Relationship between leaf stages and epistasis for resistance to Stagonospora nodorum in durum wheat

Ten varieties and eight generations (2F1, 2F2, 2B1 and 2B2) of durum wheat derived from two crosses were evaluated for resistance to natural infection by Stagonospora nodorum blotch (SNB) at the 2-3 and 6-7 leaf stages at two sites over two years. There were significant differences in the incidence of SNB between leaf stages in most of the wheat varieties, with resistance being most evident at the 6-7 leaf stage. Separate analyses of the mean values for each generation showed that the genetic mechanism of defense against the pathogen depended upon the leaf stage. At the 2-3 leaf stage, only additive and dominance effects were implicated in the control of SNB for the two crosses at the two sites and for the two replications. For the 6-7 leaf stage, inheritance was more complicated and an epistatic effect was involved. Narrow-sense heritability values (range: 0.63-0.67) were consistent between crosses and leaf stages. These findings indicate a lack of resistance to SNB at the 2-3 leaf stage whereas resistance was observed at the 6-7 leaf stage and involved the genetic mechanisms of plant defense such as epistasis.     

Identification of novel QTLs for seedling and adult plant leaf rust resistance in a wheat doubled haploid population

Pyramiding of genes that confer partial resistance is a method for developing wheat (Triticum aestivum L.) cultivars with durable resistance to leaf rust caused by Puccinia triticina. In this research, a doubled haploid population derived from the cross between the synthetic hexaploid wheat (SHW) (×Aegilotriticum spp.) line TA4152-60 and the North Dakota breeding line ND495 was used for identifying genes conferring partial resistance to leaf rust in both the adult plant and seedling stages. Five QTLs located on chromosome arms 3AL, 3BL, 4DL, 5BL and 6BL were associated with adult plant resistance with the latter four representing novel leaf rust resistance QTLs. Resistance effects of the 4DL QTL were contributed by ND495 and the effects of the other QTLs were contributed by the SHW line. The QTL on chromosome arm 3AL had large effects and also conferred seedling resistance to leaf rust races MJBJ, TDBG and MFPS. The other major QTL, which was on chromosome arm 3BL, conferred seedling resistance to race MFPS and was involved in a significant interaction with a locus on chromosome arm 5DS. The QTLs and the associated molecular markers identified in this research can be used to develop wheat cultivars with potentially durable leaf rust resistance.     

胚和胚乳基因效应对水稻幼苗生物量的影响研究

本文利用和胚乳遗传模型[研究了水稻早期胚后生长生物量性状的遗传控制,结果表明：在两个时期水稻幼苗生物量性状中,除了第16天时根鲜重（RFW）主要受到胚乳显性效应控制外,叶鲜重（LFW）,叶干重（LDW）,根干重（RDW）主要受到胚基因显性效应和胚乳基因加性效应的控制,胚加性和乳乳加性效应占总遗传方差的40－54％,说明对生物量性状进行早期选择有效,各个性状都检测到显著的胚狭义遗传率和胚乳狭义遗传率,说明在早期世代即可估计选择进程,对亲本的遗传效应值的预测表明,对根部性状的选择在第8天进行比较合适,并以亲本P1,P3和P6较好,它们既可提高RFW又可提高RDW,而对地上部分性状的选择在第16天时进行比较合适,并以P4,P9和P10为最好。     

