Genetical alterations and phytosanitary status promote the variability and modify the appearance of vine. Old vine varieties in old vineyards are highly variable and well adapted to selection. Clonal selektion is based on a visual performance: valuable individuals (clones) are picked out according to visible symptoms or characters. The genetica...l stability of clones is proved by testing the vegetatively propagated progenies on the basis of morphological and molekular (SSR, AFLP, SMPL, RAPD) markes. Authors take great care of the visual phytosanitary selection as part of the clonal selection being the oreliminary step to develop pathogen-free propagation stocks. In Serbia (Vojvodina) the selection breeding has been carried on for several decades resulted in comparative clone trials with home and imported clones of Welsch Riesling, Chardonnay, Pinot gris, White Riesling. Among the clones of home selection SK.54 Welsch Riesling clone is the most valuable. Its clearing from pathogene is being carried on in an interregional IPA programme (HUSRB/0901/214/123) in Kecskemét. In Kecskemét, the centre of the Hungarian Danube vine region 5 vine clones have been registered (Cegléd szépe K.73, Irsai Olivér K.11, Kövidinka K.8, Hárslevelû K.9, Pannónia kincse K.56). Besides them 18 virus-tested clones have also been qualified.Works aiming at their complete exemption are going on in order to obtain clones free of propagation wood-borne diseases.
We have concluded the selection tests of the `Mézes körte' seedlings planted in the spring of 2006, with special emphasis on the cotyledonary, foliage leaf and the height of plant. Out of the 75 seeds planted in rows, there were 40-45 pieces growing out, so during the first cotyledonary test we had to calculate with almost 40% decay. On 12th...April 2006, we recorded some of the important characteristics of the seedlings in their cotyledonary stage which characteristics were important from the point of view of selection (cotyledonary form, cotyledonary length, cotyledonary thickness, cotyledonary colour, cotyledonary petiole length, cotyledonary petiole thickness, cotyledonary petiole colour). The above morphological characteristics are shown in Table No. 1-6. We have also tested the seedling in foliage leaf state, paying special attention on the development stage of the plants (colour of foliage leaf , height of plant). We have completed statistical calculations of the two above mentioned characteristics. The result of that is summarised in Table No. 8-9. The variation coefficient show smaller value in the case of the foliage leaf number (15-32%), while the wider range of spread of the data referring to the height of the plant is shown by the 33-61% CV values. On charts No 4-9. we present the relationship between the height of the plant and the number of foliage leaf, as well as the differences between the two graphs. Based on the above charts and graphs it can be defined that the 40% destruction of the developing seedlings during the period till the next measurement reached 70-80% level. In spite of this however some seedlings showed strong and balanced growth (A44, B42, C25, D16, E5, E39, F38), the further testing and selection of those is to be completed in the future.
Since the isolation of morphine by Sertümer in 1805 more than 40 alkaloids have been isolated from the poppy (Papaver somniferum L.). Some of them have high biological-pharmacological activity and economical importance, while others have none, or restricted ones. The increasing demand for poppy alkaloids is the consequence of the wide...ning of the medical application of morphine and its related compounds: the quantity of morphine used for the treatment of pain reached a record level of 17.9 tonnes in 1997, compared with an annual average of 2.2 tonnes used during the period 1978-1983. However, the production of raw material (either opium, or dried capsule is produced) has to be re-evaluated taking into consideration the UN Convention signed in 1988 against Illicit Traffic in Narcotic Drugs and Psychotropic Substances. The countries were forced by the Convention to introduce new arrangements in poppy production including selection and introduction of new cultivars.
In the present work up to date results of poppy selection are reviewed explaining the biosynthetic and eco-physiological background of their alkaloid accumulation. The effectiveness and the possibilities of traditional selection methods as well as the probability of the application of biotransformation for producing cultivars accumulating low or high alkaloid content or plant material with special alkaloid spectrum (codeine, thebaine, narcotine) are discussed. The examples of Hungarian cultivars 'Monaco', 'Kék Gemona' and 'Tebona' are given in more detail.
In the present study, g2ps1 gene from Gerbera hybrida coding for 2-pyrone synthase which contribute for fungal and insect resistance was used. The aim was to work out an efficient approach of genetic transformation for apple cvs. ‘Golden Delicious’, ‘Royal Gala’ and ‘MM111’, ‘M26’ rootstocks for improving their fungal resistance... using genetic engineering techniques. Adventitious shoot formation from leaf pieces of apples studied was achieved using middle leaf segments taken from the youngest leaves from in vitro-grown plants.
