Bean yellow disorder virus: Parameters of transmission by Bemisia tabaci and host plant range

Abstract Bean yellow disorder virus (BnYDV) was recently identified as the first crinivirus (family Closteroviridae) that infects members of the family Leguminosae. It was first observed during the autumn of 2003, causing heavy losses in French bean (Phaseolus vulgaris L.) grown commercially in Spain. The virus is transmitted by the sweetpotato whitefly, Bemisia tabaci (Hemiptera: Aleyrodidae) Q‐biotype, and disease symptoms resemble nutritional disorders consisting of interveinal mottling and yellowing in leaves, combined with stiffness or brittleness, and are typically produced on the middle to lower parts of the plant. Transmission experiments showed that 50% and 100% of B. tabaci adults acquired the virus after a feeding period of 3 and 7 h, respectively. Viruliferous whiteflies infected 66% and 100% of P. vulgaris plants after a feeding period of 12 and 24 h, respectively. The transmission efficiency of single whiteflies was 37% and persistence of BnYDV in the vector lasted up to 2 weeks with a half‐life of 9 days. BnYDV was transmitted to P. vulgaris, Pisum sativum L., Lens culinaris Medik., and Vicia faba L., but not to Vigna unguiculata L., Glycine max (L.) Merr., Cicer arietum L., and to crop species belonging to families of the Solanaceae and Cucurbitaceae. No virus was detected in field samples collected from 30 different species from Boraginaceae, Asteraceae, Geraniaceae, Lamiaceae, Leguminosae, Malvaceae, Scrophulariaceae, Thymelaeaceae and Verbenaceae. The restricted host range and efficient management of crops regarding whitefly infestation may be key elements in the control of BnYDV.     

Polyclonal Antibodies to the Bacterially Expressed Coat Protein of Faba Bean Necrotic Yellows Virus

Specific rabbit polyclonal antibodies against bacterially expressed coat protein of Faba bean necrotic yellows virus (FBNYV, genus Nanovirus) were produced using a recombinant DNA approach. The FBNYV capsid protein (CP) gene located on component 5 was cloned in an expression vector pQE‐9 (Qiagen, QIAGEN Inc., Chatswortch, CA91311, USA). Expression of the CP with an N‐terminal hexahistidine tag in Escheri‐ chia coli M15 cells was induced by adding isopropyl‐3‐D ‐1‐thiogalactoside (IPTG) to a final concentration of 2 mM . About 8 mg of bacterially expressed CP (BE‐CP) was purified from 1 litre of bacterial liquid culture using a Ni‐NTA resin column (Qiagen). The expressed CP which migrated as a protein of approximately 23 kDa in sodium dodecyl sulphate (SDS)‐polyacrylamide gel electrophoresis (PAGE) was identified by its strong reaction with polyclonal antibodies produced against FBNYV particles and 2‐5H9 FBNYV‐monoclonal in Western blots. Expressed and purified CP (SDS‐PAGE 23 kDa band) was injected into a white rabbit, using seven intramuscular injections at weekly intervals. The antiserum produced was evaluated for FBNYV detection in double antibody sandwich (DAS)‐enzyme‐linked immunosorbent assay (ELISA), triple antibody sandwich (TAS)‐ELISA, tissue blot immunoassay (TBIA), dot blot, Western blot and goat antimouse coating (GAMC)‐ELISA using 13 different FBNYV monoclonal antibodies. The antiserum raised against the BE‐CP gave strong FBNYV‐specific TBIA reactions and very weak background reactions with non‐infected tissue, similar to those produced by monoclonal antibodies. Furthermore, BE‐CP polyclonal antibody reacted weakly with FBNYV‐infected tissue and strongly with BE‐CP in DAS‐ELISA, but not with FBNYV‐infected tissue in TAS‐ELISA when 13 detecting monoclonal antibodies were used. In addition, BE‐CP polyclonal antibody reacted strongly with BE‐CP in TAS‐ELISA only when 2‐5H9 detecting monoclonal was used. When monoclonals were used as primary antibody and BE‐CP polyclonal as detecting antibody (GAMC‐ELISA), FBNYV‐infected tissue gave moderate reactions with 2‐5H9 and strong reactions with 3‐2E9 monoclonal, whereas BE‐CP gave equally strong reactions with both monoclonals. These results showed that the BE‐CP polyclonal antibody is useful for the detection of FBNYV in infected tissue by TBIA and dot blot tests.     

