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1.
The inheritance of the resistance to Fusarium oxysporum f. sp. melonis (F.o.m.) races 0 and 2 in ‘Tortuga’, a Spanish cantalupensis accession, was studied from crosses of ‘Tortuga’ by the susceptible line ‘Piel de Sapo’ and the resistant one ‘Charentais-Fom1’ that carries the resistance gene Fom-1. The segregation patterns observed in the F2 (‘Tortuga’ × ‘Piel de Sapo’) and the backcross (‘Piel de Sapo’ × (‘Tortuga’ × ‘Piel de Sapo’) populations, suggest that resistance of ‘Tortuga’ to races 0 and 2 of F.o.m. is conferred by two independent genes: one dominant and the other recessive. In the F2 derived from the cross between accessions ‘Tortuga’ and ‘Charentais-Fom1’, the lack of susceptible plants indicated that the two accessions are carrying the same resistance gene (Fom-1). The analysis of 158 F2 plants (‘Tortuga’ × ‘Piel de Sapo’) with a Cleaved Amplified Polymorphic Sequence marker 618-CAPS, tightly linked to Fom-1 (0.9 cM), confirmed that ‘Tortuga’ also carries a recessive gene, that we propose to symbolize by fom-4.  相似文献   

2.
The objective of this work was to check the possible allelism between two sources of resistance to the root-knot nematode Meloidogyne incognita race 1 in lettuce (‘Grand Rapids’ and ‘Salinas-88’). The experiments were carried out in greenhouses, in expanded 128-cell polystyrene trays filled with commercial substrate. Lettuce cultivars ‘Salinas 88’ and ‘Grand Rapids’ were tested along with the populations F1 (‘Grand Rapids’ × ‘Salinas-88’), F2 (‘Grand Rapids’ × ‘Salinas-88’), F3 (‘Grand Rapids’ × ‘Salinas-88’), and with F4 families derived from the latter population. Seedlings were inoculated 15 days after sowing with a nematode egg suspension equivalent to 30 eggs ml−1 of substrate. Plants were evaluated for apparent gall incidence, gall scores, egg mass scores and extracted egg numbers 45 days after the inoculation date. There was evidence that two different genes are involved in control of resistance to M. incognita race 1 in lettuce cultivars Grand Rapids and Salinas-88. Lines with higher levels of nematode resistance than either Grand Rapids or Salinas-88 could be selected in the F4 generation of the cross between these resistant parental lines.  相似文献   

3.
The nutritional value of cucumber (Cucumis sativus L.) can be improved by the introgression of β-carotene (i.e., provitamin A and/or orange flesh) genes from “Xishuangbanna gourd” (XIS; Cucumis sativus var. xishuangbannanesis Qi et Yuan) into US pickling cucumber. However, the genetics of β-carotene content has not been clearly defined in this US market type. Thus, three previous populations derived from a US pickling cucumber (‘Addis’) × XIS mating were evaluated for β-carotene content, from which the high β-carotene inbred line (S4), ‘EOM 402-10’, was developed. A cross was then made between the US pickling cucumber inbred line ‘Gy7’ [gynoecious, no β-carotene, white flesh; P1] and ‘EOM 402-10’ [monoecious, possessing β-carotene, orange flesh; P2] to determine the inheritance of β-carotene in fruit mesocarp and endocarp tissue. Parents and derived cross-progenies (F1, F2, BC1P1, and BC1P2) were evaluated for β-carotene content in a greenhouse in Madison, Wisconsin. While F1 and BC1P1 progeny produced mature fruits possessing white, light-green, and green (0.01–0.02 μg g−1 β-carotene) mesocarp, the F2 and BC1P2 progeny mesocarp segregated in various hues of white, green, yellow (0.01–0.34 μg g−1 β-carotene), and orange (1.90–2.72 μg g−1 β-carotene). Mesocarp and endocarp F2 segregation adequately fit a 15:1 [low-β-carotene (0.01–0.34 μg g−1): high-β-carotene (1.90–2.72 μg g−1)] and 3:1 (low-β-carotene: high-β-carotene) ratio, respectively. Likewise, segregation of carotene concentration in mesocarp and endocarp tissues in BC1P2 progeny adequately fit a 3:1 (low-β-carotene: high-β-carotene) and 1:1 (low-β-carotene: high-β-carotene) ratio, respectively. Progeny segregations indicate that two recessive genes control the β-carotene content in the mesocarp, while one recessive gene controls β-carotene content in the endocarp. Single marker analysis of F2 progeny using the carotenoid biosynthesis gene Phytoene synthase determined that there was no association between this gene and the observed β-carotene variation in either fruit mesocarp or endocarp.  相似文献   

