Cereal Biotechnology research

Group Leader: Dr. Navreet Bhullar

Rice is a staple food for half of the world’s population and is grown in different continents. For many of the world’s poorer populations, it is often the sole available source for daily caloric energy and therefore, also for micronutrients. In Asia, around 3 billion people depend on rice for 35–59% of their energy and in many other developing countries, the dietary contributions of rice are substantially higher. In light of the growing population, widespread malnutrition and biotic and abiotic stresses that increasingly threaten rice production, it is critically important to develop rice that maintains good grain quality and high yield under adverse conditions. We work to improve rice for its nutritional quality as well as to find novel genes to protect rice against biotic and abiotic stresses (see projects below).

Nutritional enhancement of cereal grains

Iron biofortification of rice

Most of the essential micronutrients are almost exclusively stored in the husk, aleurone and embryo of rice, which are removed during the polishing process. Polishing of rice is required as the oil-rich aleurone layer turns the seed rancid upon storage and therefore making rice unsuitable for consumption. Consequently, the rice endosperm that comprises the edible part of rice for humans lacks or contains only small amount of key micronutrients (e.g., iron, zinc, protein, provitamin A, and other vitamins) that are essential for a healthy diet. Considering the facts above and severity of widespread micronutrient malnutrition, iron biofortification in rice endosperm is a promising strategy to overcome iron deficiency effectively.
We aim to develop nutritionally improved rice lines with high levels of bio-available iron. We use gene technology for tissue specific expression of genes responsible for uptake, transport, accumulation and availability of iron. Recently, transgenic rice lines (NFP lines) with more than 6-fold increase of iron content in polished rice grains relative to conventional mega rice varieties have been developed in our research group (Wirth et al, 2009). Our research group is currently working to further elevate the iron content of rice endosperm to nutritionally relevant levels for human consumption. We study the effect of metal transporters and combination of relevant genes expressed tissue specifically for this purpose. We are extending our study to identify tissue specific promoters in rice that can potentially be used in the biofortification strategies requiring multiple genes expressed in parallel.

Figure 1: Element sensitive mapping of the iron concentration in the rice grain using micro-X-ray fluorescence spectrometry. A) Control accession Taipei309 B) High iron rice lines produced in our research group (NFP lines). The color indicates the iron concentration (see intensity scale).

Characterization of cereal genes related to metal homeostasis

Plants are known to maintain metal ion homeostasis through sophisticated molecular mechanisms that tightly control the acquisition and distribution of metal ions to the specific compartments and for storage. A better understanding of the key genes underlying the complex homeostatic molecular processes governing micronutrient composition in the cereal grains is very important. We undertake gene expression profiling in rice and wheat to understand these molecular processes and to identify genes that play role in re-mobilization of micro-nutrients from flag leaves to grains, focusing on iron and zinc. The interesting information on candidate genes generated through this project could be usefully followed up in breeding strategies or genetic engineering approaches to improve grain micronutrient content, such as zinc and Fe, in cereals.

A) Rice growing at the rice greenhouse facility of the ETH Zurich
B) Experiments with rice grown on hydroponic system being conducted at the rice greenhouse facility of the ETH Zurich

Revealing the hidden gene treasures

Allele mining for novel rice blast resistance sources

Rice blast is considered to be a most important constraint in rice production and it has been spreading to some of the non-endemic areas where earlier it was not reported. The pathogen Magnaporthe grisea can infect rice crop at all the stages and yield loss may go as high as 80% if favorable conditions prevail. Among the various strategies available for management of rice blast, deployment of host plant resistance is considered to be the most appropriate strategy being economic and eco-friendly. Resistance conferred by some R genes has been broken down rapidly by the blast fungus and therefore, it is critically important to further enrich the reservoir of favorable blast resistance genes/alleles for improved rice breeding.
Gene banks represent rich stocks of genetic diversity encompassing enriched source of novel and potent resistant alleles and are capable of contributing significantly for the future crop improvement. In this project, we explore the valuable potential of genetic resources for finding new resistance alleles against rice blast from gene bank accessions, making best utilization of available genomic sequence information of rice and blast fungus as well. We also aim to refine the understanding of genetic basis of resistance, molecular rice-rice blast interactions and molecular evolution of blast R genes. The identification of novel alleles of effective resistance genes is expected to contribute in increasing the degree and spectrum of resistance and therefore would play an important role in molecular rice breeding against rice blast.

Allele mining for novel drought tolerance sources in rice

Climatic changes pose further risks to rice productivity and aggravate the situation in Asian and African countries that are already regularly affected by flood, drought, and other calamities. In recognition of the fact that an increasing number of people are affected by hunger and food insecurity because they live on marginal land with no or little access to fertilizer, global rice breeding efforts are now intensified to develop rice that produces a higher yield in stress-prone environments and that is less vulnerable to abiotic and biotic stresses.
Identifying genes from un-adapted rice varieties that have poor agronomic performance but stronger tolerance mechanisms, with their subsequent transfer to elite high-yielding varieties has proven to be a good strategy of producing stress-tolerant cultivars in the past. Based on previous work and rice genome data, it is now established that the most valuable tolerance genes are derived from traditional aus-type rice varieties (S. Heuer, IRRI; personal communication). In modern varieties, many of these tolerance mechanisms have been lost since varieties were developed for high-input, irrigated systems and were usually not selected under stress. Identifying novel tolerance traits and the underlying high-value genes from aus-type varieties provides a unique and important opportunity to develop new rice varieties for marginal, stress-prone environments. In this project, we take advantage from next-generation sequencing strategies to identify novel root-specific genes from aus-type varieties with a potential to increase yield under drought and/or Phosphorous deficiency in rainfed rice environments.

Experiment running at IRRI screenhouse (Collaboration: S. Heuer, IRRI)

Members:
Navreet Bhullar (Group Leader)
Jassmine Zorrilla (Post Doc)
Kulaporn Boonyaves (PhD candidate)
Jonghwa Park (PhD candidate)
Kumar Vasudevan (PhD candidate)
Meng Wang (PhD candidate)
Simrat Pal Singh (PhD candidate)
Marlen Müller (PhD candidate)

Former members:

Terhi Hahl (Trainee)
Isabell Janack (Trainee and Bachelor's thesis)
Renato Guidon (Master's thesis)

Contact: Dr. Navreet Bhullar, Prof. Dr. Wilhelm Gruissem