Breeding tomatoes for salt tolerance: inheritance of salt tolerance and related traits in interspecific populations

Summary Interspecific segregating populations derived from a cross between tomato (Lycopersicon esculentum) cv M82-1 -8 (M82) and the wild species L. pennellii accession LA-716 (Lpen716) were used to study the genetic basis of salt tolerance and its implications for breeding. BC₁ (M82 x (M82 x Lpen716)) and BC₁ S₁ (progenies of selfed BC₁ plants) populations were grown under arid field conditions and irrigated with water having electrical conductivities of 1.5 (control), 10 and 20 dSm^-1. The evaluation of salt tolerance was based on total fruit yield (TY), total dry matter (TD) and TD under salinity relative to the control (RD). Sodium, potassium and chloride concentrations were measured in the leaves and stems. The methods for estimating heritability were adapted to BC₁ plants and BC₁S₁ families. TY, TD and RD had heritability estimates of 0.3–0.45, indicating that salt tolerance can be improved by selection. Genetic correlations between traits indicated that high yield may be combined with salt tolerance and that ion contents are not likely to provide an efficient selection criteria for salt tolerance. Genetic correlations between performances under various salinity levels suggested that similar mechanisms affect the responses to salinity treatments of 10 and 20 dSm^-1. Responses to paper selection confirmed that salt tolerance of the tomato may be improved by selection, and that this selection should be based on dry matter and yield parameters under salinity.Passed away May 1986     

Variation in phosphorus and sulfur content shapes the genetic architecture and phenotypic associations within the wheat grain ionome

Dissection of the genetic basis of wheat ionome is crucial for understanding the physiological and biochemical processes underlying mineral accumulation in seeds, as well as for efficient crop breeding. Most of the elements essential for plants are metals stored in seeds as chelate complexes with phytic acid or sulfur‐containing compounds. We assume that the involvement of phosphorus and sulfur in metal chelation is the reason for strong phenotypic correlations within ionome. Adjustment of element concentrations for the effect of variation in phosphorus and sulfur seed content resulted in drastic change of phenotypic correlations between the elements. The genetic architecture of wheat grain ionome was characterized by quantitative trait loci (QTL) analysis using a cross between durum and wild emmer wheat. QTL analysis of the adjusted traits and two‐trait analysis of the initial traits paired with either P or S considerably improved QTL detection power and accuracy, resulting in the identification of 105 QTLs and 617 QTL effects for 11 elements. Candidate gene search revealed some potential functional associations between QTLs and corresponding genes within their intervals. Thus, we have shown that accounting for variation in P and S is crucial for understanding of the physiological and genetic regulation of mineral composition of wheat grain ionome and can be implemented for other plants.     

QTL analysis of genotype × environment interactions affecting cotton fiber quality

Cotton is unusual among major crops in that large acreages are grown under both irrigated and rainfed conditions, making genotype x 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.     

Genetic diversity for grain nutrients in wild emmer wheat: potential for wheat improvement

Background and Aims

Micronutrient malnutrition, particularly zinc and iron deficiency, afflicts over three billion people worldwide due to low dietary intake. In the current study, wild emmer wheat (Triticum turgidum ssp. dicoccoides), the progenitor of domesticated wheat, was tested for (1) genetic diversity in grain nutrient concentrations, (2) associations among grain nutrients and their relationships with plant productivity, and (3) the association of grain nutrients with the eco-geographical origin of wild emmer accessions.

Methods

A total of 154 genotypes, including wild emmer accessions from across the Near Eastern Fertile Crescent and diverse wheat cultivars, were characterized in this 2-year field study for grain protein, micronutrient (zinc, iron, copper and manganese) and macronutrient (calcium, magnesium, potassium, phosphorus and sulphur) concentrations.

Key Results

Wide genetic diversity was found among the wild emmer accessions for all grain nutrients. The concentrations of grain zinc, iron and protein in wild accessions were about two-fold greater than in the domesticated genotypes. Concentrations of these compounds were positively correlated with one another, with no clear association with plant productivity, suggesting that all three nutrients can be improved concurrently with no yield penalty. A subset of 12 populations revealed significant genetic variation between and within populations for all minerals. Association between soil characteristics at the site of collection and grain nutrient concentrations showed negative associations between soil clay content and grain protein and between soil-extractable zinc and grain zinc, the latter suggesting that the greatest potential for grain nutrient minerals lies in populations from micronutrient-deficient soils.

