Mapping QTLs for plant height and flowering time in a Chinese summer planting soybean RIL population

Soybean is a primary source of plant oil and protein and has a high nutritional value. Plant height (PH) and flowering time (FT) are two important agronomic traits in breeding programs for soybean. In this study, we mapped QTLs associated with PH and FT in three environments using a population with determinate growth including 236 recombinant inbred lines (NJZY-RIL) derived from a cross between two summer planting varieties, ZXD and NN1138-2. A high-density genetic map with 3255 SLAF-markers was constructed that spanned 2144.85 cM of the soybean genome with an average marker distance of 0.66 cM. Altogether, six QTLs controlling PH and eleven QTLs controlling FT were mapped using mixed-model-based composite interval mapping and composite interval mapping methods. qPH-1-1 and qFT-15-2 were two novel main effect QTLs identified in this study; qFT-6-2, qFT-15-2, qFT-16-1, qPH-1-1, qPH-15-1 and qPH-16-1 were consistently detected across environments and by the two mapping methods. Two pairs of QTLs, qFT-15-2 and qPH-15-1 as well as qFT-16-1 and qPH-16-1, which were located in the same marker interval on chromosomes 15 and 16, respectively, were found to have close linkage or pleiotropy. These results may increase our understanding of the genetic control of PH and FT in soybean and provide support for implementing marker-assisted selection in developing soybean cultivars with high yield and early maturity in summer planting regions.     

Identification of the <Emphasis Type="Italic">S</Emphasis> locus core sequences determining self-incompatibility and <Emphasis Type="Italic">S</Emphasis> multigene family from draft genome sequences of radish (<Emphasis Type="Italic">Raphanus sativus</Emphasis> L.)

The S core and its flanking sequences were identified from two independent draft genome sequences of radish (Raphanus sativus L.). After gap-filling with PCR, the S core regions and full-length S receptor kinase (SRK) genes from two radish genomes were obtained. Phylogenetic analysis of the SRK genes clearly showed that one S core region belonged to the class I S haplotypes, but the other was included in the class II S haplotypes. Three sequences showing homology with known transposable elements were identified in the core regions, and one intact copia-type long terminal repeat (LTR)-retrotransposon containing a 4125-bp open reading frame (ORF) was identified in the class I S haplotype. A total of 61 genes showing homology with the SRK genes were identified from two draft genome sequences. Among them, the RsKD1 showed the highest homology with the SRK genes. There was 90% nucleotide sequence identity between the RsKD1 and RsSRK1 genes in the kinase domains. The phylogenetic tree of SRK genes and 13 most closely related homologs showed that all homologs were more closely related to the class II SRK genes than to the class I SRKs. Physical mapping of radish SRK-homologous genes and their B. rapa orthologs showed that two radish homologs and their B. rapa orthologs were tightly linked to the SRK genes in radish and B. rapa genomes. Sequence information about multiple SRK-homologs identified in this study would be helpful for designing reliable primer pairs for faithful PCR amplification of the SRK alleles, leading to improvement of the S haplotyping system in radish breeding programs.     

Resistance to <Emphasis Type="Italic">Cucumber green mottle mosaic virus</Emphasis> in <Emphasis Type="Italic">Cucumis sativus</Emphasis>

Cucumber green mottle mosaic virus (CGMMV) is a severe threat for cucumber production worldwide. At present, there are no cultivars available in the market which show an effective resistance or tolerance to CGMMV infection, only wild Cucumis species were reported as resistant. Germplasm accessions of Cucumis sativus, as well as C. anguria and C. metuliferus, were mechanically infected with the European and Asian strains of CGMMV and screened for resistance, by scoring symptom severity, and conventional RT-PCR. The viral loads of both CGMMV strains were determined in a selected number of genotypes using quantitative RT-PCR. Severe symptoms were found following inoculation in C. metuliferus and in 44 C. sativus accessions, including C. sativus var. hardwickii. Ten C. sativus accessions, including C. sativus var. sikkimensis, showed intermediate symptoms and only 2 C. sativus accessions showed mild symptoms. C. anguria was resistant to both strains of CGMMV because no symptoms were expressed and the virus was not detected in systemic leaves. High amounts of virus were found in plants showing severe symptoms, whereas low viral amounts found in those with mild symptoms. In addition, the viral amounts detected in plants which showed intermediate symptoms at 23 and 33 dpi, were significantly higher in plants inoculated with the Asian CGMMV strain than those with the European strain. This difference was statistically significant. Also, the amounts of virus detected over time in plants did not change significantly. Finally, the two newly identified partially resistant C. sativus accessions may well be candidates for breeding programs and reduce the losses produced by CGMMV with resistant commercial cultivars.     

