Overview

The Plant Pathology Division of AREU provides the focus for research on all aspects on the biology, prevention and control of plant diseases in the non-sugar sector. The Division also operates a Plant Health and Advisory Unit, delivering a quality service related to diagnosis and devising of appropriate solutions for crop protection problems encountered by the planting community and the general public at large.

Objective

The objective of the Division is to serve the planting community by reducing the negative impact of diseases with the development of adequate, pragmatic and sustainable solutions through cost-effective high quality research.

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Research Programme

The purpose of research in Plant Pathology is to overcome crop disease problems, in order to increase productivity. The policy of the Division is thus to conduct strategic and adaptive research. The Division also ensures that there is rapid transfer of technology generated by research into relevant production systems for the benefit of planters.

Research projects of the Division are formulated according to the needs of the planting community and in line with the government’s policy. They are centred on the following thrusts:

Potato Seed Production – Performance test evaluation for seed certification

Field performance tests are an important component in seed certification. They allow, at the moment of planting, an assessment of seed quality in terms of physical appearance, rotting (soft and dry rots), viability, germination capacity and uniformity, and most importantly the presence of seed borne diseases, particularly viruses. As one whole bag of seed is planted for each seed lot planted, observations can be made on a wider scale than in potted plants grown in the glasshouse.

Study of diseases affecting seeds and potato seeds and their management practices

Mauritius annually imports an average of 1.5 tonnes of seeds including mainly potato seeds. They are imported under specific prescribed phytosanitary conditions to exclude risks of introducing exotic pests/diseases, particularly of quarantine importance. However, no systematic seed health testing of imported seeds and planter produced seeds is effected in Mauritius. It is therefore fundamental to carry out seed health control on seeds on imported or produced by local growers by themselves or under AREU’s Quality Declared Seed Scheme (QDS).

Development of a forecasting system for the preventive management of late blight disease on tomato crops and diseases of other crops.

Late blight is a disease of high economic importance that affects tomato crops in Mauritius. It is caused by the fungal pathogen Phytophthora infestans. The latter requires predisposing factors such as excessive humidity (above 90% R. H) and a temperature below 24º C for development of the disease. When these factors prevail together, disease conditions are favoured and spread rapidly in tomato and potato crops resulting in economic losses in these crops. Damage can even result in 100% crop failure as in 2004 when an epidemic decimated the potato crop in the central part of Mauritius. A major solution to the problem can be resolved by the setting up of a disease forecasting system which will allow the timely management of the late blight disease resulting in a decrease in pesticide load, in environmental pollution and in risks to consumers.

Detection of seedborne transmission of Zucchini yellow mosaic virus (ZYMV) and Cucumber mosaic virus (CMV) on squash (Cucurbita pepo).

Zucchini yellow mosaic virus (ZYMV) and Cucumber mosaic virus (CMV) aggressive viruses (members of the potyvirus and cucumovirus groups respectively) have spread rapidly throughout the world, suggesting an efficient transmission from plant to plant by several aphid species in a non-persistent manner. The rate of disease transmission via seed is low and difficult to prove. There is some evidence for seed transmission in the case of zucchini. This work focused on studying the seed borne virus transmission on squash.

Status of Citrus diseases in Mauritius and Rodrigues.

Citrus fruits are well appreciated in Mauritius and Rodrigues. Crops are grown mostly in backyards, but few commercial orchards also exist. Official figures for 2011 reveal a local production of 1550T of citrus fruits and during the same year 7691 T of mixed citrus fruits (oranges, mandarine, lemons) were imported (Anon, 2011), thus revealing that there is scope to increase local production in this sector. However citrus fruits produced either in Mauritius or Rodrigues are often not of good quality since recommended disease management practices are not always respected by growers. Till date there are no records of Spiroplasma citri on citrus in Mauritius. Moreover in the context of food security and attaining self- sufficiency in local food production, a timely disease identification and optimal disease management strategies could give a boost to local citrus industry both in terms of quantity and quality of fruits produced

Major diseases of fruit trees at nursery stage.

It is within government policy to increase local fruit production during the coming years, in order to increase fruit consumption at local level and at the same time cut down on imports. Thus, production of fruit crops are being encouraged in the context of a healthy lifestyle promotion for the population and fruit trees are also being proposed as an interesting alternative on ex-sugar cane lands. Production figures for 2011 indicate local production of fresh fruits of 22 966 T and imports of fresh fruits amounting to 17 866 T. During the same year 2 336 T of fresh fruits were exported. Although figures indicate a scope for increase in local production and exports, the quality of fruits produced locally needs to be improved especially in terms of disease management in order to fetch a better price and share on the market.

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  • Evaluation of fungicide Revus SC 250 (Mandipropamid) for preventive control of Late Blight disease caused by (Phytophthora infestans) in potato.
  • Efficacy of the fungicidal action of Amistar Top® (Azoxystrobin + Difenoconazole) as preventive measure for control of powdery mildew, leaf spots, rusts, Anthracnose, black leaf spot and other important diseases in papaya.
  • Evaluation of fungicide Amistar Top 325 for control of Powdery mildew (Podosphaera xathii) in cucurbits.
  • Status and management of bacterial spot disease on tomato.
  • Evaluation of the performance of herbicides for weed control in horticultural crops.
  • Evaluation of the performance of herbicides for weed control in horticultural crops.
  • Management of Bacterial Wilt disease
  • Management of powdery mildew in rose/gerbera
  • Management of citrus fruit rot caused by Phytophthora citrophthora.
  • Management of downy mildew disease in Cucurbits.
  • Screening of Tomato varieties for resistance / tolerance to Late Blight disease.
  • Screening of Tomato, Eggplant & Chili varieties for resistance / tolerance to Bacterial Wilt disease.
  • Assessment of the economic impact of Tomato yellow leaf curl virus (TYLCV) on tomato yield.
  • Improvement of Banana and Tomato varieties through the use of Nuclear Techniques for mutation induction and biotechnology.
  • Increasing production of nutritious food through mutation breeding and biotechnology (RAF/5/050) – in collaboration with Agronomy division.
  • Evaluation of advanced potato clones for disease tolerance/resistance by the intentional exposure technique
  • Development of short day onion varieties through mutation breeding and selection for biotic and abiotic stresses (collaborative work with RMD and Agronomy divisions).