Optimum conditions for ‚direct’ shoot organogenesis resulted in high regeneration efficiency of 0%, 95%, 92%, 94% in the studied apples respectively. Putative transgenic shoots could be obtained on MS media with B5 Vitamins, 5.0 mg l-1 BAP, or 2.0 mg l-1 TDZ with 0.2 mg l-1 NAA in the presence of the selection agent “PPT” at 3.0-5.0 mgl-1. Shoot multiplication of transgenic shoots was achieved on: MS + B5 vitamins + 1.0 mg l-1 BAP + 0.3 mg l-1 IBA, 0.2 mg l-1 GA3+1.0 g/l MES+ 30 g/l sucrose + 7.0 g/l Agar, with the selection agent PPT at 5.0 mg l-1 and were subcultured every 4 weeks in order to get sufficient material to confirm transformation of the putative shoots obtained. Six, seven, one and six transgenic clones of the apples studied respectively have been obtained and confirmed by selection on the media containing the selection agent “PPT” and by PCR analysis using the suitable primers in all clones obtained for the presence of the selection” bar gene (447 bp) and the gene-of- interest “g2PS1” (1244 bp), with transformation efficiency of 0.4%, 0.6%, 0.1% and 0.3% respectively. These transgenic clones were multiplied further in vitro in the presence of the selection agent ‘PPT’ and rooted in vitro. Rooted transgenic plantlets were successfully acclimatized and are being kept under-containment conditions according to the biosafety by-law in Syria to evaluate their performance for fungal resistance .
Black locust (Robinia pseudoacacia L.) is the most important fast growing stand-forming tree species in Hungary. Its importance is increasing in many other countries, too. As a result of a new selection programme 13 black locust clones have been improved for setting up clones trials and seed orchard. In 2003 five of them (R.p. ...>`Bácska', `Homoki', 'Szálas', `Oszlopos' and `Vacsi') were registered as cultivarcandidates. Tissue culture method has proved as a suitable mean of propagating superior individuals. The micropropagated plants have been growing successfully in the clone trials.
Red wine culture in Hungary was developed due to the grapevine variety ‘Kadarka’, originated from the Balkans, from the 16th and 17th centuries. ‘Kadarka’ was the first grapevine variety cultivated on the largest area in Hungary until the 1950’s, but its production area has been reduced significantly in the past decades. In the period... of Hungarian grapevine reconstruction (from the 1960’s), the selection of the grapevine varieties and clones was determined by the system of cultivation (large growing space, large load and mechanized technology) that was based on the aspects of quantity. It did not promote the majority of the autochton and regional grapevine varieties to remain competitive. ‘Kadarka’ is a grapevine variety having an extraordinary variability in forms; however, a considerable part of its old stocks has disappeared. Nowadays, only two of its high yield clones are cultivated. ‘Kadarka’ becomes more differentiated from other, red wine producing, grapevine varieties, more preferred and newly requested by the fine aroma, spice, unique harmony of its wine less rich in tannin. The new market and environmental challenges in the field of wine production necessitate the preservation and improvement of the biological basis. In 2001 the Institute of Viticulture and Enology Pécs analyzed an old stock having a variability in forms in order to preserve the development and variability of the biological basis of ‘Kadarka’. Clones of great biological value were selected from it, with which the quality and yield security of ‘Kadarka’ can be increased. In 2010 and in 2012, six clones were submitted for state approval.
The effects of kanamycin and hygromycin-based selection and co-culture temperature ranging from 22 to 28 °C upon eggplant transformation efficiency were evaluated. Both morphogenic pathways, somatic embryogenesis and organogenesis, were adopted using cotiledonary and hypocotyl explants, respectively. Somatic embryos were recovered in the prese...nce of both antibiotics, although lesser escapes were observed in hygromycin-supplemented medium. Indeed, selection provided by this antibiotic was more efficient compared to kanamycin, nevertheless, shoot regeneration was not observed with hygromycin. Significant difference on the frequency of cotiledonary explants displaying callus (FEC) was observed as embryogenesis was concerned, although a higher number of embryos was observed in hygromycin selective media. The frequency of explants presenting callus (FEC), embryos (FEE) and shoots or buds (FERG) did not differ statistically for the tested co-culture temperatures, although higher regenerant number was observed at 24 °C.