Identification of QTLs controlling low-temperature germinability and cold tolerance at the seedling stage in rice (<Emphasis Type="Italic">Oryza Sativa</Emphasis> L.)

Both low-temperature germinability (LTG) and cold tolerance at the seedling stage (CTS) are important traits for rice. In this study, a rice population of recombinant inbred lines (RILs), derived from the backcross population of a cross between Dongnong422 and Kongyu131, was developed to detect quantitative trait loci (QTL) affecting LTG and CTS by using seed of different storage times. Correlation analysis indicated that there was no significant relationship between LTG and CTS, suggesting that cold tolerance might be genetic differences for LTG and CTS. In total, Twelve and twenty-three major QTLs were detected for LTG and CTS, respectively, which could explain greater than 10% of the phenotypical variation. Eight (qCG12-1, qGI12-1, qGV9-1, qMLIT12-1, qPV6-1, qMDG12-1, qLDWcold10-1, qLFWcold10-1) significant QTLs were mapped for different storage time, it concluded that such QTLs were not affected by environment (storage time) and were closely related QTLs to cold tolerance. One or more QTLs were identified for each trait with some of these QTLs co-locating, qMLIT7-1, qCG7-1, and qGI7-1 for LTG, qLFWcold10-1, and qLDWcold10-1 for CTS with contributions over 15% were mapped common marker interval, respectively, co-location of QTLs for different traits can be an indication that a locus has pleiotropic effects on multiple traits due to a common mechanistic basis. Two lines, RIL128 and RIL73, might be valuable to improve the LTG and CTS through a combination of crosses. The identified QTLs might be applicable to improve the rice cold tolerance by the marker-assisted selection approach.     

Resistance screening of breeding lines and commercial tomato cultivars for <Emphasis Type="Italic">Meloidogyne incognita</Emphasis> and <Emphasis Type="Italic">M. javanica</Emphasis> populations (Nematoda) from Ethiopia

Soil and root samples were collected from major tomato growing areas of Ethiopia during the 2012/2013 growing season to identify root-knot nematode problems. DNA-based and isozyme techniques revealed that Meloidogyne incognita and M. javanica were the predominant Meloidogyne species across the sampled areas. The aggressiveness of different populations of these species was assessed on tomato cultivars Marmande and Moneymaker. The two most aggressive populations of each species were selected and further tested on 33 tomato genotypes. The resistance screening and mechanism of resistance was performed after inoculation with 100 freshly hatched (<24 h) second-stage juveniles (J2). Eight weeks after inoculation the number of egg masses produced on each cultivar was assessed. For the resistance mechanism study, J2 penetration and their subsequent development inside the tomato roots were examined at 1, 2, 4 and 6 weeks after inoculation. On both cultivars Marmande and Moneymaker all M. incognita and M. javanica populations formed a high number of egg masses indicating highly aggressive behaviour. Populations from ‘Jittu’ and ‘Babile’ for M. incognita and ‘Jittu’ and ‘Koka’ for M. javanica were selected as most aggressive. None of the 33 tomato genotypes were immune for these M. incognita and M. javanica populations. However, several tomato genotypes were found to have a significant effect on the number of egg masses produced indicating possible resistance. For M. javanica populations there were more plants from cultivars or breeding lines on which no egg masses were found compared to M. incognita populations. The lowest number of egg masses for both populations of M. incognita was produced on cultivars Bridget40, Galilea, and Irma while for M. javanica it was on Assila, Eden, Galilea, Tisey, CLN-2366A, CLN-2366B and CLN-2366C. Tomato genotypes, time (weeks after inoculation) and their interaction were significant sources of variation for J2 penetration and their subsequent development inside the tomato roots. Differential penetration was found in breeding lines such as CLN-2366A, CLN-2366B and CLN-2366C, but many of the selected tomato genotypes resistance for the tested M. incognita and M. javanica populations were expressed by delayed nematode development. Therefore, developing a simple screening technique to be used by local farmers or extension workers is crucial to facilitate selection of a suitable cultivar.     

