Antioxidant metabolism in pearl millet genotypes during compatible and incompatible interaction with downy mildew pathogen

In this study, the ascorbic acid content, lipid peroxidation product, reactive oxygen generation and scavenging enzyme activities were determined in pearl millet [Pennisetum glaucum (L.) R.Br.] leaves. These parameters were analysed at two stages: (i) pre-infection [45 days after sowing (DAS)] and (ii) post-infection [7 days after infection (DAI), i.e. 57 DAS]. Lipid peroxidation product (malondialdehyde content) was recorded higher in compatible interaction at pre-infection stage while it was increased in incompatible interaction at post-infection stage. Resistant genotypes had higher ascorbic acid content at both the stages of analysis. Superoxide dismutase (SOD) activity was higher in susceptible genotypes at pre-infection but after infection it was found to be higher in resistant genotypes. Ascorbate peroxidase, catalase (CAT) and lipoxygenase activities were higher in resistant genotypes at both the stages of analysis. Native PAGE isozyme banding pattern of SOD, CAT, APX and esterase showed some inducible band(s) due to disease infection.     

Characterisation of downy mildew resistant and susceptible pearl millet (Pennisetum glaucum (L.) R.Br.) genotypes using isozyme,protein, randomly amplified polymorphic DNA and inter-simple sequence repeat markers

In the present investigation, downy mildew resistant and susceptible pearl millet genotypes were characterised using seed protein and isozymes at pre- [45 days after sowing (DAS)] and post-infection (57 DAS, i.e. 7 days after infection) stage, as well as molecular markers at seedling stage without infection. Native polyacrylamide gel electrophoreis (PAGE) isozyme banding pattern of superoxide dismutase (SOD), peroxidase (POX), catalase (CAT), ascorbate peroxidase (APX) and esterase showed some inducible band(s) due to disease infection and differentiated resistant and susceptible genotypes. Total seed protein profiling revealed the presence of two unique protein of ～97 and ～100 kDa in resistant genotypes. Randomly amplified polymorphic DNA (RAPD) analysis did not show any specific marker for disease resistant and susceptible genotypes. However, inter-simple sequence repeat (ISSR) markers showed six markers in resistant genotypes viz., UBC-825 (900 bp), UBC-827 (900 bp), UBC-857 (1000 bp, 700 bp, 375 bp and 200 bp). Moreover, a single unique band UBC-857 (400 bp) was present in only susceptible genotypes. Overall pooled analysis of isozymes, protein profiling, RAPD and ISSR data showed two distinct clusters of resistant and susceptible genotypes. These results suggested that seed protein profiling and ISSR markers may be used for large scale screening of germplasm for disease reaction trait.     

Biochemical alterations in leaves of resistant and susceptible cotton genotypes infected systemically by cotton leaf curl Burewala virus

Leaf curl disease caused by Cotton Leaf Curl Burewala virus (CLCuBuV) has been recognized as serious threat to cotton in Indian subcontinent. However, information about cotton–CLCuBuV interaction is still limited. In this study, the level of phenolic compounds, total soluble proteins, and malondialdehyde (MDA) and the activities of phenylalanine ammonia-lyase (PAL), peroxidase (POX), catalase (CAT), proteases, superoxide dismutase (SOD), and polyphenol oxidase (PPO) were studied in leaves of two susceptible (CIM-496 & NIAB-111) and two resistant (Ravi and Co Tiep Khac) cotton genotypes. Disease symptoms were mild in the resistant genotypes but were severe in highly susceptible genotypes. The results showed that phenolic compounds, proteins, PAL, POX, CAT, proteases, SOD, PPO, and MDA play an active role in disease resistance against CLCuBuV. The amount of total phenols, proteases, MDA, and PPO was significantly higher in leaves of CLCuBuV-inoculated plants of both resistant genotypes as in non-inoculated plants, and decreased in CLCuBuV-inoculated plants of both susceptible genotypes over their healthy plants. POX, protein content, SOD, and PAL activities showed lower values in resistant genotypes, while they decreased significantly in susceptible genotypes as compared to the noninoculated plants except PAL, which showed non-significant decrease. CAT was found to be increased in both susceptible and resistant genotypes with maximum percent increase in resistant genotype Ravi, as compared to non-inoculated plants. The results showed significantly higher concentrations of total phenols and higher activity of protease, MDA, SOD, and PPO in resistant genotype Ravi after infection with CLCuBuV, suggesting that there is a correlation between constitutive induced levels of these enzymes and plant resistance that could be considered as biochemical markers for studying plant-virus compatible and incompatible interactions.     