4.
Cytoplasmic male sterility (CMS) is an indispensable trait for F1 hybrid seed production in bunching onion (Allium fistulosum L.). Expansion of the cytoplasmic diversity of F1 hybrid cultivars by introduction of various CMS resources has great potential to eliminate vulnerability to cytoplasm type-specific diseases. This study aimed to evaluate appearance frequency of male sterile plants in several bunching onion accessions and to identify CMS resources. In eight (‘Nogiwa Aigara’, ‘Bansei Hanegi’, ‘Amarume’, ‘Kimnung’, ‘Zhangqiu’, ‘INT/CHN/1990/GOTOU’, ‘Natsunegi’ and ‘Guangzhou’) of 135 accessions collected from Japan, China, Mongolia, Korea and Taiwan, male sterile plants appeared with varied frequencies from 1.7% (‘Nogiwa Aigara’ and ‘Bansei Hanegi’) to 24.5% (‘Zhangqiu’). The inheritance mode of Zhangqiu- and Guangzhou-derived male sterility was confirmed to be CMS by sib-crossings and interbreed crossings. Microscopic examination of microsporogenesis in the CMS plants revealed that microspore protoplasm rapidly degenerated without mitotic division after the release of microspores from tetrads. The CMS germplasm described here would be useful for the development of “A” lines to be used in F1 hybrid seed production of bunching onion. Male fertility in ‘Nogiwa Aigara’, ‘Bansei Hanegi’, ‘Kimnung’, ‘INT/CHN/1990/GOTOU’ and ‘Natsunegi’ was verified to be controlled by a single fertility restoration locus.  相似文献   

5.
The color of the seed coats of ‘Dorado’ (Phaseolus vulgaris L.) is garnet brown (dark red kidney bean color) and differs from most other dry bean varieties in the Honduran red bean market class. A genetic investigation of the color of ‘Dorado’ (same as DOR364) and G19833 (Liborino market class) seed coats was conducted. Crosses with genetic tester stocks demonstrated that the gene for garnet brown (GB) in ‘Dorado’ was not allelic with the R gene for dominant red (oxblood) seed coat. An allelism test between the ‘Dorado’ gene for GB seed coat and the rk drv gene for recessive expression of GB demonstrated allelism. We propose the gene symbol for Rk r for the ‘Dorado’ GB seed coat color gene. Rk r expresses partial dominance over Rk, where Rk r/Rk expresses a paler and highly variable intermediate red color. The interactions of Rk r, rk drv, and c u are discussed. Segregation analysis in the mapping population made up of DOR364 (same as ‘Dorado’) × G19833 recombinant inbred lines showed that the Rk r gene mapped to linkage group 1. The new allele at Rk was located at a distance of 17 cM from the RFLP marker Bng130 with a LOD > 3.0.  相似文献   

6.
We previously surveyed chromosomal regions showing segregation distortion of RFLP markers in the F2 population from the cross between a japonica type variety ‘Nipponbare’ and an indica type variety ‘Milyang23’, and showed that the most skewed segregation appeared on the short arm of chromosome 3. By comparison with the marker loci where distortion factors were previously identified, this region was assumed to be a gametophytic selection-2 (ga2) gene region. To evaluate this region, two near isogenic lines (NILs) were developed. One NIL had the ‘Nipponbare’ segment of this region on the genetic background of ‘Milyang23’ (NIL9-23), and the other NIL had the ‘Milyang23’ segment on the genetic background of ‘Nipponbare’ (NIL33-18). NIL9-23 and ‘Milyang23’, NIL33-18 and ‘Nipponbare’, and ‘Nipponbare’ and ‘Milyang23’ were respectively crossed to produce F1 and F2 populations. The F1 plants of NIL9-23 × ‘Milyang23’ and NIL33-18 × ‘Nipponbare’ showed high seed fertility and the same pollen fertility as their parental cultivars, indicating that ga2 does not reduce seed and pollen fertility. Segregation ratio of a molecular marker on the ga2 region in the three F2 populations was investigated to clarify whether segregation distortion occurred on the different genetic backgrounds. Segregation distortion of the ga2 region appeared in the both F2 populations from the NIL9-23 and ‘Milyang23’ cross (background was ‘Milyang23’ homozygote) and the ‘Nipponbare’ and ‘Milyang23’ cross (background was heterozygote), but did notin the F2 population from the NIL33-18 and ‘Nipponbare’ cross (background was ‘Nipponbare’ homozygote). This result indicates that ga2 interacts with a ‘Milyang23’ allele(s) on the different chromosomal region(s) to cause skewed segregation of the ga2 region. In addition, segregation ratio was the same between the F2 populations from NIL9-23 × ‘Milyang23’ and ‘Nipponbare’ × ‘Milyang23’ crosses, suggesting that the both genotypes, ‘Milyang23’ homozygote and heterozygote, of gene(s) located on the different chromosomal region(s) have the same effect on the segregation distortion. This revised version was published online in July 2006 with corrections to the Cover Date.  相似文献   