Karyotype analysis of eight wild <Emphasis Type="Italic">Tulipa</Emphasis> species native to China and the interspecific hybridization with tulip cultivars

The information of ploidy, karyotype and genetic relationship is useful for interspecific hybridization in ornamental plants. For Tulipa species native to China, very limited cytological information is available now. The objective of this study was to verify the chromosome number, karyotype and genetic relationship of the eight Tulipa species: T. edulis, T. schrenkii, T. iliensis, T. thianschanica, T. altaica, T. sinkiangensis, T. heterophylla and T. buhseana. And the interspecific crosses were made between T. altaica and ten tulip cultivars to obtain novel germplasm. The ovary-swelling, fruit-setting and bulblet formation rates were surveyed when different ploidy cultivars were used as female parents. This work confirmed that all eight species collected in China were diploid (2n?=?2x?=?24), among which chromosome numbers of T. thianschanica, T. sinkiangensis and T. heterophylla were firstly reported and the karyotypes of all any other species except for T. edulis were determined for the first time. The karyotypes of eight Tulipa species were classified as 3A, 4A or 3B. The results of interspecific hybridization showed significant difference when different ploidy cultivars were used as female parents. The highest fruit-setting rate was obtained when diploid cultivars were used as female parents crossed with diploid T. altaica, whereas the ovary swelling was observed in two out of four triploid cultivars as female parents, and no seeds were harvested when tetraploid cultivars were used as female parents. Our findings provided an effective means of cultivar improvement in tulip.     

Hybrids of ryegrasses and meadow fescue and their value for grass breeding

1. 1.
   In attempts to intercross Lolium perenne and L. multiflorum with Festuca pratensis in a glasshouse, 13,284 emasculated flowers of diploid, triploid and tetraploid Lolium plants were provided with pollen of diploid and tetraploid Festuca plants. Only the combinations 2n\sx4n and 3n\sx4n produced hybrids, viz. on average 5.3 and 1.0 mature hybrid plants per 100 pollinated flowers. In crosses performed in winter these averages were 12.0 and 4.9 respectively.     
   
   

Natural and experimental hybrids of ryegrasses and meadow fescue

1. 1.
   Chromosome numbers, male and female fertility and morphological characters were studied on about 90 plants from each of two natural populations of hybrids between Lolium perenne and Festuca pratensis.     
   
   

Overcoming unilateral incompatibility in crosses with wild allotetraploid potato species <Emphasis Type="Italic">Solanum stoloniferum</Emphasis> Schldtl. &amp; Bouchet

The germplasm of valuable for breeding wild allotetraploid potato species Solanum stoloniferum is rarely used because of pre- and postzygotic reproductive barriers with cultivated potatoes. One of the factors that complicate crosses between S. stoloniferum and S. tuberosum is unilateral incompatibility (UI). Here, we present the results of application of S. verrucosum and S _v S _v -lines for overcoming UI in crosses with S. stoloniferum and of generating male fertile hybrids derived from this species. S _v S _v -lines are F2 S. tuberosum dihaploid × S. verrucosum that are male fertile and have D/γ-type cytoplasm. Since they are homozygous for S _v gene from S. verrucosum, they were expected to have the same ability for elimination of prezygotic incompatibility as this species. Three accessions of S. verrucosum and seven S _v S _v -lines were pollinated by 26 accessions of S. stoloniferum. The crosses with S. verrucosum failed or had low efficacy (1.5–2.4 seeds per pollination). On the other hand, use of S _v S _v -lines was more efficient: 15.8 seeds per pollination. In spite of low percentage of germination (1.9%), 40 seedlings of interspecific hybrids were produced. The experiment on hybridization between S _v S _v -lines and S. stoloniferum has been reproduced with the accession PI 205522 of the wild species, which had DNA markers of PVY and LB resistance genes and W/γ cytoplasm: 950 hybrid seeds and 12 viable seedlings were produced. The genome of the seedlings was doubled by colchicine treatment, which generated hexaploids that formed highly fertile pollen and set seeds from self-pollination. We were able to cross them as females with the variety Katahdin.     

