Resistant Cvs Research Articles

Результати визначення стійкості до фузаріозного в’янення сортів робочої колекції калістефусу китайського (Callistephus chinensis (L.) Nees)

The purpose of the researches was establishing the resistance of Callistephus chinensis (L.) Nees working collection cvs to Fusarium oxysporum f. sp. callistephi (Beach) Snyder et Hansen under the condition of the Kyiv region. The object was the working collection of the of Callistephus chinensis (L.) Nees genetic fund of the Institute of Horticulture, NAAS of Ukraine. The valuation of the collection resistance has shown that 70 samples are practically not affected with the mentioned disease, 20 varieties do weakly, 5 strains severely and 5 cultivars very sevely. Most of resistant cvs concerning the household use are just plants assigner for cutting off (the bouquet formation). The appreciation of the affection level of the varieties in the collection has shown that 70 strains, that is 70 % of all the cultivars may be considered the most resistant ones, 50 cvs, that is 50 % of the whole collection are of high quality and those which are affected with the investigated disease were 5-20 %. Besides, the varieties which are high resistant belong to the varieties Pryncesa, Khudozhnia, Troiandopodibna and other. The analysis of the Callistephus chinensis (L.) Nees plants seeds productivity (g/bush) has shown that this index of the non-resistant strains is average. Thus, the results of the studies have shown that 70 cultivars, that is 70 % of the collection are the sources of the Fusarium causative agent (8.8 points). Cvs bred at IH NAAS (Zolota, Rozkishna, Kniagynia, Litnia Nich, Tsarivna, Shokoladka, Sophiia, Yantarna, Krasunia, Flamingo, Mariia etc.) blong to this group as well as 50 varieties of high or namentality (95-99 points), that is 50 % of the total collection are affected with the explored disease (5-20 %). The longer the plants flowerig stage lasts the oftener they prove to have F. oxysporum f. sp. callistephi (Beach) Snyder et Hansen.

Специфіка процесів проростання насіння калістефусу китайського (Callistephus chinensis (L.) Nees.)

The morphological peculiarities of the 10 Callistephus chinensis (L.) Nees. cultivars (Anastasia, Angelina, Kirswell, Lybid, Oksana, Polina, Pryntsesa, Roksolana, Rozkishna, Rubinovyie Zviozdy, Yabluneva) of the different genetic origination and 10 hybrid forms (143-4, 151-4, 178-4, 193-3, 210-1, 256-4, 261-2, and 265s-2-1 bread at Institute of Horticulture of National Academy of Agrarian Sciences of Ukraine were analyzed in order to carry out the resultative selection of resistant cvs, preserve their genetic fund and enlarge the assortment of the floral and ornamental plants. The authors have, presented the results of studying the morphological peculiarities of the researched crop seeds, indices of their generation biology, seed productivity level of different varieties and hybrids. The obtained results confirm the high efficiency of the Calistephus chinensis (L.) Nees. cultivars and hubris forms seed reproduction. The tendency has been detected of the increase of the average mass of 1000 seeds of cvs and hybrids of the flowering late terms. The hybrid form 210-1 distinguished it self for the highest respective index (2.75 g), the variety Rubinovyie Zviozdy had the lowest one (1.59 g).Yabluneva and 210-1 had the largest seeds linear size. According the average indicators of the seed vigour and germination rate the group of the cultivars and hybrids of the early bloom term exceeds considerably the rest of cvs and hybrid forms. The indices of the seed laboratory germination rate correlate with those of the germination vigour. Among the varieties of the average and Yabluneva distinguish them selves for the high seed material sowing qualities and have appeared the most perspective for the effective reproduction. The Calistephus chinensis (L.) Nees. plants seed productivity depends substantially the cultivar peculiarities and foreign cv Kirbiwell has distinguished itself for this high indicator (5.8 g/bush) when sowing in the sheltered ground under the constitution of the collectional patch of/the Laboratory of the Floral, Ornamental and Medicinal Crops of IH NAAS.

