Different Drought Tolerance Strategy of Wheat Varieties in Spike Architecture

Spike characteristics include spike length, total spikelet number per spike, number of fertile flowers, spike density, spike fertility, grain number, thousand kernel weight, the number of spikes per square meter, harvest index and the grain yield during the flowering and ripening stage. The six winter and one facultative variety differed in earliness, derived in part from the allele of the Ppd-D1 gene and phenological observation. The two sites significantly differed in the soil moisture, which varied during continual microclimate monitoring. The spike architecture of winter wheat was affected by drought. The plant samples from the site FIELD 2 (more drought stressed) showed a higher reduction in spike characteristics such as a lower spike length, total spikelet number, number of fertile flowers and spike fertility, leading to a lower yield than the site FIELD 1. Both early and late varieties possess compensatory abilities to create the grain yield during drought stress; however, the timing and duration of exposure to drought determine the application and success of the compensatory ability. In our experiment, the late varieties (photoperiod sensitive) performed better in yield than the early varieties during both growing seasons. That is at odds with the generally recommended "drought escape strategy" (early varieties) and suggests a possible direction for variety selection and breeding in arid areas in Central Europe.O

Relationship Between Dehydrin Accumulation and Winter Survival in Winter Wheat and Barley Grown in the Field

Low temperatures represent a crucial environmental factor determining winter survival (WS) of barley and wheat winter-type varieties. In laboratory experiments, low temperatures induce an active plant acclimation response, which is associated with an enhanced accumulation of several stress-inducible proteins including dehydrins. Here, dehydrin accumulations in sampled wheat (WCS120 protein family, or WCS120 and WDHN13 transcripts) and barley (DHN5 protein) varieties grown in two locations for two winters were compared with the variety WS evaluated by a provocation wooden-box test. A high correlation between dehydrin transcripts or protein relative accumulation and variety WS score was found only in samples taken prior vernalization fulfillment, when high tolerant varieties accumulated dehydrins earlier and to higher level than less tolerant varieties, and the plants have not yet been vernalized. After vernalization fulfillment, the correlation was weak, and the apical development indicated that plants reached double ridge (DR) in barley or stayed before DR in wheat. Dehydrin proteins and transcripts can be thus used as reliable markers of wheat or barley variety winter hardiness in the field conditions; however, only at the beginning of winter, when the plants have not yet finished vernalization. In wheat, a higher correlation was obtained for the total amount of dehydrins than for the individual dehydrin proteins.HIGHLIGHTS-More tolerant winter-type wheat and barley plants reveal higher threshold induction temperatures for dehydrin accumulation in comparison to less tolerant varieties. Thus, more tolerant winter cereals have higher dehydrin levels than the less tolerant ones upon the same ambient temperature in November samplings.-A significant correlation between dehydrin transcript/protein accumulation and winter survival was found in both winter wheat and winter barley plants in the field conditions, but only prior to vernalization fulfillment

Drought stress response in maize: molecular, morphological and physiological analysis of tolerant and sensitive genotypes

The aim of this work was to develop a physiological method based on transpiration in combination with molecularmethods, i.e., dehydrin gene expression analysis, for identifying the reactions of maize (Zea mays L.) plants thatdisplay different levels of tolerance to drought stress during the generative growth stage. Drought stress wasinduced in two genotypes, 2087 and 2637, by four irrigation treatments. The rate of transpiration and the expressionof the dehydrin genes ZmDHN1 and ZmDHN2 were dependent on genotype and duration and intensityof stress. The yield components were affected by the level of dehydrin gene expression and transpiration rate.Compared with genotype 2637, genotype 2087 a) maintained higher transpiration intensity, even under strongdrought stress conditions, b) exhibited an earlier onset and a higher level of expression both at a lower stressintensity and during the initial phases of the stress reaction, c) showed higher values of yield components, andd) was characterized by a lower water-use efficiency of cob yield. Drought tolerance is of increasing importanceand is one of the breeding targets in maize. However, traditional breeding methods have numerous limitations.The simultaneous use of new molecular genetic techniques and physiological methods could therefore help toelucidate the genetic and physiological basis of plant responses to drought stress and provide more accurateevaluation for screening parental breeding material

Use of ABA Treatment for the Activation of Drought Protective Mechanisms in Barley Under Non-stress Conditions

The present study evaluated the sensitivity of three different barley genotypes to stress simulated by the application of exogenous abscisic acid (20 µmol.l−1) at the early stage of the plant development. We used RIA method, instantaneous water use efficiency (WUE), the discrimination of 13C (Δ13C) and the expression levels of Dhn4 gene. The increase of ABA concentration in leaves after exogenous ABA application was detected in all tested genotypes; however, the lowest amount was found in the most tolerant genotype. Increased level of the instantaneous WUE after ABA treatment was found in all genotypes. The Δ13C in ABA treated plants decreased, however, relatively drought-tolerant genotype Tadmor showed lower discrimination even in control variant. The genotype-dependent differences were observed in the expression levels of Dhn4 gene in the leaves. High expression level of this gene was observed in Tadmor. Based on the exogenous ABA level, it was possible to distinguish two types of response of plants to exogenous ABA. Tadmor represented one of them as manifesting high sensitivity to exogenous ABA, leading to fast induction of Dhn4 gene relative expression. Conversely, spring genotypes of Jersey and Malz manifested slower response to exogenous ABA as well as lower WUE values and relative expression of Dhn4. The results supported the idea that ABA application may activate similar stress reactions in plants as drought conditions and additionally the intensity of this reaction is genotype dependent

Fungi of the Fusarium genus in the grains of conventional hybrids and transgenic Bt-hybrids of maize (Zea mays L.) in the Czech Republic

Fungi of the Fusarium genus, the agent of ear rot in maize, not only causes decrease in yields but also negatively affects grain quality and, in relation to mycotoxins production, the health of humans and animals. This study focuses on determining the species range of Fusarium fungi in naturally infected stands of conventional hybrids and transgenic Bt-hybrids of maize in the Czech Republic during 2008 and 2009. Individual species of the Fusarium genus were determined on the basis of morphological characteristics and using polymerase chain reaction. Ten mycotoxigenic species were identified in hybrid maize grains: F. subglutinans (40.4%), F. graminearum (19.8%), F. verticillioides (18.2%), F. poae (9.3%), F. proliferatum (4.0%), F. avenaceum (3.8%), F. oxysporum (1.7%), F. sporotrichioides (1.3%), F. sambucinum (1.3%) and F. culmorum (0.2%). The species F. subglutinans, F. graminearum and F. verticillioides were dominant in both years. The frequency of individual Fusarium species did not significantly differ between conventional and transgenic Bt-hybrids. Differences in species representation were determined between individual years and sites. The hypothesized markedly lower infection of individual Bt-hybrids with fungi of the Fusarium genus was not statistically significant, although most Bt-hybrids did demonstrate lower infection without that being statistically significant. The average level of infection by the Fusarium genus in 2008 was 13.2% for grains of conventional hybrids and 6.6% for Bt-hybrids (50% lower). In 2009, the average infection level was 13.6% for conventional hybrids and 12.6% for Bt-hybrids (7.4% lower). The average infection level for grains of Bt-hybrids by the species F. subglutinans, F. graminearum and F. proliferatum was lower than that for grains of conventional hybrids in both years