Host‐mediated induction of α‐amylases by larvae of the Mexican bean weevil Zabrotes subfasciatus (Coleoptera: Chrysomelidae: Bruchinae) is irreversible and observed from the initiation of the feeding period

Larvae of Zabrotes subfasciatus secrete α‐amylases that are insensitive to the α‐amylase inhibitor found in seeds of Phaseolus vulgaris. By analyzing amylase activities during larval development on P. vulgaris, we detected activity of the constitutive amylase and the two inducible amylase isoforms at all stages. When larvae were transferred from the non α‐amylase inhibitor containing seeds of Vigna unguiculata to P. vulgaris, the inducible α‐amylases were expressed at the same level as in control larvae fed on P. vulgaris. Interestingly, when larvae were transferred from seeds of P. vulgaris to those of V. unguiculata, inducible α‐amylases continued to be expressed at a level similar to that found in control larvae fed P. vulgaris continuously. When 10‐day‐old larvae were removed from seeds of V. unguiculata and transferred into capsules containing flour of P. vulgaris cotyledons, and thus maintained until completing 17 days (age when the larvae stopped feeding), we could detect higher activity of the inducible α‐amylases. However, when larvae of the same age were transferred from P. vulgaris into capsules containing flour of V. unguiculata, the inducible α‐amylases remained up‐regulated. These results suggest that the larvae of Z. subfasciatus have the ability to induce insensitive amylases early in their development. A short period of feeding on P. vulgaris cotyledon flour was sufficient to irreversibly induce the inducible α‐amylase isoforms. Incubations of brush border membrane vesicles with the α‐amylase inhibitor 1 from P. vulgaris suggest that the inhibitor is recognized by putative receptors found in the midgut microvillar membranes. © 2010 Wiley Periodicals, Inc.     

Variation in pathogenicity among isolates of Elsinoe phaseoli from Phaseolus species

Expanding primary leaves of 11 cultivars of Phaseolus vulgaris, and one each of Phaseolus coccineus, Phaseolus lunatus and Vigna unguiculata were inoculated with 23 isolates of Elsinoe phaseoli from Phaseolus spp. and one from Vigna unguiculata. On the basis of the macroscopic and microscopic appearance of the lesions, symptoms were placed into five classes. Spore yields from the lesions in each class were used to classify the types of lesions as representing resistance or susceptibility to each isolate. There was a differential response of cultivars to isolates. According to the reaction of five cultivars of P. vulgaris to infection, isolates were placed in four pathogenicity groups. In addition to the differential reaction of cultivars, there was some evidence of host specificity among the isolates. Thus, P. lunatus was susceptible to most of the P. vulgaris isolates but resistant to the ones from P. coccineus. Vigna unguiculata was susceptible only to the V. unguiculata isolate and was resistant to all the isolates from Phaseolus spp. The isolate from V. unguiculata failed to infect any of the bean cultivars or the other Phaseolus spp. The need to select suitable isolates for challenging cultivars in a breeding programme is stressed.     

Lipids from Bean, Barley and Sugar Beet in Relation to Salt Resistance

A comparison was made between the lipid and fatty acid composition of the salt-sensitive bean (Phaseolus vulgaris L. cv. Saxa), the less salt-sensitive barley (Hordeum vulgaris L. cv. Wisa) and the salt-tolerant sugar beet (Beta vulgaris L. cv. Kawemono). Sugar beet roots showed a higher content of sterol components and sulfolipid as compared with bean and barley roots. The lipids of sugar beet roots contained more linoleic acid and less linolenic acid than those of bean and barley roots. For barley and sugar beet roots a higher amount of extra-long chain fatty acids was observed than for bean roots. It was concluded that differences in membrane structure are correlated with differences in membrane permeability to sodium and chloride and in salt-resistance of the studied species.     

Expression of the Arcelin 1 gene from Phaseolus vulgaris L. in cowpea seeds (Vigna unguiculata L.) confers bruchid resistance

Persistent decrease in the productivity of cowpea (Vigna unguiculata L.) has been partly due to attack by bruchids including Zabrotes subfasciatus and Callosobruchus maculatus. Resistance to these insects in Phaseolus vulgaris L. has been shown to be associated with arcelins, a family of seed proteins encoded by a multigenic family of lectins on the APA locus. In this work, we report the construction of an expression vector containing Arc1 gene isolated from P. vulgaris and introduced into cowpea as a strategy to confer resistance to insect attack. Following transformation and selection, feeding experiments in which C. maculatus and Z. subfasciatus were fed with transgenic (L3 and L5) and non-transgenic (control) grains showed that introduced gene protected the transgenic line. Significant differences (p < .05 and p < .01) were found in the number of eggs laid, the number of emerging insects and the loss of grain mass in L3, compared with control, for both insects. Similar observations were made in L5 with the exception of the number of laid eggs. The strategy here described may form the basis for the development of a cowpea variety tolerant to bruchids in a crop cultivated by farmers throughout Latin America and Africa.     

