Serotiny in Melocactus matanzanus (Cactaceae) and role of cephalium in dispersal of seeds after the individual's death

Serotiny is a strategy in which the retention of mature seeds in parent structures allows plants to cope with environmental variability like heat, drought or fire. Although this phenomenon might be common in Cactaceae, and particularly in Melocactus, it has generally been scarcely addressed. The main goal of our work is to investigate if there are seeds hidden in the cephalium of Melocactus matanzanus and if there are, determine whether or not these seeds maintain their viability. We also discuss some advantages the cephalium may offer as diaspore after the death of individuals. Cephalia collected from dead individuals were divided into four slices and their seeds counted; we also assessed the viability and photoblastic response of the seeds by using growth chambers at 25/30°C, and by a cut test on the seeds that did not germinate. Our results showed retention of viable seeds of different ages in all slices of the cephalium. Seeds were photoblastic positive with germination between 11–22% and viability above 50% in the portion of the lots that did not germinate.

The UV RESISTANCE LOCUS 8-Mediated UV-B Response Is Required Alongside CRYPTOCHROME1 For Plant Survival Under Sunlight In The Field

As sessile organisms, plants are subjected to fluctuating sunlight including potentially detrimental ultraviolet-B radiation (UV-B). In Arabidopsis thaliana, experiments under controlled conditions have shown that UV RESISTANCE LOCUS 8 (UVR8) controls photomorphogenic responses for acclimation and tolerance to UV-B; however, its long-term impacts on plant performance remain poorly understood in naturally fluctuating environments. Here we quantified the survival and reproduction of different Arabidopsis mutant genotypes in diverse field and laboratory conditions. We found that uvr8 mutants produced more fruits than wild type in growth chambers with artificial low UV-B conditions but not in natural field conditions. Importantly, independent double mutants of UVR8 and the blue-light photoreceptor gene CRYPTOCHROME 1 (CRY1) in two genetic backgrounds showed a drastic reduction in fitness in the field. UV-B attenuation experiments in field conditions and supplemental UV-B in growth chambers demonstrated that UV-B caused the conditional cry1 uvr8 lethality phenotype. RNA sequencing in different conditions revealed a large number of genes with statistical interaction of UVR8 and CRY1 mutations in the presence of UV-B in the field. Among them, Gene Ontology analysis identified enrichment of categories related to UV-B response, oxidative stress, photoprotection and DNA damage repair. Our study demonstrates the functional importance of the UVR8-mediated response across life stages in natura, which is partially redundant with CRY1, and provides an integral picture of gene expression associated with plant environmental responses under diverse environmental conditions.

Wood vinegar for control of broadleaf weeds in dormant turfgrass

Wood vinegar, a product of pyrolysis, can induce phytotoxicity on plants when applied at an adequate rate and concentration. The objective of this research was to investigate wood vinegar obtained from the pyrolysis of apple tree branches for weed control in dormant zoysiagrass. In environment-controlled growth chambers, white clover visual injury and shoot mass reduction compared to the nontreated control were evaluated after wood vinegar application at 1000, 2000, or 4000 L ha-1 under 10 or 30 C temperature conditions. Averaged across rates, wood vinegar rapidly desiccated white clover and caused 83 and 71% visual injury at 10 and 30 C, respectively, at 1 d after treatment (DAT). Averaged across temperatures, wood vinegar at 1000, 2000, and 4000 L ha-1 reduced white clover shoot mass by 56, 81, and 98% from the nontreated control at 10 DAT, respectively. In field experiments, weed control increased as wood vinegar rates increased from 1000 to 5000 L ha-1 in dormant zoysiagrass. The effective application dose of wood vinegar required to provide 90% control (ED90) of annual fleabane, Persian speedwell, and white clover was determined to be 2450, 2300, and 4020 L ha-1, respectively, at 2 weeks after treatment. Turf quality did not differ among the wood vinegar treatments and the nontreated control when zoysiagrass completely recovered from dormancy. Overall, results illustrate that wood vinegar resulting from the pyrolysis of apple tree branches can be used as a nonselective herbicide in dormant turfgrass, offering a new non-synthetic herbicide option for weed control in managed turf.

