Saeed Rauf

Biomass Partitioning and Genetic Analyses of Salinity Tolerance in Sunflower (Helianthus annuus L.)

Biomass partitioning was studied in sunflower (Helianthus annuus L.) inbred lines and their hybrids differing in salinity resistance. Differential biomass partitioning was observed among resistant and susceptible lines as well as within resistant lines, which were grown in large pots. Traits such as number of dead leaves and total number of nodes may be used as dominant markers for understanding the mechanism of resistance to salinity. Multi-location trials differing for salinity levels showed low and non-significant heritabilities across the environment for biochemical traits showing their sensitivity to the environment and a significant G X E interaction. Thus selection could only possible within the salinity level for these traits. Contrastingly, morphological traits such as number of nodes showed significant heritabilities (narrow or broad sense) across the environment. These traits may be exploited by the selection of inbred lines across or with salinity levels. Among various salinity levels, 12 dSm−1 was found to be feasible for screening and selection as it promoted the additive type of gene action.

Handling sunflower (Helianthus annuus L.) populations under heat stress

Sustainable sunflower yield is under threat by a significant rise in global temperatures. Therefore, the development of a heat-resistant sunflower breeding population or hybrid is important for sustainable yield under high temperatures. Although there are a significant number of studies aimed at understanding the mechanism of heat resistance, only few direct approaches were made to improve heat resistance in sunflower. When breeding for heat resistance, the selection criteria are important. A desirable screening criterion should be rapid, highly heritable, and allow for the discrimination of resistant and susceptible ecotypes before reproductive maturity so that undesirable plants can be eliminated. In contrast, destructive selection criteria are not applicable for a segregating population. On the basis of an extensive review of data and experimentation, traits such as leaf and head orientation at the time of anthesis are proposed for practical utilization of sunflower heat-resistant breeding. These traits could be utilized as markers linked with heat avoidance. The traits are simply inherited, non-destructive, non-laborious, and show no impact of the environment and are independent of genotype × environment.

Breeding Strategies to Enhance Drought Tolerance in Crops

Global climate change is expected to increase the occurrence and severity of drought episodes due to increasing temperatures and evapotranspiration. Therefore, food security in the twenty-first century will increasingly depend on the release of new cultivars with improved adaptation to drought conditions. However, selection for drought tolerance is difficult due to a complex genotype and by environment interactions. Recent progress in genomics makes possible a more efficient assessment and enhanced diversity in germplasm collections, introgression of valuable traits from new sources and identification of the genes that control key traits. Marker-assisted selection helps to reduce the environmental impact of breeder selection. Significant advances have been made in the development of in vitro selection methods. The broader use of traits from alien species and the manipulation of heterosis and polyploidy create new perspectives for improving yield potential and adaptation to abiotic stresses. The use of the knowledge generated by these approaches should clarify the functional basis of drought adaptation traits. The integration of these new methods and tools into breeding programs and their potential impact in the development of drought-tolerant germplasm are discussed.

Utilization of leaf temperature for the selection of leaf gas-exchange traits to induce heat resistance in sunflower (Helianthus annuus L.)

Heat stress is a major production constraint of sunflower worldwide. Therefore, various populations (parental, F1, F2, F3, and plant progenies) of sunflower were screened for leaf gas-exchange traits with the objectives to formulate selection criteria of heat resistance and development of heat-resistant lines. Initial screening and F2 seeds exposed to heat stress (45°C) resulted in the development of an adapted F2 population that showed leaf gas-exchange and morphological traits better than the unadapted population. Correlation coefficients of traits were partitioned into direct and indirect effects via a path analysis technique to determine the cause of their relationship with a basic parameter such as a reproductive head mass (HM). Path analysis showed a positive direct effect of leaf temperature (Tleaf) (0.32) on HM and also an indirect effect (0.77) of the transpiration rate (E) on HM. Moreover, Tleaf showed high heritability estimates. Tleaf was used to select superior plants within the F2 population. This selection brought about an improvement in the net photosynthetic rate (PN) and E as it was indicated from progeny performance and realized heritability. Progenies selected on the basis of Tleaf also showed an increase in achene yield and heat resistance over unselected F3 progenies and a commercial hybrid.

Progress in Modification of Sunflower Oil to Expand its Industrial Value

Increasing the sunflower seed oil content as well as improving its quality makes it compatible for industrial demands. This is an important breeding objective of sunflower which increases its market value and ensures high returns for the producers. The present review focuses on determining the progress of improving sunflower seed oil content and modifying its quality by empirical and advanced molecular breeding methods. It is known that the sunflower oil content and quality have been altered through empirical selection methods and mutation breeding programmes in various parts of the world. Further improvement in seed oil content and its components (such as phytosterols, tocopherols and modified fatty acid profile) has been slowed down due to low genetic variation in elite germplasm and complex of hereditary traits. Introgression from wild species can be carried out to modify the fatty acids profile and tocopherol contents with linkage drags. Different transgenes introduced through biotechnological methods may produce novel long-chain fatty acids within sunflower oil. Bio-engineering of sunflower oil could allow it to be used in diverse industrial products such as bio-diesel or bio-plastics. These results showed that past and current trends of modifying sunflower oil quality are essential for its further expansion as an oilseed crop.