Defense response of resistant and susceptible genotypes of castor (Ricinus communis L.) to wilt disease

The biochemical basis of resistance in castor (Ricinus communis L.) to Fusarium wilt, caused by the pathogen Fusarium oxysporum f. sp. ricini, was investigated. Induction of plant defence against pathogen attack is regulated by a complex network of different signals. Thus changes in various biochemical defenses including antioxidant enzymes, phenolic compounds and pathogenesis related (PR) proteins were investigated in the roots of resistant and susceptible genotypes of castor at 0, 24, 48 and 72 h.a.i. Infection by F. oxysporum significantly increased the superoxide dismutase (SOD) and peroxidase (POX) activities in the roots of susceptible genotypes, while the catalase (CAT) activities were appreciably higher in the roots of resistant genotypes at different stages. Constitutive levels of ascorbate peroxidase (APX) and polyphenol oxidase (PPO) were higher in the resistant genotypes. Also, the activities of phenylalanine ammonia lyase (PAL) and β 1, 3 glucanase significantly increased in the roots of the resistant genotypes after infections. The rate of increment of thiobarbituric acid reactive substances (TBARS) was higher in resistant genotypes after infection. Analysis of isozyme banding pattern of SOD, POX, PPO and esterase on native PAGE electrophoresis revealed that interaction between plant and fungi invoked various isozymes at 48 h of infection. SOD 3 was observed only in resistant genotypes at 24 h.a.i. except Geeta. Similarly induction of POX 5 was observed only in resistant genotypes at 48 h of infection, though the intensity of POX 5 was very less.     

Polyamine metabolism and lipoxygenase activity during Fusarium oxysporum f. sp. ricini -Castor interaction

Polyamine oxidase and lipoxygenase enzymes are key players for hyper sensitive reaction (HR) during incompatible interaction of host-pathogen. Thus, the role of lipoxygenase and polyamines was studied in the wilt pathogen infected and non infected tissues of resistant and susceptible genotypes of castor at 0 days after infection (DAI), 5 DAI and 10 DAI (30 days after sowing). The lipoxygenase (LOX) and polyamine oxidase (PAO) activities were higher in the incompatible interaction at all the stages of analysis. The constitutive level of malondyaldehyde (MDA) content, a product of lipid peroxidation was higher in susceptible genotypes (VP-1 and VI-9), while induced level was higher in resistant genotypes (48–1 and SKP-84) at 5 DAI and 10 DAI . Polyamine profiling using HPTLC showed higher spermidine and spermine content in resistant genotypes at 10 DAI. Furthermore, spermidine was detected only in the roots of resistant genotypes at 10 DAI. These results suggest the role of high titers of polyamines, LOX and PAO in disease resistance possibly through HR induction.     

Comparison of Hexaploid and Tetraploid Wheat Cultivars in their Responses to Water Stress

We studied the effect of water stress imposed at anthesis and pre-anthesis stages on oxidative stress and antioxidant activity in four wheat cultivars, two hexaploid Triticum aestivum cultivars, drought resistant cv. C 306 and drought susceptible cv. Hira, and two tetraploid cultivars, T. durum cv. A 9-30-1 and T. dicoccum cv. HW 24. Water stress decreased relative water content (RWC), membrane stability index (MSI), and increased H₂O₂ and malondialdehyde (MDA) contents as well as activity of superoxide dismutase (SOD), catalase (Cat) and peroxidase (POX) in all the genotypes at all the stages. Both the tetraploid cultivars showed higher RWC, MSI and SOD activity, and lower H₂O₂ and MDA contents under water stress than hexaploid ones. Cat and POX activities were highest in C 306.     

