Response of leguminosae to cadmium exposure

Bush bean and pea plants grown in a sandy substrate and treated daily with nutrient solutions containing either 50 and 125 pM cadmium (Cd), added as cadmium nitrate [Cd(NO₃)2], were analyzed for dry matter production, total Cd content, and extractable Cd. Cadmium depressed dry matter production of both plant species. Bush bean plants accumulated larger amounts of Cd in tissues and displayed lower Cd tolerance than pea plants. The high accumulation of Cd in roots of bush bean does not seem to prevent Cd translocation. Pea plants show a higher exclusion capacity at the root level, suggesting that membrane selectivity rather than apoplastic compartmentation may act as a defence mechanism against Cd toxicity. Gel‐permeation chromatography and voltammetric analyses showed that part of water‐soluble Cd extracted from tissues of pea and bush bean was as free metal ion (Cd²⁺). In addition, Cd into the nutrient solution induced progressively the synthesis of water‐soluble proteins at low molecular weigth in tissues of both plant specie. In root extracts of pea and bush bean, Cd was also associated with “like‐protein”; fraction with apparent molecular weight >30 KDa.     

Phosphorus nutrition of white lupine grown on a Calciaquoll

Abstract

White lupine (Lupinus albus L.) and navy bean (Phaseolus vulgaris L.) are legumes with and without the proteoid root characteristic, respectively. The influence of P (0, 40, 80, and 120 mg/kg of NaH₂PO₄‐P) and source of nitrogen (N) [inoculation with Bradyrhizobium lupini or Rhizobium phaseoli vs. NH₄NO₃] on phosphorus (P) uptake by navy bean and white lupine grown on a Calciaquoll low in available P and N was studied under greenhouse conditions. Both species responded to P fertilizer, but P accumulation in navy bean tops was much greater than in white lupine. Inoculated white lupine plants accumulated more P than their NH₄NO₃‐treated counterparts. Growth and P uptake of 17‐day‐old flax (Linum usitatissium L.) plants grown in pots previously planted to white lupine, but not in their navy bean counterparts, was severely retarded. White lupine did not enhance the availability of soil P in the calcareous soil.     

Composition of Proteins Extracted from Two Species of Leguminous Bauhinia Grains

There is a growing demand for alternative protein sources for industrial applications. Bauhinia are underutilized protein‐rich oilseed legumes primarily grown as ornamental plants. In this study, the composition and structure of proteins extracted from two Bauhinia species, B. galpinii and B. petersiana, were determined in comparison with soya bean. Albumin and globulin (75%) were the major storage proteins of Bauhinia. Albumin content of B. galpinii was substantially high (28%), about twice those of soya and B. petersiana. Bauhinia grains were good sources of lysine (approximately 4 g/100 g of protein). By SDS‐PAGE, Bauhinia proteins showed three major protein bands ranging from 17,000 to 76,000 for both species. Only one subunit (17,000) of the basic glycinin (11S) seemed to be present in Bauhinia compared with soya. Bauhinia proteins had more β‐sheet conformation (42%) than α‐helix (22%). Bauhinia grains may provide a new opportunity of protein for industrial applications.     

The influence of phosphorus nutrition on the physiological response of moth bean genotypes to drought

Four genotypes of moth bean (Vigna aconitifolia Jacq. Marechal), including two early (RMO‐257 and CZM‐18) and two late flowering types (CAZRI moth‐1 and Jawala) were grown at two levels of phosphorus (0 and 40 kg ha^–1) and subjected to drought by withholding of water until wilting at the pre‐flowering stage in a pot trial. Drought significantly decreased plant water potential, relative water content, rate of net photosynthesis, contents of chlorophyll, starch, soluble protein, and nitrate reductase activity in all genotypes. The adverse effects of drought were less pronounced in early than in late flowering genotypes. Phosphorus application significantly ameliorated the negative effects of drought on above parameters, particularly in the late genotypes. We conclude that P addition to moth bean may be justified even in low‐rainfall years because of its ability to improve yield under water‐limited conditions.     