Obtainment of an intergeneric hybrid between <Emphasis Type="Italic">Forsythia</Emphasis> and <Emphasis Type="Italic">Abeliophyllum</Emphasis>

Forsythia suspensa and F. ‘Courtaneur’ were used as female parents to cross with Abeliophyllum distichum in 2011 and an intergeneric hybrid of F. suspensa × A. distichum was obtained, though with very low seed set. The morphological characteristics, flower fragrance and volatile organic compounds of flowers were analysed. The intergeneric hybrid had intermediate morphological characteristics of both parents and flower fragrance and was confirmed as a true intergeneric hybrid by amplified fragment length polymorphism (AFLP) markers. Compared with its mother parent (F. suspensa), flowers of the intergeneric hybrid are pale yellow with delicate fragrance. Volatile organic compounds of flowers were retrieved by purge-and-trap techniques, and determined by gas chromatography and mass spectrometry (GC–MS). The main volatile organic components of F. suspensa were isoprenoids, while the main volatile organic components of A. distichum and the hybrid of F. suspensa × A. distichum were aliphatics. To determine the time and the site of intergeneric hybridizing barriers occured, the pollen tubes’ behavior after pollination was observed under fluorescence microscopy. It was found that significant pre-fertilization incompatibility existed in intergeneric crossing combinations [F. ‘Courtaneur’ (Pin) × A. distichum (Thrum) and F. suspensa (Pin) × A. distichum (Thrum)], and only a few pollen tubes of A. distichum penetrated into the ovaries of Forsythia. In our research, an intergeneric hybrid between Forsythia and Abeliophyllum was obtained for the first time, which will provide a solid foundation for expanding the flower color range of Forsythia and breeding fragrant-flowered cultivars.     

Breeding male sterile lines of dutch onion varieties as a preliminary to the breeding of hybrid varieties

1. 1.
   By means of test crossings to American male sterile varieties N ms ms plants were found in Netherlands onion varieties.     
   
   

Notes on the genetics of a few leaf characters in the genus citrus

In a few hybridization experiments data were collected on the genetical basis of:

1. a.
   the red-brown colour of the young flush of Meyer lemon (Citrus limon)     
   
   

Identification and characterization of seedling and adult plant resistance to <Emphasis Type="Italic">Puccinia hordei</Emphasis> in selected African barley germplasm

A collection of 112 African barley accessions were assessed for response to Puccinia hordei in seedling greenhouse tests using 10 pathotypes and in adult plant field tests over three successive field seasons in Australia. One of the 10 pathotypes (viz. 5457P+) used in seedling tests was also used in field tests to allow assessment of the presence of adult plant resistance (APR) in lines that were seedling susceptible to this pathotype. The seedling resistance genes Rph1, Rph2, Rph3, Rph9.am and Rph9.z were postulated in a number of accessions, singly and in various combinations, with Rph2 and Rph9.z being the most common. Twenty-six accessions carried seedling resistance that was either uncharacterized or could not be determined using the 10 P. hordei pathotypes. One accession carried high levels of APR and 11 accessions showed moderate levels of APR, all of which were susceptible to all P. hordei pathotypes at the seedling stage. All barley accessions were genotyped for the presence of marker alleles that are closely linked to the APR genes Rph20 and Rph23 (bPb-0837 and Ebmac0603, respectively). No accession was positive for bPb-0837, suggesting that Rph20 is not frequent in African germplasm. Thirteen accessions were postulated to carry Rph23 based on the presence of the marker allele Ebmac0603 found in Yerong (Rph23), and 10 out of the 11 accessions with moderate APR lacked the bPb-0837 and Ebmac0603 marker alleles, indicating that they likely carry new uncharacterized APR genes. Inheritance studies were performed using populations derived from four of the accessions that carried APR (Clho 9776, Clho 11958, Mecknes Maroc and Sinai) by crossing with the susceptible barley genotype Gus. Chi squared analysis of the phenotypic data from F₃ populations suggested that CIho9776 carried a single APR gene and CIho11958, Mecknes Maroc and Sinai each carried two genes for APR to leaf rust.     