7.
The interspecific cross between Chrysanthemum × grandiflorum (Ramat.) Tzvel. ‘rm20-12’ (R, 2n = 54) and C. makinoi Matsum., and Nakai (M, 2n = 18) was achieved using embryo rescue, and a single backcross progeny using C. × grandiflorum ‘rm20-12’ as paternal parent was obtained. The morphology of the two independent F1 hybrids (MR1 and MR2) differed from that of both parents. MR1 had a larger inflorescence diameter along with narrow leaves and a reduced number of ray and tubular florets. MR2 was shorter and its inflorescence developed fewer tubular florets than either M or R. The BC1F1 hybrid was similar to its maternal plant MR2 in terms of leaf length and width, inflorescence diameter and the number of ray florets, while it produced fewer tubular florets than either MR2 or R. The flower color in both F1 hybrids was lavender, while the BC1F1 plant bore purple flowers. The aphid resistance and heat tolerance of MR1, MR2 and the BC1F1 hybrid were both significantly superior to that of C. × grandiflorum ‘rm20-12’. Interspecific hybridization followed by backcrossing shows clear potential for cultivar improvement in chrysanthemum.  相似文献   

8.
Ni Ma  Zai-yun Li 《Euphytica》2007,154(1-2):231-238
Parents and their F1 and F2 progenies were evaluated for density of type IV glandular trichomes and resistance to Tetranychus urticae Koch during three stages of the plant growth. Results indicated significant differences between density of type IV glandular trichomes on F1 and F2 populations at different sampling times. As age of plant increased, density of type IV glandular trichomes and resistance to two-spotted spider mite increased. Density of type IV glandular trichomes on F2 individuals showed a broad range of variability (0–42 trichomes/mm2). The estimated heritability was very high (>85%) for damage score and density of type IV glandular trichomes at different sampling times. Acylsugars content in Lycopersicon pennellii ‘‘LA2963’’ was more than two-folds high than those found in L. esculentum ‘‘Nandi’’, F1 and F2 populations, indicating that recessive gene(s) are responsible for the high acylsugar contents in L. pennellii ‘‘LA2963’’.  相似文献   

9.
Melon (Cucumis melo L.) fruit production in U.S. can be improved through the introgression of early fruit maturity (FM) and the enhancement of fruit color [i.e., quantity of β-carotene (QβC); orange mesocarp]. However, the genetics of FM and QβC have not been clearly defined in U.S. Western Shipping market class melons (USWS). Thus, a cross was made between the monoecious, early FM Chinese line ‘Q 3-2-2’ (non-carotene accumulating, white mesocarp) and the andromonecious, comparatively late FM USWS line ‘Top Mark’ (carotene accumulating; orange mesocarp) to determine the inheritance of FM and QβC in melon. Parents and derived cross-progenies (F1, F2, F3, BC1P1, and BC1P2) were evaluated for FM and QβC at Hancock, Wisconsin over 2 years. Estimates of narrow-sense heritability (h N2) for QβC and FM as defined by F1, F2, and BC (by individuals) were 0.55 and 0.62, respectively, while estimates based on F3 families were 0.68 and 0.57, respectively for these traits. Mesocarp color segregation (F2 and BC1P2) fit a two gene recessive epistatic model, which in turn, interacts with other minor genes. Although the inheritance of QβC and FM is complex, introgression (e.g., by backcrossing) of early FM genes resident in Chinese germplasm into USWS market types is possible. Such introgression may lead to increased yield potential in USWS market types while retaining relatively high β-carotene fruit content (i.e., orange mesocarp), if stringent, multiple location and early generation family selection (F3–4) is practiced for FM with concomitant selection for QβC.  相似文献   