Productivity of mung bean and sesame grown on residual fertility in multiple cropping systems

Abstract

Field experiments were conducted on an Entisol from 1984 to 1987 at Bidhan Chandra Agricultural University, West Bengal, India, to study the residual effects of N, P, and K on productivity of mung bean (Vigna radiatus Roxb.) and sesame (Sesamum indicum L.) in irrigated multiple cropping with rice‐potato‐mung bean and rice‐potato‐sesame cropping systems. The crops were grown with or without application of farmyard manure or incorporation of crop residues. Different quantities of inorganic fertilizers based on locally recommended practices for fertilization were applied to rice and potato and their residual effects on succeeding mung bean or sesame crops were assessed. Application of fertilizers at a higher rate than the recommended amounts to rice and potato in the system showed no significant residual effect on yields of succeeding mung bean or sesame compared to the yields obtained with the application of N, P, and K at 100% of the recommended rate or 75% of the recommended rate with manure or residues. Any reduction in the application of recommended amounts of fertilizers to rice or potato without compensating amounts coming from other organic sources resulted in lower productivity of succeeding mung bean and sesame.     

Protein synthesis in green beans under salt stress conditions

Salinity is a major agricultural problem in arid and semi‐arid regions, resulting in retarded plant growth and reduced crop yield. The purpose of this study was to evaluate the effects of NaCl stress on nitrogen metabolism and protein synthesis in three varieties of green beans, and to select the most salt tolerant and suitable cultivar among the three for cultural practices. To achieve this goal, protein synthesis and protein‐¹⁵N content of three green bean cultivars (Phasedus vulgaris L., cv. ‘Tender Improved’, ‘Slim Green’, and ‘Kentucky Wonder') were compared. This comparison was done by using ¹⁵N under three different NaCl salinity levels (Control = 0.3, 2.5, and 5.0 bars osmotic pressures), in Hoagland nutrient solution, in a growth chamber. The 7‐day‐old bean seedlings were grown for 7 additional days in complete Hoagland solution before and 7 days after the completion of salinization with NaCl. This was followed by a 15‐day ¹⁵N uptake period after ^1SNH₄ ¹⁵NO₃ addition to the culture solutions. Plant tissues were analyzed for crude protein and protein‐N (total and ¹⁵N) content. The crude protein and protein‐N (total and ¹⁵N) content of plants decreased with increased salinity for all three cultivars, however, the Tender Improved variety was the least severely affected by salinity among the three cultivars. Total crude protein and protein‐N content were substantially higher for shoots than for the roots. Nevertheless, shoots were more severely influenced than roots by salt stress when salinized plants were compared with the controls for each plant part. The adverse effect of salinity on protein synthesis was more severe at the highest (5.0 bars osmotic pressure) level of stress. Based on the results of this study, for growing conditions similar to this experiment, the Tender Improved cultivar appears the most salt tolerant and suitable among these three for cultural practices.     

Differential responses of soybean and dry bean to zinc deficiency 1

Whether a legume obtains its nitrogen (N) from the air, through dinitrogen fixation, or from the soil, as nitrate (NO₃), may influence its susceptibility to zinc (Zn) deficiency. The influence of N source [potassium nitrate (KNO₃)+ native soil N versus rhizobium‐inoculated seed + native soil N] and phosphorus (P) (0 and 200 mg P/kg), and Zn fertilizers (0, 1, and 8 mg Zn/kg) on growth and nutrient composition of soybean (Glycine max L. cv. McCall) and navy bean (Phaseolus vulgaris L. cv. Seafarer) grown on a calcareous soil were studied under greenhouse conditions. Inoculated plants, but not their KNO₃‐treated counterparts, had root nodules. However, due to N deficiency resulting from suboptimal N fixation, growth of these inoculated plants, especially of navy bean, was poorer than that of similarly treated KNO₃‐fed plants. As a consequence of this restricted growth, responses to P and Zn fertilizers were generally greater in KNO₃‐treated plants. Added P decreased the yield of KNO₃‐treated navy bean in the absence of added Zn, but P‐induced Zn deficiency had little effect on the growth of similarly treated inoculated plants. Plant excess bases (EB)/total plant N ratios [EB = 1/2 Ca + l/2Mg + Na + K ‐ Cl ‐ total S (S = divalent) ‐ total P (P = monovalent)] were less in KNO₃‐treated soybean than in correspondingly treated navy bean. Therefore, rhizosphere pH values around navy bean roots were probably less than those around soybean roots. Despite the hypothesized lower rhizosphere pH values, KNO₃‐treated navy bean was more susceptible to Zn deficiency than soybean. This greater susceptibility of navy bean to Zn deficiency was apparently at least partly due to poor translocation of Zn from the roots to the tops.     