Conclusions

Wild emmer wheat germplasm offers unique opportunities to exploit favourable alleles for grain nutrient properties that were excluded from the domesticated wheat gene pool.     

Identification and mapping of PmG16, a powdery mildew resistance gene derived from wild emmer wheat

The gene-pool of wild emmer wheat, Triticum turgidum ssp. dicoccoides, harbors a rich allelic repertoire for disease resistance. In the current study, we made use of tetraploid wheat mapping populations derived from a cross between durum wheat (cv. Langdon) and wild emmer (accession G18-16) to identify and map a new powdery mildew resistance gene derived from wild emmer wheat. Initially, the two parental lines were screened with a collection of 42 isolates of Blumeria graminis f. sp. tritici (Bgt) from Israel and 5 isolates from Switzerland. While G18-16 was resistant to 34 isolates, Langdon was resistant only to 5 isolates and susceptible to 42 isolates. Isolate Bgt#15 was selected to differentiate between the disease reactions of the two genotypes. Segregation ratio of F_2-3 and recombinant inbreed line (F₇) populations to inoculation with isolate Bgt#15 indicated the role of a single dominant gene in conferring resistance to Bgt#15. This gene, temporarily designated PmG16, was located on the distal region of chromosome arm 7AL. Genetic map of PmG16 region was assembled with 32 simple sequence repeat (SSR), sequence tag site (STS), Diversity array technology (DArT) and cleaved amplified polymorphic sequence (CAPS) markers and assigned to the 7AL physical bin map (7AL-16). Using four DNA markers we established colinearity between the genomic region spanning the PmG16 locus within the distal region of chromosome arm 7AL and the genomic regions on rice chromosome 6 and Brachypodium Bd1. A comparative analysis was carried out between PmG16 and other known Pm genes located on chromosome arm 7AL. The identified PmG16 may facilitate the use of wild alleles for improvement of powdery mildew resistance in elite wheat cultivars via marker-assisted selection.     

A rhizosphere fungus enhances Arabidopsis thermotolerance through production of an HSP90 inhibitor

The molecular chaperone HEAT SHOCK PROTEIN90 (HSP90) is essential for the maturation of key regulatory proteins in eukaryotes and for the response to temperature stress. Earlier, we have reported that fungi living in association with plants of the Sonoran desert produce small molecule inhibitors of mammalian HSP90. Here, we address whether elaboration of the HSP90 inhibitor monocillin I (MON) by the rhizosphere fungus Paraphaeosphaeria quadriseptata affects plant HSP90 and plant environmental responsiveness. We demonstrate that MON binds Arabidopsis (Arabidopsis thaliana) HSP90 and can inhibit the function of HSP90 in lysates of wheat (Triticum aestivum) germ. MON treatment of Arabidopsis seedlings induced HSP101 and HSP70, conserved components of the stress response. Application of MON, or growth in the presence of MON, allowed Arabidopsis wild type but not AtHSP101 knockout mutant seedlings to survive otherwise lethal temperature stress. Finally, cocultivation of P. quadriseptata with Arabidopsis enhanced plant heat stress tolerance. These data demonstrate that HSP90-inhibitory compounds produced by fungi can influence plant growth and responses to the environment.     

MAP Kinase analyser: A tool for plant kinase and substrate analysis

MAPK (Mitogen Activated Protein Kinase) is a Ser/Thr kinase, which plays a crucial role in plant growth and development, transferring the extra cellular stimuli into intracellular response etc. Manual identification of these MAPK in the plant genome is tedious and time taking process. There are number of online servers which predict the P-site (phosphorylation site), find the motifs and domain but there is no specific tool which can identify all them together. In order to identify the P-Site, phosphorylation site consensus sequences and domain of the MAPK in plant genome, we developed a tool, MAP Kinase analyzer. MAP kinase analyzer take protein sequence as input in the fasta format and the output of tool includes: 1) The prediction of the phosphorylation site viz., Serine (S), Threonine (T), and Tyrosine (Y), Contex, Position, Score and phosphorylating kinase as well as the graphical output; 2) Phosphorylation site consensus sequence pattern for different kinases and 3) Domain information about the MAPK's. The MAP kinase analyser tool and supplementary files can be downloaded from http://www.bioinfogbpuat/mapk_OWN_1/.