Integrated Analysis Of Phenology Traits And Qtl In The Drought Tolerant Sorghum Genotypes Btx642 And Rtx7000

The growth and development of two sorghum drought tolerant genotypes BTx642 (post-flowering drought tolerant, "stay green") and RTx7000 (pre-flowering drought tolerant) were characterized and compared. Differences in phenology and the growth and development of leaves and stalks were identified that could contribute to variation in shoot biomass, grain yield and response to water deficit. An F12 recombinant inbred line (RIL) population derived from the two parents was genotyped using the Illumina Genome Analyzer II platform and the information used to generate a genetic map useful for analysis of quantitative trait loci (QTL). Seventy-two different traits were measured in the RIL population at anthesis and at grain maturity. Plants were grown in well-watered environments in greenhouse conditions and in field conditions near College Station, TX in 2008-2010. QTL mapping was used to analyze the genetic basis of trait variation in the population and to detect associations between traits. A total of 477 QTL were identified that in combination modulate leaf size (length, width, and area), shoot biomass accumulation (shoot, stalk, stem, leaf, and leaf sheath), panicle weight, root size and architecture (length, surface area, and volume, number of tips, forks and nodal roots, and root biomass), stalk and stem length, and flowering time. Six flowering time QTL were identified and variation in time to anthesis affected the expression of several other traits including leaf size and biomass accumulation. However, QTL infrequently had an impact on traits associated with different organs. The specificity observed is consistent with independent genetic control of traits associated with leaves, stems and roots. Nine QTL that modulated shoot biomass accumulation were detected that were not affected by flowering time. Of these, four shoot biomass QTL co-localized with leaf size traits. Eight QTL for panicle biomass were detected with two coincident with QTL for upper leaf size. A QTL for leaf width at anthesis was found to co-localize with a stay green locus.

Sorghum (Sorghum bicolor [L.] Moench) is the fifth most economically important cereal grown worldwide and is a source of food, feed, fiber and fuel. Sorghum, a C4 grass and a close relative to sugarcane, is adapted to hot, dry adverse environments. Some genotypes of sorghum called stay-green have delayed leaf senescence during grain ripening under drought stress conditions which allows normal grain filling whereas most sorghum lines senesce early under post-anthesis drought. Eight sources of stay-green have been identified in the sorghum germplasm collection, most originating from Sudan and Ethiopia. The diversity of the eight sources of staygreen was analyzed using 55 simple sequence repeats (SSR) markers with genome coverage. This analysis showed that the sources of stay-green are quite diverse and can be divided into five groups based on race or working group. Three sources of stay-green have been used to identify 12 major quantitative trait loci (QTL) that modulate this trait. The origin of favorable alleles for stay-green was traced backward to ancestral lines and forward into breeding materials derived from stay-green germplasm. The analysis of the origin of favorable alleles for stay-green helped explain why subsets of stay-green QTL were identified in different studies and provided evidence that there may be more than one favorable allele in the sorghum germplasm for several of the stay-green QTL. Analysis of stay-green breeding lines from three public sorghum-breeding programs revealed that one of the main QTL identified in mapping studies was not being used in the breeding programs (0/13), most likely due to its association with an allele for lemon yellow seeds. In addition, a subset of the regions containing favorable alleles for staygreen from the genotype BTx642 were over represented in stay-green breeding lines. Nearly isogenic lines containing favorable alleles from BTx642 for Stg1, Stg2, Stg3, and Stg4 in a RTx7000 (senescent) background were characterized and each NIL was shown to exhibit a stay-green phenotype. Based in part on this information, fine-mapping of Stg1 was undertaken by crossing the Stg1 NIL to RTx7000. Overall, these results revealed the origin of favorable alleles for stay-green and the current utilization of alleles for stay-green in public breeding programs. In addition, this study identified additional stay-green sources that could be used for further QTL analysis and highlighted the genetic complexity of the stay-green trait.