Protein synthesis in green‐beans under salt stress with two nitrogen sources

Nitrogen metabolism and protein synthesis in plants are severely affected by salt stress, resulting in abnormal plant growth and lower crop yield. The purpose of this investigation was to compare protein synthesis in three green bean (Phaseolus vulgaris L.) cultivars ('Tender Improved’, ‘Slim Green’, and ‘Kentucky Wonder') under normal (non‐saline) and salt stress with two sources of nitrogen (ammonium‐¹⁵N and nitrate‐¹⁵N separately). This comparison was achieved by using ¹⁵N under normal (control = 0.3 bars osmotic pressure) and NaCl stress (3.0 bars osmotic pressure), in Hoagland nutrient solution, in a growth chamber. The 5‐day‐old green bean seedlings were grown for 5 additional days in one‐half strength Hoagland solution before and 5 days after the completion of salinization with NaCl. This was followed by a 15‐day ¹⁵N uptake period after either (¹⁵NH₄)₂SO₄ or K¹⁵N0₃ addition to the culture solutions for the ammonium‐¹⁵N or nitrate‐¹⁵N treatments, respectively. Plant tissues were analyzed for the crude protein and protein‐N (total and ¹⁵N) contents. The crude protein and protein‐N (total and ¹⁵N) content of all cultivars significantly decreased under stress conditions for both sources of nitrogen. However, the Tender Improved appeared the least and the Slim Green the most severely affected by salinity among the three cultivars. For all cultivars at each harvest, shoots were more adversely influenced than roots by salt stress when comparing the salinized plants with the controls for each plant part for either source of ¹⁵N. The control (non‐salinized) plants contained substantially higher crude protein and protein‐N (total and ¹⁵N) when treated with NO₃‐N as compared with NH₄‐N source of ¹⁵N.     

Nodulation and root growth increase in lower soil layers of water‐limited faba bean intercropped with wheat

Below‐ground niche complementarity in legume–cereal intercrops may improve resource use efficiency and root adaptability to environmental constraints. However, the effect of water limitation on legume rooting and nodulation patterns in intercropping is poorly understood. To advance our knowledge of mechanisms involved in water‐limitation response, faba bean (Vicia faba L.) and wheat (Triticum aestivum L.) were grown as mono‐ and intercrops in soil‐filled plexiglass rhizoboxes under water sufficiency (80% of water‐holding capacity) and water limitation (30% of water‐holding capacity). We examined whether intercropping facilitates below‐ground niche complementarity under water limitation via interspecific root stratification coupled with modified nodulation patterns. While no significant treatment effects were measured in intercropped wheat growth parameters, water limitation induced a decrease in shoot and root biomass of monocropped wheat. Likewise, shoot biomass and height, and root length of monocropped faba bean significantly decreased under water limitation. Conversely, water limitation stimulated root biomass of intercropped faba bean in the lower soil layer (15–30 cm soil depth). Similarly, total nodule number of faba bean roots as well as nodule number in the lower soil layer increased under intercropping regardless of water availability. Under water limitation, intercropping also led to a significant increased nodule biomass (48%) in the lower soil layer as compared to monocropping. The enhanced nodulation in the lower soil layer and the associated increase in root and shoot growth provides evidence for a shift in niche occupancy when intercropped with wheat, which improves water‐limited faba bean performance.     

Nodulation and N2 fixation of faba bean (Vicia faba L.) after soil amendment with crop residues

The effect of prior soil amendment with different N sources at 50 mg N (kg soil)^—1 on nodulation and N₂ fixation of faba bean (Vicia faba L. cv. Troy) using wheat (Triticum aestivum L. cv. Star) as reference crop was assessed in a pot experiment. Four treatments viz legume manure (LEGM) as clover shoots, cereal manure (CEREM) as barley straw, N fertilizer (FERT‐N) as Ca(NO₃)₂, and no‐manure control (NOMAN) were investigated consecutively at 45, 70, and 90 days after sowing (DAS). Faba bean nodulated profusely, with an increase on average from 629 nodules per pot at 45 DAS to nearly 2.3‐ and 3.3‐fold at 70 and 90 DAS, respectively. Low nodule numbers and nodule dry matter occurred under FERT‐N and CEREM, whereas high values were found for NOMAN and LEGM. Soil amendment affected percent N₂ fixation in relation to N source and plant age. Highest percent N₂ fixation (≥ 90 %) was found under the lowest N‐supplying amendments, no‐manure, and cereal manure, respectively. FERT‐N depressed N₂ fixation particularly at 45 DAS when N₂ fixation was reduced to as low as 23 %. The rise in N₂ fixation thereafter suggests that faba bean adjusted after depletion of mineral N in the soil. N₂ fixation was also decreased after cereal straw application, even though N concentration in faba bean plants was high. The results indicate that plant residues, both with high and low N concentration, applied to soil to raise its fertility may interfere with N₂ fixation of faba bean.     