Wheat Resistance to Spot Blotch Potentiated by Silicon

Spot blotch, caused by the fungus Bipolaris sorokiniana, is one of the most important diseases on wheat. The effects of silicon (Si) on this wheat disease were studied. Plants of wheat cultivars BR‐18 and BRS‐208 were grown in plastic pots containing Si‐deficient soil amended with either calcium silicate (+Si) or calcium carbonate (?Si). The content of Si in leaf tissue was significantly increased by 90.5% for the +Si treatment. There was no significant difference between Si treatments for calcium content, so variations in Si accounted for differences in the level of resistance to spot blotch. The incubation period was significantly increased by 40% for the +Si treatment. The area under spot blotch progress curve, number of lesions per cm² of leaf area, and real disease severity significantly decreased by 62, 36 and 43.5% in +Si treatment. There was no significant effect of Si on lesion size. The role played by total soluble phenolics in the increased resistance to spot blotch of plants from both cultivars supplied with Si was not clear. Plants from cultivar BR‐18 supplied with Si showed the highest values for concentration of lignin‐thioglycolic acid derivatives during the most advanced stages of fungus infection. Chitinase activity was high at the most advanced stages of fungus infection on leaves from both cultivars supplied with Si and may have had an effect on fungus growth based on the reduction of the components of resistance evaluated. Peroxidase activity was found to be high only at 96 h after inoculation of both cultivars supplied with Si. Polyphenoloxidase activity had no apparent effect on resistance regardless of Si treatments. Results revealed that supplying Si to wheat plants can increase resistance against spot blotch.     

南亚热带不同演替阶段森林优势树种叶片构建成本与机械抗性的协同关系

为探究不同演替阶段森林优势种叶片资源获取策略的差异以及叶片构建成本与机械抗性的关系,对我国南亚热带不同演替阶段森林14优势种的叶片构建成本、机械抗性、角质层厚度和比叶重等结构性状进行测定。结果表明,与演替早期相比,演替晚期优势种具有更高的单位面积叶片构建成本、叶片撕裂力以及穿透力,但其叶片最大光合速率较低;同时,单位面积叶片构建成本与机械抗性呈显著正相关关系,而叶片角质层厚度、比叶重等结构性状也与叶片构建成本、机械抗性均呈显著正相关。因此,从叶片能量投资策略上反映了南亚热带森林演替进程中叶片构建成本与机械抗性的协同关系。     

Effect of Growth Stage and Initial Inoculum Level on Leaf Rust Development and Yield Loss Caused by Puccinia recondita f. sp. tritici

The effects of the combinations of leaf rust inoculation at different growth stages and initial inoculum levels on leaf rust development and yield of winter wheat cultivars, McNair 1003 and Coker 762 were evaluated. Disease onset stage and initial inoculum level affected the rate of leaf rust development and shape of the disease progress curves in both cultivars. Epidemics with common onset stages and different initial inoculum levels differed in area under the disease progress curve (AUDPC). Leaf rust epidemics initiated at Feeke's growth stages 5, 7, and 10 reduced yield in both cultivars. Leaf rust epidemics initiated early with high inoculum levels had the greatest deleterious effect on yield. Maximum losses due to leaf rust were 30–40 %. Yield loss was directly related to AUDPC when the AUDPC varied from 500 to 1700 in McNair 1003 and from 250 to 1700 in Coker 762. Yield reduction was mainly due to reduction in grain weight.     

转双价基因抗虫棉及其杂交F1代对棉铃虫幼虫的抗性研究

利用室内生物测定法和田间调查法研究双价抗虫棉及其杂交F1代不同生育期主茎功能叶和花铃期不同组织器官的抗虫性。结果表明:双价抗虫棉及其杂交F1代的抗虫性变化规律与B t基因棉的抗虫性变化规律相近,为生育前期(苗期、蕾期)抗性强,生育后期(花铃期、吐絮期)抗性弱,在花铃期为:棉铃>棉蕾>花>棉叶,且差异极显著。与B t基因棉相比,生育前期双价抗虫棉及其杂交F1代的抗虫性略弱,但差异不显著;生育后期双价抗虫棉及其杂交F1代的抗虫性显著强于B t基因棉。     

Leaf stage-associated resistance is correlated with phytohormones in a pathosystem-dependen manner

