In field non-invasive sensing of the nitrogen status in hybrid bermudagrass (Cynodon dactylon × C. transvaalensis Burtt Davy) by a fluorescence-based method

The level of N fertilization and the content of leaf N in Cynodon dactylon × C. transvaalensis Burtt Davy cv. ‘Tifway 419’ bermudagrass were evaluated non-destructively with a fluorescence-based method. It was applied directly into the field by using the Multiplex portable fluorimeter during two consecutive seasons (2010 and 2011). In the 2010 experiment, the nitrogen balance index (NBI₁) provided by the sensor was able to discriminate (at P < 0.05) six different N levels applied, up to 250 kg ha⁻¹, with a precision (root mean square error, RMSE) in the rate estimate of 3.29 kg ha⁻¹. In 2011, the index was insensitive to the N treatment between 150 kg ha⁻¹ and 250 kg ha⁻¹ N rates, and its precision was 39.98 kg ha⁻¹. Calibration of the sensor by using the destructive analysis of turf samplings showed a good linear regression between NBI₁ and the leaf N content for both 2010 (R² = 0.81) and 2011 (R² = 0.93) experiments. This allowed mapping of the leaf N spatial distribution acquired by the sensor in the field with a prediction error of 0.21%. Averaging the overall estimates of leaf N content per N treatment provided an upper limit of 200 kg ha⁻¹ for the required fertilization, corresponding to a critical level of leaf N of about 2.3%. Our results confirm the usefulness of the new fluorescence-based method and sensor for a precise management of fertilization in turfgrass.     

Effect of sustained deficit irrigation on physicochemical properties,bioactive compounds and postharvest life of pomegranate fruit (cv. ‘Mollar de Elche’)

In this study, the influence of sustained deficit irrigation (SDI; 32% of reference evapotranspiration (ET₀)) on physicochemical and sensory quality and bioactive compounds of pomegranates stored for 30, 60 and 90 days in air at 5 °C + 4 days at 15 °C, at each storage period, was studied and compared to a control (100% ET₀). Fruit from SDI had higher peel redness and greater firmness, soluble solids contents, vitamin C (27%), phloretin (98%) and protocatechuic acid (10%) levels, and total antioxidant capacity (TAC) (46%) than the control. Cold storage and shelf-life did not induce significant changes in soluble solids, pH, titratable acidity, and chroma and Hue. SDI fruit had retarded development of chilling injury (CI) symptoms, which appeared after 60 days of storage in comparison to 30 days in the controls. Anthocyanins, catechin, phloretin and protocatechuic, caffeic, p-coumaric and caffeic acids contents had greater increases in SDI fruit than in controls throughout the postharvest life. TAC was significantly (P < 0.05) correlated to anthocyanins, gallic acid and total vitamin C contents. Generally, after long term storage, the fruit grown under SDI showed higher sensory and nutritional quality, more health attributes and a longer shelf-life (up to 90 days at 5 °C + 4 at 15 °C) than fruit irrigated at 100% ET₀.     

Assessment of the origin of new citrus tetraploid hybrids (2<Emphasis Type="Italic">n</Emphasis> = 4x) by means of SSR markers and PCR based dosage effects

We report the accurate determination of the allelic configurations of a total of eight new citrus tetraploid hybrids by means of SSR analysis, coupled with capillary electrophoresis, and PCR based dosage effects. Tetraploid hybrids were spontaneously obtained from different interploid crosses (2x × 4x) between diploid ‘Femminello’ lemon and the allotetraploid somatic hybrid (2n = 4x = 36) ‘Key’ lime + ‘Valencia’ orange, and between diploid ‘Wilking’ and ‘Fortune’ mandarins and an autotetraploid ‘Dancy’ mandarin (2n = 4x = 36). To understand the opportunity to employ them in further backcross programs, the cytological mechanisms underlying their ploidy level were unambiguously determined using six SSR primers. PCR conditions were optimized and skewness in template/product ratios were verified. Tetraploid allelic configurations were determined from PCR based dosage effects using electropherogram peak heights to estimate the copy number per allele. In all the tetraploid hybrids we found out that diploginy (2n eggs) has occurred, contributing the extra haploid genome in the tetraploids. According to the marker genotypes, it was further inferred that the 2n eggs in ‘Femminello’ lemon resulted from first division restitution (FDR), while in ‘Wilking’ and ‘Fortune’ mandarins 2n eggs occurred in second division restitution (SDR). These new genotypes, with their improved genetic female background, can be therefore considered very valuable in our citrus genetic improvement program as pollen donors in backcrosses suitable to eliminate negative traits.