Effects of Kocide 101® on the bean (Phaseolus vulgaris L.)‐Rhizobium symbiosis

A glasshouse study was undertaken to investigate the effects of the copper fungicide Kocide 101 and its residues in soil on the growth, nodulation and nitrogen fixation of beans (Phaseolus vulgaris L.). The soil used was a sandy clay loam classified as Typic Rhodustalf. The bean variety SUA 90 was used as test crop. The bean rhizobia strains CIAT 899, PV, and a local isolate were used. Kocide 101 applied at the recommended rate (equivalent to 1.7 mg kg^‐1 soil) had no significant negative effects on the growth, nodulation or nitrogen fixation of bean plants. Higher levels of Kocide 101 significantly (P < 0.05) reduced plant growth, nodulation and nitrogen fixation. The bean plants inoculated with the “local isolate”; rhizobia had the highest dry matter weights, nodule numbers and nodule dry weights, and also had more N fixation. They were followed by those inoculated with the PV, strain and, lastly, those inoculated with CIAT 899. The growth and nodulation of bean plants were still curtailed by the Kocide 101 residues four months after the fungicide was first applied to the soil. Therefore, occurrence of high levels of Kocide 101 in soils can have long‐term effects on the performance of the bean‐rhizobia symbiosis.     

Changes in soil nitrogen,phosphorus, and potassium under intensive cropping in sub‐humid tropics of India

Abstract

Efficient soil fertility management is essential for sustained production of high crop yields. Field experiments were conducted on an Entisol soil during 1984 to 1987 at Bidhan Chandra Agricultural University, West Bengal, India, to study the changes in soil N, P, and K in sub‐humid tropics under irrigated intensive cropping in rice‐potato‐mung bean (Oryza sativa L.‐ Solanum tuberosum L.‐ Vigna radiatus Roxb.) and rice‐potato‐sesame (O. sativa L.‐ S. tuberosum L.‐ Sesamum indicum L.) cropping sequences. The crops were grown with or without application of farmyard manure and with or without incorporation of crop residues. Different quantities of inorganic fertilizers based on locally recommended practices for fertilization were applied to rice and potato, and their residual effects on succeeding mung bean or sesame crops were assessed. At the end of experimentation, the total N status of soil improved more under the rice‐potato‐mung bean sequence than under the rice‐potato‐sesame sequence. The available phosphorus status of soil showed a positive balance in both sequences except in the treatment receiving 50% of the recommended amounts of N, P, and K. A reduction in the recommended fertilization without a compensating application of manure or crop residues resulted in the depletion of soil‐available K. All treatments reduced nonexchangeable K, and depletion was low wherever manure or crop residues were added into the cropping system. Integration of inorganic fertilizers with organic fertilizers, such as manure or crop residues, maintained soil N, P, and K under intensive agriculture and sustained soil productivity.     

Proton toxicity interferes with the screening of common bean (Phaseolus vulgaris L.) genotypes for aluminium resistance in nutrient solution

Common bean (Phaseolus vulgaris L.) proved to be very sensitive of low pH (4.3), with large genotypic differences in proton sensitivity. Therefore, proton toxicity did not allow the screening of common bean genotypes for aluminium (Al) resistance using the established protocol for maize (0.5 mM CaCl₂, 8 μM H₃BO₃, pH 4.3). Increasing the pH to 4.5, the Ca²⁺ concentration to 5 mM, and addition of 0.5 mM KCl fully prevented proton toxicity in 28 tested genotypes and allowed to identify differences in Al resistance using the inhibition of root elongation by 20 μM Al supply for 36 h as parameter of Al injury. As in maize, Al treatment induced callose formation in root apices of common bean. Aluminium‐induced callose formation well reflected the effect of Ca supply on Al sensitivity as revealed by root‐growth inhibition. Aluminum‐induced callose formation in root apices of 28 bean genotypes differing in Al resistance after 36 h Al treatment was positively correlated to Al‐induced inhibition of root elongation and Al contents in the root apices. However, the relationship was less close than previously reported for maize. Also, after 12 h Al treatment, callose formation and Al contents in root apices did not reflect differences in Al resistance between two contrasting genotypes, indicating a different mode of the expression of Al toxicity and regulation of Al resistance in common bean than in maize.     

