Samuel Mendlinger

Adaptive traits of wild barley plants of Mediterranean and desert origin

Abstract. Reciprocal introduction of seeds and seedlings was used to test for local adaptation and to identify a set of co-adapted traits of Mediterranean and desert ecotypes of wild barley Hordeum spontaneum. Evidence for local adaptation was found in seedling introductions into intact environments and from ecotype colonization success in the first generation after seed dispersal. Estimates of fitness were obtained at particular stages of the life cycle (seed, seedling and adult). Experiments that manipulated the environment (vegetation removal, different plant density) demonstrated the intensity and direction of natural selection in different life history episodes, but there was no strong evidence for local adaptation under these circumstances. The observed genetically determined differences between Mediterranean and desert ecotypes can be summarized as the following: reproductive output was higher in desert plants, with smaller seeds than in Mediterranean plants. There was a higher competitive ability of Mediterranean than desert plants. Plants of desert origin had significant reductions in yield when grown in mixed stands with Mediterranean plants; no such effect was observed for plants of Mediterranean origin. Seed germination and seedling survival was lower in seeds of desert origin. This was due to both: genetically determined higher dormancy of desert seeds and a trade-off between no. of seeds and their size (directly related to seed/seedling vigour).

Effect of increasing plant density and salinity on yield and fruit quality in muskmelon

Abstract The melon cultivar ‘Galia’ was grown at three plant densities (2, 4 and 8 plants m−2) and four irrigation salinity levels (ECw 1.2–8.0 dS m−1). Increasing plant density significantly increased the number of fruits per area but decreased mean fruit weight, whereas increasing salinity only decreased mean fruit weight. Total yield was not affected by increasing density but decreased with increasing salinity. No significant interaction was found between density and salinity in yield parameters. The reduction in mean fruit weight with increasing density and salinity was constant for all fruits within each treatment. Total soluble solids increased with increasing salinity but decreased with increasing density. Density and salinity appear to act independently on most yield and quality parameters.

Phenotypic selection and regulation of reproduction in different environments in wild barley.

Plasticity of the phenotypic architecture of wild barley, Hordeum spontaneum, was studied in response to water and nutrient stress. Direct and indirect selection on several vegetative and reproductive traits was estimated and path analysis used to reveal how regulating pathways via maternal investment differed between environments. Vegetative traits displayed differential regulating effect on fitness across experimental environments: (1) increase in size was selected for under optimal conditions and under water stress, but not under nutrient stress; (2) allocation to root biomass was selected for under optimal conditions, but it had no effect under nutrient stress and was strongly selected against when water was limiting; (3) delayed onset of reproduction was selected under nutrient limitation whereas earlier onset was selected under water stress. The regulating effect of reproductive traits on final reproductive output also differed across treatments, operating either at the ‘early’ stage of plant development through varying the number of initiated spikelets per spike (no stress and water stress treatment) or at the ‘late’ developmental stage adjusting the fertile spikelet weight (no stress and nutrient stress treatment). Reproductive output was regulated via seed abortion under no stress and water stress treatments. Although the underlying mechanism of the regulation through abortion has yet to be discovered, the specific mechanism of abortion under water stress appears to be different from that under optimal conditions. Our results demonstrate that not only is the character architecture in wild barley plastic and sensitive to changing availability of water and nutrients, but the regulating mechanism of maternal investment is also environmentally sensitive.

Phenotypic variation and stress resistance in core and peripheral populations of Hordeum spontaneum

The phenotypic variation and response of plants to water stress were studied in a field trial in populations of wild barley, Hordeum spontaneum Koch. from Israel and Turkmenistan. Populations from the species distributional core and periphery were compared and contrasted for phenotypic variation in 16 phenological and morphological traits. The peripheral populations (six) were found to be phenotypically more variable and more resistant to water stress than core populations (12). The association of water-stress resistance with high phenotypic variability gives support to the hypothesis that populations that are genetically more variable are better adapted or pre-adapted to environmental changes and are thus valuable for conservation.

PHENOTYPIC AND ALLOZYME VARIATION IN MEDITERRANEAN AND DESERT POPULATIONS OF WILD BARLEY, HORDEUM SPONTANEUM KOCH

Abstract Populations of wild barley, Hordeum spontaneum Koch, were collected in two distinct climatic regions, desert and Mediterranean. Plants from five desert and five Mediterranean populations were compared and contrasted for extent and structure of phenotypic variation. These same 10 and one other population from each region were analyzed for allozyme variation. In a field trial of phenotypic diversity, two phenological and 14 morphological traits were examined. Study of allozyme variation was performed using eight enzyme systems encoding for 13 loci. Plants from the desert and Mediterranean regions were significantly different in seven of 16 phenotypic traits, exhibited a high (30%) interregional component of phenotypic variation, and showed a high degree of segregation on a principal component scattergram indicating ecotypic differentiation. Mediterranean populations were twice as variable as desert populations in reproductive growth parameters (stem and spike length) and grain filling (spikelet weight), but half as variable for onset of reproduction. The extent and structure of phenotypic and allozyme variation did not match. The Mediterranean and desert populations did not differ in amount of allozyme variation as estimated by mean number of alleles per locus, effective number of alleles, polymorphism, and gene diversity (na, ne, P, and He), did not segregate on the basis of population genetic distances, and exhibited a low proportion of interregion allozyme diversity (2%). No effect of selection on allozyme distribution was detected. Our results suggest that the adaptation of plants originating from desert and Mediterranean environments is reflected in phenotypic but not in allozyme variation.