Genesis of ultra-specialized histology with stable traits in mesophyll of drought tolerant apple cultivars

Even if some biological defense responses are activated instantaneously after stress occurrence, but other mechanisms of drought tolerance could be probed, detected and diagnosed as sable traits at mesophyll level. The present observations demonstrated multilateral modifications in different leaf parts, specialized parenchyma tissues and cribro-vascular bundles that facilitate vital activities in tolerant apple cultivars. In 2006, long deficit irrigation occurred in commercial apple collection containing 93 cultivars located in Karaj-Iran. Entire bearing 16-Year-old trees lost completely the crop except 16 CVs which were assessed for yield per tree since June drop to physiological maturity. Based on thehypothesis, stable traits were developed against drought stress through phenomenon of genesis. 19 different anatomical traits of mesophyll were accurately assessed in the selected resistant CVs compared with the susceptible "Golden Delicious" and native "Assali" as the controls. Microscopic studies computed on the transversal sections of mesophyll prepared by microtome ascertained ultra-specialized histological traits in the selected CVs. Morphologically, basal part of the main vein was completely spherical, outfitted, highly ordered and tidy tissues. Epidermis underlying layer was composed of well-organized tissues containing uniform cells by shape and size, inserted consistently next to one another in neat order with no intercellular space. Contrarily, controls showed opposite rhythm in all examined characters. Also, the mean number of epidermis layers at leaf margin resulted higher related to susceptible CVs. The mean number of vascular bundles and stomata decreased in tolerant CVs. These observations put in evidence some stable ultra-specialized histological traits of mesophyll, as a result of genesis route.

Changes in Aggressiveness of the Ascochyta lentis Population in Southern Australia.

Anecdotal evidence identified a change in the reaction of the resistant lentil cv Nipper to ascochyta blight in South Australia in 2010 and subsequent seasons, leading to infection. This study investigated field reactions of lentil cultivars against Ascochyta lentis and the pathogenic variability of the A. lentis population in southern Australia on commonly grown cultivars and on parental germplasm used in the Australian lentil breeding program. Disease data recorded in agronomic and plant breeder field trials from 2005 to 2014 in southern Australia confirmed the change in reaction on the foliage of the previously resistant cvs Nipper and Northfield. Cultivar responses to seed staining from A. lentis did not change. The change in foliar response was confirmed in a series of controlled environment experiments using single, conidium-derived, isolates of A. lentis collected over different years and inoculated onto differential host sets. Specific isolate/cultivar interactions produced a significant range of disease reactions from high to low aggressiveness with a greater percentage of isolates more aggressive on cvs Nipper, Northfield and PBA Flash than previously detected. Specific isolates were tested against Australian lentil cultivars and breeding lines in controlled conditions, again verifying the aggressiveness on cv Nipper. A small percentage of isolates collected prior to the commercial release of cv Nipper were also able to infect this cultivar indicating a natural variability of the A. lentis population which subsequently may have been selected in response to high cropping intensity of cv Nipper. Spore release studies from naturally infested lentil stubbles collected from commercial crops also resulted in a high percentage of infection on the previously resistant cvs Nipper and Northfield. Less than 10% of the lesions developed on the resistant differentials ILL7537 and cv Indianhead. Pathogenic variation within the seasonal populations was not affected by the cultivar from which the stubble was sourced, further indicating a natural variability in aggressiveness. The impact of dominant cultivars in cropping systems and loss of effective disease resistance is discussed. Future studies are needed to determine if levels of aggressiveness among A. lentis isolates are increasing against a range of elite cultivars.

English

Novel strategies for Plutella xylostella management in cabbage need to be evaluated in order to increase its control and reduce adverse impacts on the environment. Thus, we evaluated the combined effects of the cabbage cultivars Ruby Ball, Matsukase Sakata, and Sessenta Dias, the aqueous extracts of Azadirachta indica, Aspidosperma pyrifolium, and Melia azedarach, and the parasitoid Oomyzus sokolowskii on P. xylostella control and selectivity to the parasitoid. This study attempted to give insights to further elaborate an IPM strategy for cabbage crop. The first assay recorded P. xylostella mortality, and the second assay recorded the number of parasitoids emerged from P. xylostella pupa and O. sokolowskii immature development in two successive generations. Cultivar Ruby Ball treated with A. pyrifolium extract increased P. xylostella mortality over 85%. Parasitism by O. sokolowskii combined with A. pyrifolium or A. indica extracts provided up to 95% mortality, regardless of the cabbage cultivar. Cultivar Matsukase Sakata treated with M. azedarach or A. indica extracts affected adversely O. sokolowskii development. The number of parasitoids emerged from P. xylostella pupa was increased from the first to the second generation on the resistant cvs. Ruby Ball and Matsukase Sakata. Further experiments are encouraged to confirm in greenhouse and field the high mortality rates of P. xylostella and selectivity to O. sokolowskii, in order to elaborate an efficient IPM program for cabbage against the diamondback moth. Key words: Brassica oleraceae var. capitata, diamondback moth, host plant resistance, integrated pest management, Oomyzus sokolowskii, plant extracts.