Can tropical grasses grown as cover crops improve soil phosphorus availability?

Tropical grasses grown as cover crops can mobilize phosphorus (P) in soil and have been suggested as a tool to increase soil P cycling and bioavailability. The objective of this study was to evaluate the effect of tropical grasses on soil P dynamics, lability, desorption kinetics and bioavailability to soya bean, specifically to test the hypothesis that introducing grass species in the cropping system may affect soil P availability and soya bean development according to soil P concentration. Three grass species, ruzi grass (Urochloa ruziziensis ), palisade grass (Urochloa brizantha ) and Guinea grass (Megathyrsus maximus ), were grown in soils with contrasting P status. Soya bean was grown after grasses to assess soil P bioavailability. Hedley P fractionation, microbial biomass P, phytase‐labile P and the diffusive gradient in thin films were determined, before and after cultivation. It was found that grasses remobilized soil P, reducing the concentration of recalcitrant P forms. The effect of grasses on changing the P desorption kinetics parameters did not directly explain the observed variation on P bioavailability to soya bean. Grasses and microorganisms solubilize recalcitrant organic P (P_o) forms and tropical grasses grown as cover crops increased P bioavailability to soya bean mainly due to the supply of P by decomposition of grass residues in low‐P soil. However, no clear advantages in soya bean P nutrition were observed when in rotation with these grasses in high‐P soil. This study indicates that further advantages in soya bean P nutrition after tropical grasses may be impeded by phytate, which is not readily available to plants.     

Analysis of dry matter and protein contents in fresh yam bean tubers by near‐infrared reflectance spectroscopy

Abstract

Fast screening methods are needed for plant breeding. The objective of this research was to evaluate the potential of near‐infrared reflectance spectroscopy (NIRS) for the simultaneous analysis of dry matter and protein contents in intact discs of fresh yam bean (Pachyrhizus spp.) tubers. Discs from 210 tubers were extracted with a punch few hours after harvesting and scanned by NIRS using a specially designed adapter. External validation revealed a close relationship between NIRS and reference methods for dry matter content (r²=0.94; standard error of performance, SEP=1.2%) and protein content (r²=0.87; SEP=1.94%). The calibration for protein content was compared with another one developed using dried‐ground tuber samples (r²=0.97; SEP=0.97%). These results suggested that NIRS can be used to determine dry matter and protein contents in fresh tuber samples of yam beans with acceptable accuracy. Further research will have to determine if additional traits can be incorporated into this scheme.     

Rice and common bean growth and nutrient concentration as influenced by aluminum on an acid lowland soil

Aluminum (Al) toxicity is a major limiting factor for crop production in many acid soils in Brazil. Two greenhouse experiments were conducted to evaluate response of rice (Oryza saliva L.) and common bean (Phaseolus vulgaris L.) to Al levels on a Low Humic Gley acid soil. The Al levels created by liming were: 0,0.03, 0.10, 0.23, 1.03, and 3.83 cmol_c kg^‐1 of soil. Rice dry matter and grain yield were significantly improved (P<0.05) with increasing Al levels in the soil solution. However, common bean dry matter as well as grain yield were significantly (P<0.01) decreased with increasing Al levels. At 3.83 cmol_c Al kg^‐1 of soil, bean did not produce any dry matter or grain yield. On an average, Al decreased nutrient concentrations in the tops of rice plant except zinc (Zn) and manganese (Mn), but in bean crop almost all the nutrients concentrations were increased with increasing Al levels. Rice showed tolerance to Al toxicity, whereas, common bean was susceptible to toxicity of this element. For successful intensive crops production lime application will be necessary in Varzea soils especially for legume production.     

Soil property differences among high‐ and average‐yielding soya bean areas in Arkansas,USA

Soya bean [Glycine max (L.) Merr] yields >6719 kg/ha (100 bu/ac) have only recently and infrequently been achieved. Quantifying soil property differences between high‐ and average‐yielding areas can help to further identify non‐plant‐related properties contributing to soya bean yield potential. The objective of this study was to evaluate the effects of region and soil depth on soil property differences between high‐ and average‐yielding areas. In each of the seven regions of the ‘Grow for the Green’ yield contest in Arkansas, prior to or just after harvest in 2014 and 2015, soil samples were collected from the top 20 cm of one contest high‐yield (HY ) area that was in close proximity to an average‐yield (AY ) area. Across all regions and both years, soya bean yields differed (P  <  0.05) between yield areas, averaging 4701 and 5498 kg/ha in AY and HY areas, respectively. Averaged across soil depth and years, numerous soil properties differed (P  <  0.05) between HY and AY areas within at least one of seven regions. Total soil C content was at least 20.2% greater in the HY than in the AY area in three of seven regions. Extractable soil P content was, on average, 19.4 kg/ha greater in HY than in AY areas in three of the seven regions. Results from this study have the potential to help producers better understand soil properties that contribute to or hinder achieving ultra‐high (>6719 kg/ha) soya bean yields.     