10.
The use of resistant cultivars is one of the best methods for nematode control and reduction of economic losses caused by these pathogens. Studies of inheritance of nematode resistance in common bean (Phaseolus vulgaris L.) are nonetheless scarce. The present paper reports on the estimation of genetic parameters associated with resistance to the root nematode Meloidogyne incognita race 1 in common beans. Two contrasting bean lines, ‘Aporé’ (P1 = nematode resistant) e ‘Macarr?o Rasteiro Conquista’ (P2 = susceptible), and the generations F1 (P1 × P2), F2 (P1 × P2), BC1(P1) = (F1 × P1) and BC1(P2) = (F1 × P2), were assessed 45 days after nematode inoculation, through a scale related to the number of eggs per gram of root tissue. Dominant genetic effects were inferior in magnitude to additive effects, indicating incomplete dominance of nematode resistance. Dominance was in the direction of increased nematode resistance (i.e., lower number of eggs per g root). Resistance to Meloidogyne incognita race 1 in common bean is under control of a single gene locus, with incomplete dominance of the resistance allele present in ‘Aporé’, but modifier genes affecting its expression appear to be present in the susceptible parent ‘Macarr?o Rasteiro Conquista’.  相似文献   

11.
D. Rubiales  A. Martín 《Euphytica》1999,109(3):157-159
The inheritance of resistance to yellow mosaic virus spread by Bemisia tabaci Gen. in Glycine soja (Linn.) Seib. & Zucc. was studied following natural infection in the field condition. The resistant wild accession, Glycine soja was crossed with susceptible cultivars ‘Ankur’, ‘Bragg’, ‘PK 472’ and ‘Kalitur’ of Glycine max (Linn.) Merr. Resistance reactions of F1 and F2 plants, and individual F2 plant derived F3 families indicated that resistance was controlled by a single dominant gene. This revised version was published online in July 2006 with corrections to the Cover Date.  相似文献   

12.
Maize dwarf mosaic is one of the devastating and wide spread viral diseases in the world. The present investigation was carried out to develop DNA markers closely linked to the resistance gene mdm1 (t). Linkage between the markers and phenotypes was confirmed by analyzing an F2 population obtained from a cross between a resistant parent ‘Huangzaosi’ and a susceptible parent ‘Mo17(478)’. Four AFLP markers were found in the maize dwarf mosaic resistant plants. By using (BSA) bulked segregant analysis, two of the four AFLP markers were transformed into Sequence-characterized amplified regions markers (SCARs), nominated Rsun-1 and Rsun-2. The two amplified fragment length polymorphism (AFLP) markers, RHC-1and RHC-2, from the amplification products of primer combination E-AGC/M-CAA and E-AGC/M-GAA, showed linkage with the mdm1 (t) gene in a genetic distance 1.6 and 2.0 cM, respectively. The results indicate that the new SCAR markers will be valuable to distinguish resistant plants from susceptible plants in plantlets growing in seedbeds. The markers developed in this study are suitable for marker-assisted selection for maize dwarf mosaic resistance.  相似文献   

13.
Caused by Aphanomyces cochlioides Drechsler, Aphanomyces root rot is a serious disease of sugar beet (Beta vulgaris L.), for which sources of resistance are scarce. To identify the segregation pattern of the rare resistance trait found in Japanese sugar beet line ‘NK-310mm-O’, F1 and BC1F2 seedings, drawn from a cross between ‘NK-310mm-O’ and susceptible line ‘NK-184mm-O’, were inoculated with zoospores and their survival evaluated in the greenhouse. Resistance segregation followed was that of a single dominant gene, which was designated Acr1 (Aphanomyces cochlioides resistance 1). Molecular markers tightly linked to Acr1 were identified by bulked segregant analysis of two BC1F2 populations. Fourteen AFLP markers linked to Acr1 were identified, the closest located within ±3.3 cM. Three F5 lines and two BC2F1 lines, selected on the basis of their Acr1-AFLP markers, were tested for their resistance to Aphanomyces root rot in a highly infested field. Results indicated that Acr1 conferred significant resistance to Aphanomyces root rot at the field level. Based on its linkage with CAPS marker tk, a representative marker for chromosome III, Acr1 was located on this chromosome. The clear linkage between tk and Rhizomania resistance trait Rz1, suggests the clustering of major disease resistance genes on chromosome III.  相似文献   