Role of salicylic acid in systemic resistance induced by Pseudomonas fluorescens and Trichoderma harzianum against Alternria solani in tomato

Tomato growers are suffering all over the world from massive losses due to root rot diseases, the study aims mainly to study the effect of treatment with many safe fungal and bacterial biological control agents as indicative signal particles to induce host systemic resistance under greenhouse conditions. Some essential parameters and evidences of resistance were determined, i.e. accumulation of salicylic acid (SA).One week after inoculation tomato seedlings with A. solani, previously pretreated with the tested biological inducers, endogenous SA content showed significant increase in all the tested cultivars. Moreover, SA content in resistant cvs were higher, compared with susceptible cvs (1.04-fold over that of susceptible CV).

고추약한모틀바이러스 병원형에 대한 파프리카 품종의 저항성 스크리닝

파프리카에 고추약한모틀바이러스가 감염되면 과일에 검은 반점이 형성되어서 상품과를 생산할 수 없다. 파프리카 10품종을 대상으로 PMMoV 병원형 <TEX>$P_{1.2}$</TEX> 및 <TEX>$P_{1.2.3}$</TEX>에 대한 저항성 품종 선발을 목적으로 생물 검정과 유전자 마커를 이용하여 분석하였다. 이들 품종에서는 Tobamovirus에 대한 저항성 저항성 마커형 <TEX>$L^1$</TEX>, <TEX>$L^3$</TEX> 및 <TEX>$L^4$</TEX>가 존재가 확인되었으나, <TEX>$L^2$</TEX> 저항성 마커형은 검출되지 않았다. SCAR와 CAPS 마커를 이용한 파프리카 품종의 저항성 마커형을 분석한 결과, 'Magnipico'와 'Easy'는 <TEX>$L^4L^4$</TEX>, 'Scirocco'와 'Orange glory F1'는 <TEX>$L^4L^3$</TEX>, 'Special F1'는 <TEX>$L^4L^1$</TEX>, 'Fiesta', 'Piero' 및 'Derby'는 <TEX>$L^3L^3$</TEX>, 'Cupra'와 'Mazzona F1'는 <TEX>$L^3L^1$</TEX>이 확인되었다. 2종의 병원형에 대한 저항성 품종은 'Magnipico', 'Easy', 'Scirocco F1', 'Orange glory' 및 'Special F1'이었고, 감수성 품종은 'Fiesta', 'Piero', 'Derby', 'Cupra' 및 'Mazzona F1'이었다. <TEX>$L^4$</TEX>의 유전형이 부재한 이들 감수성 품종은 PMMoV-<TEX>$P_{1.2.3}$</TEX>을 접종시 전신 감염되었다. 하지만 이들 품종은 저항성 마커형 <TEX>$L^3$</TEX>가 존재함에도 불구하고 PMMoV-<TEX>$P_{1.2}$</TEX>를 접종시 접종엽은 엽맥을 따라 괴사가 일어나면서 식물체의 상단부위는 과민감한 괴사 증상이 나타났다. The Paprika plant infected with Pepper mild mottle virus (PMMoV) do not produce commercial fruit as causing necrotic spots symptom on the fruit. Ten cultivars of paprika were analyzed to select the resistance cultivars against PMMoV pathotypes, <TEX>$P_{1.2}$</TEX> and <TEX>$P_{1.2.3}$</TEX>, using bioassay and genetic markers. <TEX>$L^1$</TEX>, <TEX>$L^3$</TEX>, and <TEX>$L^4$</TEX> genotypes expressing resistance to the pathotypes existed in those cultivars but <TEX>$L^2$</TEX> genotype did not. <TEX>$L^4L^4$</TEX> in cvs. Easy and Magnifico, <TEX>$L^4L^3$</TEX> in cvs. Scirocco and Orange glory F1, <TEX>$L^4L^1$</TEX> in cv. Special F1, <TEX>$L^3L^3$</TEX> in cvs. Fiesta, Piero and Derby, and <TEX>$L^3L^1$</TEX> in Cupra and Mazzona F1 were identified with SCAR and CAPS markers. The resistant cvs. to the 2 pathotypes were Magnipico, Easy, Scirocco F1, Orange glory and Special F1 and the susceptible cvs. were Fiesta, Piero, Derby, Cupra and Mazzona F1. The susceptible cvs. of the absence of <TEX>$L^4$</TEX> genotype showed systemic infection when inoculated with PMMoV-<TEX>$P_{1.2.3}$</TEX>. However, those cvs. despite the presence of <TEX>$L^3$</TEX> genotype showed vein necrosis on the inoculated leaf and hypersensitive necrosis symptom on the upper parts when inoculated with PMMoV-<TEX>$P_{1.2}$</TEX>.