Antioxidative enzymes and isozymes analysis of taro genotypes and their implications in <Emphasis Type="Italic">Phytophthora</Emphasis> blight disease resistance

Assessment of the differential expression of antioxidative enzymes and their isozymes, was done in 30 day-old ex vitro raised plants of three highly resistant (DP-25, Jhankri and Duradim) and one highly susceptible (N-118) genotypes of taro [Colocasia esculenta (L.) Schott]. Antioxidative enzymes were assayed in the ex vitro plants, 7 days after inoculation with the spores (15,000 spores ml⁻¹ water) of Phytophthora colocasiae Raciborski to induce taro leaf blight disease. Uninoculated ex vitro plants in each genotype were used as control. The activity of superoxide dismutase (SOD) and guaiacol peroxidase (GPX) increased under induced blight condition when compared with control. Increase in antioxidative enzymes was more (67–92%) in the resistant genotypes than that (21–29%) of the susceptible genotype. The zymograms of SOD and GPX in the resistant genotypes, with pathogenic infection, showed increased activity for anodal isoform of SOD and increased expression and/or induction of either POX 1 or POX 2 isoforms of GPX. In susceptible genotype, expression of the above isoforms was faint for SOD and nearly absent for GPX under both blight free and induced blight conditions. Induction and/or increased activity of particular isoform of SOD and GPX against infection of Phytophthora colocasiae in the resistant genotypes studied led to the apparent conclusion of linkage of isozyme expression with blight resistance in taro. This might be an important criterion in breeding of taro for Phytophthora leaf blight resistance.     

Activity profile of defence-related enzymes in rice genotypes (Oryza sativa L.) against rice blast (Magnaporthe oryzae)

The control and infected leaf samples of blast resistant and susceptible rice genotypes were evaluated for activities of defence-related enzymes viz., total phenol content, chitinase, phenylalanine ammonia lyase (PAL), β-glycosidase, antioxidative enzymes, superoxide dismutase, peroxidase and ascorbate peroxidase. The level of total phenol content and the activity profile of chitinase, PAL and β-glycosidase significantly increased in both blast-resistant and susceptible rice genotypes with comparatively higher level induction Tetep, NLR-20104 and Swarnadhan the blast-resistant genotypes. The antioxidative enzymes were comparatively higher in the leaf samples of blast-resistant genotypes recording highest increase in NLR-20104 and KJT-5. The constitutive levels of total phenols and activity of defence-related and antioxidative enzymes in the control leaf samples differed among the genotypes and were even higher in the two blast susceptible genotypes (EK-70 and Chimansal). However, the level of induction as evident from the activity profile differences between control and infected leaf samples suggests higher level of induction was more which is indicative of the induced defence response. The genotype recording maximum induction of defence-related and antioxidative enzymes activity could be useful criteria in screening for blast resistant genotype in rice.     

Basal expression of abscisic acid inducing immunity against Karnal bunt of wheat

In order to understand the intricate mechanism of differential immunity against Karnal bunt (KB), basal levels of carotenoids, abscisic acid (ABA), total protease and protease inhibitor were determined in resistant and susceptible genotypes during transition from vegetative to developing stages of wheat spikes. The lower levels of carotenoid precursor of ABA in resistant genotype than in susceptible genotype could be explained by more inter-conversion of carotenoids into ABA pool which was evident from the results of determining ABA by enzyme-linked sorbent assay. The ABA was significantly higher in resistant genotype at all stages than in susceptible genotype, while a sharp increase was observed at S2 stage. The activity of total protease was higher at initial stages of resistant genotype and gradually declined in later stages after anthesis. In contrast to the protease activity, a reverse trend was observed for the levels of cysteine protease inhibitor, suggesting a negative correlation with each other. Level of cysteine protease inhibitor was observed to be three-folds higher at S2 stage in the resistant genotype than in the susceptible genotype. The results provided the clue for the involvement of ABA-dependent pathways in upregulation of cystatin that leads to induction of differential immunity against the KB pathogen.     

Intercellular proteins and β-1,3-glucanase activity associated with leaf rust resistance in wheat

To investigate biochemical aspects of resistance conferred by the Lr35 gene for adult-plant resistance in wheat ( Triticum aestivum L.) to leaf rust, pathogen development was related to intercellular protein composition and β -1,3-glucanase (EC 3.2.1.39) activities at three growth stages in infected and uninfected resistant (RL6082 [Thatcher/ Lr35 ]) and susceptible (Thatcher) plants. Leaf rust symptoms produced by pathotype UVPrt9 of Puccinia recondita f. sp. tritici showed that resistance conferred by Lr35 was most effective at the flag leaf stage. Furthermore, fluorescence microscopy indicated that resistance was strongly associated with hypersensitive cell death of invaded tissue. According to polypeptide profiles, intercellular proteins with molecular masses of 35, 33, 31 and 26 kDa were constitutively present at higher levels in resistant than in susceptible plants at the flag leaf stage. Four intercellular proteins (35, 33, 32 and 31 kDa) serologically related to β -1,3-glucanase were present in resistant and susceptible genotypes during all stages of plant growth. Resistance was associated with high constitutive levels of β -1,3-glucanase activity. Susceptibility on the other hand was associated with low constitutive levels of β -1,3-glucanase, while high levels were induced by infection during more advanced stages of colonization. Our results suggest that β -1,3-glucanase is involved in the defense response controlled by the Lr35 gene.     

