Watermelon Genome Could Hold the Key to Improved Varieties With Fewer Pest Problems

A research team led by the Beijing Academy of Agriculture and Forestry Sciences have produced the complete genomic sequence of watermelon (Citrullus lanatus). It is hoped that the genomic data from this study will shape future research into watermelon genetics and provide a good resource for crop genetics and future plant breeding projects, resulting in improved watermelon cultivars with a greater degree of pest resistance.

Watermelons suffer large yield losses due to many pests and diseases and it is hoped that new genetic research can be used to improve varieties to make them less susceptible to pathogens ©Steve Evans via Wikimedia Commons (License CC-BY-2.0).

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Discovery of genes for resistance to black Sigatoka in bananas

Banana plant showing symptoms of black Sigatoka disease (Fred Brooks, University of Hawaii at Manoa, bugwood.org CC BY licence)

Researchers at Equador’s Biotechnology Research Centre (CIBE) have isolated the genes that are responsible for conferring resistance to black Sigatoka in the naturally resistant banana variety Musa Calcutta-4. Scientists have now been able to develop a protocol for the genetic transformation of banana cultivars Williams and Orito as well as the plantain cultivars Barraganete and Dominico. This involved creating the embryonic cell suspensions needed to complete these transformations. Black Sigatoka is caused by the fungus Mycosphaerella fijiensis, which affects the leaves of banana plants, leaving them discoloured and wilting. Continue reading

Epigenetics – a new dimension to understanding plant disease

Coast live oak showing sudden oak death symptoms (Credit: Joseph O’Brien, USDA Forest Service, Bugwood.org)

The history of diseases that have affected a plant can determine the ability of its progeny to cope with similar diseases. Studies have revealed that, in many cases, progeny of a plant that was diseased develops tolerance to similar stresses in just a few generations, far too quick to be explained by chance mutations. It is here that scientists believe epigenetic mechanisms play a role. Continue reading

Wheat rust and climate change – a possible connection

A possible link between wheat stripe rust and climate change was observed by researchers meeting at the International Wheat Stripe Rust Symposium, which convened in Aleppo, Syria last week.

The symposium organised by the International Center for Agricultural Research in the Dry Areas (ICARDA) aimed to review the current global status of wheat stripe rust epidemics that have severely affected crop yields in Central and West Asia, the Middle East and North and East Africa in recent years. More than 100 scientists and policymakers from 31 countries participated and an important feature of the meeting was to share experience and approaches to manage wheat rust through breeding and control strategies in affected countries in Asia and Africa.

Recently, severe epidemics of stripe (yellow) rust have been reported in Morocco, Ethiopia, Uzbekistan, Tajikistan, Kyrgyzstan, Turkey, Azerbaijan, Afghanistan, Iran, Pakistan, India, and Syria. “Some of the countries affected by rust epidemics have invested very little in agricultural research and development,” said Hans Braun, director of the Global Wheat Program at the International Maize and Wheat Improvement Center (CIMMYT) in Mexico. At the meeting, he challenged policymakers to recognize the link between scientific research and food security and to invest more heavily in agricultural research. “To combat the problem of wheat rusts, farmers in these regions need to adopt new varieties of wheat that have durable resistance to both stem and stripe rust,” said Ronnie Coffman, vice chair of the Borlaug Global Rust Initiative.

Climate change, in terms of rising temperatures, and the timing and increasing variability of rainfall, is contributing to the spread and severity of rust diseases, said the press release. Emerging races of rust are showing adaptations to extreme temperatures not seen before. Scientists around the globe are working on monitoring and surveillance of stem rust and stripe rust to insure rapid detection and reporting so farmers, policymakers, and agricultural research centres can respond more quickly to initial outbreaks.

Wheat rust has been a problem for many decades, as reported in various papers in the CAB Abstracts database (Newton, 1922; Tehon, 1927; Zekl, 1934; Naoumova, 1935; Beilin, 1938; and Roche et al., 2008). Interestingly, the paper by Beilin, published in 1938 in the Bull. Acad. Sci. in 1938 and abstracted in CAB Abstract in 1939, discussed the problems related with developing hardy wheat cultivars with resistance to drought, without paying attention to their response to diseases; and how the climatic conditions exacerbated the disease spreading.

Beilin reported that Russian breeding work at the time had been concerned mainly with the development of hardy, prolific and drought-resistant wheat varieties with no focusing on their response to smut and rusts. As a result, the most popular standard wheat varieties then were highly susceptible to various rusts, including Puccinia, graminis, and the climatic conditions of the main area under winter wheat permitted overwintering of the rusts. The relatively high day temperature in June and abundant rainfall and dew in May and June facilitated their rapid development. The use of susceptible varieties under these conditions and the absence of correct crop rotations led to severe rust epidemics, lowering the quality of the grain and reducing the yields in some years and districts to about half the normal.