Common bunt resistance of Czech and European winter wheat cultivars and breeder lines

Winter wheat cultivars recently registered in the Czech Republic were tested in three-year field tests for resistance to common bunt. Seeds were inoculated with a mixture of local strains of Tilletia tritici and T. laevis. None of the cultivars displayed a higher level of resistance compared with the resistant checks. The mean percentage of bunted ears in the three test series including checks was 39%. Mean bunt infection in resistant and susceptible checks was 2% and 63%, respectively. In the European Tilletia cooperative test performed in Prague-Ruzyně, thirty-five winter wheat cultivars from six countries were tested during 2007&amp;ndash;2013. The cultivars Bill, Nadro, Quebon, Samurai, Stava and Tommi exhibited infection levels below 10% in the respective years of the test. Additionally, 75 breeding lines from six countries were tested. Infection levels below 1% were recorded in 56% of the lines and 1&amp;ndash;10% levels in 19% of the lines. A close relationship between the resistant cvs. Tommi and Globus was confirmed using SSR allelic markers.

Differential Induction of 3-deoxyanthocyanidin Phytoalexins in Relation to Colletotrichum falcatum Resistance in Sugarcane

Sugarcane secrets a reddish pigment presumed to contain phytoalexin compounds in the stalk tissues in response to infection of Colletotrichum falcatum, causing red rot. To identify the phytoalexin compounds involved in red rot resistance, detailed HPLC analyses were conducted using the phytoalexin standards in a set of sugarcane cultivars varying in red rot resistance, after pathogen inoculation. We found nine different 3-deoxyanthocyanidin phytoalexin compounds, which are differentially induced upon C. falcatum infection in sugarcane varieties with varying degrees of disease resistance. Among the nine compounds, four compounds were identified as luteolinidin, 5-methoxy luteolinidin, apigeninidin and arabinosyl-5-O-apigeninidin. Multifold induction of luteolinidin, apigeninidin and arabinosyl-5-O-apigeninidinin were recorded in the stalk tissues in disease resistant cvs Co 93009, BO 91 and Baragua, respectively after pathogen inoculation as compared to the susceptible cv CoC 671. In addition to the known compounds one to three unknown compounds were detected in the resistant cultivars. The susceptible cultivars exhibited a placid induction of phytoalexin compounds after pathogen infections. The results very clearly demonstrated a specific induction of 3-deoxyanthocyanidins in resistant cultivars at a higher level as compared to susceptible cultivars after C. falcatum infection in sugarcane. Total extracts of the induced phytoalexins in the calorimetric assays, also revealed similar results. Probably induction of either luteolinidin or apigeninidin compounds alone or in combination at higher concentrations in the resistant cultivars may enable the effective arrest of pathogen invasion and further development inside the stalk tissues.

OVERCOMING OF THE RESISTANCE IN RESISTANT GENOTYPES OF DRY PEA (PISUM SATIVUM) BY AN ISOLATE OF ERYSIPHE PISI IN ITALY

Powdery mildew (PM), caused by Erysiphe pisi DC, is the major disease of dry pea in southern Italy and the use of resistant cultivar is the best choice to control it. Screening field trials were conducted with eleven pea genotypes in four different farms located in the typical pea-growing areas of the Campania region (Scafati, Caserta, Acerra and Eboli). All resistant varieties showed no symptoms in three (Scafati, Acerra and Eboli) of the tested environments, whereas at Caserta, three of the cultivars i.e. Fallon, SW Carousel, and ISCI 7/06-2, which are reported to carry the powdery mildew resistance gene er1 showed symptoms, whereas the resistance of cv. Stirling was confirmed. Following artificial inoculation under greenhouse conditions, the three above cultivars supposed to carry er1 gene showed severe PM symptoms when exposed to the fungal isolate EpCE2 from Caserta. No symptoms were obtained with the other three isolates tested. The cv. Stirling maintained its resistance both in the field and greenhouse. Morphological and molecular analyses of the fungus that induced disease on resistant cultivars proved that the isolates used as inoculum belong to E. pisi. This result was confirmed by the molecular analysis performed on the leaves of resistant cvs Fallon, SW Carousel and ISCI 7/06-2 inoculated with the EpCE2 isolate from Caserta. Thus, the resistance conferred by the er1 gene can be broken and further investigations are needed to clarify the different behavior of resistant cultivar. To our knowledge, this is the first time that breaking of er1 resistance is reported in Italy.

