Searching for answers in the weeds of wheat fields in Morocco

Lee Hickey and Maricelis Acevedo
Thursday, June 26, 2014

Being a scientist, travel is certainly one of the perks of the job and our recent visit to Morocco was truly an eye-opening experience and one we rank highly among the many countries we have visited. Morocco is beautiful, home to friendly people, amazing food and perhaps most important, exquisite coffee.

While we certainly enjoyed these finer things in life, the main purpose of our visit centred on establishing new collaborations with both the wheat and barley breeding programs of ICARDA.

We were fortunate to have a fabulous host – Dr. Filippo Bassi (Durum breeder at ICARDA), who provided an authentic Moroccan experience. We travelled around the countryside, visiting the many field trials of ICARDA. One of the days, we travelled to the research station of Annoceur on the Atlas mountains, which is some 1,600m above sea level. ICARDA uses this location to test for cold resistance of wheat and barley, with temperatures during winter that reach -10 C and snow coverage that extends for two months (yes, Morocco can be cold too!). In summer, the cooler temperatures and availability of good irrigation water at this station allows for ideal off-season planting conditions. The early generations (F2 and F4) are typically grown at the high-plateau (420 m) station of Marchouch under rain-fed conditions (200 – 350 mm), harvested in early June and re-planted in Annoceur by early July.

The field site at Annoceur is a beautiful setting. For a wheat or barley breeder, it feels like you are in the middle of a fairy-tale. The cereal field trials are surrounded by trees and mountains – oh the serenity! The station also houses various fruit and herb breeding programs. Needless to say, in between looking at wheat and barley plots, the cherries in season were hard to resist.

In addition to this scenic backdrop, there were many small weeds with beautiful flowers – some blue, some red. The weeds in Australia certainly don’t appear as delightful. Dr Bassi pointed out that one of the weeds, which had small blue flowers was called Anchusa (A. Italica) – the alternate host of one of the wheat leaf rust pathogens, Puccinia tritici-duri, in Morocco. The amazing thing was that the Anchusa was even growing amongst the wheat and barley plots!

We don’t have any of the alternate hosts required for sexual recombination for wheat rust diseases in Australia. However, we do have the Star of Bethlehem, the alternate host of barley leaf rust (Puccinia hordei), growing throughout South Australia.

Revealing the hidden wheat leaf rust pathosystem

Despite decades of intense research in cereal-rust pathosystems, there are still many questions to answer. Understanding the relationship and evolution between hosts and pathogens may provide the path to discovering new ways to manage crop diseases. The sexual stage of the wheat leaf rust pathogens has been generally regarded as an unimportant part of the epidemiological cycle of the disease. This is mostly due to the fact that research has shown that the P. triticina populations hold many characteristics of clonal populations. Moreover, high virulence diversity is observed in regions where Thalictrum spp., alternate host of Puccinia triticina, is absent or where no susceptible alternate host has been identified.  However, in the Mediterranean region a second wheat leaf rust pathogen Puccinia tritici-duri (P. recondita complex Group II) is known to occur. The P. tritici-duri alternate host Anchusa italica, belongs to the Boraginaceae family and is distributed throughout the Mediterranean region and Asia. Ezzahiri et al., (1992) reported that in Morocco heavily infected durum wheat was observed in fields where A. italica was present.  Similarly, there are reports of P. tritici-duri samples collected in southern Portugal with virulence on durum and hexaploid wheat (Anisker, 1997).  Despite these reports, little is known about the role of P. tritici-duri in this region and as part of the worldwide leaf rust disease complex. Thus, the extent of functionality of an alternate host in the Mediterranean and North African region represents an important question to answer for future disease management. Sexual recombination of the pathogen on the alternate host may lead to higher diversity and faster virulence evolution in the pathogen population. Moreover, durum wheat is extremely important in Morocco (nearly 1M ha), in North Africa (3M ha), and in the whole Mediterranean basin (approx. 6 M ha). It is a major component of the people’s caloric intake in this region, with nearly 8 meals per week derived from semolina products. Therefore, it is of significant interest to dissect the leaf rust pathogens regional epidemiological cycle and evolution.

Current efforts by Maricelis Acevedo at North Dakota State University in collaboration with James Kolmer at the USDA aim to characterize the leaf rust pathogen population from leaf rust samples collected from bread (common) wheat and durum wheat from the region.

Acevedo plans to revisit the field locations in Morocco during the winter and early spring months when aecia on Anchusa should be evident in the lower altitudes.

Lee Hickey is a Research Fellow at the Queensland Alliance for Agriculture and Food Innovation (QAAFI) at the University of Queensland.  Follow him on Twitter @DrHikov.
Maricelis Acevedo is an Assistant Professor at North Dakota State University.  She received the Jeanie Borlaug Laube Women in Triticum Early Career award in 2010. Follow her on Twitter @MaricelisAceve1

Anikster, Y., W. R. Bushnell, T. Eilam, J. Manisterski, and A. P. Roelfs, 1997: Puccinia recondita causing leaf rust on cultivated wheats, wild wheats and rye. Can. J. Bot. 75, 2082—2096.

Ezzahiri, B., Diouri, S. & Roelfs, A.P. 1992. The-Role of the alternate host, Anchusa italica, in the epidemiology of Puccinia recondita f. sp. tritici on durum wheats in Morocco. In F.J. Zeller & G. Fischbeck, eds. Proc. 8th European and Mediterranean Cereal Rusts and Mildews Conf., 1992, p. 69-70. Heft 24 Weihenstephan, Germany.