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1.
The objective of this study was to determine the mode of inheritance of field resistance to downy mildew (Peronospora parasitica (Pers. ex Fr.) Fr.) in broccoli (Brassica oleracea var.italica) at the adult plant stage. The F1, F2 and F3 progeny of resistant and susceptible plants of broccoli were tested in the field under natural infection, in central Portugal,
from August to December in two successive years. The plants were evaluated for resistance to downy mildew at maturity using
a five-class scale of increasing susceptibility to the disease, which took into account the number of infected leaves and
the size of the sporulating lesions. The F1 was completely resistant, the F2 segregated a clear 3 resistant: 1susceptible and the F3 confirmed the F2 segregation, which suggests a dominant character controlled by a single locus. This resistance has good potencial for direct
use in commercial broccoli breeding or for transfer to other Brassica vegetables.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
2.
Summary Inheritance of downy mildew (Peronospora parasitica) resistance in three resistant x susceptible crosses, one susceptible x susceptible and one resistant x resistant cross were studied in Indian cauliflower (Group III) over the two years (1990 and 1991). No significant difference was observed between the years for various estimates and hence pooled data are presented. Downy mildew resistance in crosses cc×HR 5-4 and 3-5-1-1×244 (R×S) is governed by single dominant gene PPA3 but in cross cc×244 (R×S), recessive epistasis was observed. The resistance level was not improved in both the cc×3-5-1-1 (R×R) and 244×267-6-9 (S×S) crosses. Exploitation of downy mildew resistance from cc and 3-5-1-1 in F1 hybrid is explained in detail. 相似文献
3.
Summary Forty-four landraces of Portuguese coles (Brassica oleracea L.), representing different morphotypes, were screened at the cotyledon stage for downy mildew resistance, caused by Peronospora parasitica. Two isolates of the pathogen, PHW 630 and PHW 828, were used in the experiment. The mean disease interaction phenotype varied among the landraces. Overall, the Portuguese coles have shown resistance to both isolates, particularly to isolate PHW 828. Some landraces were identified with differential reaction to the two P. parasitica isolates. Some of the Portuguese coles are, therefore, good sources of resistance genes to P. parasitica, and could be used in breeding programs or in the development of a downy mildew host differential set. Among the morphotypes tested, Couve Algarvia (ISA 207), Couve Galega (ISA 243 and 187) and Couve Glória de Portugal (ISA 84) have presented the highest resistance interaction. For the development of host differential sets, the landraces ISA 2 (Penca de Mirandela), ISA 35 (Couve de Valhascos) and ISA 600 (Penca Espanhola) could be further selected for the differentiation of P. parasitica isolates. They are resistant to PHW 828 and susceptible to PHW 643.The same morphotypes and landraces were also screened at the seedling stage for resistance to clubroot, caused by Plasmodiophora brassicae Woron.. Although some variation for resistance could be noticed in some the landraces tested, mainly Galega kale types, none of them presented a sufficient level of resistance as to be directly be useful in breeding for resistance to race 6 of P. brassicae. 相似文献
4.
Summary Powdery mildew development was assessed on squash (Cucurbita pepo) plants of a susceptible cultivar, a resistant accession, their F1, and their F2 in an early summer planting in the field, covered or not covered with a shading net. Three reaction types were observed: susceptible, powdery mildew on stems and on both, the upper and lower leaf surfaces, as in the susceptible parent; resistant, no powdery mildew on leaves or stems, as in the resistant parent; and partially resistant, powdery mildew on upper leaf surfaces only, as in the F1. Disease presence on the stem was associated with susceptibility. Shading hastened the appearance of powdery mildew and increased the severity of infection on partially resistant and susceptible plants, facilitating identification of resistant individuals in the F2 population.Contribution No. 1613-E from the Agricultural Research Organization, Bet Dagan, Israel 相似文献
5.
Summary An analysis of adult plant resistance of powdery mildew in 15 F1, F2 and F3 populations of pea derived from crossing 15 diverse and susceptible lines with one resistant line revealed that resistance to powdery mildew is controlled by duplicate recessive genes. The genes were designated as er1 and er2.Disease reaction showed independent segregation with three known markers in the resistant parent, namely, af (afila, chromosome 1), st (stipule reduced, chromosome 3) and tl (clavicula, chromosome 7).Contribution form the Department of Genetics and Plant Breeding Banaras Hindu University, Varanasi-221005, India. 相似文献
6.
