African Crop Science Journal, Vol. 9. No. 2, pp. 393-400
Calcium tolerance and ion uptake of Egyptian lupin landraces on calcareous soils
S. Raza, A. Abdel-Wahab1, B. Jørnsgård and J. L.
(Received 23 February, 2000; accepted 20 September, 2000)
Code Number: CS01021
White lupin (Lupinus albus L.) is a calcifuge susceptible to iron chlorosis making it grow poorly on calcareous soils (Tang et al., 1995b). In general cultivation is only possible on acid to neutral soils with moderate calcium content. This has been a major constraint to development of the lupin crop in Europe (Duthion, 1992; Siddons et al.,1994), and Australia (Tang et al.,1995a). The growth reduction may be caused by several factors such as high pH, high bicarbonate content, Fe deficiency or Ca toxicity. Thus, both root and shoot growth (Tang and Thomson, 1996) were reduced in L. albus at pH 7.5 compared to 6.0. Also the nodulation was negatively affected by increasing pH above 6.0 (Tang and Robson, 1993). The poor growth may also be caused by iron deficiency related to low uptake on alkaline soil (White and Robson, 1989). The severity of iron chlorosis correlates, however, poorly with shoot growth and seed yield in the field (Tang et al., 1995b), especially for plants showing iron chlorosis at early growth stages (White and Robson, 1989; Tang et al., 1995b).
The cause of poor growth in alkaline soil may also be Ca toxicity. Thus, Duthion (1992) showed that plant growth was related to the CaCO3 level but not to extractable Fe or soil pH. Similarly, Jessop et al. (1990) found that the weight of shoot and roots decreased when the concentration of calcium in the soil increased. De Silva et al. (1994) has explained the adverse effect of high soil Ca found in L. luteus as a result of uncontrolled Ca uptake resulting in poor growth and reduced CO2 uptake, but it is not known if a similar mechanism exists in L. albus. Because of its susceptibility to calcareous soils white lupin is generally not grown on soils with a pH above 7.5. However, white lupin is an ancient crop in Egyptian agriculture, where soils generally have a high calcium content with pH ranging from 7.4 to 9.0 (Raza et al., 1999). It could therefore be anticipated that germplasm of lupin adapted by Egyptian farmers would present a source of calcium tolerant genotypes. A collection of Egyptian landraces was undertaken in 1996 (Christiansen et al., 1999). The main objective of the present experiment was to screen this collection to identify potential tolerant accessions and access the effect of a high content of calcium on growth and ion uptake in white lupin.
MATERIALS AND METHODS
Field experiment. A collection of 92 landraces of white lupin from Egypt (Raza et al., 1999), six lines from Australia and the Egyptian cultivars Giza 1 and Giza 2 (Table 1), developed by The Agricultural Research Centre, Egypt about 30 years ago (Anon., 1994) were tested in a triple lattice design in Nubaria (West Delta). This location has a calcareous soil (20-26 % CaCO3). Eight randomly selected soil samples from the experimental plot were analysed for chemical and physical characteristics (Table 2). The experiment was sown on 22 November 1997. Each plot was composed of two rows of 3 m with inter-row spacing of 0.6 m (i.e., plot size 3.6 m2). Seeds were sown in hills 15 cm apart with 2 seeds per hill. Basal doses of N, P and K were added at a rate of 30 kg of N (as urea 46%N), 60 kg of P (15.5% P2O5) and 40 kg of K (48% K2O). The experiment was irrigated twice. The first irrigation took place immediately after sowing and the second just before flowering. Harvest took place at full maturity. Ion uptake of N, Fe, Mn and Ca were determined 60 days after sowing in five tolerant and five susceptible accessions among the 43 surviving accessions. N content was measured by the micro-Kjeldahl method using acid digest of sulphuric-perchloric solution, (Eastin, 1978; Page, 1982). Fe, Mn and Ca were measured by atomic absorption spectrophotometer using ascorbic acid extraction (Watanabe and Olsen, 1965). Analysis were based on a sample of five plants from each replication. At harvest 5 plants in each plot were taken at random to record plant height, number of branches per plant, number of pods per plant, number of seeds per plant, and seed weight per plant. Seed yield per plot was also recorded.
Glasshouse experiment. Three tolerant accessions from the previous experiment (Giza 1, accession 1 and 24) and three French varieties (CH30470, La625 and Lublanch) were grown in pots at nine different levels of calcium (0, 3, 5, 7, 10, 13, 15, 17 and 20% CaCO3). The calcium level was adjusted by adding CaCO3 to a sandy loamy soil. Seeds were inoculated with a suspension of Bradyrhizobium (Lupin). Irrigation from below was done to maintain 100% water holding capacity. Chlorosis was recorded on a 1-5 scale described by White and Robson (1989). Plants were harvested at flowering stage, 70 days after planting. Dry weight of the biomass as well as nodule number were recorded.
