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The reproductive traits in Gagea are affected by both abiotic and biotic environmental factors. However, further intrinsic drivers, like the ploidy level, could also have a significant influence on the sexual efficiency of these geophytes. Here, we present a comparative study involving the reproductive biology of five species of Gagea occurring in southern Italy, and representing different ploidy levels. The experimental investigations included flower phenology, pollen quality (i.e., morphology, viability, and germination), and stigma receptivity. Such data were then combined with information on seed-set available from previous work. All the studied species showed a gradual pollen presentation, and an early and durable stigma receptivity. Such traits represent effective functional adaptations to prevent pollen limitation under the unpredictable weather dynamics typical of the early blooming season of these plants. The use of a diluted substrate favoured the rate of pollen germination in vitro and, likely, it represents a further adaptation versus adverse environmental conditions (i.e., rain damage on exposed pollen). However, the rates of pollen viability and germination were generally low and appeared related to the ploidy level. Data inherent pollen quality (i.e. morphology, viability and germination) and seedset indicated the hexaploid G. lutea as the most fertile species, while the heptaploid G. fragifera had the lowest scores for all the considered traits. Finally, by considering the isolation and reduced size of the studied population, the unexpected low fertility found in the diploid G. minima was possibly due to inbreeding depression related to the relict status of this species in southern Italy. [ABSTRACT FROM AUTHOR]

Impedance flow cytometry (IFC) is a versatile lab-on-chip technology which enables fast and label-free analysis of pollen grains in various plant species, promising new research possibilities in agriculture and plant breeding. Hazelnut is a monoecious, anemophilous species, exhibiting sporophytic self-incompatibility. Its pollen is dispersed by wind in midwinter when temperatures are still low and relative humidity is usually high. Previous research found that hazelnut can be characterized by high degrees of pollen sterility following a reciprocal chromosome translocation occurring in some cultivated genotypes. In this study, IFC was used for the first time to characterize hazelnut pollen biology. IFC was validated via dye exclusion in microscopy and employed to (i) follow pollen hydration over time to define the best pre-hydration treatment for pollen viability evaluation; (ii) test hazelnut pollen viability and sterility on 33 cultivars grown in a collection field located in central Italy, and two wild hazelnuts. The accessions were also characterized by their amount and distribution of catkins in the tree canopy. Pollen sterility rate greatly varied among hazelnut accessions, with one main group of highly sterile cultivars and a second group, comprising wild genotypes and the remaining cultivars, producing good quality pollen. The results support the hypothesis of recurring reciprocal translocation events in Corylus avellana cultivars, leading to the observed gametic semi-sterility. The measured hazelnut pollen viability was also strongly influenced by pollen hydration (R adj 2 = 0.83, P ≤ 0.0001) and reached its maximum at around 6 h of pre-hydration in humid chambers. Viable and dead pollen were best discriminated at around the same time of pollen pre-hydration, suggesting that high humidity levels are required for hazelnut pollen to maintain its functionality. Altogether, our results detail the value of impedance flow cytometry for high throughput phenotyping of hazelnut pollen. Further research is required to clarify the causes of pollen sterility in hazelnut, to confirm the role of reciprocal chromosome translocations and to investigate its effects on plant productivity. [ABSTRACT FROM AUTHOR]