Expression of resistance to downy mildew at cotyledon and adult plant stages in Brassica oleracea L.
This research compared the expression of resistance to downy mildew at cotyledon and adult plant stages in seven Brassica oleracea genotypes against two P. parasitica isolates of different virulence. Seven day old seedlings were dual inoculated under controlled environment by depositing
two 10 μl droplets of a spore suspension of a different isolate on each cotyledon and the interaction phenotype (IP) evaluated
7 days later using a 0–5 scale of increasing susceptibility. The seedlings were transplanted to 16 cm pots and grown in the
greenhouse for 110 days (15 to 28 leaves). Adult plants were tested using a single leaf inoculation method that allowed the
same plant to be simultaneously inoculated with the two P. parasitica isolates. Leaves were scored 10 days after inoculation using a 0–5 scale of increasing susceptibility. The inoculation of
the same plant with the two isolates produced different combinations of cotyledon (CT) and adult-plant (AP) interaction-phenotype
according to the genotype. CrGC 3.1 was susceptible at CT and AP stages, ‘Algarvia’ resistant at CT and AP stages, and broccoli
‘A’ susceptible at CT and resistant at AP stage against the two isolates. ‘Murciana’ and broccoli ‘B’ were differential at
CT and AP stages. Savoy and Shetland cabbages were differential at CT stage and resistant to both isolates as adult plants.
Cotyledon resistance could not be used to predict adult-plant resistance since the two types of resistance were very poorly
correlated. Resistance can be race specific either at cotyledon or at adult-plant stage.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
7.
The genetics of resistance to Phomopsis stem blight caused by Diaporthe toxica Will., Highet, Gams & Sivasith. in narrow-leafed lupin (Lupinus angustifolius L.) was studied in crosses between resistant cv. Merrit, very resistant breeding line 75A:258 and susceptible cv. Unicrop.
A non-destructive glasshouse infection test was developed to assess resistance in the F1, F2, selected F2-derived F3 (F2:3) families, and in selfed parent plants. The F1 of Unicrop × 75A:258 (and reciprocal cross) was very resistant, and the F2 segregated in a ratio of 3:1 (resistant: susceptible), which suggested the presence of a single dominant allele for resistance
in 75A:258. In Merrit × Unicrop (and reciprocal), the F1 was moderately resistant, and the F2 segregated in a ratio of 3:1 (resistant: susceptible). Thus Merrit appeared to carry an incompletely dominant resistance
allele for resistance. The F1 of Merrit × 75A:258 (and reciprocal) was very resistant and the F2 segregated in a ratio of 15:1 (resistant: susceptible), which supported the existence of independently segregating resistance
alleles for resistance in 75A:258 and Merrit. Alleles at loci for early flowering (Ku) and speckled seeds (for which we propose the symbol Spk) segregated normally and independently of the resistance alleles. Resistant F2 plants gave rise to uniformly resistant or segregating F2:3 families, whereas susceptible F2 plants gave rise only to susceptible F2:3 families. However, the variation in resistance in the F2 and some F2:3 families of crosses involving 75A:258, from moderately to extremely resistant, was greater than that expected by chance or
environmental variation. We propose the symbols Phr1 to describe the dominant resistance allele in 75A:258, and Phr2 for the incompletely dominant resistance allele in Merrit. Phr1 appears to be epistatic to Phr2, and expression of Phr1 may be altered by independently segregating modifier allele(s).
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
8.
Summary Twenty three accessions of nine Portuguese cabbage and kale land races from different geographic origins were tested at the seedling stage for resistance to several important brassica diseases. Resistance to downy mildew (Peronospora parasitica), expressed as necrosis of the cotyledon mesophyll, was found in all the accessions. Type A resistance to cabbage yellows (Fusarium oxysporum f. sp. conglutinans race 1) was present in most of the landraces. Resistance to clubroot (Plasmodiophora brassicae race 6) was found in one accession of the Portuguese tree kale. High resistance to blackleg (Leptosphaeria maculans) and white rust (Albuco candida) was not detected, although several accessions showed 20 to 30% of plants with intermediate expression of resistance. All Portuguese cole accessions were susceptible to blackrot (Xanthomonas campestris pv. campestris). 相似文献
9.