14.
Nicotiana wuttkei Clarkson and Symon discovered in the 1990s in Australia may be of potential interest to breeders as it carries resistance to Peronospora hyoscyami de Bary. The crossability between N. wuttkei (2n = 4x = 32) and three N. tabacum (2n = 4x = 48) cultivars (‘Puławski 66’, ‘Wiślica’ and ‘TN 90’) and the morphology and cytology of their amphihaploid hybrids (2n = 4x = 40) were studied. Seeds were produced only when N. wuttkei was used as the maternal parent, but under normal germination all seedlings died. Viable F1 hybrids of N. wuttkei × N. tabacum cv. ‘Puławski’ and N. wuttkei × N. tabacum cv. ‘Wiślica’ were obtained only by in vitro cotyledon culture. The amphihaploid plants were intermediate between the parents for most morphological traits. In 46.4% of the PMC’s, only univalents were present. The remainder of the cells had 1–5 bivalents and 1–2 trivalents. In spite of a detectable frequency of monads (2.6%), dyads (2.6%) and triads (4.5%), the hybrids were self and cross sterile.  相似文献   

15.
S. H. Jalikop 《Euphytica》2007,158(1-2):201-207
Summary Inheritance of fruit acidity in pomegranate (Punica granatum L.) was studied in 3 sweet or low acid (‘Ganesh’, ‘Ruby’ and ‘Kabul Yellow’) and 3 sour or high acid (‘Nana’, ‘Daru’ and ‘Double Flower’) varieties and their progenies. The F1 and F2 data of ‘Ganesh’ × ‘Nana’ showed that fruit acidity is monogenically controlled and the sour nature is dominant over sweet. Further, whether a genotype produces sweet or sour fruit is determined by a major gene (SS) while a few modifiers with small effects cause fluctuations in the acidity levels within sour and sweet types. All the trees of 3 crosses involving ‘Daru’ produced acidic fruits but those of (‘Ganesh’ × ‘Nana’) × ‘Daru’ reached acidity as high as 71.2 g/l which could be because of cumulative influence of modifying genes derived from the two acidic varieties ‘Nana’ and ‘Daru’. Pollination of functionally sterile ‘Double Flower’ variety with single (normal) flower types revealed that ‘Double Flower’ is a dominant mutant from an acidic fruited genotype (Ss). The segregation pattern in F1 indicated the possible linkage between genes governing total acidity and flower type. All the F1 hybrids between ‘Kabul Yellow’ and ‘Ganesh’ (sweet × sweet) were sour fruited with almost 8-fold jump in fruit acidity over the mid-parental value. The steep increase in acidity cannot be convincingly attributed to overdominance which is certainly rare at major gene level. Alternatively, linked dominant alleles or epistatic effect of neighboring loci which readily simulate overdominance (pseudo-overdominance) could have caused a major shift in F1 fruit acidity.  相似文献   

16.
Sequence-related amplified polymorphism (SRAP), simple sequence repeats (SSR), inter-simple sequence repeat (ISSR), peroxidase gene polymorphism (POGP), resistant gene analog (RGA), randomly amplified polymorphic DNA (RAPD), and a morphological marker, Alternaria brown spot resistance gene of citrus named as Cabsr caused by (Alternaria alternata f. sp. Citri) were used to establish genetic linkage map of citrus using a population of 164 F1 individuals derived between ‘Clementine’ mandarin (Citrus reticulata Blanco ‘Clementine) and ‘Orlando’ tangelo’ (C. paradisi Macf. ‘Duncan’ × C. reticulata Blanco ‘Dancy’). A total of 609 markers, including 385 SRAP, 97 RAPD, 95 SSR, 18 ISSR, 12 POGP, and 2 RGA markers were used in linkage analysis. The ‘Clementine’ linkage map has 215 markers, comprising 144 testcross and 71 intercross markers placed in nine linkage groups. The ‘Clementine’ linkage map covered 858 cM with and average map distance of 3.5 cM between adjacent markers. The ‘Orlando’ linkage map has 189 markers, comprising 126 testcross and 61 intercross markers placed in nine linkage groups. The ‘Orlando’ linkage map covered 886 cM with an average map distance of 3.9 cM between adjacent markers. Segregation ratios for Cabsr were not significantly different from 1:1, suggesting that this trait is controlled by a single locus. This locus was placed in ‘Orlando’ linkage group 1. The new map has an improved distribution of markers along the linkage groups with fewer gaps. Combining different marker systems in linkage mapping studies may give better genome coverage due to their chromosomal target site differences, therefore fewer gaps in linkage groups.  相似文献   