Aphid resistance in raspberry and feeding behaviour of Amphorophora idaei

The raspberry aphid Amphorophora idaei is a major pest of the raspberry plant and a vector of different viruses like Raspberry leaf mottle virus (RLMV), Raspberry leaf spot virus (RLSV), Black raspberry necrosis virus (BRNV) and Rubus yellow net virus (RYNV). Aphid resistant raspberry genotypes additionally show a reduced occurrence of viruses, thus the aim of this study was to investigate whether the feeding behaviour of A. idaei differs between aphid resistant and susceptible plants. In a biotest the cultivars (cvs.)‘Titan’,‘Rumiloba’,‘Nootka’,‘Schoenemann’,‘Williamette’ and‘Autumn Bliss’ show different levels of resistance. A significantly lower population was observed after 27 d on the resistant cvs.‘Rumiloba’ and‘Autumn Bliss’ in comparison to the other cultivars tested. The number of aphids on cv.‘Nootka’ was higher than on the resistant cultivars but significantly lower than on the susceptible cvs.‘Titan’,‘Williamette’ and‘Schoenemann’. The feeding behaviour was studied over a period of 12 h on plants of the cvs.‘Rumiloba’,‘Nootka’,‘Schoenemann’ and‘Autumn Bliss’ by using the electrical penetration graph (EPG) technique. Overall between 62% and 68% aphids tested per cultivar made probes on the leaves and penetrated into the phloem. On the resistant cv.‘Rumiloba’ the aphids started to probe considerably later (49.3 min) than on the other cultivars (12.1 to 33.1 min). In contrast, the first probe on‘Rumiloba’ was shorter (2.2 min) than on the resistant cultivars (23.9 to 63.5 min). On average the aphids attained the phloem on the susceptible cv.‘Schoenemann’ considerably earlier (221.1 min) than on the resistant cultivars (349.5 to 370.4 min). On the resistant cv.‘Nootka’ significant differences were found for the duration of phloem salivation (E1-pattern, 810.9 s in comparison to 24.3 to 176.9 s), the number of phloem salivation phases (2.7 in comparison to 0.1 to 0.2) and the number of phloem contacts before the sustainable phloem feeding (> 10 min) started (1.1 in comparison to 0.1 to 0.2). No differences were found between the cultivars for the number and duration of potential drops (cell penetrations) during the pathway to the phloem, analysed during the first 2 hours of the experiments. The obtained results indicate that the probing and feeding behaviour of A. idaei, which is responsible for virus transmission, is not sufficiently different between resistant and susceptible cultivars to be the reason for virus resistance.

APHID TOLERANCE OF DIFFERENT HOP GENOTYPES: FIRST ATTEMPTS TO DEVELOP A SIMPLE BIOTEST FOR HOP BREEDING BY THE USE OF PHORODON HUMULI

A keystone of future pest management in hops is the breeding of cultivars (cvs.) that are tolerant or resistant to Phorodon humuli infestation. During 2006 and 2007 first attempts were made for the development of a biotest concerning the aphid susceptibility of different hop genotypes. We chose for these tests the susceptible cvs. 'Hallertauer Magnum' (HM) and 'Herkules' (HS), the aphid-tolerant or -resistant cvs. 'Spalter Select' (SE) and 'Boadicea' (BO), and two apparently resistant genotypes from our germplasm - the male accession 38 and the wild hop Jena 49. Aphid cages were mounted to leaves taken from potted greenhouse plants of these six genotypes, and each cage was equipped with an aphid larva with known day of birth. The leaves (12 replications per genotype) were stored in a climate chamber, and the 72 cages opened three times a week to count and remove all newborn larvae. The mother aphids stayed in their cages until the death of the last aphid marked the end of a series. Altogether eight series were conducted. The cumulative alive offspring of one aphid was highest on HM, with an overall mean number of 66.2 larvae, and lowest on 38, with 14.9 larvae. However, overall means of the other cvs. were not significantly lower - 59.7 on HS, 59.6 on SE and 57.6 on BO. The maximum number of larvae produced by one aphid was 115 on HM. The lifespan of the aphids was longest on HM, with an overall mean of 39.8 days, and shortest on 38, with 24.4 days. The other genotypes produced similar lifespans from 31.7 to 34.3 days. The record holder survived on HM for 69 days. These results, especially concerning the aphid-tolerant cvs. BO and SE, demonstrate that for the development of a practical, simple aphid biotest there is still a long way to go.