It has been reported in several pathosystems that disease resistance can vary in leaves at different stages. However, how general this leaf stage-associated resistance is, and the molecular mechanism(s) underlying it, remain largely unknown. Here, we investigated the effect of leaf stage on basal resistance, effectortriggered immunity(ETI) and nonhost resistance, using eight pathosystems involving the hosts Arabidopsis thaliana, Nicotiana tabacum, and N. benthamiana and the pathogens Sclerotinia sclerotiorum, Pseudomonas syringae pv. tabaci, P. syringae pv. tomato DC3000, and Xanthomonas oryzae pv. oryzae(Xoo). We show evidence that leaf stage-associated resistance exists ubiquitously in plants, but with varying intensity at different stages in diverse pathosystems. Microarray expression profiling assays demonstrated that hundreds of genes involved in defense responses, phytohormone biosynthesis and signaling, and calcium signaling, were differentially expressed between leaves at different stages. The Arabidopsis mutants sid1, sid2-3, ein2, jar1-1, aba1 and aao3 lost leaf stage-associated resistance to S. sclerotiorum, and the mutants aba1 and sid2-3 were affected in leaf stage-associated RPS2/Avr Rpt2t-conferred ETI, whereas only the mutant sid2-3 influenced leaf stage-associated nonhost resistance to Xoo. Our results reveal that the phytohormones salicylic acid,ethylene, jasmonic acid and abscisic acid likely play an essential, but pathosystem-dependent, role in leaf stageassociated resistance.     

The Effects of Increased Illumination and Shading on the Low-Light-Induced Decline in Photosynthesis in Cotton Leaves

An experiment was carried out to study whether low-light-induced damage to the photosynthetic system in leaves of cotton (Gossypium hirsutum cv. Deltapine) which are below the compensation point in the canopy can be arrested and reversed by increased illumination. In addition it was intended to find out whether the photosynthetic system in leaves of shade plants show a greater resistance to low-light-induced damage than leaves of plants from more exposed habitats. The plants were grown at high density, and increased illumination to the shade leaves in the canopy was achieved by thinning the stand. Thinning was carried out at two stages and its effects on the decline in the photosynthetic capacity of the 4th leaf were followed. An early thinning was carried out shortly after the 4th leaf dropped below the compensation point and a late thinning 2 weeks later. Comparison was also made between the low-light-induced damage to the photosynthetic capacity of the 4th leaf in plants grown under two light regimes during the progressive increase in self-shading of the 4th leaf within the canopy. It was observed that both types of thinning arrested the low-light-induced damage to the photosynthetic system in shade leaves. The decline in photosynthetic capacity of the 4th leaf was stopped after both early and late thinning. The dry weight of the shoot system in the early and late thinned plants was not significantly different. It was double that of the control plants. The plants thinned early did not have higher shoot weight than the late thinned plants since there was a rapid shedding of flowers and fruits after early thinning. The 4th leaf in the early thinned plants showed a 30% increase in chlorophyll content and dry weight per unit leaf area. It is suggested that shedding of flowers and fruits, and increases in chlorophyll and dry weight per unit leaf area in the early thinned plants were caused by a change in the hormonal balance of the plants. The photosynthetic system in leaves of shade plants showed a greater resistance to damage by low light intensity than the photosynthetic system in leaves of plants grown at higher light intensities.     

The mechanism and inheritance of adult plant leaf rust resistance in 12 wheat lines.

Twelve lines of wheat (Triticum aestivum L.) were developed that had susceptible infection types to leaf rust (Puccinia recondita Rob. ex Desm. f.sp. tritici) race UN 15 in the seedling stage but were resistant in the adult plant stage in the field. The lines were developed from four crosses, each involving four parents (eight in total) that had originally been selected for adult plant or field resistance to stem rust (Puccinia graminis Pers. f.sp. tritici Eriks, and Henn.). The objectives of the present study were to determine the mechanism of resistance to leaf rust and its inheritance in the 12 lines. The 12 lines were grown in an artificially inoculated field nursery in Saskatoon, coefficients of infection (CI) were determined at four dates, and the areas under the disease progress curve (AUDPC) were calculated. Four representative lines were grown in a growth chamber to measure the latent period and pustule size at the two-leaf and flag-leaf stages. Eight lines were crossed and backcrossed to a susceptible check and the parents, F1, F2, F3, and BC1F2 generations were grown in a field nursery. The 12 lines showed wide ranges in CI and AUDPC but all were significantly more resistant than the susceptible check. The four lines studied in the growth chamber had longer latent periods and smaller pustules than the susceptible check at both stages. The differences tended to be greater at the flag-leaf stage. The inheritance studied showed that resistance was recessive or partially recessive and was controlled by two or more genes in each line of the eight lines. In three of the eight lines, Lr34 may be one of the genes and in the other five both Lr13 and Lr34 could be present. However, additional genes are clearly involved. A single gene by itself had only a small effect, but in two and three gene combinations the effects appeared to be greater. This type of resistance appears to occur frequently and may be durable because its complex inheritance may make it more difficult for the rust fungus to overcome. It should be used in breeding wheat for areas where leaf rust is a major problem.     