EFFECT OF TIME OF SALINIZATION ON FLOWERING, YIELD AND FRUIT QUALITY FACTORS IN MELON, CUCUMIS MELO L.

Emergence, flowering, yield and fruit quality factors were examined in three salinity treatments in melons. They were: (i) fresh water (electrical conductivity ECW = 1.2 dS/m) for germination and all growth; (ii) saline water (ECW = 6.5 dS/m) for germination and all growth; and (iii) fresh water for germination and initial growth and then saline water for subsequent growth. Three cultivars were examined, Galia, BG3 and BG5. Salinity did not affect the percent emergence or the number of hermaphrodite flowers in any of the cultivars, although the fresh water treatment produced slightly more staminate flowers. Salinity reduced both initial and total vegetative growth in all cultivars. Salinity also reduced mean fruit weight in the three cultivars, although not to the same degree. Salinity did not affect the number of fruit produced. Fruit constituent factors were for the most part unaffected by salinity. After emergence and initial growth, the two salinity treatments did not differ in vegetative growth, yiel...

The Influence of Space in Genetic‐Environmental Relationships When Environmental Heterogeneity and Seed Dispersal Occur at Similar Scale

We tested the importance of microenvironmental topographic parameters as predictors of emmer wheat genetic variation using three classes of single‐locus (or at most several‐loci) genetic markers (allozymes, glutenins, and qualitative traits) and two classes of markers of polygenic inheritance (phenological and morphological traits). Canonical correspondence analysis (CCA) and redundancy analysis (RDA) detected a significant effect of spatially structured environmental variation on genetic differences between plants for allozymes, glutenins, and quantitative morphological and phenological traits. However, after removing a spatial component of variation in partial CCA and partial RDA, the relationship of the remaining environmental variation with these genetic markers could be explained by chance alone, allowing us to rule out microniche topographic specialization in emmer wheat. Topographic autocorrelation exhibited a certain degree of similarity with genetic marker autocorrelation, indicating similar scales of environmental heterogeneity and seed flow. The detected population genetic structure agrees with one expected under isolation by distance as a result of limited gene flow. A negative relationship of genetic similarity with the logarithm of distance between plants was detected for both molecular markers and quantitative traits, which differed in the strength but not the pattern of association.

EFFECTS OF SUBOPTIMAL LOW TEMPERATURE ON YIELD, FRUIT APPEARANCE AND QUALITY IN MUSKMELON (CUCUMIS MELO L.) CULTIVARS

SummaryThe effects of suboptimal low temperature were investigated on an array of yield, fruit appearance and fruit quality characters in 23 cultivars of melon, Cucumis melo L. The cultivars were grown in two temperature regimes: (I) a heated greenhouse (T1) with temperatures similar to those used in commercial cultivation in the winter in Israel; and (ii) an unheated greenhouse (T2) that had significantly lower night temperatures than T1. Significant differences were found among the cultivars in all characters. Plants from T2 showed an extended fruiting period, more fruits and higher total yield but smaller and lighter fruits than in T1. Fruits from T2 also had significantly more netting and higher amounts of total soluble sugars (TSS), sucrose and fructose than fruits from T1. Hybrid cultivars showed significantly higher electrical conductivity (EC), pH, acidity, TSS, sucrose, fructose and total sugars than open pollinated cultivars. Three trends were found among the characters in respect to the perform...

Effect of calcium on growth of submerged Terfezia boudieri mycelium

The effect of Ca2+ on mycelial growth in Terfezia boudieri was studied. Terfezia boudieri Chatin (Ascomycotinae) occurs in mycorrhizal association with Helianthemum shrubs in deserts with calcareous soils. External Ca2+ stimulated mycelial growth in both liquid media and solidified substrates. The response to Ca2+ was very faint in well-aerated culture but pronounced in mycelia immersed in the medium, indicating dependence on mycelial aeration. 2,4-Dinitrophenol (DNP), an inhibitor of oxidative phosphorylation, and succinate, a potential cytoplasm acidifier, inhibited mycelial growth but enhanced the stimulatory effect of Ca2+. This effect was reduced by the Ca2+ channel blocker verapamil.

Optimization of agrotechniques for cultivating Momordica charantia (karela)

Germination requirements, flowering pattern, planting date, density and growing regimes were examined for Momordica charantia L. (karela). Germination was optimum at temperatures between 25 and 35°C and inhibited at 8,12,40 and 45°C. Increasing salinity delayed germination but did not reduce final percentage. Flowering pattern was affected by planting season with significantly more female flowers being produced in spring- summer under long days and high temperatures than in autumn-winter under short days and low temperatures. A high yield of 45-51 Mg ha-1 was achieved at densities of 10 000 and 20 000 plants per ha and at both growing regimes examined (ground versus trellises). Ground-cultured plants yielded a higher percentage of small, green, firm, marketable fruit. Fruits showed least deterioration under cold storage, and at 4°C a shelf life of about two weeks was demonstrated.