SOME QUALITY CHARACTERS AND INVERTASE ENZYME ACTIVITY IN RELATION TO CERCOSPORA LEAF SPOT DISEASE CONTROL IN SUGAR BEET

Screen house experiment was carried out at Sakha Agricultural Research Station, Kafr El-Sheikh Governorate during 2007/2008 season to study the relation between fungicide and plant extract application on Cercospora beticola incidence and related characters as well as invertase enzyme on sugar beet. Two cultivars of sugar beet were selected; the two cultivars; Ras Poly and Fareda were used and planted in a split plot design. Topsin M70 (1 gm/liter) and plant extract Khella “Ammi visnaga” or pick-tooth (4000 ppm) were sued to control the disease. Artificial inoculation was done by using conidiospores suspension of Cercopora beticola. Inoculation was done 90 days after planting. Chemicals were applied three days before inoculation. Different traits were measured like, disease severity (%), root weight/plant, sugar percentage, sugar loss to molasses %, invertase enzyme activity, impurities in leaves and roots (Na+, K+ and a-amino-N), TSS %, chlorophyll content of leaves, purity (%), loss % for root and sugar. Seven readings to asses the disease incidence were taken. Disease severity (%) of cercospora leaf spot disease incidence was increased gradually especially for Ras Poly cv. than Fareda cv. under infected condition, but showed less values when treated with Topsin M70 followed by Khella. On the other hand, root weight, TSS%, sugar percentage, purity were highly affected than those under fungicide and plant extract treatments and loss percentages for root and sugar reached to maximum for Ras Poly than Fareda cv. Enzymatic activity of invertase reached the maximum under inoculation, while it was less when treated by Topsin M 70 and Khella plant extract. Na+ and a-amino N increased by increasing disease severity (%), while K+ behaved in different manner. Concerning reducing sugars in roots, recoverable sugar (%) and sugar loss to molasses increased by increasing disease severity (%), low values were obtained under fungicidal and plant extract treatment. Plant extract and resistant cvs, must be recommended to reduce the pollution either in water or in the soil of sugar beet plantations.

COMPARISON OF SCREENING METHODS FOR THE EVALUATION OF OLIVE RESISTANCE TO VERTICILLIUM DAHLIAE KLEB.

Three inoculation methods for screening olive germplasm for resistance to Verticillium dahliae Kleb. were compared: (i) dipping soil-free washed roots into inoculum (WRI); (ii) dipping root balls with soil into inoculum (RBI); (iii) direct introduction of the inoculum into a stem incision (SII). The effectiveness of the methods was compared in their capacity to differentiate levels of resistance/susceptibility to Verticillium wilt in olive germplasm. Genetically homogeneous clones of the olive cvs Frantoio, Coratina and Leccino, which have different degrees of resistance/susceptibility to wilt, were inoculated with one defoliating and two nondefoliating V. dahliae pathotypes. Results indicate that the three screening methods had different sensitivity in identifying variable levels of olive resistance to Verticillium wilt. Inoculation of washed roots (WRI) was the most drastic and may be used to identify higher levels of resistance (such as that of cv. Frantoio), but was not sensitive enough to detect lower levels of resistance. Inoculation of root balls with soil (RBI) was less destructive and allowed detection of lower resistance expression (such as that of cv. Coratina), not detected by WRI. Stem incision inoculation (SII) failed to discriminate between resistant (cvs Frantoio and Coratina) and susceptible (cv. Leccino) germplasm.

Chitinase levels in rice cultivars correlate with resistance to the sheath blight pathogen Rhizoctonia solani

Various rice cultivars were selected and screened for their reaction to sheath blight in the greenhouse. Cluster analysis of percent relative lesion height (% RLH) generated four groups of cultivars with a coefficient of similarity of 3.27. Chitinase activities were detected 24 h after inoculation of moderately resistant cvs Betichikon, Dudruchi, Khatochalani, Padi Pulut Malat, Kakua, IR72, Khakibinni. But in the susceptible cv. IR58, chitinase activity was detected only 36 h after inoculation. Western blot analysis showed that class 1 and class 2 chitinases were induced following Rhizoctoniasolani infection of these cultivars. The % RLH and the number of infection cushions were negatively correlated with the level of chitinase activity. Moderately resistant rice cultivars had higher levels of chitinase activity and lower disease severity and numbers of infection cushions formed compared to IR58.