Broadly the success of genetic transformation of plants requires non-chimeric selection of transformed tissues and its subsequent regeneration. With rare exceptions, most plant transformation protocols still heavily utilize antibiotics for the selection of transgenic cells containing an antibiotic-degrading selectable marker gene. The morphogen...ic capacity of in vitro chrysanthemum and tobacco stem and leaf explants change with the addition of aminoglycoside antibiotics (AAs). Of 6 antibiotics tested, phytotoxicity occurred at 10-25 and 50-100 pgml-I in chrysanthemum and tobacco explants, respectively, depending on the size of the explant and the timing of application. The presence of light or darkness also had a significant effect. The use of transverse thin cell layers (tTCLs) in conjunction with high initial AA selection levels supported the greatest regeneration of transgenic material (adventitious shoots or callus) and the lowest number of escapes. Flow cytometric analyses demonstrate that regeneration can be predicted in both species, depending on the ploidy level of the callus. Endoreduplication was not observed in chrysanthemum, even at high AA levels, but occurred (8C or more) in tobacco callus, even at low AA concentrations (5-10 pgml-1). The higher the AA level, the greater the DNA degradation and the lower the 2C and 4C values.
The aim of the first Hungarian apple breeding program for multiple resistance started in the beginning of the nineties is to widen Hungarian apple assortment by good quality, resistant apple cultivars with excellent productivity and ecological capability to the most important fruit growing areas in Hungary. In the first years of seedling produc...tion we made early selection for susceptibility to apple scab in greenhouse. Alter this, field observation of susceptibility to powdery mildew, scab and canker and a yearly negative selection was carried on. From 1997, fruit quality was evaluated as well, and from 2001 the resistance of shoots to Erwinia ainylovora (Burrill/Winslow et al.) was examined using inoculations in greenhouse conditions. From the progenies of crosses in 1992 and 1993, six candidates were announced to national recognition out of hybrids examined for more than a decade. Descriptions of these selections from 'Prima' progenies and the most important data of their resistance, growing habit, morphological characteristics and fruit quality are shown in this article.
GIS utilization in the site selection of a new fruit plantation
Results in table beet breeding (Review)
The choice of varieties among medicinal plant species is relatively small, compared to other horticultural crops. In Hungary, only poppy (Papaver somniferum) and mustard (Sinapis alba) have several cultivars. Recognising the problem, in the recent years breeding activity has been intensified all over the world, in spite of fin...ancial, technical and legal difficulties. The article reports on the results of breeding at the Department of Medicinal and Aromatic Plants of the Szent István University, 11 varieties of which has been officially registered till 2000. Main goals of genetic improvement are: increasing of the production capacity of utilised plant organs, enhancement of active material accumulation capacity, improvement of sensory quality and technological properties. The most often applied methods are selection, and recently, cross breeding, the results of which can be measured on new materials of caraway (Carum carvi), hyssop (Hyssopus officinalis), marjoram (Majorana hortensis), poppy (Papaver somniferum), etc. Efficacy of breeding work is established by additional, regular research on the genetics, physiology, floral and reproductive biology, chemosyndromes of medicinal plant species.
For the wide implementation of Levisticum officinalе C. Koch in Transcarpathia into production it is necessary to widen its sort composition, as it is rather poor in Ukraine. Solving this problem is possible by enriching the source material with the samples of different ecological and/or geographical origin, by studying the influence...of abiotic factors on the formation of green mass and seed productivity, separating the specimens best adapted to the conditions of growing, involving them into the selection process and creating new, highly productive sorts on this basis. The scientists of the Transcarpathian State Agricultural Experimental Station (TSAES) conducted researches (during 2011-2016) on the adaptive potential of the source material of the type of Levisticum officinalе C. Koch, which counts seven samples (Ukraine – 5 samples, Poland – 1, and Romania – 1), the selection work on creating new varieties for the given region is being done. The investigations were made on soddy podzolic gleyed low-humus soils with low content of nutrients. The results were obtained on the basis of generally accepted methods of investigation, i.e.: laboratory, field, visual, measuring-weighing, biochemical, mathematically statistic, and comparative-calculating. In the conditions of Transcarpathia the spicy greens of the high quality L. officinalе C. Koch are being gathered on days 25-30, the output of the essential oil makes up from 0.72 tо 1.89% on c.d.s., depending on the climate conditions of growing. The plants pass through all the stages of development, the bush is 55.4 to 92.7 сm in height, the plants form a big amount of rosette-shaped stems (11-34 pieces), the productivity of spicy greens is between 9.9 and 42.1 t hа1. The scientists of TSAES created the following sorts – Mriya (А. с. 06131 Ukraine, first registered in the State register of plant varieties of Ukraine) and Coral (Pat. on the variety № 140830). Economic effect from growing of the Coral variety in the conditions of Transcarpathia is 10230 UAH/ha and the level of profitability is 28.4%. The geographic position and agroclimatic conditions of Transcarpathia, as well as the unpretentiousness of L. officinalе C. Koch. tо the conditions of growing contribute to the enrichment of the local flora with useful plants; and the rich chemical composition contributes to the spread of this culture in the given region.