Expression of the <Emphasis Type="Italic">Ga1-s</Emphasis> gametophyte factor in <Emphasis Type="Italic">shrunken2</Emphasis> sweet corn

Outcrossing is an important problem in specialty maize (Zea mays L.) that can be prevented by using gametophyte factors, such as Ga1-s, which preserve maize plants from pollen contamination. Our objective was to check if the gametophyte factor Ga1-s can protect sweet corn homozygous for sh2 in an efficient and stable way. We combined Ga1-s and sh2 by crossing two popcorn and three sweet corn inbred lines, respectively, in a North Carolina Design II, followed by an ear-to-row breeding program with selection for sh2 phenotype and absence of outcrossing. The released inbred lines homozygous for Ga1-s and sh2 were used for obtaining five hybrids that were evaluated for outcrossing and agronomic performance. Our results show that the gametophyte factor Ga1-s effectively protects the sh2 plants and that this effect was stable across environments. However, the agronomic performance of these inbred lines must be improved. Popcorn donors and sweet corn receptors of Ga1-s were unevenly represented in the released Ga1-s / sh2 inbred lines, suggesting that the viability of sh2 is affected by the genotypes involved. Therefore, breeders should pay attention to the choice of donors of Ga1-s that favors the viability of sh2.     

<Emphasis Type="Italic">Er3</Emphasis> gene,conferring resistance to powdery mildew in pea,is located in pea LGIV

Three genes for resistance to Erysiphe pisi, named er1, er2 and Er3 have been described in pea so far. er1 gene is located in pea linkage group VI, while er2 gene has been mapped in LGIII. SCAR and RAPD markers tightly linked to Er3 gene have been identified, but the position of these markers in the pea genetic map was unknown. The objective of this study was to localize Er3 gene in the pea genetic map. Towards this aim, the susceptible pea cv. Messire (er3er3) and a resistant near isogenic line of Messire (cv. Eritreo, Er3Er3) were surveyed with SSRs with known position in the pea map. Three SSRs were polymorphic between “Messire” and “Eritreo” and further surveyed in two contrasting bulks formed by homozygous Er3Er3/er3er3 individuals obtained from a F₂ population derived from the cross C2 (Er3Er3)?×?Messire (er3er3). A single marker, AA349, was polymorphic between the bulks. Subsequently, other ten markers located in the surrounding of AA349 were selected and analysed in Er3Er3 and er3er3 plants. As a results, another SSR, AD61, was found to be polymorphic between Er3Er3 and er3er3 plants. Further linkage analysis confirmed that SSRs AA349 and AD61 were linked to Er3 and to the RAPD and SCAR markers previously reported to be linked to this gene. Er3 gene was located in pea LGIV at 0.39 cM downstream of marker AD61. The location of Er3 gene in the pea map is a first step toward the identification of this gene.     

Genetic mapping of resistance to <Emphasis Type="Italic">Puccinia hordei</Emphasis> in three barley doubled-haploid populations

The success of breeding for barley leaf rust (BLR) resistance relies on regular discovery, characterization and mapping of new resistance sources. Greenhouse and field studies revealed that the barley cultivars Baronesse, Patty and RAH1995 carry good levels of adult plant resistance (APR) to BLR. Doubled haploid populations [(Baronesse/Stirling (B/S), Patty/Tallon (P/T) and RAH1995/Baudin (R/B)] were investigated in this study to understand inheritance and map resistance to BLR. The seedlings of two populations (B/S and R/B) segregated for leaf rust response that conformed to a single gene ratio (\({\text{X}}_{1:1}^{2}\) = 0.12, P > 0.7 for B/S and \({\text{X}}_{1:1}^{2}\) = 0.34, P > 0.5 for R/B) whereas seedlings of third population (P/T) segregated for two-gene ratio (\({\text{X}}_{1:1}^{2}\) = 0.17, P > 0.6) when tested in greenhouse. It was concluded that the single gene in Baudin and one of the two genes in Tallon is likely Rph12, whereas gene responsible for seedling resistance in Stirling is Rph9.am (allele of Rph12). The second seedling gene in Tallon is uncharacterized. In the field, APR was noted in lines that were susceptible as seedlings. A range of disease responses (CI 5–90) was observed in all three populations. Marker trait association analysis detected three QTLs each in populations B/S (QRph.sun-2H.1, QRph.sun-5H.1 and QRph.sun-6H.1) and R/B (QRph.sun-1H, QRph.sun-2H.2, QRph.sun-3H and QRph.sun-6H.2), and four QTLs in population P/T (QRph.sun-6H.2, QRph.sun-1H.2, QRph.sun-5H.2 and QRph.sun-7H) that significantly contributed to low leaf rust disease coefficients. High frequency of QRph. sun-5H.1, QRph. sun-6H.1, QRph. sun-1H.1, QRph. sun-2H.2, QRph. sun-6H.2, QRph. sun-7H (based on presence of the marker, closely associated to the respective QTLs) was observed in international commercial barley germplasm and hence providing an opportunity for rapid integration into breeding programmes. The identified candidate markers closely linked to these QTLs will assist in selecting and assembling new APR gene combinations; expectantly this will help in achieving good levels of durable resistance for controlling BLR.     