Genetic analysis of loci associated with partial resistance to <Emphasis Type="Italic">Sclerotinia sclerotiorum</Emphasis> in rapeseed (<Emphasis Type="Italic">Brassica napus</Emphasis> L.)

Sclerotinia stem rot is the most devastating disease of rapeseed (Brassica napus L.) in China. Quantitative trait loci (QTLs) involved in resistance to Sclerotinia sclerotiorum were detected in a rapeseed population of 128-F(2:3) families derived from a cross between the male sterility restorer line H5200 and a partial resistant line Ning RS-1. A total of 107 molecular markers including 72 RFLPs, 30 AFLPs, 3 SSRs and 2 RAPDs were employed to construct a genetic linkage map with 23 linkage groups covering 1,625.7 cM with an average space of 15.2 cM. Resistance was assessed empirically at two developmental stages: with a detached leaf inoculation at the seedling stage and in vivo stem inoculation at the mature plant stage. The observed resistance was scored for each plant as leaf resistance at the seedling stage (LRS) and stem resistance at the mature plant stage (SRM). A total of 13 loci were identified by one-way ANOVA and six QTLs were detected with MapMaker-QTL. We found that three of the six QTLs were associated with leaf resistance at the seedling stage and collectively accounted for 40.7% of the total phenotypic variation, each accounting for 23.2%, 16.6% and 13.6% respectively. Three QTLs were found corresponding to the disease resistance at the mature plant stage, explaining 49.0% of the phenotypic variation. Epistasis was observed for the resistance and the additive by additive interactions were the predominant type of epistasis. It was concluded that both single-locus QTLs and epistatic interactions played important roles in Sclerotinia resistance in rapeseed.     

Changes in water status during water stress at different stages of development in wheat

The dynamics of stomatal resistance and osmotic adjustment in response to plant water deficits and stage of physiological development was studied in the leaves of spring wheat ( Triticum aestivum L., GWO 1809). Plants were germinated and grown in pots in a growth chamber at the Duke University Phytotron to four physiological stages of development (4th leaf, 7th leaf, anthesis, and soft dough), during which time stomatal resistance, total water potential and osmotic potential were measured on the last fully developed leaf of water stressed and non-stressed plants. Pressure potential was obtained by difference. Stomatal closure of the abaxial and adaxial surfaces were independent of each other, each having a different critical total water potential. The total water potential required to close the stomata on the last fully developed leaf were different at different stages of physiological development, decreasing as the plants grew older. The development of osmoregulation in wheat allows the closure of stomata during the vegetative stage at a high total water potential, but insures that stomata remain open from anthesis through the ear filling period to a lower total water potential.     

The phenotypic expression of QTLs for partial resistance to barley leaf rust during plant development

Partial resistance is generally considered to be a durable form of resistance. In barley, Rphq2, Rphq3 and Rphq4 have been identified as consistent quantitative trait loci (QTLs) for partial resistance to the barley leaf rust pathogen Puccinia hordei. These QTLs have been incorporated separately into the susceptible L94 and the partially resistant Vada barley genetic backgrounds to obtain two sets of near isogenic lines (NILs). Previous studies have shown that these QTLs are not effective at conferring disease resistance in all stages of plant development. In the present study, the two sets of QTL–NILs and the two recurrent parents, L94 and Vada, were evaluated for resistance to P. hordei isolate 1.2.1 simultaneously under greenhouse conditions from the first leaf to the flag leaf stage. Effect of the QTLs on resistance was measured by development rate of the pathogen, expressed as latency period (LP). The data show that Rphq2 prolongs LP at the seedling stage (the first and second leaf stages) but has almost no effect on disease resistance in adult plants. Rphq4 showed no effect on LP until the third leaf stage, whereas Rphq3 is consistently effective at prolonging LP from the first leaf to the flag leaf. The changes in the effectiveness of Rphq2 and Rphq4 happen at the barley tillering stage (the third to fourth leaf stages). These results indicate that multiple disease evaluations of a single plant by repeated inoculations of the fourth leaf to the flag leaf should be conducted to precisely estimate the effect of Rphq4. The present study confirms and describes in detail the plant development-dependent effectiveness of partial resistance genes and, consequently, will enable a more precise evaluation of partial resistance regulation during barley development.     

