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Biology and the integrated control of red rice (bicorer)

Contract nr: FAIR-CT96-1450
Project nr: 1450
Project type: SC
Starting date: 01/01/1997
Duration: 36 months
Total cost: 613,230 EUR
EC Contribution: 569,780 EUR
Scientific Officer: Arnaud BORCHARD
Research topic: Plant health
Acronym: BICORER

Red rice is considered to be the most troublesome weed in European rice fields. Last year in these cultivation areas, the weed spread more widely, particularly after the diffusion of less competitive cultivated varieties. In these conditions, weed infestations have been favoured by the use of rice seed polluted by grains of wild plants and because of the lack of a successful means of control. Rice growers are often induced to rotate rice with other crops, but in most situations saline and hydromorphic soils severely limit this option.

The project proposal originates from the pressing need to find effective and environmentally friendly methods of managing the spread of this weed. The importance of this research has also been stressed by the Concerted Action - EC-DG AGRI (n° AIR3-PL93-2518 - Quality and Competitiveness of European Rices).
In particular, this research project has the following aims:
1) to characterise and identify red rice biotypes, through molecular markers, and to assess their relations to the crop as well as their ability to be a weed;
2) to find simple diagnostic tests for red rice grain identification in rice seeds;
3) to evaluate the competitiveness of the most popular cultivated rice varieties with main red rice biotypes, in different culture conditions;
4) to study red rice population dynamics according to different environmental and agronomical conditions;
5) to assess the emergence of red rice in relation to a tillage system, straw and water management;
6) to test the effectiveness of mechanical and chemical means against red rice, before and after rice planting and in rotational crops;
7) to develop and test strategies of integrated weed management, based on the findings of studies on the biology, and the results of specific control measures.

These objectives will be pursued by:
1) characterising red rice biotypes using molecular markers;
2) studying biological red rice behaviour;
3) carrying out an inventory of and evaluating measures of weed control;
4) testing the combination of agronomical practices and direct and indirect control measures giving the best sustainable management of the weed.
The results of the proposed research will provide substantial benefits from a scientific, technical and environmental point of view.
The research fits with the objectives of the FAIR work programme (areas 4.1.1-4.1.2-4.4.1) and with the policies of EU regulation 2078/92 (agri-environmental measures) in the area of the weed management.

Current situation/results:
In 1998, the project participants carried out a research activity on the following four programmed tasks:
1) characterisation of red rice biotypes using molecular markers;
2) study of red rice biology;
3) evaluation of red rice control techniques;
4) integrated red rice management.
Task 1. Characterisation of red rice biotypes using molecular markers
Heredity of weed characteristics has been studied by the use of Doubled Haploid (DH) population. The DH lines have been characterised to score the segregation of morphological traits related to weed behaviour: seedling vigour, anthocyan pigmentation, tillering ability, plant morphology, awning etc. All traits were significantly different between the parents.
Survey of the two parental lines has permitted detection of a high level of polymorphism, though parental lines belong to temperate japonica subspecies. Therefore, genetic mapping was considered in spite of the genetic closeness of the two parental lines.
Sixty-nine SSRs showing polymorphism on parental survey were mapped into the population.
The Kruskall-Wallis test was performed using Map Quantitative Traits Loci (QTL) 2.4. A significance threshold of p0.01 was used to identify QTL. A total of 18 QTLs for traits were identified and located on seven chromosomes. Most of the QTLs identified for weed characteristics were closely linked on chromosomes 1, 3, 7, 8 and 9.
Trials were also started on organising the collection of red rice seeds in the participants' main cultivation areas. These seeds will be characterised both in relation to their phenological and genetic features.
Task 2. Study of the red rice biology.
Different studies have been carried out in Italy, Portugal and Greece to determine dormancy, seed longevity, depth of emergence and time required by the seeds after flowering to become viable.
Trials were carried out to study the competitive ability of the most important rice varieties against red rice, at 2 N rate and 4 densities of the weed. This research showed that shattering is related to genetic features, and is only slightly influenced by agronomical and environmental conditions, such as N supply and condition of competition. The results showed that a weed density of 40 plants/m2 resulted in a yield reduction of about 40%.
Two experiments, started in 1997, and continued in 1998 in Italy and Spain, showed that certified seed without red rice grains determined the emergence of about 1 plant/1000m2 .
Task 3. Evaluation of red rice control techniques
Researchers in all countries continued the experiments started in 1997 to compare old and new direct mechanical and chemical methods of weed control, to screen the more suitable means against this weed in practical conditions of cultivation.
In pre-emergence of the weed, the best herbicides were dimethenamid, pretilachlor, acetochlor and alachlor. In post-emergence of the weed, good results were obtained applying the false seeding technique, combined with dalapon or quizalofop treatment, before rice planting. Minimum tillage and water-saturated soil determined the greatest number of emergences.
In crop post-emergence, panicle cutting (with two interventions) provided efficient prevention of weed dissemination.
Partner 3 (CFR, subpartner INRA) carried out a study aimed at identifying all farmers' red rice control strategies applied in Camargue rice fields. The survey showed that about 35% of the farmers controlled red rice by chemical means, and 16% by crop rotation.
Italian and French partners also carried out research to assess the effects on red rice spread in these rotational conditions. After 1 year of soyabean cultivation, the weed seed bank was reduced by 90%.
Task 4. Integrated red rice management
In order to assess the best systems of red rice management, both in rotational crops and in rice in monoculture, several experiments were carried out in all the project partners' countries.
The results showed that all crop rotation systems (corn, soybean, soybean with minimum tillage and delayed crop planting) associated with appropriate herbicide application, were able to assure outstanding red rice control.
In all countries, experiments were carried out in rice monoculture based on the most rational combination of control techniques applied in pre- and post-emergence of the weed.
Best results were obtained:
1) in highly infested fields - applying the false seeding technique, performed with minimum tillage followed by a dalapon treatment;
2) in less infested fields - simply adopting ploughing, which reduced red rice emergence remarkably.

Università degli Studi di Torino
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