The original features of rice (Oryza sativa L.) genetic diversity and the importance of within-variety diversity in the highlands of Madagascar build a strong case for in situ conservation

In situ conservation of crop genetic resources is widely recommended but, as yet, no methods have been developed to rank the genetic entities to preserve and the social organisations to involve. The highlands of Madagascar have been identified as a key site for rice, Oryza sativa, genetic diversity. To define conservation strategies, we performed multidisciplinary analysis of rice genetic diversity and factors shaping its distribution in the target region. Along with the indica and japonica rice subspecies of O. sativa, we confirmed the presence of an atypical rice group with a preferential habitat of 1,250–1,750 m. Spatial distribution of genetic diversity was uneven. The most determining factor of this unevenness was the altitude authorising or not the presence of different rice cropping systems and the associated types of varieties. Village and individual farmer’s wealth also had a determining role on the amount of rice diversity they hosted. While molecular variance between villages in a given interval of altitude represented 16 % of the total variance, within-village variance represented more than 75 % of the total, and within-farm variance 70 % of within-village variance. This hierarchical distribution of molecular variance suggests that a small number of samples per scale (altitude interval, village and farm) could allow to capture most of the genetic diversity observed. However, within-variety diversity was also important making ex situ conservation strategies impractical and costly. Implications of the within-variety diversity are discussed in terms of adaptive advantages, evolutionary processes, and need for in situ conservation.     

Effect of different seed treatments on dormancy breaking and germination in three species in arid and semi-arid lands

Seeds of many woody plant species have one of several types of dormancy. They do not germinate unless specific environmental signals are in place or events occur. This study was conducted to evaluate the effects of scarification treatments on seed dormancy and germination of Acacia nilotica (L.) Willd. ex Del., Prosopis juliflora (Sw.) DC. and Dodonaea viscosa (L.) Jacq. The following treatments were applied: T1, untreated seed (control); T2, sulphuric acid (97%) for 45 min; T3, boiling water for 5 min. The seeds were cultured on a Murashige and Skoog (MS) medium after sterilization. The responses of seeds to treatments were compared with each other and with the control treatment. Germination was observed daily for a 30-day period. Results indicated positive responses to treatments, while impermeable seed coats may be responsible for low germination rates in intact seeds as seen experimentally in the untreated control. The highest germination was obtained for P. juliflora and D. viscosa acid-scarified seeds (80.8%-90.8%) and for scarified seeds of A. nilotica (50.2%) boiled in water. The germination indices, i.e., final germination percentage (FG), mean daily germination (MDG) and germination rate (GR), were significantly affected by treatments and species (p<0.01).     

Presence of β-glucanase activity in wheat and dairy ingredients and use of organic salts as potential enzyme inhibitors

Depolymerization of mixed linkage cereal β-glucans has been observed during the mixing and fermentation of multigrain breads. To maintain the bioactivity of β-glucans in bread and other foods, control of β-glucanase activity during production is needed. β-Glucanase activity in wheat and dairy ingredients was determined by adding them to β-glucan solutions and following the change in the molecular weight of β-glucan at 50 °C for 60 min. The activities in six wheat and six dairy ingredients ranged from undetectable to a 98% reduction in molecular weight. Calcium propionate, potassium sorbate, and sodium benzoate are salts of organic acids commonly used as food preservatives. Low concentrations of these additives (0.1–1.0%) were found to have an inhibitory effect on the β-glucanases found in wheat flour and whey protein isolate. The depolymerization rate of β-glucan was reduced by up to 76% by the three additives.     

Tissue distribution of infectious pancreatic necrosis virus serotype Sp in naturally infected cultured rainbow trout,Oncorhynchus mykiss (Walbaum): an immunohistochemical and nested‐PCR study

This study investigates the occurrence and distribution pattern of infectious pancreatic necrosis virus (IPNV) within the pancreas, liver, kidney and spleen of naturally infected cultured rainbow trout, Oncorhynchus mykiss (Walbaum), using immunohistochemistry (IHC). A nested PCR was also employed to confirm the presence of the virus in the pooled tissues of the specimens. All the examined tissues except spleen were immunohistochemically positive for IPNV, but staining intensity and distribution pattern varied. The kidney tubules had the most intense and widespread staining by IHC, indicating a specific tissue tropism at least for this particular serotype. The nucleotide sequence had the greatest identity with the Sp serotype confirming the presence of the nucleic acid of IPNV in the pooled tissues. Based on the present findings, it could be concluded that the absence of lesions consistent with infectious pancreatic necrosis (IPN) disease in the H&E‐stained sections cannot rule out the presence of the IPNV, and the use of an alternative rapid confirmatory method such as IHC with formalin‐fixed, paraffin‐embedded tissue sections is helpful for the final diagnosis of IPN in rainbow trout.     