Histo-chemical changes induced by PGPR during induction of resistance in pearl millet against downy mildew disease

Plant growth-promoting rhizobacteria Bacillus pumilus strain INR-7 effectively induced downy mildew resistance in pearl millet. The histo-chemical analysis of B. pumilus INR-7 mediated systemic resistance showed that induced resistance is associated with the expression of hypersensitive response (HR), enhanced lignification, callose deposition, and hydrogen peroxide in addition to the increased expression of the defense enzymes β-1,3-glucanase, chitinase, phenylalanine ammonia lyase (PAL), peroxidase (POX), and polyphenol oxidase (PPO). There was rapid expression of HR in the resistant pearl millet as well as the susceptible seedlings induced by treatment with INR-7 after pathogen infection when compared to the susceptible seedlings, which expressed HR at later hours. Examination of inoculated pearl millet tissues by microscopy showed that lignin, callose, and hydrogen peroxide accumulated earlier and to higher levels in resistant and induced resistant seedlings. Accumulation of various defense enzymes was an immediate response to Sclerospora graminicola infection and preceded the development of induced resistance elicited by strain INR-7. Tissue print analysis showed that defense enzymes were found to be localized in the vascular bundles and revealed the visual difference in the expression pattern of β-1,3-glucanase, chitinase, PAL, POX, and PPO whose intensity varied among resistant, INR-7 treated, and susceptible pearl millet seedlings. This study clearly demonstrated that the differences between the responses, susceptible, INR-7 treated or resistant pearl millet seedlings recorded differences in the speed, intensity, and pattern of different histo-chemical responses to S. graminicola infection.     

Spatial and temporal dynamics of peroxidase and amine oxidase activity is linked to polyamines and lignin in wheat grains

The regulation of contents and activities of peroxidase (POX), diamine oxidase (DAO) and polyamine oxidase (PAO) were determined in relation to polyamines and lignin content in wheat (Triticum aestivum L.) grains. Two cultivars WH 542 (heat susceptible) and PBW 343 (heat tolerant) were used. Activities of POX, DAO and PAO were substantially higher in PBW 343 as compared with WH 542 and appeared to be independently regulated. POX and PAO showed peak activities at mid-milky stage (15 d post anthesis) while the activity of DAO showed continuous decline. Histochemical localization of POX and PAO in situ revealed their presence in the chalazal cell walls, crease and seed coat. Substantially higher activities of enzymes in PBW 343 correlated well with a higher degree of lignification in the chalazal cells as compared to WH 542.     

Reactive oxygen species generation and peroxidase activity during Oidium neolycopersici infection on Lycopersicon species.

Histochemical and biochemical study of plant tissue responses were carried out on three Lycopersicon spp. accessions differing in response to Oidium neolycopersici. High production of superoxide anion was observed mainly in infected leaves of highly susceptible Lycopersicon esculentum cv. 'Amateur' during the first hours post inoculation (hpi). The production of hydrogen peroxide as well as an increase of peroxidase (POX) activity were detected mainly in resistant accessions at 4-12 hpi. A signal confirming the presence of very active POX was found in the apical part of tubes of germinating fungus and inside dead conidia. Increased soluble POX and catalase activity in leaf extracts of resistant accessions L. chmielewskii (LA 2663) and L. hirsutum (LA 2128) (20 hpi) correlated with the percentage of dead cells in infection sites. The correlation between production of reactive oxygen species (ROS) and activity of enzymes participating in their metabolism and hypersensitive response was evident during plant defence response.     