Marker Assisted Pyramiding of QTLs for Heat Tolerance and Escape Upgrades Heat Resilience in Rice (Oryza Sativa L.)

High temperature at flowering stage of rice causes low spikelet fertility and low yield. To cope with high temperature stress brought by climate change, two strategies were proposed to develop heat-resilient rice varieties. One is to escape the high temperature by flowering early in the morning, another is to enhance tolerance to high temperature stress per se. Two promising QTLs for early morning flowering (qEMF3) and heat tolerance (qHTSF4.1) were introgressed into IR64 background, and near isogenic lines (NILs) IR64+qEMF3 (IR64EMF3) and IR64+qHTSF4.1 (IR64HT4) were developed in previous studies. In this study, a QTL pyramiding line IR64+qHTSF4.1+qEMF3 (IR64HT4EMF3) was developed by marker assisted selection of the progenies of previous NILs. The NILs were subjected to different high temperature regimes in the indoor growth chambers and different locations in the field. In the indoor growth chambers, when high temperature starts early (before 11:00 am), IR64HT4 and IR64HT4EMF3 had higher spikelet fertility than IR64EMF3; when high temperature comes later (after 11:00 am), IR64EMF3 and IR64HT4EMF3 had higher spikelet fertility than IR64HT4. The flowering pattern of the IR64HT4EMF3 was earlier than IR64HT4, but similar to IR64EMF3 in the glasshouse, field and indoor growth chambers. IR64HT4EMF3 showed higher spikelet fertility than IR64EMF3 and IR64HT4 in the field in the Philippines. Thus, combination of early morning flowering and heat tolerance QTLs is an elegant breeding strategy to cope with future extreme climate.

High temperature disturbs ovule development in field pea (Pisum sativum L.)

High temperatures affect reproductive growth and lead to yield loss in many crops. Field pea is heat sensitive, but little is known about the effect of high temperature on ovules. We investigated heat impact on ovules of flowers at various reproductive nodes of field pea using growth chambers. Six cultivars exhibiting diverse heat tolerance were exposed to four days of heat (35°C day/18°C night) during early flowering. Post-treatment ovules and embryo sacs were assessed employing clearing by light, and fluorescence, microscopy. Results indicated that greater ovule and embryo sac development occurred on some nodes, but poor ovule and embryo sac expansion resulted on other nodes of the same heat-treated plants. While advanced ovule and embryo sac development were identified on heat-tolerant cultivars, a combination of advanced and less advanced ovule and embryo sac development occurred in intermediate and heat-sensitive cultivars. More than 90% of the affected ovules displayed embryos at various stages of development, which indicated disruption around fertilization or shortly thereafter. Callose accumulation around the vascular bundle within ovules suggested disruption of assimilate transport to the embryo sac. The contrasting pattern of ovule development at different nodes implied a conflict between early aging and maternal supply of heat-treated plants.

Effects of Various Environmental Conditions on the Growth of Amaranthus patulus Bertol. and Changes of Herbicide Efficacy Caused by Increasing Temperatures

Understanding the effects of climate change on weed growth and herbicide activity is important for optimizing herbicide applications for effective weed control in the future. Therefore, this study examined how climate change affects the growth of Amaranthus patulus and the efficacy of soil and foliar herbicides at different temperatures. Although the control values for A. patulus differed between herbicides and temperature, the control values increased with increasing time after the herbicide treatments. Under growth conditions in which the temperature remained constant, the efficacy of soil-applied herbicides, ethalfluralin, metolachlor, linuron, and alachlor, on A. patulus was highest when the weeds were grown at high temperature. In particular, 100% control values of A. patulus were achieved in response to metolachlor treatments at the total recommended dosage in growth chambers at 35 °C. The efficacy of foliar herbicides, glufosinate-ammonium, bentazone, and mecoprop, on A. patulus was also highest when the plant was grown at high temperature, except for glyphosate isopropylamine, which had similar efficacy rates regardless of the temperature. A. patulus was 100% controlled in response to glufosinate-ammonium, bentazone, and mecoprop at the recommended dosages in growth chambers at 30 and 35 °C. Under growth conditions in which the temperature changed from day to night, the efficacy of soil-applied herbicides, alachlor and linuron, on A. patulus was highest when the weeds were grown at high temperature. On the other hand, the efficacy of the soil-applied herbicides metolachlor and linuron on A. patulus was similar regardless of the temperature. The efficacy of foliar herbicides, glyphosate isopropylamine, glufosinate-ammonium, bentazone, and mecoprop, on A. patulus was highest when the weeds were grown at high temperature. Although herbicide efficacy varied depending on whether the weeds were grown at constant or alternating temperatures, herbicide efficacy was generally highest when the temperature was high.