Localization of carbonic anhydrase in legume nodules

Extracts of the central infected zone and the surrounding cortex of nodules from Lupinus angustifolius L., Vigna unguiculata L. (Walp), Pisum sativum L., Phaseolus vulgaris L., Vicia faba L. and Medicago sativa L. contained significant activities of carbonic anhydrase (CA). Immunoassay of extracts using antisera to a putative nodule CA (Msca1) cloned from M. sativa also indicated expression in both tissue types. Quantitative confocal microscopy using laser scanning imaging and a fluorescent CA‐specific probe (5‐dimethylaminonaphthalene‐1‐sulfonamide [DNSA]) localized expression to the infected cells in the central zone tissue and a narrow band of 2–3 files of cells in the cortical tissue that corresponded to the inner cortex. In the infected cells, the enzyme activity was distributed evenly in the cytosol, but in the inner cortical cells, it was restricted to the periphery – possibly to the plasma membrane or cell wall. The functions of CA in these two tissues are considered in relation to the carbon metabolism of nodules and the participation of the inner cortex in the regulation of gaseous diffusive resistance.     

Bean common mosaic virus and cucumber mosaic virus naturally infecting Aristolochia spp. plants in Brazil

In April 2022, Aristolochia plants with symptoms of mosaic were observed in a garden at Jardim Botânico Plantarum, Nova Odessa, São Paulo State, Brazil. Potyviridae-like particles were observed by transmission electron microscopy in leaf extracts. Total RNA extracted from symptomatic plants used in RT-PCR with universal and BCMV-specific primers detected the potyvirus bean common mosaic virus (BCMV). The cucumovirus cucumber mosaic virus (CMV) was identified only in Aristolochia littoralis plants that tested negative by RT-PCR for BCMV. Phylogenetic analysis grouped samples of Aristolochia in a different clade among samples of Phaseolus vulgaris. Phylogenetic analysis indicated that the CMV isolate from Aristolochia belongs to the CMV group IA. BCMV was mechanically transmitted to healthy plants of A. fimbriata, Chenopodium quinoa, P. vulgaris cv. Jalo and Macroptilium lathyroides. CMV was mechanically transmitted to plants of A. fimbriata and C. quinoa. The BCMV and CMV were aphid transmitted only by Aphis gossypii to Aristolochia plants. This is the first report of BCMV and CMV infecting Aristolochia plants in Brazil.     

Chlorophyll a Fluorescence Analysis in Response to Excitation Irradiance in Bean Plants (Phaseolus vulgaris L. and Vigna unguiculata L. Walp) Submitted to High Temperature Stress

Bean plants Phaseolus vulgaris L. (cv. Carioca and Negro Huasteco) and Vigna unguiculata L. Walp (cv. Epace-10) were grown in a growth chamber with a photosynthetic photon flux density of 200 mol m^–2 s^–1 at leaf level and air temperature of 25+1 °C. Fully expanded, first pair leaves of 12-d-old plants were submitted for 90 min to high temperature (25, 30, 35, 40, 45, and 48 °C). Chlorophyll a fluorescence parameters (ETR, q_P, q_N, and F₀) were investigated using a modulated fluorimeter at 25 °C during recovery considered here as 48 h after stress induction period. An accentuated decrease in q_P and an increase in q_N at 48 °C in Carioca and Negro Huasteco was not observed in Epace-10. In response to excitation irradiance a great potential for ETR was found in Negro Huasteco at 25 °C, also demonstrated by net photosynthetic rate. At 48 °C ETR was high for Epace-10 while it was equal to zero for Carioca and Negro Huasteco. Tolerance to high temperature observed in Epace-10 provided important information about the adaptative characteristics of Vigna cultivars to warm climates.     