There is an increasing need to improve crop water-use efficiency (WUE) (ratio of whole-plant biomass to cumulative transpiration) due to decreased water availability and increased food and energy demands throughout the world. The objective of the study was to estimate the genetic variation and genetic basis for transpiration efficiency A:E (CO2 assimilation rate (A) divided by transpiration rate (E)) trait and its relationship to WUE related to pre-flower drought tolerance in recombinant inbred lines (RILs) of sorghum and associated QTLs. A greenhouse study was conducted at Bushland, TX, 2008, using 71 RILs derived from cross of Tx430 x Tx7078. A randomized complete block experimental design was used, with both genotype and water regime (40 and 80 percent water regime) as experimental factors, and four replications. Genotype had a significant effect on A, E and A:E under both the environments. Among the RILs, entry means for A:E ranged from 1.58 to 3.07 mmol CO2 mol^-1 H2O and 1.18 to 4.36 mmol CO2 mol^-1 H2O under 80 percent and 40 percent water regime, respectively. Heritability estimates based on individual environments for A:E, A and E were 0.77, 0.45 and 0.37 under 80 percent water regime and 0.90, 0.33 and 0.71 under 40 percent water regime, respectively. A genetic map was constructed by digital genotyping method using Illumina GAII sequencer with 261 informative indel/ single-nucleotide polymorphism (SNP's) markers distributed over 10 linkage groups. Three significant QTLs associated with transpiration efficiency were identified; two on SBI-09 and one on SBI-10 with one logarithmic of odds (LOD) interval length ranging from 5.3 to 5.7 cM and accounting for 17 percent - 21 percent of the phenotypic variation. In field and greenhouse evaluation of agronomic of traits at College Station and Halfway, TX, 91 QTL that control variation in six major agronomic traits such as plant height, flowering, biomass, leaf area, leaf greenness and stomatal density were identified. Co-localization of transpiration efficiency QTLs with agronomic traits such as leaf area, biomass, leaf width and stomatal density indicated that these agronomically important QTLs can be used for further improving the sorghum performance through marker assisted selection (MAS) under pre-flowering drought stress conditions.

Crops adapted to dry conditions are essential to meet future food, feed and energy needs. Knowledge of interaction between drought tolerance traits and their response to varying water supply conditions would improve selection for yield stability traits. This study focused on determining the association between the QTL regulating the staygreen trait in sorghum with improved canopy temperature depression (CTD) as regulated by total and compositional epicuticular wax content in a recombinant inbred line population derived from BTx642 and RTx7000. Phenotypic data were collected in 3 replicated field trials and 1 greenhouse trial. Plants with higher leaf EWL had cooler canopies. Our results also confirmed that staygreen genotypes are able to maintain cooler canopy than the non-stay-green genotypes under drought and hot conditions. We have suggested that wax might offer a more stable indicator for selection of drought tolerance under a variety of weather conditions. Composite interval mapping identified a total of 28 QTL, fifteen of which had significant overlaps. The overlap between QTL for cuticular leaf wax and QTL for staygreen exhibits a departure from the QTL overlaps for other traits with that of cuticular leaf wax. We have also suggested that under drought stress, the QTL for staygreen may be expressed earlier in time (at anthesis) than had been previously believed.

Sorghum (Sorghum bicolor L. Moench) is the fifth most economically important cereal crop grown worldwide and adapted to a wide range of climatic conditions. Drought stress has been ranked as one of the most significant causes of crop yield loss with its effects on yield and yield components. Conservative water use by plants is one of the strategies that can be used as a drought coping mechanism. The slow wilting trait has been associated with conservative water use and has been found in some sorghum genotypes. The purpose of this study was to use canopy temperature to screen for drought tolerance in sorghum, evaluate water use efficiency for slow wilting sorghum genotypes and determine variability in root morphology and response to drought among sorghum genotypes. Canopy temperature studies were conducted under field conditions using infrared (IR) sensors while water use efficiency and root studies were conducted under greenhouse conditions. Our results showed a distinct separation in canopy temperature among genotypes under field conditions at 2:00 pm to 6:00 pm. Midday canopy temperature depression (CTD) was positively correlated to yield (R2 = 0.19) and harvest index (R2 = 0.11). CTD was also stable for all the genotypes during the period from 1:00 pm to 7:00 pm. There was a negative correlation between CTD and crop water stress index (CWSI) (R2 = 0.34) and a positive one between canopy temperature and CWSI (R2 = 0.50). Evaluation of genotypes for water use efficiency revealed significant variability among sorghum genotypes in the amount of water used (10.48 - 13.52 kg) and transpiration efficiency (TE) (2.64 - 7.11 g kg−1) among genotypes. Slow wilting genotypes were high in TE. Rooting depth increased for some genotypes under drought stress with genotype SC1124 recording the largest increase (180%). Total root length for some genotypes increased by 11 - 113% with genotypes SC224 and SC1019 recording the greatest increase. There was a positive correlation between water used and root length (R2 = 0.21). These results show that there is potential for selection of drought tolerance in sorghum and that genotypes with the slow wilting traits are efficient in water use.