In Hungary, detection of virus and virus-like diseases of grapevine began in 1960's at the Research Institute for Viticulture and Enology by János Lehoczky and his colleagues. At present, sixteen virus and virus-like diseases of Vitis vinifera are known to occur in Hungary.
Regular virological screening of grapevine varieties...started in 1972. The present system of screening (visual selection, indexing, ELISA) has been established using methods with continuous improvement according to recommendations of international organizations.
In the first year symptomless grapevine plants are selected and marked during surveys carried out twice in the vegetation period: at about flowering and in the second half of September. At the first selection time plants are sampled for ELISA.
In the spring of the second year, overwintered canes are checked by woody indexing on 8 indicator species in the field.
In the third and fourth years the nursery is evaluated twice again. At the end, the marked grapevine plants, giving negative results on all indicators in every case, are considered virus-free.
In autumn of the fourth year, the virus-free material is planted out under screenhouse and also in a special mother block (nuclear stock) for maintenance and propagation.
Mother blocks of virus-free scion varieties have been established on 2 ha and those of rootstock varieties on 0.5 ha planted with the following number of varieties included in the national list: 71 European scion — and 12 rootstock varieties or variety candidates/clones. It is necessary to increase the area of Pre-base, Base and Certified stocks exclusively with tested virus-free (clean) material.
We have found that 50 mg/I kanamycin and 0.8 Mo1/1 mannitol concentration was sufficient to kill the control callus of bean (Phaseolus vulgaris L.) and differentiate transgenic from the non-transgenic cells. The GeneBooster particle delivery system was used for the bombardment of bean callus. The kanamycin resistance g...ene was used as a selectable marker. The test was made by transferring the healthy white callus, subcultured for three months on selective and non-selective medium. After selection on kanamycin containing media, several kanamycin resistant calli had been obtained, survived and grew. After selection on mannitol containing media no drought resistant calli had been obtained. Resistance of the selected calli were verified by their ability to grow repeatedly on selective medium containing 150 mg/I kanamycin. Selective pressure was maintained over a period of 8 months.
In the past years zucchini yellow mosaic virus (ZYMV) has been appeared as a new pathogen of cucurbitaceous plants in Hungary. It caused severe disease outbreaks on the fields of pickling cucumber hybrids which are highly tolerant to cucumber mosaic virus (CMV). Preliminary inoculation tests have showed that all of the important pickling cucumb...er hybrids produced in Hungary were susceptible to ZYMV-P. However, a selection of Chinese Long and the breeding line I- KS 10C proved to be highly tolerant. The Fl plants of the crosses between the tolerant lines and the susceptible genotype H I were susceptible to ZYMV-P. F2 populations segregated for susceptible and tolerant individuals at a ratio of 3:1. The results strongly suggest that the resistance to ZYMV in our sources is controlled by a single recessive gene. Inoculations of the ZYMV and CMV susceptible cultivar Budai csemege and the CMV tolerant hybrid Perez Fl with the complex of ZYMV+CMV resulted extremely severe symptoms (strong mosaic and necrotic spotting of the leaves) on both cultivars. On the Chinese Long line, which is tolerant to ZYMV and CMV, respectively, the complex of the two viruses caused mild symptoms. The results show a synergistic pathological effect of ZYMV and CMV on differrent cucumber genotypes. More detailed studies on the interactions among the plant genotypes, viruses and virus strains are needed to develop cucumber hybrids that are highly resistant to the ZYMV+CMV complex.