Feeding‐induced changes in defence enzymes and PR proteins and their implications in host resistance to Nilaparvata lugens

Six rice genotypes showing susceptible and resistant reactions to brown planthopper (BPH), Nilaparvata lugens were studied for feeding‐induced changes in defence enzymes and pathogenesis‐related (PR) proteins. The high resistant genotypes PTB 33, ADT 45 and ASD 7 and moderately resistant genotypes CO 43 and KAU 1661 recorded the greater expression of defence enzymes peroxidase, polyphenol oxidase, phenylalanine ammonia lyase, total phenol and β‐1,3 glucanase in response to N. lugens feeding at 1 day after infestation (DAI) compared with susceptible genotype TN1. The greater activity of chitinase was observed in resistant cultivars at 3 DAI and the activity was sustained for more than 1 week compared with susceptible TN1. In conclusion, the current study revealed that these defence enzymes and PR proteins might attribute to the resistance mechanisms in rice plants against BPH infestation.     

Changes in specific activities of peroxidase, chitinase and phenylalanine ammonia-lyase and phenolic content in cucumber leaves inoculated with Podosphaera fusca, the causal agent of powdery mildew

In this investigation, the effects of powdery mildew disease [caused by Podosphaera fusca (syn. Sphaerotheca fuliginea)] on specific activities of several defense-related enzymes and phenolic content were studied in cucumber leaves. Spore suspension of the fungus was sprayed on cucumber (cv. Super Dominus) plants in greenhouse and leaves from both inoculated and non-inoculated control plants were sampled at 0, 24, 48, 72 and 144 hours after inoculation (HAI). Spore germination and tissue colonization of P. fusca were microscopically studied on the inoculated surface of leaf samples. Further, Phenolic content (PHE) and specific activities of peroxidase (POX), chitinase (CHI) and phenylalanine ammonia-lyase (PAL) were spectrophotometrically measured in leaf extracts. Time-course of disease progress on the leaf surface showed that maximum spore germination occurred within 24 HAI and host penetration and disease development process began during 24-48 HAI. Evaluation of enzyme activities showed that POX specific activity in inoculated plants significantly increased at 72 HAI onwards and reached 2.5 times of that of control at 144 HAI. CHI specific activity showed a transient reduction in inoculated plants between 48-72 HAI and thereafter increased significantly in relation to control. PAL specific activity in inoculated plants was not significantly different from that of control. PHE in inoculated plants showed a significant increase compared to control at 48 HAI and thereafter. Comparison of time-course of disease progress with changes in enzyme activities indicated that POX activity had an increasing trend during disease progress whereas CHI activity showed a transient decrease at the early stages and then increased during the later stages of infection: PAL activity did not show any changes during the infection and PHE increased at the early stages of infection process and remained constant at rest of the time.     

Antioxidative defense system in pigeonpea roots under waterlogging stress

Pigeonpea [Cajanus cajan (L.) Millsp.] is a waterlogging-sensitive legume crop. We studied the effect of waterlogging stress on hydrogen peroxide (H₂O₂) content, lipid peroxidation and antioxidant enzyme activities in two pigeonpea genotypes viz., ICPL-84023 (waterlogging resistant) and MAL-18 (waterlogging susceptible). In a pot experiment, waterlogging stress was imposed for 6 days at early vegetative stage (20 days after sowing). Waterlogging treatment significantly increased hydrogen peroxide accumulation and lipid peroxidation, which indicated the extent of oxidative injury posed by stress conditions. Enzyme activities of peroxidase (POX), catalase (CAT), ascorbate peroxidase (APX), superoxide dismutase (SOD) and polyphenol oxidase (PPO) increased in pigeonpea roots as a consequence of waterlogged conditions, and all the enzyme activities were significantly higher in waterlogged ICPL-84023 than in MAL-18. POX activity was the maximum immediately after imposing stress, therefore, it was suggested to be involved in early scavenging of H₂O₂, while rest of the enzymes (CAT, APX, SOD and PPO) were more important in late responses to waterlogging. Present study revealed that H₂O₂ content is directly related to lipid peroxidation leading to oxidative damage during waterlogging in pigeonpea. Higher antioxidant potential in ICPL-84023 as evidenced by enhanced POX, CAT, APX, SOD and PPO activities increased capacity for reactive oxygen species (ROS) scavenging and indicated relationship between waterlogging resistance and antioxidant defense system in pigeonpea.     

Evaluation of elite genotypes of mungbean against Cercospora leaf spot disease (CLS) caused by Cercospora canescens

The AUDPC is the best measurement of CLS disease of mungbean, since it is based on several readings of disease intensity from the early to the mature stage. Thirty-one genotypes of the mungbean crop showed similar disease reactions at later stages both under the polyhouse and field conditions. Under field conditions, 22 genotypes were found moderately resistant, seven susceptible and two genotypes were highly susceptible, and under polyhouse conditions eight genotypes showed resistance, 19 moderate resistance and four genotypes were found susceptible.     

