High temperature stress responses of Salvia splendens and Viola X wittrockiana

One of the greatest impediments affecting growth and development of bedding plants is high temperature stress. The deleterious effects of high temperature stress are the most pronounced during plug transplant and/or during the transition period from the nursery to the landscape. High temperature stress responses were investigated in Salvia splendens and Viola x wittrockiana to determine the morphological and physiological mechanism associated with the heat tolerance. Two genotypes for each species were used; a heat tolerant Vista and a heat sensitive Sizzler cultivar of salvia and Crystal Bowl Purple (CBP) a heat tolerant and Majestic Giant Red (MGR) a heat sensitive cultivar of pansy. Morphological traits such as short stature, greater total leaf area/plant, extensive root system; physiological traits like stomatal conductance, greater transpiration, and net photosynthesis were found to be characteristic traits of heat tolerant cultivars. Greater cell membrane thermostability (CMT) and expression of a heat shock protein of low molecular weight approximately 27kD may be responsible for heat tolerance in Vista and CBP. Primary soluble sugars sucrose and raffinose found in both the salvia cultivars, and greater concentrations in Vista at high temperatures, may be involved in stabilization of membrane lipid bilayer and/or acting as osmoprotectants under stress conditions. Short duration (3 h) heat preconditioning at 35 °C and 30 °C for salvia and pansy respectively during initial stages of growth helped to develop acquired thermotolerance. Heat sensitive cultivars acquired heat tolerance with heat preconditioning and acclimated to subsequent challenging temperatures. Preconditioning enhanced already existing traits of heat tolerant cultivars. Increased stomatal frequency and leaf thickness in salvia acquired during preconditioning. Cell membrane thermostability measured at a single temperature with increasing time of exposure was closely associated with increased gas exchange rates, leaf relative water content and overall marketable quality in salvia. These simple laboratory techniques to test heat tolerance have a greater advantage over time and space consuming field trials and may be an accurate and more efficient measure of heat tolerance

Erinea in the 'Ansonica' grapevine cultivar: trichome complement, histological effects and analysis of chlorophyll fluorescence in affected leaves

Grapevine leaves are usually characterized by trichomes, specialized epidermal cells. They are interesting in ampelography and also important for the plant ecological responses in biotic and abiotic interactions. In nature, the trichome development is a genetic trait but it can be modified by pests as eriophyid mites. Colomerus vitis is quite common and its economic value is sometime substantial. Here, we studied the leaf erineum induced by C. vitis on 'Ansonica' ('Inzolia'), an important grapevine cultivar characterized by a low level of leaf trichome coating. To date, the interaction between C. vitis and grape has been investigated in few pedo-climatic conditions and no data are reported in 'Ansonica'. Therefore, our objectives were: (1) the analysis, in a Tuscan environment, of the morphology and histology of trichomes in 'Ansonica' leaves unaffected or affected by C. vitis; (2) evaluation, in mature leaves, of the effects of the mite both on pigment content and chlorophyll a fluorescence parameters. 'Ansonica' was devoid of glandular trichomes but it has been established the presence of few simple trichomes strictly associated with the veins. In the erineal sectors, a dense proliferation of simple trichomes in the abaxial epidermis and the development of hyperplasia in the adaxial surface were observed. Moreover, the leaf sections in the erineal regions were thicker due to an abnormal development of the lacunar parenchyma, and trichome proliferation was also extended to interveinal regions. Leaves with erinea showed a deficient content of carotenoids, in comparison to unaffected leaves. In 'Ansonica' leaves, C. vitis induced a decrease in the steady-state operational efficiency of photosystem II associated to a reduction in photochemical quenching and an increase in non-photochemical quenching values. In leaves with erinea, the reduction of photosystem II efficiency was extended to foliar areas not directly affected by galls. The collected results highlight that 'Ansonica' is susceptible to attacks by C. vitis and in the case of widespread leaf attacks the productive damage should not be underestimated

Salinity shock in jatropha curcas leaves is more pronounced during recovery than during stress time / O efeito da a salinidade em folhas de pinhão-manso é mais pronunciado durante a recuperação do que durante o estresse

To verify the possible morphological and ultrastructural differences in the Jatropha curcas leaves, in response to high-intensity salt stress, three genotypes were evaluated (CNPAE183, JCAL171, and CNPAE218). In all the genotypes, 750mM NaCl, added to the nutrient solution, was applied to test its salt tolerance. For the analysis, the leaves were collected at three time points: (i) before stress (time 0 hour); (ii) during stress time (time 50 hours); and (iii) in the recovery period (time 914 hours) when the stressed plants recovered and demonstrated measurements of net photosynthetic with values similar to those demonstrated by the control plants. We showed that regardless of the genotype, saline shock caused an increase in the thickness of the mesophyll, and after the removal of NaCl, the thicker mesophyll remained in the JCAL171 and CNPAE218 genotypes, while the values observed in the CNPAE183 genotype were similar to those before stress. Scanning electron microscopy indicated that the stomata of CNPAE183 are smaller and have a stomatal index higher than the values demonstrated in JCAL171 and CNPAE218. Therefore, among the genotypes analyzed, CNPAE183 demonstrates that it could be considered a promising genotype for future studies of genetic improvement that seek elite genotypes tolerant to salinity.