Breeding for pest and disease resistance comes as a major objective behind the fruit traits. To increase the effectiveness of fruit resistance breeding application of the Marker Assisted Selection ( MAS) is advantageous. For generating molecular markers which enable the following of interesting traits basically two methods are available: target...ed marker design based on conservative region of already known Resistance ( R) gene sequences or randomly generated markers. The creation and the application of these homology based markers are the object of this review in the main temperate zone fruit species.
Utilization of the Randomly Amplified Polymorphic DNA (RAPD) technique as a molecular marker was tested to investigate the relationships between some representative grapevine cultivars and hybrids established at the Department of Genetics and Plant Breeding (CUB), to distinguish clones as well as to characterize various hybrids between spec...ies or cultivars and their parents. Vitis vinifera cultivars were easily and successfully distinguished by the RAPD technique and they were grouped according to the traditional taxonomic classification. RAPD patterns of the examined Pinot gris clones proved to be completely identical. Number of generations was reflected by the value of genetic distance of the examined hybrids. Genetic identity of parents and their offsprings was influenced by the selection applied in the process of plant breeding. Parental phenotypic and morphologic characteristics showed high degree of segregation in hybrids, but RAPD analysis revealed that their genetic similarity is considerable. The three Vitis anntrensis clones were properly discriminated from every cultivar and hybrid of Vitis vinifera, i.e. hybrids are much closer to the cultivated grapevine than to V. anzurensis due to the phenotypic selection carried out during the life-cycle of one or two generations.
Researches concerning the selection of some nectarine varieties as genitors for the breeding program in Romania
The black elder (Sambucus nigra L.) is a native plant in Hungary represented by extended and very variable populations. Cultivation of elderberry started during the late 90-ies because of the growing interests of the processing industry. High anthocyanin content, nutritive value of the berries and aromatic compounds of the flowers have been the... esteemed constituents.
At the moment, there are about 3000 hectares elder plantations in Hungary, which is more than of any of the other European countries. Unfortunately, the cultures are planted to the Austrian selections of Haschberg, in spite of the fact that about 10-15 other selections of other foreign countries have been registered and planted elsewhere. In addition to that, the wild population of Hungary may offer a precious opportunity of further selection. Since 1970, Aladár Porpáczy at Fertőd and the Department of Fruit Growing of the former University of Horticulture in the 1980-ies started the selection in Hungary too.
The present study deals with 7 genotypes, their morphology of berries and inflorescences. Results are concentrated on four genotypes: Szcs1, Szcs-2, Szcs-3 and Szcs-5, which are all earlier ripening than the Haschberg varieties, and are superior in characters of fruit and inflorescence.
Widespread application for herbal medicines based on Hyperici herba has been experienced in the last few years, especially in the treatment of depression syndrome. As the wild origins could not satisfy the market demands neither in quantitative nor in qualitative respect, the necessity of the development of intensive growing methods...has been raised. In the course of our investigations we intended to clear up the morphological and chemical variability among and within populations of different origin in order to start a new breeding program. According to our data, growth dynamics of populations could be characterised by a logistic curve. According to the time of flowering the populations formed early, middle and late groups. Morphological diversity among populations was measurable in differences of flower length, plant height, different leaf types and plant habit, according to which characteristics groups were distinguished. Generally, the accessions were the most homogenous in plant height (CV: 7-15%), followed by inflorescence-lengths (CV: 11-36%) and the least uniform characteristics proved to be the number of flowering shoots (CV: 14-59%). The greatest morphological heterogeneity was experienced in the accessions of wild origin as it has been expected. In the second vegetation period generally a much better homogeneity was obtained, than in the first year. The most outstanding accessions produced 1.2 t of dry flowers and 4 t of dry flowering shoots, calculating to one hectare area. The individual yields varied on a large scale in each population (CV: 18-70%).
The content of hypericin varied between 1,85 and 9,9 mg/g in 1996, and between 0,18 and 2,70 mg/g in 1997, showing high individual divergences. Flavonoid values -including first of all hyperosid, rutin and quercitrin - reached 17-39 mg/g in the first and 15-20 mg/g in the second year, respectively. Individual and seasonal variation was less than in hypericin. A joint high level of these two compound groups seems to have low frequencies.
The superior population were selected for further breeding.