Water Potential and Stomatal Resistance of Sunflower and Soybean Subjected to Water Stress during Various Growth Stages

Plants of two varieties of soybean (Glycine max (L.) Merr.) and two varieties of sunflower (Helianthus annuus L.) were grown in controlled environments and subjected to water stress at various stages of growth. Leaf resistances and leaf water potentials were measured as stress developed. In soybeans the upper leaf surface had a higher resistance than the lower surface at all leaf water potentials and growth stages. Resistance of the upper surface began to increase at a higher water potential and increased more than the resistance of the lower surface. Resistances returned to prestress values 4 days after rewatering. In sunflowers upper and lower leaf surfaces had similar resistances at all water potentials and growth stages. Leaf resistances were higher in sunflower plants stressed before flowering than in those stressed later. Sunflower plants stressed to −16 bars recovered their prestress leaf resistance and water potential a few days after rewatering, but leaves of sunflower plants stressed to −23 bars died. Leaves of soybean and sunflower plants stressed before flowering suffered less injury than those of older plants and sunflowers stressed after flowering suffered more injury than soybeans.     

Isolate-specific QTLs for partial resistance to Puccinia hordei in barley

By using a high-density AFLP marker linkage map, six QTLs for partial resistance to barley leaf rust (Puccinia hordei) isolate 1.2.1. have been identified in the RIL offspring of a cross between the partially resistant cultivar ’Vada’ and the susceptible line L94. Three QTLs were effective at the seedling stage, and five QTLs were effective at the adult plant stage. To study possible isolate specificity of the resistance, seedlings and adult plants of the 103 RILs from the cross L94×’Vada’ were also inoculated with another leaf rust isolate, isolate 24. In addition to the two QTLs that were effective against isolate 1.2.1. at the seedling stage, an additional QTL for seedling resistance to isolate 24 was identified on the long arm of chromosome 7. Of the eight detected QTLs effective at the adult plant stage, three were effective in both isolates and five were effective in only one of the two isolates. Only one QTL had a substantial effect at both the seedling and the adult plant stages. The expression of the other QTLs was developmental-stage specific. The isolate specificity of the QTLs supports the hypothesis of Parlevliet and Zadoks (1977) that partial resistance may be based on a minor-gene-for-minor-gene interaction. Received: 16 February 1999 / Accepted: 20 February 1999     

Amino acid composition and level affect Bt protein concentration in Bt cotton

Low insect resistance has been widely observed in Bacillus thuringiensis (Bt) transgenic cotton. The objective of this study was to investigate the effects of amino acid compositions and their concentration on the Bt toxin content in Bt cotton to gain a better physiological understanding of the observed phenomenon. In the 2010 study, the leaf amino acid composition, contents, and Bt protein concentrations were investigated under high temperature (36?°C) and low temperature(18?°C) at both square and boll stage respectively. In 2011, the leaves were sprayed with ethionone sulfoximine (MSO), aminooxyacetic acid (AOA) or combination of MSO and AOA at the two developing stages, and the leaf amino acid composition and Bt protein concentrations were investigated. In 2012, 17 amino acid compositions were used to spray cotton plants at the same two stages, and the Bt protein concentration were measured. In comparison to the control, more amino acids changed and greater concentration changes had been observed under the extreme temperatures at boll stage compared to that at square stage, which were conformity to the changes of the leaf Bt protein concentration. More amino acids reduced and greater reduction was noted with the application of MSO, AOA or combined MSO and AOA at boll period than that at square period, which resulted in the reduction of the leaf Bt toxin concentration. The external uses of Aspartic acid, Glutamic acid, Glycine, Proline, Tyrosine, Methionine, Phenylalanine, Histidine and Arginin enhanced the leaf Bt toxin level significantly at boll stage. However, only Aspartic acid, Glutamic acid, Proline, Methionine, Arginin could increase Bt protein concentration markedly at square period and the bolstered extent were low. Therefore, it was concluded that cotton amino acid composition and concentration was more sensitive to external factors at boll stage. In addition, there are close relationship between leaf Bt toxin content and Aspartic acid, Glutamic acid, Glycine, Proline, Tyrosine, Methionine, Phenylalanine, Histidine and Arginin and their concentrations.     