This book details sorghum breeding technologies, grain compounds, nutrition and digestibility, biotechnology methods, broad renewable applications and an economic study. Chapters are divided into five review chapters, five case study chapters, and nine protocol chapters providing comprehensive reviews, new study results or state-of-the-art protocols. Written in the highly successful Methods in Molecular Biology series format, chapters include introductions to their respective topics, lists of the necessary materials and reagents, step-by-step, readily reproducible laboratory protocols, and tips on troubleshooting and avoiding known pitfalls. Authoritative and cutting-edge, Sorghum: Methods and Protocols aims to provide useful information and tools to an array of readers looking to research and utilize sorghum.

The Saccharinae clade of the Poaceae (grass) family of flowering plants includes several important crops with a rich history of contributions to humanity and the promise of still-greater contributions, as a result of some of the highest biomass productivity levels known, resilience to drought and other environmental challenges that are likely to increase, amenability to production systems that may mitigate or even reverse losses of ecological capital such as topsoil erosion, and the recent blossoming of sorghum as a botanical and genomic model for the clade. In Genomics of the Saccharinae, advances of the past decade and earlier are summarized and synthesized to elucidate the current state of knowledge of the structure, function, and evolution of the Sorghum, Saccharum, and Miscanthus genera, and progress in the application of this knowledge to crop improvement. As a backdrop, it is important to understand the naturally occurring diversity in each genus, its organization and distribution, and its evolutionary history. Genomic tools and methods for Saccharinae biology and improvement have improved dramatically in the past few years – a detailed summary of these tools and their applications is a central element of this book. Application of genomic tools to priorities in crop improvement, including understanding and manipulating plant growth and development, composition, and defense, as well as increasing the quality and productivity of seed/grain, sugar, biomass, and other value-added products under a range of conditions and inputs, are addressed. In particular, as the first native African crop to emerge as a genomic model, sorghum offers an excellent case study of challenges and opportunities in linking new advances in biosciences to solving some of Africa’s major agricultural problems. Several members of the clade, exemplified by Sorghum halepense (Johnsongrass) offer insights into weediness and invasion biology. The first sequence for a member of the clade, sorghum, as well as progress and challenges toward sequencing of additional members and the new opportunities that this will create, are also explored. Indeed, the very complexities that have hindered study of some clade members also offer intriguing opportunities to gain insight into fundamental questions such as roles of polyploidy in agricultural productivity and post-polyploidy evolution.

Sorghum is among the top five cereals and one of the key crops in global food security efforts. Sorghum is a resilient crop under high-stress environments, ensuring productivity and access to food when other crops fail. Scientists see the potential of sorghum as a main staple food in a future challenged by climate change. The contributors provide a comprehensive review of sorghum knowledge. The discussion covers genetic improvements, development of new hybrids, biotechnology, and physiological modifications. Production topics include water and nutrient management, rotations, and pest control. Final end uses, sorghum as a bioenergy crop, markets, and the future of sorghum are presented. IN PRESS! This book is being published according to the “Just Published” model, with more chapters to be published online as they are completed.

In the wake of urbanization and technological advances, public green spaces within cities are disappearing and people are spending more time with electronic devices than with nature. Urban Horticulture explores the importance of horticulture to the lives, health, and well-being of urban populations. It includes contributions from experts in researc

A readable account of how, where and when humans learned to domesticate plants and animals.