Statistical design and analysis. The field experiment was planted in a triple (10x10) lattice design and the pot experiment was laid in a randomised complete block design with three replicates. The proc LATTICE and the proc GLM procedures, respectively were used in the statistical analysis of the SAS (1988) programme.
RESULTS AND DISCUSSION
Field experiment. Germination for all accessions in the trial were successful, but 57 of the 100 accessions died within three weeks after planting. The surviving 43 accessions, all landraces, developed well indicating superior tolerance to calcareous soil conditions (Table 3). Some accessions, however, showed symptoms of iron chlorosis. The trial error in the experiment was rather high and the lattice design was only slightly more efficient (103.4 % - 106.9 %) than the randomised complete block design in the combined analyses.
There were significant differences (P<0.001) among genotypes for plant height and number of branches. The highest plants were obtained from the most tolerant accession, and these also produced the highest number of branches. Thus, the most tolerant accession, accession number 1, was 58.6 cm tall with 4 branches per plant and the most susceptible, accession number 40 only 19.9 cm tall with 1 branch (Table 3).
The results of the yield components analysis is presented in Table 3. There was a significant variation in grain yield of the surviving accessions varying from 1124 kg ha-1 for accession 1 to 105 kg ha-1 for accession 40 (Table 3). Seed number per pod varied from 4 to 1 and pod number per plant from 15 to 1. Variation in seed yield varied from 15 to 2.6 grams per plant. Plant height and branch number affected the yield components significantly (P<0.001). The highest seed yield per plant was obtained from the plants with the highest pod number per plant. The ranking of accessions based on the yield component analysis was in good agreement with yields from the whole plot harvest (Table 3). Giza 1 and Giza 2, the two local varieties were tolerant compared to the 57 non surviving accessions and varieties, but results show that a number of the collected landraces were better adapted to the newly reclaimed area with high soil calcium.
Ion concentration and uptake. Table 5 reveals a significant difference in the uptake of N between landraces. The highest N concentration was recorded in accessions with the largest values of dry weight (Table 4).
The ranking in dry weight was similar to that of plant height. Results suggest a better nitrogen fixation in the calcium tolerant accessions. The susceptible accessions had the highest Ca concentration in the tissues, ranging from 26 mg g-1 plant-1 in the most susceptible accession (number 40) to 11 mg g-1 plant-1 in the resistant accessions number 1 and 23 (Table 4). The results indicate that susceptible accessions had an uncontrolled uptake of Ca as earlier found in L. luteus ( De Silva et al., 1994). There was a non significant variation in the uptake of Fe (1.8-2.5 mg g-1 plant-1) and Mn (0.3-0.8 mg g-1 plant-1), but the rather high concentrations of both elements may be explained by activity of proteoid roots (George et al., 1997). The high Fe concentration also in the most susceptible accessions suggests that tolerance is not caused by low Fe uptake but may be related to translocation in the plant (White and Robson, 1989).
Glasshouse experiment. The data show a large variation in chlorosis. Scores ranged from 0 (leaves green) in tolerant accessions to 5.0 (leaves bright yellow) in susceptible lines. Accessions from Egypt were the most resistant to chlorosis compared to the French varieties (Fig. 1a). In the French varieties chlorosis sensitivity was closely related to the Ca content in the soil. Nodulation were significantly reduced with increasing Ca content in the soil, strongest for the sensitive French varieties( Fig. 1c). Biomass production for the Egyptian accessions tended to be higher than for the French varieties, especially for Giza 1 ( Fig. 1b). The reaction of the tolerant Egyptian accessions compared to the French varieties confirms the results from the field experiment that calcium tolerant genotypes are available among local landraces.
From the current field and glasshouse experiments it can be concluded that material tolerant to alkaline soil conditions is available in Egyptian landraces. These tolerant accessions can provide a basis for breeding new lupin varieties for new reclaimed areas in Egypt as well as for other parts of the world, where lupin has not yet been adopted due to high soil calcium content. The mechanisms behind the calcium tolerance is still unclear, but a reduced Ca uptake in tolerant plants may play a role. In view of the large trial error found in the field experiment a reliable laboratory test to identify tolerant material should be developed for screening in breeding programmes.
Germplasm collection of the Egyptian accessions was carried out as part of a joint research project between the Agricultural Research Centre (ARC) in Egypt and the Royal Veterinary and Agricultural University (KVL), Denmark, with financial support from the Danish International Development Assistance (Danida).
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