Heritability of Latent Period Estimated from Wild-Type and Selected Populations of Puccinia triticina

ABSTRACT Durability of partially resistant wheat cultivars to wheat leaf rust depends on the amount of genetic variation in parasitic fitness within populations of the pathogen Puccinia triticina. To assess the durability of partial resistance, selection experiments were used to explore quantitative variation in parasitic fitness of P. triticina. Fungal populations 881-WT and 882-WT were selected for shortened latent period on partially resistant cvs. CI 13277 and Sw 72469-6 for multiple generations. Fitness components were measured for wild-type and selected fungal populations. Responses to selection and selection differentials were calculated, and broad-sense, realized heritabilities for latent period were estimated for wild-type fungal populations on CI 13227 and on Sw 72469-6. Selected populations had fitness characteristics, not limited to latent period, that could provide greater fitness in nature. Generally, more cycles of selection had greater effects on fitness. In particular cases, selected populations on a partially resistant cultivar had values for latent period, uredinium area, and sporulation no different from those of a susceptible host-pathogen combination. Heritabilities of latent period of populations 881-WT and 882-WT on CI 13227 or populations 881-WT and 882-WT on Sw 72469-6 ranged from 0.65 to 0.76 and 0.17 to 0.24, respectively. Our results suggest the variation to overcome quantitative host resistance exists in extant populations of P. triticina. In addition, because more of the variation in latent period for populations of P. triticina on CI 13227 was genetic than for populations on Sw 72469-6, CI 13227 is likely to be more vulnerable to pathogen adaptation despite its exceptionally long latent period.

Microscopic and Macroscopic Studies of the Development of Puccinia hemerocallidis in Resistant and Susceptible Daylily Cultivars.

Infection and colonization of eight daylily cultivars, which varied in resistance to daylily rust, by Puccinia hemerocallidis was studied macroscopically and microscopically. After germination of urediniospores, appressoria formed at the tip of germ tubes and the fungus penetrated the host through stomatal openings 2 days after inoculation (DAI). Under the infection sites, intercellular hyphae aggregated and formed uredia, which released urediniospores 8 DAI. Resistant cultivars, characterized by the development of rapid death of host cells, were separated into three qualitative categories based on absence and presence of necrotic lesions without or with sporulation. In highly resistant cvs. Prairie Blue Eyes and Bertie Ferris, no macroscopic disease symptoms were observed on leaf surfaces although a few collapsed cells were detected microscopically. Both resistant and moderately resistant reactions were characterized by necrotic lesions with many collapsed cells under infection sites. The difference between these two reactions was that uredia and urediniospores were observed in the moderately resistant cv. Chicago Apache, but not in resistant cvs. Buttered Popcorn and Stella De Oro. Susceptible cultivars, characterized by the absence of a hypersensitive response, were separated into two qualitative categories based on restriction of intercellular hyphal growth that delayed development of uredia and formation of urediniospores. Compared to the susceptible cv. Pardon Me, moderately susceptible cvs. Mary Todd and Chorus Line had a delayed latent period and reduced amount of sporulation. The results indicate that hypersensitive cell death is one of the resistance responses to daylily rust. Necrotic lesions on leaf surfaces are associated with the number of collapsed host cells. Delayed latent period and reduced sporulation that resulted from restriction of intercellular hyphal growth could represent another type of resistance response in the daylily-rust pathosystem.

Characterization of a leucine-rich repeat receptor-like protein kinase (LRPK) gene from Japanese pear and its possible involvement in scab resistance

