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  • Author or Editor: A. Marani x
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Abstract

Roselle (Hibiscus sabdariffa L.) is an annual herbaceous subshrub believed to be indigenous from India to Malaysia (2). It is a short-day plant (1), and when grown at the latitude of Israel (32°N), the earliest possible date of flower initiation is 5 Aug. Preliminary studies have indicated that vegetative and reproductive growth ceases in autumn (5), which may be due to exposure to low night temperatures. The objective of this study was to determine the sensitivity of roselle to chilling at different growth stages.

Open Access

Salt tolerance of 59 cultigens of tomato (Lycopersicon esculentum Mill.), seven wild Lycopersicon accessions (acc.), and one interspecific hybrid was studied under arid field conditions. Evaluation of salt tolerance was based on relative total dry matter (RD) and relative total yield (RY), calculated as the ratio between performances of salinetreated and control plants. The tomato cultigens were irrigated with water having electrical conductivities (ECi) of 1.5 (control), 5, 10, or 15 dS·m−1. Considerable variation in salt tolerance was found among the cultigens, but at 15 dS·m−1 all showed reduced RD and RY (<0.6). The cultivar M82-1-8 (M82), one accession of L. cheesmanii (Lc), three accessions of L. pennellii (Lpen), three of L. peruvianum (Lper), and an interspecific F1 hybrid (M82 × Lpen acc. LA-716) were examined for RD at three salinity levels, ECi = 1.5, 10, and 20 dS·m−1, in three annual trials. The salt tolerance of Lpen and Lper were higher than those of M82 and Lc; the interspecific F1 was the most tolerant and was usually unaffected by even the highest salinity level. The results of this study indicate the existence of a genetic potential for high salt tolerance in wild Lycopersicon germplasm.

Free access

Abstract

A computer program was developed for predicting the times of emergence, flowering, turning stage, and harvesting of processing tomatoes. The program was validated and calibrated by using 1972-1980 tomato data from 44 fields at 2 locations in Israel. Predictions are based on accumulation of heat units defined in terms of “physiological days”, where 1 physiological day is equivalent to a calendar day with a constant temperature of 26°C. The growing season was divided into 4 stages: from sowing to emergence, from emergence to flowering, from flowering to turning stage, and from turning stage to harvesting. Accumulation of physiological days during the first 2 stages is based on a linear function. During the last 2 stages, a quadratic function is used to calculate daytime heat units wherever the daily average temperature is above 20°. The maximum rate of development is at 26°. In the last stage, soil stress index also is taken into account. Use of the model makes it possible to predict the day of harvest with a precision of ±3 days, as compared with ±9 days when a daily mean systems is employed.

Open Access

Accessions of four tomato species, Lycopersicon esculentum Mill. (Le), L. pennellii (Corr.) O'Arey (Lpen), L. cheesmanii Riley (Lc), and L. peruvianum (L.) Mill., (Lper), and interspecific populations were irrigated with saline water under field conditions and concentrations of Na, K, Cl, Ca, and Mg in leaves and stems were determined. Potassium: sodium ratios in leaves and stems of salt-tolerant genotypes were higher under salinity and were moderately changed by salinity compared to the sensitive genotypes. In the tolerant wild accessions and F1(Le × Lpen), Cl concentrations in leaves and the ratio between Cl in leaves to Cl in stems were lower than in the sensitive Le cultivar. Regulation of the K: Na ratio was found in tolerant wild accessions and tolerant Le cultivars, while regulation of Cl concentration in leaves was found only in the wild germplasm. The effects of ion concentrations on dry matter of interspecific segregating populations, F2(Le × Lpen) and BC1(Le × (Le × Lpen)), were studied by regression analyses. Dry matter was positively correlated with the K: Na ratio in stems and negatively correlated with the Cl concentrations in leaves and stems, thus confirming the results obtained by comparison between the tolerant and sensitive accessions.

Free access