• Anthesis and pollen functionality were compared in an apricot germplasm collection. • Early, intermediate, late-flowering cultivars showed high initial pollen viability. • Pollen germination was assessed within the effective pollination period. • Pollen germination was differently affected by 5 °C, 15 °C, and 25 °C treatments. • High temperature significantly decreased pollen germination in most cultivars. Prunus armeniaca L. is widely cultivated in the Mediterranean area including Southern Italy where local cultivars are recognized for their excellent quality. Gradual warming and abrupt variations of seasonal temperatures are expected to significantly impact the Mediterranean area with potential implications on many crops including apricot. In this scenario, the identification of physiological processes involved in heat-stress responses and the selection of genotypes resilient/tolerant to high temperatures and heat waves are necessary. The aim of this study was to investigate possible differences in flowering phenology and the effect of different temperatures on pollen functionality of 13 apricot cultivars traditionally cultivated in the Campania region (Southern Italy). According to phenological data collected in the field, the studied cultivars were grouped in early, intermediate, and late flowering cultivars. Single flower anthesis was on average 4.9 days in early and intermediate flowering cultivars, whereas late flowering cultivars showed a shorter duration (4.0 days). Pollen of flowers at balloon stage showed a uniformly high viability among all cultivars. To investigate on possible effects of temperature during the effective pollination period (EPP), pollen from the different cultivars was pre-incubated at 5 °C, 15 °C, and 25 °C for 48-h and germinability was then assessed after further 24 h in-vitro germination at the same temperature treatments. The first two temperature values correspond respectively to the minimum and maximum average temperatures of the local area; whereas 25 °C simulated the heat waves recently recorded in the farm during apricot flowering periods. As regard pollen germinability, 15 °C revealed to be the most suitable temperature for apricot pollen to germinate within the EPP. Conversely, 5 °C and 25 °C significantly reduced pollen germination in most cultivars and particularly in intermediate flowering cultivars. Noticeably, a few cultivars showed no difference in pollen germination under the different temperature treatments, preserving high pollen germinability (>70%) even at high temperatures. Overall, our findings highlighted that pollen germination is extremely sensitive to temperature with significant variations among apricot genotypes. Results confirmed that reproductive traits such as pollen germinability represent an important parameter to consider for monitoring fruit production, in the processes of cultivar selection for new orchard plantations and in breeding projects. Moreover, traditional apricot cultivars as those of the Campania region confirmed to be a precious source of genetic diversity possessing a significant pollen resilience to temperature changes. [ABSTRACT FROM AUTHOR]

Olea europaea L. is a crop typical of the Mediterranean area that has an important role in economy, society, and culture of this region. Climate change is expected to have significant impact on this crop, which is typically adapted to certain pedo-climatic characteristics of restricted geographic areas. In this scenario, the aim of this study was to evaluate the time-course response of pollen viability to different combinations of temperature and humidity. The study was performed comparing flowering time and pollen functionality of O. europaea from twelve cultivars growing at the same site belonging to the Campania olive collection in Italy. Pollen was incubated at 12 °C, 22 °C, and 36 °C in combination with 50% RH or 100% RH treatments for 5 days. The results highlighted that a drastic loss of pollen viability occurs when pollen is subjected to a combination of high humidity and high temperature, whereas 50% RH had less impact on pollen thermotolerance, because most cultivars preserved a high pollen viability over time. In the ongoing climate change scenario, it is critical to assess the effect of increasing temperatures on sensitive reproductive traits such as pollen viability to predict possible reduction in crop yield. Moreover, the results highlighted that the effect of temperature increase on pollen thermotolerance should be evaluated in combination with other environmental factors such as humidity conditions. The screening of olive cultivars based on pollen thermotolerance is critical in the ongoing climate change scenario, especially considering that the economic value of this species relies on successful fertilization and embryo development, and also that production cycle of Olea europaea can be longer than a hundred years. [ABSTRACT FROM AUTHOR]

Abiotic stresses adversely affect crop production causing yield reductions in important crops, including tomato (Solanum lycopersicum L.). Among the different abiotic stresses, drought is considered to be the most critical one, since limited water availability negatively impacts plant growth and development, especially in arid and semi-arid areas. The aim of this study was to understand how biostimulants may interact with critical physiological response mechanisms in tomato under limited water availability and to define strategies to improve tomato performances under drought stress. We investigated the physiological responses of the tomato genotype 'E42' grown in open fields under optimal conditions (100% irrigation) and limited water availability (50% irrigation) treated or not with a novel protein hydrolysate-based biostimulant (CycoFlow, Agriges, BN, Italy). Plants treated with the protein hydrolysate showed a better water status and pollen viability, which also resulted in higher yield under drought stress compared to untreated plants. The treatment with the biostimulant had also an effect on antioxidant contents and activity in leaves and fruits depending on the level of irrigation provided. Altogether, these results indicate that the application of protein hydrolysates on tomato improved plant performances under limited water availability and in different experimental fields. [ABSTRACT FROM AUTHOR]