Mutation in HvCBP20 (Cap binding protein 20) adapts barley to drought stress at phenotypic and transcriptomic levels

This work was supported by the European Regional Development Fund through the Innovative Economy for Poland 2007–2013, project WND-POIG.01.03.01-00-101/08 POLAPGEN-BD “Biotechnological tools for breeding cereals with increased resistance to drought,” task 22; National Science Centre, Poland, project SONATA 2015/19/D/NZ9/03573 “Translational genomics approach to identify the mechanisms of CBP20 signalosome in Arabidopsis and barley under drought stress.”CBP20 (Cap-Binding Protein 20) encodes a small subunit of the cap-binding complex (CBC), which is involved in the conserved cell processes related to RNA metabolism in plants and, simultaneously, engaged in the signaling network of drought response, which is dependent on ABA. Here, we report the enhanced tolerance to drought stress of barley mutant in the HvCBP20 gene manifested at the morphological, physiological, and transcriptomic levels. Physiological analyses revealed differences between the hvcbp20.ab mutant and its WT in response to a water deficiency. The mutant exhibited a higher relative water content (RWC), a lower stomatal conductance and changed epidermal pattern compared to the WT after drought stress. Transcriptome analysis using the Agilent Barley Microarray integrated with observed phenotypic traits allowed to conclude that the hvcbp20.ab mutant exhibited better fitness to stress conditions by its much more efficient and earlier activation of stress-preventing mechanisms. The network hubs involved in the adjustment of hvcbp20.ab mutant to the drought conditions were proposed. These results enabled to make a significant progress in understanding the role of CBP20 in the drought stress response.European Regional Development Fund; National Science Centre, Polan

Abiotic stress effects associated with climate change on yield and tuber quality of potato cultivars in New Zealand : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Plant Science, School of Agriculture and Environment, Massey University, Manawatu, New Zealand

The recent weather anomalies in New Zealand, particularly the summer heatwaves of 2017/18 and 2018/19, hottest and third hottest on record, respectively, have seemingly affected potato production. The purpose of this research is to determine how abiotic stress commonly associated with climate change, e.g., drought and heat, is affecting the current potato production in New Zealand, define its effects on yield and tuber quality of commercial potato cultivars, and determine if cultivars exhibit differential susceptibility. Secondary climate data in the past 60 years (1958–2018) during the potato growing months of October to March showed an increasing trend for temperature in Ohakune (+0.53 °C), Opiki (+0.36 °C), and Hastings (+0.28 °C) as well as a decreasing trend for rainfall in Ohakune (-24.8 mm) and Hastings (-48.7 mm). The increase in temperature also increased the number of days with supra-optimal atmospheric temperatures believed to delay (>25 °C) or inhibit (>30 °C) tuber growth in Hastings by 57 days (2017/18 season) and in Opiki by 103 days (2018/19 season). Baseline data from a preliminary study during the 2017/18 growing season showed that abiotic stress associated with the extreme weather conditions apparently affected the yield and tuber quality, with cultivars showing differential susceptibility. Up to 85% unmarketable tubers were recorded among the samples collected, which was attributed to the high incidence of a wide array of tuber physiological disorders. The multi-environment trial in the 2018/19 growing season showed that abiotic stress had significant effects on the different morpho-agronomic and physiological functions of the potato crop and ultimately affected the yield and tuber quality. Abiotic stress increased the incidence of tuber physiological disorders, e.g., tuber malformation, growth cracks, and second growth, which reduced the total yield and marketable yield by up to 43.3% and 45.1%, respectively. Additionally, genotype × environment analysis showed that cultivar ‘Taurus’ is the most stable and adaptable cultivar across trial sites (wide adaptation). At the same time, cultivars ‘Hermes’ and ‘Snowden’ are tolerant to heat and drought stress (Opiki) and heat stress alone (Hastings) (specific adaptation), respectively. The glasshouse and plant growth chamber trial revealed that drought stress (DS) generally reduced the plant height, number of leaves, and canopy cover but enhanced the formation of more but smaller stomata and glandular and non-glandular trichomes. DS also encouraged the closing of the stomatal aperture potentially to reduce water loss, thereby reducing the transpiration rate (E), stomatal conductance (gS), and net photosynthesis (PN), which potentially affected the final yield. Conversely, heat stress (HS) increased the plant height, canopy cover, and number of leaves and developed more and larger stomata. HS also stimulated stomatal opening, leading to enhanced E and gS and improved PN at the vegetative stage. On the other hand, in general, the combination of drought and heat stress exacerbated the adverse effects of each abiotic stress type on the different morpho-physiological parameters. As established in the various component trials of this research, different abiotic stresses associated with climate change have a significant effect on the morpho-agronomic and physiological functions of potato crops and negatively impacts the yield and tuber quality. Breeding of new cultivars, and mass selection of existing cultivars should be conducted through multi-environment trials to identify adaptable cultivars that can be used to mitigate the effects of abiotic stresses associated with climate change on potato crops in the field and to increase the resiliency of the New Zealand potato industry