Three segregating F2 populations were developed by self-pollinating 3 black rot resistant F1 plants, derived from across between black rot resistant parent line 11B-1-12 and the susceptible cauliflower cultivar ‘Snow
Ball’. Plants were wound inoculated using 4 isolates ofXanthomonas campestris pv. campestris (Xcc) race 4, and disease severity ratings of F2 plants from the three populations were scored. A total of 860 arbitrary oligonucleotide primers were used to amplify DNA
from black rot resistant and susceptible F2 plants and bulks. Eight RAPD markers amplified fragments associated with completely disease free plants following black rot
inoculation,which segregated in frequencies far lower than expected. Segregation of markers with black rot resistance indicates
that a single, dominant major gene controls black rot resistance in these plants. Stability of this black rot resistance gene
in populations derived from 11B-1-12 may complicate introgression into B. oleracea genotypes for hybrid production.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
10.
Summary In studies of the inheritance of resistance, pea seedlings of seven lines in which stems and leaves were both resistant to Mycosphaerella pinodes were crossed with a line in which they were both susceptible. With seven of the crosses resistance was dominant to susceptibility. When F2 progenies of five crosses were inoculated on either stems or leaves independently, phenotypes segregated in a ratio of 3 resistant: 1 susceptible indicating that a single dominant gene controlled resistance. F2 progenies of one other cross gave ratios with a better fit to 9 resistant: 7 susceptible indicating that two co-dominant genes controlled resistance. The F2 progeny of another cross segregated in complex ratios indicating multigene resistance.When resistant lines JI 97 and JI 1089 were crossed with a susceptible line and leaves and stems of each F2 plant were inoculated, resistance phenotypes segregated independently demonstrating that leaf and stem resistance were controlled by different genes. In two experiments where the F2 progeny of the cross JI 97×JI 1089 were tested for stem and leaf resistance separately, both characters segregated in a ratio of 15 resistant:1 susceptible indicating that these two resistant lines contain two non-allelic genes for stem resistance (designated Rmp1 and Rmp2) and two for leaf resistance (designated Rmp3 and Rmp4). Evidence that the gene for leaf resistance in JI 1089 is located in linkage group 4 of Pisum sativum is presented. 相似文献
11.
Summary Resistance to fusarium wilt, incited by Fusarium oxysporum (Schlecht.) f. sp. lycopersici (Sacc.) Snyder & Hansen race 3 in tomato (Lycopersicon esculentum Mill.) was discovered in LA 716, a L. pennellii accession. A resistant BC1F3 breeding line, E427, was developed from LA 716. E427 was crossed with the susceptible cv. Suncoast and F1, BCP1, BCP2 (to Fla 7155, a susceptible parent) F2, F3, and BCP2S1 seeds were obtained. Segregation for resistance following root dip inoculation over three experiments indicated a single dominant gene controlled resistance. Five of the 12 BCP1S1's segregated more susceptible plants, whereas one of the 12 segregated more resistant plants than expected (P<0.05). Three of 23 F3 lines segregated more susceptible plants than expected while 1 of the 23 had more resistant plants than expected (P<0.05). Segregation in all other lines fit expected ratios. Five of the 23 F3's were homozygous resistant which was an acceptable fit to expectations (P=0.1–0.5). The gene symbol I
3 is proposed for resistance to race 3 of the wilt pathogen. Deviations from expected ratios in data reported here and for other breeding lines indicate an effect of modifier genes and/or incomplete penetrance. Plant age at inoculation and seed dormancy did not affect results.Florida Agricultural Experiment Station Journal Series No. 8101. 相似文献
12.
Summary The inheritance of field resistance to downy mildew in lettuce derived from cv. Grand Rapids was studied in F2, F3 and F4 progeny from a cross with the more susceptible cv. Lobjoits Green Cos. The results for 32 randomly produced F3 families and the F2 population corresponded closely although the absolute level of resistance varied from season to season according to disease pressure and environmental conditions. The field resistance character showed a quantitative pattern of inheritance but the rapid response to selection at F3 implied that only a few genes may be involved. F4 families raised from families selected from the two extremes of the F3 distribution fell into distinct categories with resistance levels corresponding to that of their F3 parents. An association between resistance and morphological features of the resistant parent was present at F2 but not in subsequent generations when individuals and families which were as resistant as cv. Grand Rapids and yet bore little morphological resemblance to this cultivar were readily recovered. 相似文献
13.