Morphophysiological and biochemical attributes influence intra-genotypic preference of shoot fly [Atherigona soccata (Rondani)] among sorghum genotypes

Shoot fly [Atherigona soccata (Rondani)] is a destructive pest of sorghum at the seedling stage and causes huge losses to grain yield and green fodder. The host-plant resistance mechanism is the best approach to reduce the attack of insects in plants. The damage parameters, morphophysiological traits, and biochemical metabolites had been investigated in the leaves and stem of contrasting sorghum genotypes, viz., resistant (IS18551, ICSV705, ICSV700), moderately resistant (PSC-4), and susceptible (SWARNA and SL-44) at 15 and 21 days after emergence (DAE) against shoot fly infestation. The resistant genotypes recorded lowest shoot fly oviposition and incidence (0.3–0.7 eggs plant⁻¹ and 10–15%) than the susceptible genotypes (2.4–3.0 eggs plant⁻¹ and 70–80%), respectively. The susceptible genotype SWARNA recorded 50% and 80% higher deadheart formation than the resistant genotype IS18551 at 15 and 21 DAE, respectively. Resistant genotypes exhibited higher trichome density at adaxial and abaxial part of leaf (118–145 and 106–131) with pink colored leaf sheath (scale 1.50–3.25), glossy leaves (scale1.00–1.25), and lower leaf surface wetness (scale1.25–2.00) compared with susceptible genotype with 49.3–73.3 and 25.3–64.0, scale 2.50–4.00, scale 2.75–3.50, and scale 3.25–4.25 for the respective parameters. Another defense response of sorghum toward the insect attack was modulation of plant metabolism. The infested genotypes responded to insect attack by upregulation of total soluble sugar, total phenol, prussic acid, and chlorophyll content by 1.2–2.1-fold, 1.5–2.0-fold, 1.2–1.3-fold, and 1.2–3.9-fold with more induction in susceptible genotypes at 21 DAE. On the whole, the present study indicates that morphophysiological and biochemical attributes contribute toward the resistance mechanism in sorghum against shoot fly infestation.

     

Management of Bittergourd yellow mosaic virus (BGYMV) by using virus inhibiting chemical,biocontrol agents,antiviral principles (AVP) and insecticide

Abstract

Bitter gourd Yellow Mosaic Virus (BGYMV) is a Whitefly transmitted geminivirus. BGYMV causes yellow mosaic disease in bitter gourd. This disease attains significance because the virus causing this disease is capable of attacking the crop at all stages. There was a severe yield loss in bitter gourd plants due to the infection of BGYMV. Bitter gourd plants treated with Bougainvillea spectabilis challenge inoculated with BGYMV reduced the disease incidence and increased the plant growth. In the above treatment the disease incidence was 33.33% at 75 Days After Sowing (DAS). But in the inoculated untreated control the disease incidence was 100% at 75 DAS. The mean maximum plant height was 92.24 cm in plants inoculated at 65 DAS. Bougainvillea spectabilis treated plants challenge inoculated with BGYMV showed an increased activity of peroxidase, polyphenoloxidase and phenol content from 4 Days After Inoculation (DAI) to 12 DAI. The activity of all the enzymes was reduced from 16 DAI in all the treatments.     

Pathogen infection and selection on fertilization success in Cucumis sativus

We investigated whether resistant pollen genotypes can be selected for when the maternal plants are infected and whether infection can result to changes in the pistil nutrient level influencing reproductive outcome. Both resistance and susceptibility come with costs that may affect pre- and post-fertilization reproductive functions. We performed the study by crossing zucchini yellow mosaic virus resistant and susceptible pollen (from a hybrid donor) to infected and healthy maternal plants. We also analysed the pistil nutrient content in both treatments and found an increase of the susceptible and not resistant genotypes when maternal plants were infected. The level of nutrients K, P and S was higher in the pistils of the infected maternal plants than the healthy ones. Pistil nutrient level did not affect pollen tube growth rates, as indicated by seed siring patterns along the fruit. We propose that the effect on the siring ability of pollen carrying the susceptible and resistant alleles occurred at the post-fertilization stage, possibly as an indirect result of different growth rates of the two embryo genotypes under elevated nutrient conditions. We discuss our results with respect to possibilities of differential selection, costs and reproductive implications.