A gene encoding a leucine-rich repeat receptor-like protein kinase (LRPK) was identified from Japanese pear (Pyrus pyrifolia var. culta) using reverse transcription-polymerase chain reaction (RT-PCR) and rapid amplification of cDNA ends (RACE) PCR. The Japanese pear LRPKp protein was composed of a leucine-rich extracellular ligand-binding domain, a transmembrane-spanning segment, and a cytoplasmic kinase domain; it had the highest sequence homology with apple LRPKm and Arabidopsis receptor-like protein kinase (RLK). Southern blot analysis revealed that the LRPKp belongs to a multigenic family, and a polymorphism in restriction fragment length was observed among Asian and European pear cultivars. The LRPKp transcripts were present at a high level in leaves and at a low level in flowers, while no expression was detected in fruits. The expression pattern of LRPKp was also studied by real-time RT-PCR in the scab susceptible cv. Kousui and resistant cvs. Kinchaku and Flemish Beauty after challenge inoculation with Venturia nashicola, the causal agent of Japanese pear scab. Transcripts of LRPKp were transiently enhanced in both the susceptible Kousui and to a great extent in the non-host-resistant Flemish Beauty. However, in resistant Kinchaku, expression of this gene was only weakly enhanced. Moreover, treatment with a resistance inducer, acibenzolar-S-methyl (ASM), which significantly reduces scab severity on potted trees of Kousui, was also able to induce and to potentiate the expression of this gene after inoculation. This suggests that the LRPKp gene is possibly involved in ASM-induced resistance.

Variation in Infection Capacity and in Virulence Exists Between Genotypes of Sugarcane yellow leaf virus.

Two experiments, one in Guadeloupe and one in Réunion Island, were performed to transmit different genotypes of Sugarcane yellow leaf virus (SCYLV) to eight sugarcane cultivars differing in resistance to infection by the virus and to yellow leaf. Transmission was attempted from SCYLV-infected sugarcane plants or leaves to healthy tissue-cultured plantlets grown in vitro and with the aphid vector Melanaphis sacchari. After inoculation and elimination of insects with an insecticide, plantlets were transferred to Montpellier, France and grown in a greenhouse. Plants were tested for presence of SCYLV by tissue-blot immunoassay and reverse-transcription polymerase chain reaction after 5 to 6 months of growth. SCYLV genotypes BRA-PER, CUB, and REU were detected in 47, 62, and 39% of plants inoculated with these genotypes in Guadeloupe, respectively. SCYLV genotypes BRA-PER and REU and a mixed infection of genotypes BRA-PER and REU were detected in 56, 33, and 42% of plants inoculated with these genotypes in Réunion Island, respectively. Genotypes BRA-PER and CUB could be transmitted to all eight sugarcane cultivars, but genotype REU could never be transmitted to resistant sugarcane cvs. H78-4153 and H78-3567. SCYLV genotype REU was transmitted successfully to sugarcane cv. R570 in Guadeloupe, but not in Réunion Island. Genotypes BRA-PER and CUB induced yellow leaf symptoms in susceptible or highly susceptible sugarcane cultivars, whereas genotype REU induced very few symptoms. SCYLV was not found in several symptomatic plants, suggesting an association of disease with undetectable populations of the virus or a nonviral cause. This is the first report of variation in infection capacity and in virulence of SCYLV.

Characterization of Race-Specific Interactions Among Isolates ofVerticillium dahliaePathogenic on Lettuce

ABSTRACT Verticillium wilt, caused by Verticillium dahliae, poses a major threat to lettuce (Lactuca sativa) production in California. Incorporation of resistance into commercial lettuce cultivars offers the least expensive technique of sustaining production in infested areas. To test the breadth of the resistance identified in field experiments, a pair of susceptible ('Salinas' and 'Sniper') and resistant ('La Brillante' and 'Little Gem') lettuce cultivars were used as differentials and individually inoculated with 29 isolates of V. dahliae and two isolates of V. albo-atrum from several hosts, including lettuce, in replicated greenhouse experiments. The reactions of the four cultivars were determined based on the disease severity at maturity. None of the V. albo-atrum isolates or V. dahliae isolates from cruciferous hosts caused significant disease on lettuce. Both Salinas and Sniper were susceptible to many isolates of V. dahliae (21 of 23) from noncruciferous hosts, and the isolates varied in their overall virulence. However, of these, only three isolates caused significant disease on the resistant cvs. La Brillante and Little Gem. These three isolates also were distinct from the other V. dahliae isolates based on sequence data from the intergenic spacer (IGS) region of the nuclear ribosomal RNA gene, suggesting that they form a phylogenetically distinct subgroup that differs in virulence toward specific lettuce genotypes. Accordingly, isolates of V. dahliae virulent on all tested cultivars, including the resistant La Brillante and Little Gem, were designated as race 2, whereas those virulent only on the susceptible Salinas and Sniper were designated as race 1. Although a range of virulence among isolates has been described in other hosts, this is the first description of distinct virulence phenotypes in V. dahliae since a similar race structure was described in tomato in the 1960s.