Behavior of Spanish durum wheat genotypes against Zymoseptoria tritici: resistance and susceptibility

Aim of study: Septoria tritici blotch (STB), caused by the fungus Zymoseptoria tritici, is one of the most important wheat diseases worldwide, affecting both bread and durum wheat. The lack of knowledge about the interaction of durum wheat with Z. tritici, together with limited resources of resistant durum wheat material, have both led to a rising threat for durum wheat cultivation, particularly in the Mediterranean Basin. In Spain, STB has increased its incidence in the last few years, leading to higher costs of fungicide applications to control the disease. Therefore, identification of new sources of resistance through wheat breeding stands out as an efficient method of facing STB. Area of study: The experimental study was conducted in growth chambers at the IFAPA facilities in Córdoba (Spain). Material and methods: The percentage of necrotic leaf area, the disease severity, and the pycnidium development through image analysis were evaluated from 48 durum wheat Spanish accessions (breeding lines and commercial cultivars) in growth chambers against an isolate of Z. tritici from Córdoba. Main results: Two breeding lines and six commercial cultivars showed resistant responses by limiting STB development through the leaf or its reproduction ability, while the other 40 accessions presented a susceptible response. Research highlights: Provided these resources of resistance in Spanish durum wheat genotypes, future breeding programs could be developed, incorporating both agronomic traits and resistance to STB.

Polyploidy Improves Photosynthesis Regulation within the Ranunculus auricomus Complex (Ranunculaceae)

Polyploidy has substantially contributed to successful plant evolution, and is often connected to a higher resilience to environmental stress. We test the hypothesis that polyploids tolerate light stress better than diploids. The Ranunculus auricomus complex comprises diploid (2x), tetraploid (4x), and hexaploid (6x) cytotypes, the former of which occur in shaded habitats and the latter more in open, sun-exposed habitats in Central Europe. In this study, we experimentally explored the effects of ploidy and photoperiod extension on the efficiency of photosystem II in the three cytotypes in climate growth chambers. Quantum yields and various coefficients that can be calculated from light curve, Kautsky curve, and fluorescent transient OJIP experiments provided support for the hypothesis that, in comparison to diploids, the improved regulation of excess light by more efficient photochemical and non-chemical quenching in polyploids might have facilitated the adaptation to unshaded habitats. We suggest how lower stress levels in reproductive tissues of polyploids might have favored asexual reproduction.

Response of Sorghum to Cold Stress at Early Developmental Stage

Native and adapted to the semiarid tropical regions of Africa, sorghum (Sorghum bicolor) is generally sensitive to cold temperatures, especially during the early developmental stages. However, there is genetic variability within the existing germplasm in terms of tolerance to low temperatures. The highland regions of Africa possess important sources of germplasm with adaptation to cold stress, since they tend to be cooler than the low land regions. The goals of the study were to evaluate and identify sorghum lines with tolerance to cold temperature stress and make recommendations on varieties that may be planted in the East African highland regions or used in plant breeding programs for cold tolerance. Forty sorghum genotypes were evaluated for emergence, shoot, and root development at seedling stage under controlled environment in growth chambers and in the field. Significant genotypic differences were detected for all evaluated traits. Correlation between controlled environment experiments and field trial results was mostly significant, suggesting that the growth chambers can be used to predict and identify cold-tolerant genotypes. Results showed that emergence and vigor are the best surrogate traits for selecting cold-tolerant genotypes. Using rank summation index, we were able to identify the best cold-tolerant sorghum genotypes (IS 25557, IS 25558, IS 25546, BM6, BM 29, IESV 90042LT, and Cytanobe) that can be used in future breeding programs and enhance adaptation and expansion of sorghum production further into the highland regions of Africa.