW damage revealed by 63 tropical maize genotypes evaluated under artificial FAW infestation. Supplementary FIGURE S1: Diets used for rearing FAW on petri dishes. S1A- Natural diet of maize leaves and stalks. S1BArtificial diet containing wheat, soy and other ingredients. Supplementary FIGURE S2: Rearing cage for adult FAW moths.Knowledge of fall armyworm (FAW) (Spodoptera frugiperda J.E. Smith) rearing, infestation and development and precision screening protocols are preconditions for the successful introgression of resistance genes into farmer-preferred varieties. We aimed to determine FAWdevelopmental stages, screen tropical maize and select resistant lines under controlled conditions in Zambia. Field-collected FAWsamples constituting 30 egg masses and 60 larvae were reared using maize leaf- and stalk-based and soy- and wheat flour-based diets at 27 1 C, 60 5% relative humidity and 12 h day length. The resulting neonates were separated into sets A and B. The life cycles of set A and field-collected larvae were monitored to document the FAW developmental features. Set B neonates were used to infest the seedlings of 63 diverse tropical maize genotypes. Egg, larva, pupa and adult stages had mean durations of 2, 24, 20 and 12 days, respectively. Test maize genotypes revealed significant differences (p < 0.05) based on FAWreaction types, with lines TL13159, TL02562, TL142151, VL050120 and CML548-B exhibiting resistance reactions, while CML545-B, CZL1310c, CZL16095, EBL169550, ZM4236 and Pool 16 displayed moderate resistance. These genotypes are candidate sources of FAW resistance for further breeding. This study will facilitate controlled FAW rearing for host screening in the integration of FAW resistance into market-preferred maize lines.The Alliance for a Green Revolution (AGRA) through the African Centre for Crop Improvement (ACCI) and the International Foundation for Science (IFS).https://www.mdpi.com/journal/insectsam2023Zoology and Entomolog

Breeding Wheat for Powdery Mildew Resistance: Genetic Resources and Methodologies-A Review

Powdery mildew (PM) of wheat caused by Blumeria graminis f. sp. tritici is among the most important wheat diseases, causing significant yield and quality losses in many countries worldwide. Considerable progress has been made in resistance breeding to mitigate powdery mildew. Genetic host resistance employs either race-specific (qualitative) resistance, race-non-specific (quantitative), or a combination of both. Over recent decades, efforts to identify host resistance traits to powdery mildew have led to the discovery of over 240 genes and quantitative trait loci (QTLs) across all 21 wheat chromosomes. Sources of PM resistance in wheat include landraces, synthetic, cultivated, and wild species. The resistance identified in various genetic resources is transferred to the elite genetic background of a well-adapted cultivar with minimum linkage drag using advanced breeding and selection approaches. In this effort, wheat landraces have emerged as an important source of allelic and genetic diversity, which is highly valuable for developing new PM-resistant cultivars. However, most landraces have not been characterized for PM resistance, limiting their use in breeding programs. PM resistance is a polygenic trait; therefore, the degree of such resistance is mostly influenced by environmental conditions. Another challenge in breeding for PM resistance has been the lack of consistent disease pressure in multi-environment trials, which compromises phenotypic selection efficiency. It is therefore imperative to complement conventional breeding technologies with molecular breeding to improve selection efficiency. High-throughput genotyping techniques, based on chip array or sequencing, have increased the capacity to identify the genetic basis of PM resistance. However, developing PM-resistant cultivars is still challenging, and there is a need to harness the potential of new approaches to accelerate breeding progress. The main objective of this review is to describe the status of breeding for powdery mildew resistance, as well as the latest discoveries that offer novel ways to achieve durable PM resistance. Major topics discussed in the review include the genetic basis of PM resistance in wheat, available genetic resources for race-specific and adult-plant resistance to PM, important gene banks, and conventional and complimentary molecular breeding approaches, with an emphasis on marker-assisted selection (MAS)

Combining ability for grain yield and resistance to maize streak virus in maize

Combining ability effects for grain yield, yield-related traits and resistance to maize streak virus (MSV) were determined using 10 parents, 45 single crosses and five standard hybrid checks. Genotypes were evaluated at three locations (Ngaramtoni, Inyala, and Igomelo) over two seasons (2012/13 and 2013/14) using a 6 x 10 simple lattice design with two replications. Data were collected for days-to-50% silking (DSL), days-to-50% anthesis (DA), reaction to MSV disease, plant height (PHT), ear height (EHT), number of ears per plant (EPT), husk cover of cobs (HSC) and grain yield (YLD). General combining ability (GCA) and specific combining ability (SCA) effects were significant (P < 0.05) for all traits except DA and DSL. Parental line TL2012-42 was the best general combiner for YLD, while the parents TL2012-41, TL2012-1 and TL2012-42 were the best combiners for maize streak virus resistance, with negative GCA effects of -10.9%, -10.8% and -10.7%, respectively. The highest SCA effect for grain yield (4.80) was detected in the hybrid TL2012-7/TL2012-38. Crosses such as TL2012-38/TL2012-55 and TL2012-25/TL2012-26 had negative SCA effects for their MSV reaction. The above parental lines and hybrids can be recommended for direct production, or breeding to enhance grain yield and MSV resistance in maize varieties for Tanzania