Characterisation and serology of virus-like particles associated with faba bean necrotic yellows

A disease showing chlorosis, leaf rolling and stunting in Vicia faba and other legumes was observed in West Asia and North Africa during 1987–1988. The putative causal agent could not be transmitted mechanically, but could be transmitted by aphids, most efficiently by Acyrthosiphon pisum, in the persistent manner. Further studies revealed isometric virus-like particles (VLPs) closely associated with the disease, although their infectivity could not be demonstrated by membrane feeding. These particles, measuring c. 18 nm in diameter and containing a capsid protein of about 22 kDa and ssDNA of about 1 kb, are hereafter designated faba bean necrotic yellows virus (FBNYV). A high proportion of circular nucleic acid molecules of about 0.9 kb were visualised by electron microscopy. Hybridisation analysis of cloned viral DNA suggests that the circular genome is larger than 1 kb and consists of several components of similar size. An antiserum produced against FBNYV was used in ELISA, immunoelectron microscopy (IEM) and Western blot experiments for virus detection in aphids and field samples and for serological comparison with other viruses. Weak heterologous reactions between FBNYV and subterranean clover stunt virus (SCSV) were detected in IEM, but could not be confirmed in ELISA or Western blots. No serological relationship to banana bunchy top virus (BBTV) was detected. Using a direct tissue blot immunoassay (TBIA), FBNYV was detected in vascular tissue of infected faba bean leaves and stems.     

Bean arcelin

Summary SDS-PAGE of seed proteins from the seeds of a nondomesticated bean of Mexican origin (Phaseolus vulgaris L., PI 325690) revealed the presence of a novel 38 kd protein which appeared to be neither an altered phaseolin nor a lectin fraction. The protein was named arcelin, after Arcelia, the town in the state of Guerrero near which PI 325690 had been collected. The pure line, UW 325, was derived by self fertilization of the plant from a single arcelin-containing seed of PI 325690. Despite a low percentage seed phaseolin (14.6%), seed phenotype, seed germination, plant growth, pollen fertility, and percentage seed protein of UW 325 were normal. Analyses of F₂ and F₃ seeds from a single F₁ plant of the cross SanilacXPI 325690-3 revealed that arcelin expression was inherited as a single gene and that presence was dominant to absence of arcelin. The mean percentage phaseolin in the seeds of homozygous dominant Arc/Arc F₃ families (14.0%) was significantly lower than that of the homozygous recessive arc/arc seeds (44.7%). The distribution of percentage phaseolin values for seeds within segregating families was bimodal and nonoverlapping. Without exception, seeds containing arcelin (Arc+phenotype) contained a lower percentage phaseolin than seeds lacking arcelin (Arc-phenotype). Although arcelin presence was associated with low percentage phaseolin, the Arc/Arc and Arc/arc genotypes were similar for seed weight and percentage total seed protein.     

Genomic dissection of pod shattering in common bean: mutations at non‐orthologous loci at the basis of convergent phenotypic evolution under domestication of leguminous species

The complete or partial loss of shattering ability occurred independently during the domestication of several crops. Therefore, the study of this trait can provide an understanding of the link between phenotypic and molecular convergent evolution. The genetic dissection of ‘pod shattering’ in Phaseolus vulgaris is achieved here using a population of introgression lines and next‐generation sequencing techniques. The ‘occurrence’ of the indehiscent phenotype (indehiscent versus dehiscent) depends on a major locus on chromosome 5. Furthermore, at least two additional genes are associated with the ‘level’ of shattering (number of shattering pods per plant: low versus high) and the ‘mode’ of shattering (non‐twisting versus twisting pods), with all of these loci contributing to the phenotype by epistatic interactions. Comparative mapping indicates that the major gene identified on common bean chromosome 5 corresponds to one of the four quantitative trait loci for pod shattering in Vigna unguiculata. None of the loci identified comprised genes that are homologs of the known shattering genes in Glycine max. Therefore, although convergent domestication can be determined by mutations at orthologous loci, this was only partially true for P. vulgaris and V. unguiculata, which are two phylogenetically closely related crop species, and this was not the case for the more distant P. vulgaris and G. max. Conversely, comparative mapping suggests that the convergent evolution of the indehiscent phenotype arose through mutations in different genes from the same underlying gene networks that are involved in secondary cell‐wall biosynthesis and lignin deposition patterning at the pod level.     

