To investigate the effects of water withholding on 17 tomato (Solanum lycopersicum L.) landraces collected from different climatic zones of Iran and two commercial hybrids, the polyphasic OJIP fluorescence transient, relative water content (RWC), electrolyte leakage (EL) and vegetative growth parameters were analyzed. Duncan’s multiple range test (DMRT) for all the studied parameters and drought factor index (DFI) based on performance index on the absorption basis (PIabs) were used for screening the plants based on their tolerance to drought condition. Result showed that compared to the control plants, vegetative growth parameters, RWC, PIabs, relative maximal variable fluorescence (FM/F0), maximum quantum efficiency of PSII (FV/FM), quantum yield of electron transport (ΦE0) and electron transport flux per reaction center (RC) (ET0/RC) were decreased, whereas, EL, quantum yield of energy dissipation (ΦD0), specific energy fluxes per RC for energy absorption (ABS/RC) and dissipated energy flux (DI0/RC), which are closely related to the incidence of photoinhibition were increased in plants exposed to water withholding. DMRT and DFI screening results clearly categorized the landraces into three groups (tolerant, moderately sensitive and sensitive). Tolerant landraces showed less change for most of the measured parameters compared to sensitive and moderately sensitive landraces. We found that adapted landraces to dry climates had a higher tolerance to drought stress. Principal component analysis (PCA) revealed that FM/F0, FV/FM, ΦE0, ΦD0, PIabs, ABS/RC, ET0/RC and DI0/RC parameters are the most sensitive parameters for detection of impact of drought stress on tomato plants. In conclusion, the eight parameters have the potential to identify the drought injury in tomato seedlings.

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This is the first report of successful regeneration of haploid lines in iris (Iris pseudacorus) developed by in situ parthenogenesis followed by embryo rescue. Native genotypes of I. pseudacorus (2n = 38) were prepared as female parents and I. spuria was set as the males. Anthers collected from the pollen donor were irradiated by X-ray with doses of 0, 100, 200, 300, and 400 Gy in 2012. A second round of experiments was conducted in 2013 with 300 and 400 Gy. The ovaries from each pollinated flower were collected and cultured and the produced plantlets were then acclimatized. Chromosome counting and flow cytometry were used to determine the ploidy levels. The viability of irradiated pollens was also evaluated. Pollination with irradiated pollen at doses ranging from 100 to 400 Gy can significantly reduce fruit set, particularly at higher doses (300 and 400 Gy). The embryo production was reduced in I. pseudacorus as doses increased; the highest doses led to reduction in the number of regenerants with the formation of just 6 and 4 embryos at 300 and 400 Gy, respectively. Haploid plantlets were produced when the pollen grains were exposed to 300 and 400 Gy of X-ray. Irradiation at 100 and 200 Gy was found to be insufficient to cause pollen sterility. The best dose for haploid production in I. pseudacorus is hereby found to be 300 or 400 Gy of X-ray.

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