Sunflower downy mildew caused by Plasmopara halstedii is an important disease of sunflower capable of causing losses of more than 80% of production. Races 100, 300, 310, 330,
710, 703, 730 and770 of the fungus have been identified in Spain. Race 703, of high virulence, has been identified frequently
in the northeast, while race 310 seems to occur over the south, the main sunflower growing region of the country. Oil sunflower
lines RHA-274 and DM4 were studied for their resistance to races 310(RHA-274 and DM4) and 703 (DM4). In each cross, only one
plant of the resistant parent was crossed to the inbred susceptible line HA-89 (or cmsHA-89).Plants from F2 and backcross(BC1F1 to susceptible parent)generations were evaluated for fungal sporulation on true leaves and/or cotyledons. The resistant-to-susceptible
ratios obtained in the F2 and BC1F1 progenies from the crosses cmsHA-89 × RHA-274 and HA-89 × DM4suggested that one major gene in each line is responsible for
resistance to race 703.The segregations of the progenies of the cross HA-89 × DM4 inoculated with race 703also fitted the
ratios 1:1 and 3:1 (for BC1F1 and F2, respectively)corresponding to control of resistance by a single dominant gene. In RHA-274, the gene for resistance to race
310 was designated Pl
9, whereas Pl
v is tentatively proposed to designate the gene in DM4 responsible for resistance to races310 and 703.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
14.
Downy mildew on lettuce is currently controlled using host resistance genes (Dm genes) that confer race-specific resistance in seedlings. Field resistance (FR) that is active in adult plants but not seedlings was identified in the cvs. Grand Rapids and Iceberg. The goal of our study was to evaluate the utility of Grand Rapids as a source of novel Bremia resistance alleles, particularly in comparison with Iceberg. To measure FR, downy mildew symptoms were evaluated following natural infection in field experiments. The responses of Grand Rapids and Iceberg were similar in many respects. Although both cultivars had a small percentage of plants exhibiting disease symptoms, the average disease ratings were as low as for cultivars with effective Dm genes. We observed no evidence for race specificity. FR was effective over 3 years of our study, despite documented variation within pathogen populations. Both cultivars lacked all known seedling resistance genes except Dm13, which was not responsible for the resistance observed in field experiments. Similar segregation of FR was observed in F2 populations for both Grand Rapids and Iceberg. The presence of highly susceptible families within Grand Rapids × Iceberg populations suggested the presence of at least one unique resistance allele in each cultivar. Preliminary genetic analysis of FR from Grand Rapids revealed a high estimate of narrow-sense heritability that suggested simple inheritance, but single gene models did not fit the observed data. Our results suggest that Grand Rapids may represent an underutilized resource for controlling downy mildew in lettuce. 相似文献
15.
Summary The genetics of resistance to angular leaf spot caused by Pseudomonas syringae pv. tabaci in Nicotiana tabacum cultivars Burley 21 and Kentucky 14 was investigated by studying disease reactions to three isolates of parental, F1, F2 and backcross generations derived from crosses between the resistant cultivars and the susceptible cultivar Judy's Pride. Studies were conducted in the greenhouse and in field plant beds. Chi-square values were computed to determine whether the observed ratios for disease reactions deviated from expected Mendelian ratios for a single, dominant gene controlling resistance to angular leaf spot in tobacco. Based on the resistance of the F1 and the backcross generation to the resistant parent (BC-R), a 3 resistant: 1 susceptible segregation ratio in the F2, and a 1 resistant: 1 susceptible segregation ratio in the backcross generation to the susceptible parent (BC-S), it was concluded that resistance to three isolates of Pseudomonas syringae pv. tabaci is governed by a single, dominant gene. 相似文献
16.
F. J. B. Reifschneider L. S. Boiteux P. T. Della Vecchia J. M. Poulos N. Kuroda 《Euphytica》1992,62(1):45-49
Summary Inheritance studies were conducted to determine the genetic basis of adult-plant resistance in pepper (Capsicum annuum L.) to Phytophthora capsici. F1, backcrosses and F2 populations were developed using the resistant parent Criollo de Morellos 334 and susceptible parents Agronômico 10-G and Yolo Wonder. Pepper plants, at 36 days post-emergence, were inoculated near the base of the stem with an inoculum suspension of 5×104 zoospores/ml. Segregation ratios in the F2 generation of 13 resistant to 3 susceptible plants fit a 2-gene model for resistance with dominant and recessive epistasis. 相似文献
17.
