53 ref. | International audience | Fusarium head blight (FHB) caused by Fusarium culmorum is an economically important disease of wheat that may cause serious yield and quality losses under favorable climate conditions. The development of disease-resistant cultivars is the most effective control strategy. Worldwide, there is heavy reliance on the resistance pool originating from Asian wheats, but excellent field resistance has also been observed among European winter wheats. The objective of this study was to map and characterize quantitative traits loci (QTL) of resistance to FHB among European winter wheats. A population of 194 recombinant inbred lines (RILs) was genotyped from a cross between two winter wheats Renan (resistant)/Recital (susceptible) with microsatellites, AFLP and RFLP markers. RILs were assessed under field conditions For 3 years in one location. Nine QTLs were detected, and together they explained 30-45% of the variance, depending on the year. Three of the QTLs were stable over the 3 years. One stable QTL, QFhs.inra.2b, was mapped to chromosome 2B and two QTLs QFhs.inra.5a2 and QFhs.inra.5a3, to chromosome 5A; each of these QTLs explained 6.9-18.6% of the variance. Other QTLs were identified on chromosome 2A, 3A, 3B, 5D, and 6D, but these had a smaller effect on FHB resistance. One of the two QTLs on chromosome 5A was linked to gene B1 controlling the presence of awns. Overlapping QTLs for FHB resistance were those for plant height or/and flowering time. Our results confirm that wheat chromosomes 2A, 3A, 3B, and 5A carry FHB resistance genes, and new resistance factors were identified on chromosome arms 2BS and 5AL. Markers flanking these QTLs should be useful tools for combining the resistance to FHB of Asian and European wheats to increase the resistance level of cultivars.

DOI:1007/s00122-002-1140-9 | International audience

45 ref. doi: 10.1007/s00122-003-1381-2 | International audience

Cotton is unusual among major crops in that large acreages are grown under both irrigated and rainfed conditions, making genotype environment interactions of even greater importance than usual in designing crop-improvement strategies. We describe the impact of well-watered versus water-limited growth conditions on the genetic control of fiber quality, a complex suite of traits that collectively determine the utility of cotton. Fiber length, length uniformity, elongation, strength, fineness, and color (yellowness) were influenced by 6, 7, 9, 21, 25 and 11 QTLs (respectively) that could be detected in one or more treatments. The genetic control of cotton fiber quality was markedly affected both by general differences between growing seasons ('years') and by specific differences in water management regimes. Seventeen QTLs were detected only in the water-limited treatment while only two were specific to the well-watered treatment, suggesting that improvement of fiber quality under water stress may be even more complicated than improvement of this already complex trait under well-watered conditions. In crops such as cotton with widespread use of both irrigated and rainfed production systems, the need to manipulate larger numbers of genes to confer adequate quality under both sets of conditions will reduce the expected rate of genetic gain. These difficulties may be partly ameliorated by efficiencies gained through identification and use of diagnostic DNA markers, including those identified herein.

Two atrazine-tolerant barley mutants were isolated from atrazine-selection experiments performed on barley chloroplast-mutator plants. Genetic analysis demonstrated that atrazine tolerance was maternally inherited. Molecular characterization of the mutants was performed by PCR amplification of an internal fragment of the chloroplast gene psbA. The BstXI restriction patterns of the amplified fragments showed two bands in both tolerant barley mutants and only one in the atrazine-sensitive control. The 277-bp amplified fragments from the parental line and both atrazine-tolerant mutants were cloned and sequenced. Sequence analysis showed a single nucleotide substitution in both barley atrazine-tolerant mutants, i.e. A to G at the +790 position of the psbA gene-coding sequence. This point mutation corresponds to an amino-acid change of serine- to -glycine and creates a BstXI restriction site. Our results confirmed the conservative variability involved in atrazine tolerance which was previously reported for several other species. To our knowledge this is the first report on the obtention of atrazine-tolerant barley. This finding provides support to the hypothesis that, in addition to a wide variety of chlorophyll deficiencies, the barley chloroplast mutator genotype induces variability in other traits, which could include agronomically valuable mutants.

Broccoli florets contain low levels of 3-methylsuphinylpropyl and 4-methylsulphinylbutyl glucosinolates. Following tissue disruption, these glucosinolates are hydrolysed to the corresponding isothiocyanates (ITCs), which have been associated with anticarcinogenic activity through a number of physiological mechanisms including the induction of phase II detoxification enzymes and apoptosis. In this paper, we describe the development of ITC-enriched broccoli through the introgression of three small segments of the genome of Brassica villosa, a wild relative of broccoli, each containing a quantitative trait locus (QTL), into a broccoli genetic background, via marker-assisted selection and analysis of glucosinolates in the florets of backcross populations. Epistatic and heterotic effects of these QTLs are described. The ITC-enriched broccoli had 80-times the ability to induce quinone reductase (a standard assay of phase II induction potential) when compared to standard commercial broccoli, due both to an increase in the precursor glucosinolates and a greater conversion of these into ITCs.

Salt stress adversely affects the growth of rice plants. To understand the molecular basis of salt-stress response, four subtracted cDNA libraries were constructed employing specific NaCl-stressed tissues from salt-tolerant (CSR 27 and Pokkali) and salt-sensitive (Pusa basmati 1) rice cultivars. An efficient PCR-based cDNA subtraction method was employed for the isolation of the salt-stress responsive cDNA clones. In all, 1,266 cDNA clones were isolated in the course of this study, out of which 85 clones were end-sequenced. Database search of the sequenced clones showed that 22 clones were homologous to genes that have earlier been implicated in stress response, 34 clones were novel with respect to their function and six clones showed no homology to sequences in any of the public database. Northern analysis showed that the transcript expression pattern of selected clones was variable amongst the cultivars tested with respect to stress-regulation.

We investigated the association between late blight resistance and foliage maturity type in potato by means of molecular markers. Two QTLs were detected for foliage resistance against Phytophthora infestans (on chromosomes 3 and 5) and one for foliage maturity type (on chromosome 5). The QTL for resistance to late blight and the QTL for foliage maturity type on chromosome 5 appeared to be mapped on indistinguishable positions. We were interested whether this genetic linkage was due to closely linked but different genes, or due to one (or more) gene(s) with pleiotropic effects. We therefore developed an approach to detect QTLs, in which resistance to late blight was adjusted for foliage maturity type. This analysis revealed the same two QTLs for resistance against P. infestans, but the effect of the locus on chromosome 5 was reduced to only half the original effect. This is a strong indication that the two indistinguishable QTLs for foliage maturity type and for late blight resistance on chromosome 5 may actually be one gene with a pleiotropic effect on both traits. However, there was still a significant effect on resistance against P. infestans on the locus on chromosome 5 after adjusting for foliage maturity type. Therefore we cannot rule out the presence of two closely linked QTLs on chromosome 5: one with a pleiotropic effect on both late blight resistance and foliage maturity type, and another with merely an effect on resistance. In addition, the two QTLs for resistance to late blight showed an important epistatic interaction, suggesting that QTLs for resistance affect each other's expression.