Effect of drought stress on proteolytic activities in Phaseolus and Vigna leaves from sensitive and resistant plants

Although much information is available concerning the effect of senescence on cell proteolytic activities, few reports are devoted to the impact of drought stress. Our aim was to study the influence of water deficit on the cell proteolytic potential, and to determine whether or not it could be used as a physiological parameter for screening varieties for tolerance to drought. We have used Phaseolus and Vigna species differing in their senstivity to water deficit: V. unguiculata L. Walp. cv. EPACE (resistant), V. unguiculata L. Walp. cv. IT83D (moderately senstive) and P. vulgaris L. cv. Carioquinha (sensitive). The plants were subjected to controlled water conditions. Proteolytic activities were assayed using azocasein in the case of leaf extracts and [¹⁴C]-methylated casein in the case of cell compartments: soluble fraction, membrane fraction and isolated, purified chloroplasts. The results indicate that the leaf extracts contained 3 groups of proteinases with optimum pH at 4.5, 5-6 and 8.5 for the Vigna cultivars and 5.0, 6.5 and 9.0 for the Phaseolus cultivar. The sensitive P. vulgaris Carioquinha showed higher caseinolytic activities than the other tow cultivars in response to water deficit. As regards cell fractions, proteolytic activities were determined for pH values of 4.5, 6.0 and 9.0. In soluble fractions of stressed plants, proteolytic activities increased at all the pH values tested; this clearly correlated with the drought sensitivity level of the plants, especially at pH 4.5. The same phenomenon was observed in the case of membranes and purified chloroplasts of the sensitive cultivar. Under drought stress, the proteolytic potential of the cell increased especially in the vaculoar sap (soluble fraction). The higher activities observed for all the cell compartments in the sensitive cultivar could be responsible, at least partly, for the rapid degradation of leaf and chloroplast proteins under drought. The use of [¹⁴C]-methylated casein and soluble cell fractions seem to allow a clear differentiation between cultivars with respect to the drought tolerance at the cellular level.     

Uptake of Iodide by Excised Bean Roots

Mesophyll cells of leaf slices of bean (Phaseolus vulgaris L.) absorb six to ten times more K⁺ than Rb⁺ from 0.1 mM single chlorides of these cations. Absorption of ⁴²K⁺ from 0.1 mM⁴²KCl is much more inhibited by low concentrations of Rb₂SO₄ than by K₂SO₄. The isotherm for K⁺ absorption is biphasic in the range 0.1–1.1 mM, and K⁺ is more effective than Rb⁺ in causing transition from phase 1 to phase 2.     

Ultraviolet-B radiation (280–315 nm) invoked antioxidant defence systems in <Emphasis Type="Italic">Vigna unguiculata</Emphasis> (L.) Walp. and <Emphasis Type="Italic">Crotalaria juncea</Emphasis> L.

A crop legume Vigna unguiculata L. (Walp.) and a wild legume Crotalaria juncea L. were evaluated for their relative responses to the oxidative stress injury induced by various doses of UV-B radiation (UV-B, 280–315 nm; 0, 1.0, 1.4, 4.7, and 6.0 kJ m⁻² d⁻¹). A dose-dependent damage in lipid peroxidation was determined as an index of membrane injury caused by UV-B. The impact was significantly higher in V. unguiculata than in C. juncea. The specific activities of superoxide dismutase, ascorbate peroxidase, monodehydroascorbate reductase, and dehydroascorbate reductase increased directly proportional to UV-B doses. However, the activities of these enzymes were significantly higher in V. unguiculata than in C. juncea indicating that V. unguiculata was inflicted with more severe oxidative stress injury under UV-B. In C. juncea the glutathione reductase and ascorbate oxidase activities were 35 and 40 % greater than in V. unguiculata, respectively. Further, the non-enzymatic antioxidants ascorbate and glutathione, and their reduced/oxidizes ratios in C. juncea were much greater than V. unguiculata indicating C. juncea has an inherently greater antioxidative potential than V. unguiculata. Thus C. juncea is better adapted to oxidative stress than V. unguiculata by means of efficient cellular antioxidant mechanisms helping to combat the photooxidative stress injury elicited by UV-B.     