Black locust (Robinia pseudoacacia L.) was the first forest tree species introduced from North America to Europe, at the beginning of the 17th century. Its unprecedented fast spread is due to its high-grade adaptability, drought-tolerance, abundant and frequent seed crop, excellent sprouting ability, fast growth and relatively high timber yield.... Other advantages are, that it has scarcely any fungi or insect pests. This review is a short summary on black locust improvement in Hungary, giving guidance for specialists who are interested in black locust management.
Hungary is traditionally a food producer country. 63% of its total land area can be cultivated. Horticulture is one of the fundamental agricultural branches. The country has a moderate continental climate, with a mean temperature of 10 °C. The average hours of sunshine ranges 1,700 to 2,100 hours. Under the geographical condition in the Carpat...hian Basin the chemical composition of the fruits has a good harmony. The total fruit acreage is 97,000 ha with a crop of 800,000 to 900,000 tons yearly. In 1982 1,934,000 tons of fruit crop were produced since then it has decreased. The most important fruits are apple, European plum, sour cherry and raspberry. The percentage of apple reaches almost up to 60%. In the new plantings sour cherry, apple and black elderberry is popular. The most important fruit-producing region is situated at the North-eastern part of the country. More than 40% of Hungary's fruit production is concentrated there. In ranking the 2nd place is taken by fruit growing area in the middle of Hungary, where the production of stone fruits and small fruits has a considerable proportion.
In the 70s and 80s of last century there was a developed research structure and wide range of research activity in Hungary. From that time the research capacity has considerably decreased first of all in the field of technological development. The main research area is fruit breeding and variety evaluation.
Fruit scientists and fruit grower specialists are held together by the Hungarian. Society for Horticultural Sciences which has a membership in ISHS. Fruit researches and scientists having academic degree are belonged to the Horticultural Board of Hungarian Academy of Sciences.
For adequate yields in apple plantations, during the long growing period of the fruit primordia, one of the decisive factors is water supply. Indicators of stress are valuable signs for the diagnosis of drought and necessity of watering, i.e. planning the irrigation of plantations. The aim of the present study was to find reliable signs of wate...r stress on apple trees and at the same time conclude on the drought tolerance of different varieties. The plantation of apple varieties grafted on various stocks and cultivated according to different systems (irrigated, non irrigated, integrate and biological) has been examined continuously by leaf analysis. Along the period of growing fruits, measurements were made in the field, then the leaf samples were analysed in the laboratory for composition of pigments, carbohydrates and antioxidants, as well as the histology of the tissues checked. Without irrigation, the mean leaf mass and the relative chlorophyll content (SPAD) of the variety Idared on M4 stocks increases beyond the values of 50 SPAD, whereas on M26 stock and integrated system, it declines. In the collection of varieties, grown according to the „integrated” system, during the development of fruits, ‘Gála’ and ‘Remo’ varieties have been affiliated to the “less susceptible” group regarding drought tolerance because of the leaf morphology, structure and content of SPAD and antioxidants. However, ‘Idared’ and ‘Jonagold’ belong to the “susceptible” group. To the same group are ranged the ‘Akane, Red Rome vanWell, Pink Lady’ varieties. Those varieties reacted to a short period of drought by increased production (content) of carbohydrates. Regarding changes of carbohydrate content ‘Greensleeves’ and ‘Ozark Gold’ varieties belong to the moderately water dependent (requiring) group. In the field, SPAD-tests facilitated the measurement of nutrient-uptake and incorporation, which is proved by the tight correlation between the data of SPAD and the increment of leaf weight (r=0.76–r=0.88), however, this depends on the variety too. SPAD is an indicator of water supply and is related with the density of stomata, cannot used for the selection of water-exigent varieties but for (drought) tolerant ones. In integrated culture, the (drought) susceptible varieties display (water-soluble) hydrophilic and lipophilic antioxidants (ACWand ACL resp.) the quantity of which may have some role in drought tolerance.
In addition to successes achieved in certain varieties in resistance breeding based on a defense reaction of host plants involving hypersensitive tissue destruction, resistant varieties putting a very strong selection pressure on pathogens have selected more and more aggressive types of pathogens. The never-ending race between plant and pathoge...n resulting from this can only be controlled by a defense system characterised by a different strategy. In each of the plant species that we bred a defence system was found, which contrary to hypersensitive reaction strives to keep the tissues at all costs and is not pathogen specific. This is implied in the term general defense system.