Gene manipulation in plant improvement , Gene manipulation in plant improvement , مرکز فناوری اطلاعات و اطلاع رسانی کشاورزی

Gene manipulation in plant improvement

In most crop breeding programs, the rate of yield increment is insufficient to cope with the increased food demand caused by a rapidly expanding global population. In plant breeding, the development of improved crop varieties is limited by the very long crop duration. Given the many phases of crossing, selection, and testing involved in the production of new plant varieties, it can take one or two decades to create a new cultivar. One possible way of alleviating food scarcity problems and increasing food security is to develop improved plant varieties rapidly. Traditional farming methods practiced since quite some time have decreased the genetic variability of crops. To improve agronomic traits associated with yield, quality, and resistance to biotic and abiotic stresses in crop plants, several conventional and molecular approaches have been used, including genetic selection, mutagenic breeding, somaclonal variations, whole-genome sequence-based approaches, physical maps, and functional genomic tools. However, recent advances in genome editing technology using programmable nucleases, clustered regularly interspaced short palindromic repeats (CRISPR), and CRISPR-associated (Cas) proteins have opened the door to a new plant breeding era. Therefore, to increase the efficiency of crop breeding, plant breeders and researchers around the world are using novel strategies such as speed breeding, genome editing tools, and high-throughput phenotyping. In this review, we summarize recent findings on several aspects of crop breeding to describe the evolution of plant breeding practices, from traditional to modern speed breeding combined with genome editing tools, which aim to produce crop generations with desired traits annually.

https://www.mdpi.com/1422-0067/21/7/2590/pdf

Conventional and Molecular Techniques from Simple Breeding to Speed Breeding in Crop Plants: Recent Advances and Future Outlook

Microspore embryogenesis is the most commonly used method to produce doubled haploids. It is based on the ability of a single haploid cell, the microspore, to de-differentiate and regenerate into a whole plant after being exposed to stresses, such as low or high temperatures, carbon starvation and colchicine. Some stresses such as temperature treatments and carbon starvation have been used with success in many plant species, whereas others such as colchicine had limited application in a few species. Reports on the application of whole plant treatments with feminizing agents on inflorescences and buds are scarce. Furthermore, the technical means to apply some stresses such as γ-irradiation are not readily available. Recently, novel stresses such as pH, inducer chemicals, carrageenan oligosaccharides and heavy metals were reported to induce microspore embryogenesis. It remains to be seen, however, whether these stresses are effective in a wider range of species. Finally, pretreatment of cultured cells with high concentrations of 2,4-D efficiently induces somatic embryogenesis in several species (carrot, alfalfa). However, reports on the use of this particular chemical stress are not available in microspore embryogenesis. The paper presented here gives an overview of various stresses and mechanisms of action of these stresses in inducing microspore embryogenesis.

https://onlinelibrary.wiley.com/doi/pdf/10.1111/j.1399-3054.2006.00675.x

Stresses applied for the re‐programming of plant microspores towards in vitro embryogenesis

Frequency of callus formation in wheat (Triticum aestivum L. em. Thell) anthers cultured in vitro and the frequency of subsequent plantlet formation from such calli were examined in a diallel population produced from five inbred spring wheat cultivars. Two of the five cultivars were believed to possess relatively high frequencies of response and the other three relatively low response frequencies, based on previous studies. General and specific combining abilities were estimated and found to be highly significant for both traits. Reciprocal effects were also estimated and were highly significant for both traits. Of the 25 entries, the largest mean callus formation frequency was observed on anthers of ‘Kitt’ x ‘Olaf’, while the largest mean plantlet formation frequency was observed using anthers of the cultivar, ‘Fielder’. No significant correlation was observed between the two traits. Heritability estimates in the range of 0.6–0.7 suggested, however, that both traits were highly heritable, so that rapid gain from selection for these traits should be possible. Current limitations due to genetic variation in responses therefore may not constitute a major obstacle to application of in vitro techniques by wheat breeders.

Combining abilities and heritability of callus formation and plantlet regeneration in wheat (Triticum aestivum L.) anther cultures.

This brief historical review focuses on durum wheat domestication and breeding in the Mediterranean region. Important milestones in durum wheat breeding programs across the countries of the Mediterranean basin before and after the Green Revolution are discussed. Additionally, the main achievements of the classical breeding methodology are presented using a comparison of old and new cultivars. Furthermore, current breeding goals and challenges are analyzed. An overview of classical breeding methods in combination with current molecular techniques and tools for cultivar development is presented. Important issues of seed quality are outlined, focusing on protein and characteristics that affect human health and are connected with the consumption of wheat end-products.

https://www.mdpi.com/2073-4395/10/3/432/pdf

Durum Wheat Breeding in the Mediterranean Region: Current Status and Future Prospects

High production of embryoids in anther culture of pollen derived homozygous spring wheats