Ultrastructural changes during early infection of Vigna unguiculata and Phaseolus vulgaris leaves by Xanthomonas axonopodis pv. phaseoli and an unexpected association between chloroplast and mitochondrion

Common bacterial blight, caused by Xanthomonas axonopodis pv. phaseoli, is an important disease affecting beans causing considerable yield losses in many producing areas. Our aim was to investigate Xap–beans interactions in the first 48 h after infection analyzing structurally relevant changes by electron microscopy. Scanning electron microscopy analysis demonstrated morphological changes on leaf surfaces of both species. Transmission electron microscopy showed different types of chloroplast structural disorganization in both parenchyma and bundle sheath cells of Vigna unguiculata which were only observed in parenchyma cells of Phaseolus vulgaris. Additionally, we report an unexpected physical association between the chloroplasts and mitochondria observed only to P. vulgaris-infected plants.     

A Pepsin-Resistant 20 kDa Protein Found in Red Kidney Bean (Phaseolus vulgaris L.) Identified as Basic Subunit of Legumin

The digestibility of proteins in red kidney bean (Phaseolus vulgaris L.) was examined by in vitro pepsin assay. A 20-kDa polypeptide that remained highly stable after heat processing was identified as a basic subunit of legumin. The results of a monobromobimane (mBBr) labeling test implied that this protein contained rigid intramolecular disulfide bonds, which might contribute to pepsin resistance.     

Sucrose Metabolism at Three Leaf Development Stages in Bean Plants

Sucrose metabolism was studied at three leaf development stages in two Phaseolus vulgaris L. cultivars, Tacarigua and Montalban. The changes of enzyme activities involved in sucrose metabolism at the leaf development stages were: (1) Sink (9-11 % full leaf expansion, FLE): low total sucrose phosphate synthase (SPS) activity, and higher acid invertase (AI) activity accompanied by low sucrose synthase (SuSy) synthetic and sucrolytic activities. (2) Sink to source transition (40-47 % FLE): increase in total SPS and SuSy activities, decrease in AI activity. (3) Source (96-97 % FLE): high total SPS activity, increased SuSy activities, decreased AI activity. The hexose/sucrose ratio decreased from sink to source leaves in both bean cultivars. The neutral invertase activity was lower than that of AI; it showed an insignificant decrease during the sink-source transition. This revised version was published online in June 2006 with corrections to the Cover Date.     

Temporal and developmental aspects of diet-induced food preferences in larvae of the tobacco hornworm, Manduca sexta

Diet‐induced changes in food preferences in an oligophagous caterpillar were studied in order to characterize the conditions under which this induction occurs. The time course of acquisition and extinction of induced food preferences by larvae of the tobacco hornworm, Manduca sexta (Johan.) (Lepidoptera, Sphingidae), was examined by varying the food and duration of larval food experience. Larvae were given feeding experience with the host plant tomato, Lycopersicon esculentum (Mill.) (Solanaceae), or the acceptable non‐host plant cowpea, Vigna unguiculata (Walp.) (Fabaceae), or switched from one to the other during different instars. Food preferences for V. unguiculata by the fourth or fifth instar larvae were measured individually in two‐choice tests with discs of V. unguiculata and moist filter paper. The acquisition or extinction of an induced food preference for V. unguiculata was indicated by larvae preferring V. unguiculata to filter paper or the reverse, respectively. Results showed that: (1) the period required for the acquisition of induced preference for V. unguiculata can be short (36 h), (2) food experience in either the third or fourth instar period is sufficient, and (3) the most recent feeding experience appears to be important. In contrast, the period required for extinction of induced preference for V. unguiculata appeared to be longer (1–3 instars), and both the most recent feeding experience and total duration of larval experience with the inducing food seem to play a role. Experience is not restricted to a particular instar period to acquire or extinguish such an induced food preference. The induced food preference for V. unguiculata was not very rigid and could be reversed by having one instar of feeding experience on L. esculentum. The findings indicate that diet‐induced food preferences in M. sexta contains elements of habituation and associative learning, but do not support food imprinting and induction of oligophagy.     

Enhancement of Intact Bean Leaf Senescence by NaCl Salinity

Red kidney bean (Phaseolus vulgaris L.) plants were grown in nutrient solution and in nutrient solution plus four bars of added NaCl. Chlorophyll and protein decay occurred much more rapidly in intact leaves from plants subjected to four bars of added NaCl in the growth medium than in intact leaves from plants without added NaCl. Ribonucleic acid (RNA) content in intact leaves of salt treated plants was higher than in intact leaves from plants grown in nutrient solution alone. However, the tendency for RNA content variation in leaves during the experimental period was the same for both control and salt treated plants. The results support the idea that salinity enhances senescence and suggests that hormone imbalance plays an important role in this process.