17.
Seedlings derived from an Actinidia interspecific cross between the hexaploid Actinidia chinensis var. deliciosa ‘Jinkui’ and the diploid male A. eriantha × A. chinensis var. chinensis ‘Chaohong’ hybrid were analyzed using flow cytometry, SSR markers and phenotypic observations. The results show that the leaf vitamin C content of this hybrid population has a mid-parent heterosis. Separation of flower color in the progeny was also observed, progeny with red flowers lighter than ‘Chaohong’, white flowers as in ‘Jinkui’ and intermediate types with a red base to the petals and white margins were all present. Flow cytometry analysis confirmed that most of the progeny were tetraploids, and molecular marker data showed that most of these tetraploid progeny had three alleles from the hexaploid parent and one allele from the diploid parent. UPGMA analysis based on the SSR markers showed that the diploid parent was completely separated from the hexaploid parent and all the progeny.  相似文献   

18.
The inheritance of the leaf pubescence character of a Chinese local wheat cultivar ‘Hon-mang-mai’ was investigated by monosomic and telosomic analyses. Leaf pubescence was evaluated by observation of the adaxial side of the penultimate leaf of adult plants. F1 hybrids of ‘Hong-mang-mai’ with a non-pubescent cultivar ‘Chinese Spring’ had leaf pubescence, but its density was about a half of that of ‘Hong-mang-mai’. In the F2 generation, the segregation ratio of pubescent to non-pubescent plants fitted a ratio of 3: 1, suggesting that leaf pubescence was controlled by one dominant gene. Monosomic analysis revealed that the gene for pubescence is located on chromosome 7B. Telosomic analysis showed that the gene is located on the short arm of chromosome 7B with a distance of 14.3%from the centromere. This gene is not allelic with the previously reported hairy leaf gene Hl on chromosome 4B, and therefore, is designated Hl2, hairy leaf 2. This revised version was published online in July 2006 with corrections to the Cover Date.  相似文献   

19.
In a previously made cross Brassica napus cv. Oro (2n = 38) × Capsella bursa-pastoris (2n = 4x = 32), one F1 hybrid with 2n = 38 was totally male sterile. The hybrid contained no complete chromosomes from C. bursa-pastoris, but some specific AFLP (amplified fragment length polymorphism) bands of C. bursa-pastoris were detected. The hybrid was morphologically quite similar to ‘Oro’ except for smaller flowers with rudimentary stamens but normal pistils, and showed good seed-set after pollination by ‘Oro’ and other B. napus cultivars. The fertility segregation ratios (3:1, 1:1) in its progenies indicated that the male sterility was controlled by a single recessive gene. In the pollen mother cells of the male sterile hybrid, chromosome pairing and segregation were normal. Histological sectioning of its anthers showed that the tapetum was multiple layers and was hypertrophic from the stage of sporogenic cells, and that the tetrads were compressed by the vacuolated and disaggregated tapetum and no mature pollen grains were formed in anther sacs, thus resulting in male sterility. The possible mechanisms for the production of the male sterile hybrid and its potential in breeding are discussed.  相似文献   

20.
The resistance to Fusarium oxysporum f.sp. melonis (Fom) race 1.2 has been studied in melons, such as the Portuguese accession ‘BG-5384’ and in the Japanese ‘Shiro Uri Okayama’, ‘Kogane Nashi Makuwa’, and ‘C-211’, since a good characterization of the resistance is necessary before its introgression into commercial varieties. These four melon accessions showed a high level of resistance to races 0, 1, and 2 of Fom, indicating that the partial resistance to the race 1.2 previously detected may not have been race specific. To determine the mode of inheritance of the resistance to Fom race 1.2, the F1, F2, BCPR, and BCPS generations from the crosses between the four resistant accessions above and ‘Piel de Sapo’, a Fom race 1.2 susceptible melon, were developed. They were subsequently inoculated with two Fom isolates, one from the pathotype 1.2Y and the other from the pathotype 1.2W. The area under the disease progress curve was determined for each inoculated plant, and the data were analyzed. We show that the resistance seen in these accessions is polygenically inherited with a complex genetic control because many epistatic interactions were detected. The three epistatic effects; additivity × additivity, dominance × dominance, and dominance × additivity are present and significant, with differing magnitudes from one cross to the next. The relatively low heritabilities, and these epistatic effects make difficult the improvement of the resistance, from these sources, through a standard selection procedure.  相似文献   

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