Effects of manipulation of water and nitrogen regime on the water relations of the desert shrub Larrea tridentata

Summary Water and nitrogen regimes of Larrea tridentata shrubs growing in the field were manipulated during an annual cycle. Patterns of leaf water status, leaf water relations characteristics, and stomatal behavior were followed concurrently. Large variations in leaf water status in both irrigated and nonirrigated individuals were observed. Predawn and midday leaf water potentials of nonirrigated shrubs were lowest except when measurements had been preceded by significant rainfall. Despite the large seasonal variation in leaf water status, reasonably constant, high levels of turgor were maintained. Pressure-volume curve analysis suggested that changes in the bulk leaf osmotic potential at full turgor were small and that nearly all of the turgor adjustment was due to tissue elastic adjustment. The increase in tissue elasticity with increasing water deficit manifested itself as a decrease in the relative water content at zero turgor and as a decrease in the tissue bulk elastic modulus. Because of large hydration-induced displacement in the osmotic potential and relative water content at zero turgor, it was necessary to use shoots in their natural state of hydration for pressure-volume curve determinations. Large diurnal and seasonal differences in maximum stomatal conductance were observed, but could not easily be attributed to variations in leaf water potential or leaf water relations characteristics such as the turgor loss point. The single factor which seemed to account for most of the diurnal and seasonal differences in maximum stomatal conductance between individual shrubs was an index of soil/root/ shoot hydraulic resistance. Daily maximum stomatal conductance was found to decrease with increasing soil/root/ shoot hydraulic resistance. This pattern was most consistent if the hydraulic resistance calculation was based on an estimate of total canopy transpiration rather than the more commonly used transpiration per unit leaf area. The reasons for this are discussed. It is suggested that while stomatal aperture necessarily represents a major physical resistance controlling transpiration, plant hydraulic resistance may represent the functional resistance through its effects on stomatal aperture.     

Photosynthesis and growth of winter wheat in response to waterlogging at different growth stages

A study on photosynthetic and yield effects of waterlogging of winter wheat at four stages of growth was conducted in specially designed experimental tanks during the 2007–2008 and 2008–2009 seasons. Compared with the control, waterlogging treatments at tillering and jointing-booting stages reduced photosynthetic rate (P _N) and transpiration (E) significantly, it also decreased average leaf water-use efficiency (WUE, defined as the ratio of P _N to E) by 3.3% and 3.4% in both years. All parameters returned quickly to the control level after soil was drained. Damage to the photosynthetic apparatus during waterlogging resulted in a lower F_v/F_m ratio, especially at the first two stages. A strong reduction in root length, root mass, root/shoot ratio, total dry mass, and leaf area index were observed. The responses from vegetative plants at tillering and jointing-booting stages were greater than in generative plants at onset of flowering and at milky stages. The number of panicles per hectare at tillering stage and the spikelet per panicle at the stages of jointing-booting and at onset of flowering were also significantly reduced by waterlogging, giving 8.2–11.3% decrease of the grain yield relative to the control in both years. No significant difference in yield components and a grain yield was observed between the control and treatments applied at milky stages. These responses, modulated by the environmental conditions prevailing during and after waterlogging, included negative effects on the growth, photosynthetic apparatus, and the grain yield in winter wheat, but the effect was strongly stage-dependent.     

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.