The production of double haploids through androgenesis is used by breeders to produce homozygous lines in a single generation. Androgenesis can be achieved by isolated microspore culture, which, however, allows the production of green haploids with a very low efficiency. In order to improve the overall green haploid regeneration in durum wheat, we compare the efficiency of eight different pre-treatments. These pre-treatments were: cold pretreatment for 5 weeks, 0.3M mannitol for 12 days at 4°C; 0.3M mannitol for 7 days at 4°C; 0.7M mannitol for 5 days at 4°C; PEG4000 1.5% for 5 days at 4°C; PEG4000 1% for 15 days at 4°C; PEG4000 1% for 10 days at 4°C and control without pretreatment. The cold treatment for 5 weeks (4°C) is the most efficient and was used to test the androgenetic ability by microspore culture method of three Tunisian durum wheat cultivars (Razzek, Khiar and Azizi).This pretreatment improves significantly the embryogenesis induction and green plants regeneration with green/albina ratio ≈ 2for the cultivar “Khiar”. The PEG4000 1% for 10 days seems promising pretreatment and this is important to perform new experiments to advance their response.

	 

	Key words: Isolated microspore culture, double haploid, durum wheat, pre-treatment.

Effect of pre-treatment on isolated microspores culture ability in durum wheat (Triticum turgidum subsp. durum Desf.)

Plantes chlorophylliennes de blé dur obtenues par culture de microspores isolées : importance des prétraitements

Durum wheat is a very important crop in the Mediterranean basin. It is a traditional component of the Mediterranean diet and a basic ingredient in many dishes (couscous, frikey, taboule, pastas, flat breads, etc.). Similar to other Mediterranean crops, durum wheat is submitted to severe environmental constraints such as drought, frost and heat. Some diseases (barley yellow dwarf virus, rusts, powdery mildew, etc.) and parasites (Hessian fly, cyst nematodes) that are widely distributed in these regions also affect the water deficit, thus causing marked reductions in yield. Over the last 10 years, scientific collaborations have been developed with the aim of improving tolerance/resistance to these biotic and abiotic stresses, and enhancing durum wheat production. The SEWANA (South of Europe, West Asia and North Africa) durum wheat network was founded in 1995, with five main objectives: i) to study morphophysiological traits concerning tolerance to water and heat stress, to describe variations within durum wheat and related species, to conduct genetic analyses and define predictive criteria for yield stability and water-use efficiency; ii) to construct a genetic map of intraspecific and interspecific crosses and identify, using a QTL approach, regions of the genome involved in the genetic control of drought tolerance traits; iii) to improve grain quality through the use of protein and molecular markers; iv) to develop in vitro biotechnologies (haplodiploidization, cultures of immature embryos, embryogenic isolated cells and isolated microspores) and integrate them in breeding programs; v) to tap genetic resources more efficiently by improving their management and utilization. The SEWANA program combines physiological, biotechnological and molecular tools. Most laboratories involved (from research institutes, universities and international centers) are conducting research on common genetic models (checks, reference collections, mapping populations, etc.) in order to promote information exchanges and multidisciplinarity. Training, visits and workshops also favour the development of these collaborations.

/pdf/presentation-d-un-programme-international-d-amelioration-du-3g4y34u410.pdf

Présentation d’un programme international d’amélioration du blé dur pour le bassin méditerranéen

This study presents the first report comparing the efficiency of microspore culture, gynogenesis and durum wheat × maize crosses for haploid plant production from three durum wheat genotypes (Razzek, Karim and Jneh Khotifa). The results showed that the best induction, calli or embryos formation and plant regeneration rates for the three genotypes were obtained with gynogenesis (47.2, 7.6, 0.8%), followed by interspecific crosses (33.1, 1.7, 0.4%) and isolated microspore culture (8.2, 0.05, 0.01%). Interestingly, all plants regenerated by gynogenesis and durum wheat × maize crosses were green whereas all plants obtained by isolated microspore culture were albino. In the haploid production system, all steps of the process are important for the three methods. The critical steps that have greatly reduced the number of regenerated haploid plants were induction, embryogenesis and regeneration for microspore culture, forming and regeneration of calli or embryo and haploid regeneration for interspecific crosses and gynogenesis. Genotypes with good capacity of induction have not necessarily a good capacity of haploid plantlets regeneration and vice-versa. However, calli or embryos formation seems to be an indicator of the haploid production. Overall, Razzek showed a good ability to produce haploids using the three methods. Each haplomethod showed a speciﬁc advantage. Although gynogenesis is the less used method for durum wheat, it has proved to be a successful approach for green haploid plant production.  

/pdf/efficiency-of-three-haplomethods-in-durum-wheat-triticum-28uosg94o3.pdf

Efficiency of three haplomethods in durum wheat (Triticum turgidum subsp. durum Desf.): isolated microspore culture, gynogenesis and wheat × maize crosses

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