Micronutrient composition of field‐grown dry bean and wheat inoculated with Azospirillum and Trichoderma

Micronutrient deficiency and malnutrition in humans are severe problems in many developing countries, particularly in areas with calcareous soils. There is almost no information on whether inoculation with plant growth–promoting Azospirillum and/or Trichoderma can help to reduce this problem by increasing the mineral concentration of the seeds. Field experiments were conducted in Tokat (Turkey) in 2001–2002 to determine whether inoculation with Azospirillum brasilense, Trichoderma harzianum, sole or in combination, and/or the application of P fertilizers can enhance micronutrient concentrations of field‐grown bean (Phaseolus vulgaris) and wheat (Triticum aestivum). In beans, Azospirillum inoculation combined with P fertilization significantly (p < 0.05) increased seed concentrations of Mn, Zn, and Cu, from 8.8, 22.6, and 7.0 mg kg^–1 in the control to 10.3, 28.3, and 11.0 mg kg^–1, respectively. Trichoderma inoculation alone significantly (p < 0.05) reduced the concentrations of Fe, Mn, Zn, and Cu and the cumulative plant uptake of Fe and Zn in 45‐day‐old bean plants. However, it significantly (p < 0.05) increased bean‐seed Cu content and accumulation. The double inoculation resulted in significantly (p < 0.05) higher micronutrient concentrations than Trichoderma inoculation alone in 45‐day‐old plants. In contrast to beans, the effects of microbial inoculations were less in wheat. However, dual inoculation significantly (p < 0.05) increased Zn content by 45% and Zn accumulation by 40% above the uninoculated control. Inoculation with plant growth–promoting microorganisms appears to be a promising strategy to combat micronutrient deficiencies.     

Contribution of Nitrogen Fixed by Mung Bean to the Following Wheat Crop

Crop rotation is a supportive management practice in which legumes greatly improve the growth and yield of subsequent cereal crops, particularly wheat. In this study, effects of mung bean (Vigna radiata)?? on the yield and quality of grains of following wheat crop were determined. An experiment was carried out with two sets of wheat (Triticum aestivum) crops: one grown following mung bean (Vigna radiata) crop and the other grown after a fallow period. Concentrations of macronutrients, sugar, protein, amino acids, and phytohormones of wheat were determined. The grain protein concentration of wheat was improved if cultivated after mung bean, and nitrogen and other macronutrients of wheat were increased significantly. In case of phytohormone contents in the wheat crop, abscisic acid concentration showed no change, but the concentrations of gibberellin increased significantly by 41% and indole acetic acid by 30% as a result of crop rotation. Sugar content in wheat cultivated after mung bean BRM-318 showed 10% increase and wheat protein content increased by 17% and 20%, respectively. The present study demonstrated that crop rotation simulated yield and improved the nutritional value of wheat grain compared to wheat which followed the fallow period.     

Field‐Based screening methodology to improve tolerance of common bean to low‐P soils

Abstract

Phosphorus (P) limits common bean (Phaseolus vulgaris L.) production throughout sub‐Saharan Africa, where P fertilizer is not affordable to the vast majority of smallholder farmers. Genetic differences in bean performance in low‐P soils suggest that low P tolerance could be improved. Earlier breeding efforts have not been successful, in part due to the challenges of selecting genotypes with improved performance in a heterogeneous soil environment. A field based screening method for low P tolerance has been developed, based on evaluating soil status and ameliorating edaphic compounding factors. The soil is classified as an Oxic Haplustalf and is representative of the unimodal, mid‐to‐high altitude bean growing regions of Southern Africa. The soil has very low zinc (Zn) and nitrogen (N) contents, which reduced growth markedly. After amelioration of these edaphic complications, P response could be quantified. A promising genotype CAL 143 was selected which consistently expressed, over two growing seasons, low P tolerance and high yield responsiveness to moderate fertilizer P application.