Determination of drought tolerance related traits in Helianthus argophyllus, Helianthus annuus, and their hybrids

Drought is a major constraint for sunflower (Helianthus annuus) production worldwide. Drought tolerance traits have been identified in the related wild species Helianthus argophyllus. This study was initiated to develop sunflower drought-tolerant genotypes by crossing cultivated sunflower with this species and analyze drought tolerance traits in the H. annuus and H. argophyllus populations, H. annuus intraspecific hybrids, and H. annuus × H. argophyllus interspecific hybrids along with the commercial hybrid Hysun-33 under three stress regimes: exogenous application of ABA, both by foliar spray and irrigation, and 5% PEG-induced osmotic stress. H. argophyllus populations had a significantly lower leaf area and higher water-use efficiency and leaf cuticular wax content under all treatments, and maintained a higher net photosynthetic rate and stomatal conductance under osmotic stress. Small leaf area and high cuticular waxes content of the wild species were, however, not inherited in interspecific hybrids which suggested for selection in F2 for these traits. Therefore, transgressive plants were selected in the F2 population to establish F3 plant progenies with silver-leafed canopy of H. argophyllus which showed higher achene yield under stress condition. These results are discussed with a view to using H. argophyllus to improve drought tolerance in cultivated sunflower.

Genetic analysis of proline concentration under osmotic stress in sunflower (Helianthus annuus L.)

Proline concentration has been often suggested as an indicator of osmotic stress. A better understanding of the genetics of this trait is however needed. In the present study, proline concentration has been assessed, together with root and stem growth, potassium, calcium and total soluble sugars concentration and stress injury symptoms, in seedlings of sunflower hybrids and their parents grown under control and osmotic conditions. Proline strongly accumulated with osmotic stress. Its concentration exhibited a large variation among genotypes and was higher in hybrids than in parental lines. A positive association was noted between proline concentration and osmotic adjustment that was reflected in a reduction of osmotic stress induced injury, as showed by the reduced number of calli in the hybrids with higher proline concentration. Broad and narrow sense heritability was higher under osmotic stress suggesting applying the selection in osmotic stress condition. In the control treatment, dominance effects explained most of the genetic variation for proline concentration while under osmotic stress both dominance and additive variance were high. The importance of dominance and additive effects suggested that several genomic regions are controlling this trait. Good general combiners, presumably carrying positive additive alleles affecting proline concentration, were identified.

Genetic improvement of Citrus for disease resistance

Progress in the genetic improvement of Citrus species was reviewed. Tools used for the genetic improvement of Citrus were categorised as conventional (introduction, selection and hybridisation) and non-conventional methods (mutation, somatic cell hybridisation and genetic engineering) of improvement. Genes linked with the disease resistance were characterised and tagged through molecular marker techniques such as Sequenced Characterised Amplified Region and Cleaved Amplified Polymorphic Sequences. Disease resistance genes showed both monogenic and polygenic inheritance. Conventional methods for disease resistance improvement of Citrus were bottleneck due to inadequate and lengthy breeding procedures. However, non-conventional methods, such as mutation breeding and protoplast fusion, have been routinely utilised for the production of disease resistant germplasm while novel genes from variable sources were used to transform Citrus species to induce resistance against diseases. These non-conventional techniques have been shown to overcome the disadvantages of conventional breeding procedures and could be regarded as rapid methods of genetic improvement as well as helpful to overcome the interspecies barrier.

Forages: Ecology, Breeding Objectives and Procedures

Forages are integral components of grassland and pasture agro-ecosystem. They are the major source of feed and nutrition for livestock. As primary producers, they are converted by livestock into secondary production in the food chain. Forage breeding is a complex process involving plant morpho-physiological aspects (perenniality, mode of reproduction, mating systems) and aberrant plant-environment correlations affecting plant performance under various sward conditions. The ultimate aim of forage breeding is to develop cultivars with high and sustainable herbage yield under various management systems. It also encompasses development of cultivars with beneficial impacts on ecosystem functions, animal growth and health. This chapter addresses challenges for forage producers and breeders due to rapidly diminishing grassland areas and the impact on the biodiversity of grassland ecosystems and their productivity. Approaches to conserve genetic diversity and utilize forage genetic resources in an efficient way as well as breeding procedures practical use in selected forage crops are discussed.

Breaking wheat yield barriers requires integrated efforts in developing countries

Abstract Most yield progress obtained through the so called “Green Revolution”, particularly in the irrigated areas of Asia, has reached a limit, and major resistance genes are quickly overcome by the appearance of new strains of disease causing organisms. New plant stresses due to a changing environment are difficult to breed for as quickly as the changes occur. There is consequently a continual need for new research programs and breeding strategies aimed at improving yield potential, abiotic stress tolerance and resistance to new, major pests and diseases. Recent advances in plant breeding encompass novel methods of expanding genetic variability and selecting for recombinants, including the development of synthetic hexaploid, hybrid and transgenic wheats. In addition, the use of molecular approaches such as quantitative trait locus (QTL) and association mapping may increase the possibility of directly selecting positive chromosomal regions linked with natural variation for grain yield and stress resistance. The present article reviews the potential contribution of these new approaches and tools to the improvement of wheat yield in farmers fields, with a special emphasis on the Asian countries, which are major wheat producers, and contain the highest concentration of resource-poor wheat farmers.