The ICARDA press release also reported that new rust resistant varieties are in the pipeline at international and national agricultural research centres. Breeders are selecting for other important characteristics including improved yield performance, drought tolerance, and regional suitability. 

Country preparedness for outbreaks of wheat rust involves such issues as the availability of resistant varieties that are known to and accepted by farmers, the availability of sufficient quality seeds of new varieties for farmers to use, and the availability, accessibility and affordability of effective fungicides and capacity of farmers to use them.

In most cases, the bottleneck to getting resistant varieties into the field in time to protect local harvests is local capacity and the ability of national programs to rapidly multiply seeds and deliver them to market. Improving country capacity requires long-term planning, funding, and getting farmers involved earlier in the variety selection process, says the ICARDA press release.

Link to the symposium website

Link to press release

Further Reading
    1. Beilin, I. G. (1938) Recent Wheat rust epidemics in North Caucasus and factors favouring their outbreak and development. Bull. Acad. Sci. U. R. S. S. 1938 1938 No. 5-6 pp. 995-1016 pp.
    2. Naoumova, Mme N. A, (1935) Dependence of the development of yellow rust of Wheat on meteorological factors. Summ. sci. Res. Wk Inst. Pl. Prot. Leningr., pp. 64-65 pp.
    3. Newton, M. (1922) Studies in Wheat stem rust (Puccinia graminis tritici). Trans. R. Soc. Canada, 3rd series, Section V 1922 Vol. 16 pp. 153-210 pp.
    4. Roche, R.; Bancal, M. O.; Gagnaire, N.; Huber, L. (2008) Aspects of Applied Biology, No. 88 pp.
    5. Sache, I.; Suffert, F.; Huber, L. (2000) A field evaluation of the effect of rain on wheat rust epidemics. Acta Phytopathologica et Entomologica Hungarica, Vol. 35 No. 1/4 pp. 273-277.
    6. Tehon, L. R. (1927) Epidemic diseases of grain crops in Illinois, 1922-1926. The measurement of their prevalence and de-structiveness and an interpretation of weather relations based on Wheat leaf rust data. Illinois Dept. Registr. and Educ. Div. of Nat. Hist. Survey, Bull, Vol. 17 No. Art. 1 pp. 1-96 pp.
    7. Zekl, F. (1934) Causes of wheat rust. Deutsche Landwirtschaftliche Presse, Vol. 61 No. 32 pp. 397 p.
KNOWLEDGE FOR LIFE

Aid donors join forces to fight wheat rust

 Emerging strains of stem rust disease of wheat, such as Ug99, are spreading out of East Africa and threatening the world’s wheat supply. But the fight against this disease received a boost this week from a collaboration between the UK’s Department for International Development (DFID) and the Bill & Melinda Gates Foundation. The organisations have combined to fund Cornell University with US$40 million (£25 million) to continue its work to develop wheat varieties that are resistant to the new rust strains.

The Ug99 strain of rust was discovered in Uganda in February 1999 (Pretorius et al., 2000). Before that, scientists had made great strides in combating stem rust using multi-genic resistance. With the introduction of major resistant gene Sr31 and a number of other minor genes, stem rust became less of a problem to world agriculture. But now it is back with renewed virulence, and Nature reported on 28 February that in Kenya last year, Ug99 destroyed around 80% of the wheat crop. Spores have also spread to Ethiopia, Sudan, Yemen and Iran. Scientists fear the other major wheat-growing regions of the world, including North America and South Asia, will be next. Continue reading

Does rust-free rice hold the secret?

All cereals, except rice, are susceptible to rust. Wheat, maize, barley, millet, triticale, and oats all get rust. The spores of rust fungi land on a host plant, germinate, and grow toward a stomatal pore on the leaf surface to initiate infection. Rust infections produce red or yellow pustulating spores that give infected plants a “rusty” look. In susceptible plants, rust cuts off the plants’ ability to photosynthesise nutrients in their leaves and transport nutrients in their stems, causing stems to weaken and plants to fall over, making what little yield there is nearly impossible to harvest.

Rice, the “stainless steel” among cereal grasses, has long intrigued plant breeders and plant pathologists. For decades scientists have believed that, by discovering the genes that make rice immune to rusts, they might be able to introduce these genes into other cereal grains such as wheat and maize.

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