Spatially distributed monthly reference evapotranspiration derived from the calibration of Thornthwaite equation: a case study, South of Iran

The Penman-Monteith equation is the most common method for estimating reference crop evapotranspiration (ET_o). Using this method reqiures many different meteorological data, yet few stations with adequate meteorological data may exist in a region. Setting up a station that records the required data for Penman-Monteith equation is expensive. Alternatively, the Thornthwaite equation is a simpler method for estimating ET_o since it is a temperature-based method. In this study, the Thornthwaite equation was spatially calibrated based on the Penman-Monteith method (as the standard and reference method to compute ET_o) for every month of the year, using the meteorologica data of seven synoptic weather stations in Fars province, and seven synoptic stations outside the Fars province. The Thornthwaite equation using effective temperature that has been introduced recently in other studies was used (Camargo et al. in Revista Brasileira de Agrometeorologica 7:251–257, 1999). For this purpose a calibration coefficient k must be determined. The results of the spatial and temporal calibration of the new approach using the Thornthwaite equation showed that for each station different k values should be used monthly. Generally, the k values fluctuated between 0.55 and 1.12, and the mean RMSE for all stations was less than 1 mm day⁻¹, which showed good and reliable agreement between the ET_o estimations obtained from the Penman-Monteith and calibrated Thornthwaite equations. Depending on the geographical location of each station, spatial distribution maps of monthly k values were created for the study area using the inverse distance weighting (IDW) interpolation method. It is therefore possible to estimate monthly ET_o using the appropriate k map and the Thornthwaite equation for different regions of study area instead of using the Penman-Monteith method. This case study showed that the same analysis might be used for the other parts of the country or any part of the world and would result in efficient scheduling of water resources for agriculture.     

Assessment of different wheat genotypes with altered genetic background in response to different salinity levels

This experiment was conducted in a glasshouse at the Agricultural and Natural Resources Research Center of Zarghan, Iran, in 2016. Sixteen wheat genotypes were compared under four salinity levels [control, 50, 100, and 150 mM sodium chloride (NaCl)] in terms of grain yield, chlorophyll (SPAD), flag leaf area, Na⁺/K⁺ ratio, catalase, and peroxidase activities in a randomized complete block design with three replications. Overall, results indicated that apparently no single parameter or a specific group of parameters could be suggested as factors of the most responsive element to different salinity stress levels. In other words, the tolerance mechanism of wheat genotypes is a complex response of multiple factors as a network path. Furthermore, different salinity levels led to different responses of wheat genotypes, which were detectable by the results of the mean comparison and analysis of variance. These results also proved the influential effects of the genetic background on salinity response and tolerance of wheat genotypes. In addition, antioxidants acting as defense barriers against reactive oxygen species are very important constituents against salinity, since higher antioxidant activity leads to alleviate the oxidative stress caused by salinity. Higher osmolyte concentration regulating the selective uptake of useful ions can prevent excess accumulation of toxic ions, which contribute to salinity stress damages. A high variation related to the measured traits in this study under both normal and salinity stress conditions was achieved, which could be applied in screening and breeding programs for salinity stress tolerance. Moreover, the responses of different genotypes varied regarding the different traits; SU-0129 as a novel genotype has proved to be the best choice for further breeding research based on the overall traits and, in particular, grain yield and tolerance stress index.     

Plant growth and fruit quality of two pepper cultivars under different potassium levels of nutrient solutions

Potassium (K) is a major nutrient element that has effects on growth, yield, and quality production of agricultural crops. In the present study, the effects of various K concentrations in a nutrient solution including 150, 235, 300, 400, or 500 mg K L^?1 were evaluated on two pepper cultivars; chili pepper (Capsicum annuum Avicolare) and bell pepper (California Wonder) under greenhouse conditions. Hoagland's formula was used for preparation of nutrient solutions. The vegetative growth parameters including plant height, leaf area, SPAD value, and shoot fresh weight were significantly increased by 300 mg L^?1 K in both cultivars. The highest yield and fruit quality parameters including fruit length/diameter ratio, fruit dry matter percentage, fruit vitamin C, total soluble solids, and titratable acidity in chili pepper and bell pepper were obtained under application of 300 and 400 mg K L^?1 in nutrient solution, respectively. In either cultivar there was increase in leaf K, nitrogen, and zinc concentrations, while in bell pepper calcium was reduced by higher K levels in the nutrient solution. The results indicate that for better growth and quality production of pepper, higher levels of K in nutrient solutions can be beneficial.     

Use of IR thermography in screening wheat (Triticum aestivum L.) cultivars for salt tolerance

Thermography is proposed to be an alternative non-destructive and rapid technique for the study and diagnosing of salt tolerance in plants. In a pot experiment, 30 cultivars of wheat (Triticum aestivum L.) were evaluated in terms of their leaf temperature and shoot growth and their ion distribution responses to NaCl salinity at two concentration levels: the control with electrical conductivity (EC) of 1 dS m^?1 and salinity treatment with EC of 16 dS m^?1 (150 mM). A completely randomized block design with factorial treatments was employed with three replications. The results indicated that thermography may accurately reflect the physiological status of salt-stressed wheat plants. The salt stress-based increase in leaf temperature of wheat cultivars grown at 150 mM NaCl reached 1.34°C compared to the control. According to the results obtained, it appears that thermography has the capability of discerning differences of salinity tolerance between the cultivars. Three salt-tolerant wheat cultivars, namely Roshan, Kharchia and Sholeh, had higher mean shoot dry matter (0.039 g plant^?1) and higher mean ratio of leaf K⁺/Na⁺ (14.06) and showed lower increase in the mean leaf temperature (0.37°C) by thermography compared to the control. This was while nine salt-sensitive cultivars, namely Kavir, Ghods, Atrak, Parsi, Bahar, Pishtaz, Falat, Gaspard and Tajan, had lower mean plant dry matter production (0.027 g plant^?1), lower mean ratio of K⁺/Na⁺ (9.49) and higher mean increases in leaf temperature (1.24°C).