Summary Melon germplasm was screened for cucumber green mottle mosaic virus (CGMMV), powdery mildew (Sphaerotheca fuliginea), downy mildew (Pseudoperonospora cubensis) and Fusarium wilt (Fusarium oxysporum f. sp. melonis) resistance under artificial conditions except downy mildew for which screening was done under natural epiphytotic conditions. High level resistance to all the four diseases was not recorded in any of the collections tested. Nevertheless, ertheless, resistance to three diseases was located in three germplasm. Wild Cucumis species C. figarei exhibited absolute resistance to CGMMV and Fusarium wilt and high level resistance to downy mildew. Phoot or snapmelon (Cucumis melo var. momordica) — a non-dessert from of Indian origin—was highly resistant to downy mildew and resistant to CGMMV and medium resistant to Fusarium wilt. Iroquois was resistant to powdery mildew and medium resistant to downy mildew and CGMMV. 相似文献
18.
To determine and utilize RAPD markers linked to resistance to downymildew incited by Peronospora manshurica in soybean, a resistantcultivar `AGS129' was crossed to a susceptible cultivar `Nakhon Sawan 1'(NS1). F2 and BC1 populations were advanced from the F1 and evaluatedfor resistance to the disease. 2-test demonstrated that the resistancewas controlled by a single dominant gene (Rpmx). Near-isogenic lines(NILs) and bulked segregant analysis (BSA) were used to identify RAPDmarkers linked to the gene. Six DNA bulks namely F5(R), F5(S),BC6F3(R), BC6F3(S), F2(R) and F2(S) were set up by pooling equalamount of DNA from 8 randomly selected plants of each disease responsetype. A total of 180 random sequence decamer oligonucleotide primerswere used for RAPD analysis. Primer OPH-02 (5 TCGGACGTGA 3 andOPP-10 (5 TCCCGCCTAC 3) generated OPH-021250 and OPP-10831fragments in donor parent and resistant bulks, but not in the recurrentparent and susceptible ones. Co-segregation analysis using 102 segregatingF2 progenies confirmed that both markers were linked to the Rpmxgene controlling downy mildew disease resistance with a genetic distance of4.9 cm and 23.1 cm, respectively. Marker OPH-021250 was presentin 13 of 16 resistant soybean cultivars and absent in susceptible cultivars,thus confirming a potential for MAS outside the mapping population. 相似文献
19.
Summary The oat line Pc54 was found to be resistant to powdery mildew under both field and glasshouse conditions. The ratio of resistant to susceptible F2 and F2 progeny of a cross between a selection from the Pc54 line (Cc7422) and a susceptible cultivar (Selma) showed that, in addition to carrying the crown rust resistance gene Pc54 and the pg15 gene for stem rust resistance, the mildew resistance of the Pc54 line was conditioned by a single incompletely dominant gene along with additional factors which modified the expression of resistance. Previous results, that there was no linkage between genes Pc54 and Pg15, were confirmed. In addition, there was no evidence of linkage between the mildew resistance gene and gene Pc54. Evaluation of selections from within the Pc54 line showed that the expression of both stem rust and mildew resistance was modified by, or linked to, plant height. The effectiveness of genes Pc54 and Pg15, as measured by virulence frequencies, in central and eastern Europe is described. 相似文献
20.
Sunflower lines RHA‐274, HA‐61 and RHA‐325 were studied for their resistance to race 330 of downy mildew (Plasmopara halstedii). The same inbred line, with normal (HA‐89) or sterile cytoplasm (cmsHA‐89) was used in all the crosses as susceptible parent, and, in each cross, only one genotype of the resistant parent was studied. The resistant‐to‐susceptible ratios obtained in the BC1 and F2 progenies from the crosses of the lines RHA‐274 and HA‐61 to cmsHA‐89 and HA‐89, respectively, suggested that, in each resistant line, two dominant genes are responsible for resistance to this downy mildew race. One of the genes (A) is epistatic to the other (B), and the recessive allele b in homozygosity is also epistatic to aa, with plants carrying aabb genotypes being resistant. Resistance to race 330 seemed to be controlled by two complementary genes in the sunflower inbred line RHA‐325, the dominant allele of one of them being present in cmsHA‐89. In the genotypes HA‐89 or cmsHA‐89, the existence of genes that modify the expected segregations following the crosses with resistant parents is proposed. It is concluded that, although major genes have been described as responsible for monogenic resistance to downy mildew, other types of regulation of this character, such as complementarity and epistatic relationships, do occur. 相似文献