Research on mycotoxins and corn - behaviour of lines

Assessing the tolerance of maize (corn) LINES to fusariosis

This study, which began in 2001, was carried out with the aim of determining the characteristics of the parents of maize (corn) hybrids, i.e. lines, with respect to the development of fusariosis; the most tolerant lines were then given precedence in selection patterns.

4 groups of lines analysed

The lines used by Maïsadour Semences' research scientists for the process of creating varieties were classified in 4 large distinct genetic categories, specific to maize (corn) and used in the profession:

Flint
Lancaster
SSS
Iodents

Extensive analysis of the genetic material

In order to draw up a reliable classification of their genetic material and eliminate the most Fusarium sensitive lines, Maïsadour Semences' research scientists carried out extensive tests. For example in 2003 and 2004, they tested 128 and 138 elite lines respectively from all early lines.

	*Fusarium graminearum*	Fusarium Liseola
2003	55 elite lines analysed	73 elite lines analysed
2004	49 elite lines analysed	89 elite lines analysed

2 experiment areas

The research centre for early varieties (in Rhodon, 41) carried out experimentation on F. graminearum and the research centre for late varieties (in Haut Mauco, 40) was responsible for studying F. Liseola.

This distribution of work is the result of preliminary analysis and observations demonstrating significant and discriminatory occurrence of parasites depending on climatic conditions.

Tolerance of lines to Fusarium Liseola

Ear Visual?

Sanitary condition?

Classification of lines according to visual analysis of the ears in the field (VE) and sanitary analyses (ES)

Table
	Tolerant	Fairly sensitive	Sensitive
Artificial inoculation (inoculation)
Ear Visual (mark out of 100)	0 - 20	20 - 40	> 40
Sanitary condition (%)	0 - 30	30 - 60	> 60

Iodent lines

In 2003, for a certain number of iodent lines, the attacks of F. Liseola remained superficial (the fungus did not penetrate into the grain).

SSS lines

SSS lines would appear to be the most sensitive genetic group: artificial inoculation leads to a high level of contamination.

Lancaster lines

Finally, the sensitivity of Lancaster lines was found to be highly variable.

The findings for 2004 confirm the sensitivity of SSS lines, however there was a very significant difference between results.

Tolerance of lines to Fusarium graminearum

Ear Visual?

Sanitary condition?

Classification of lines according to visual analysis of the ears in the field (VE) and sanitary analyses (ES). The same lines were analysed for both types of contamination: natural and artificial.

Table
	Tolerant	Fairly sensitive	Sensitive
Natural inoculation
Ear Visual (mark out of 100)	0 - 10	10 - 20	> 20
Sanitary condition (%)	0 - 10	10 - 20	> 20

Table
	Tolerant	Fairly sensitive	Sensitive
Artificial inoculation (inoculation)
Ear Visual (mark out of 100)	0 - 20	20 - 30	> 30
Sanitary condition (%)	0 - 20	20 - 40	> 40

In experiments on Fusarium graminearum, development of the disease was observed, on the same lines, with both natural and artificial contamination. Artificial contamination therefore gives a better idea of the tolerance of lines, confirming the tolerance observed in natural conditions.

The data from experiments with Fusarium graminearum show the same results as those drawn from experiments on Fusarium Liseola.

Approved protocol improvements

It was necessary to reassess the Bolton scale in order to be more faithful to the actual condition of ears observed. The scale was refined and split into two levels.

Confirmed tolerance of several lines and development of a genetic solution

A classification system for tolerant or only slightly sensitive lines was drawn up for both types of Fusarium. It is clearer for F. graminearum than F. Liseola, since for F. Liseola the effects of European corn borer mask the potential effects of the genetic solution.