Diploid and tetraploid progenitors of wheat are valuable sources of resistance to the root lesion nematode <Emphasis Type="Italic">Pratylenchus</Emphasis><Emphasis Type="Italic">thornei</Emphasis>

The root lesion nematode Pratylenchus thornei is widely distributed in Australian wheat (Triticum aestivum) producing regions and can reduce yield by more than 50%, costing the industry AU$50 M/year. Genetic resistance is the most effective form of management but no commercial cultivars are resistant (R) and the best parental lines are only moderately R. The wild relatives of wheat have evolved in P. thornei-infested soil for millennia and may have superior levels of resistance that can be transferred to commercial wheats. To evaluate this hypothesis, a collection of 251 accessions of wheat and related species was tested for resistance to P. thornei under controlled conditions in glasshouse pot experiments over two consecutive years. Diploid accessions were more R than tetraploid accessions which proved more R than hexaploid accessions. Of the diploid accessions, 11 (52%) Aegilops speltoides (S-[B]-genome), 10 (43%) Triticum monococcum (A ^m -genome) and 5 (24%) Triticum urartu (A ^u -genome) accessions were R. One tetraploid accession (Triticum dicoccoides) was R. This establishes for the first time that P. thornei resistance is located on the A-genome and confirms resistance on the B-genome. Since previous research has shown that the moderate levels of P. thornei resistance in hexaploid wheat are dose-dependent, additive and located on the B and D-genomes, it would seem efficient to target A-genome resistance for introduction to hexaploid lines through direct crossing, using durum wheat as a bridging species and/or through the development of amphiploids. This would allow resistances from each genome to be combined to generate a higher level of resistance than is currently available in hexaploid wheat.     

Breeding opportunities for early,free-threshing and semi-dwarf <Emphasis Type="Italic">Triticum monococcum</Emphasis> L.

Einkorn wheat, Triticum monococcum L. (2n = 2x = 14, A^mA^m genome), is a primitive, cultivated form of diploid wheat. The shortcoming of einkorn is that it lacks the free-threshing habit. Early heading and semi-dwarf traits are also required to fit modern agricultural practice. In the present study we developed T. monococcum pre-breeding germplasm having early, free threshing traits by utilizing an early heading source, two sources of soft glume (spike) and three sources of semi-dwarfism to combine their phenotypes into pre-breeding materials. We found two different genes determined free threshing of einkorn wheat. One of them was the sog (soft glume) gene from Triticum sinskajae Filat. et Kurkiev (2n = 2x = 14, A^mA^m genome) and another was the sos (soft spike) gene, which was completely linked or pleiotropic with the gene for semi-dwarfism. The genes sos, spd (short peduncle) and sd17654 (semi-dwarf CItr 17654) were utilized to develop semi-dwarf T. monococcum lines. Field performance of 6 early and free-threshing pre-breeding materials with sos and spd genes were tested over three crop seasons. Five semi-dwarf pre-breeding materials (PBMs) were obtained. However, these materials had slightly less grain yield than #252 (tall and hulled check) and PBM-1 (tall free-threshing check). Harvest index of the pre-breeding materials was improved due to the presence of sos and spd genes. If optimized cultivation practice is performed, these pre-breeding materials can be utilized as sources of early, free-threshing and semi-dwarf traits to produce modern T. monococcum varieties.     

Sources of resistance to <Emphasis Type="Italic">Phytophthora</Emphasis> root rot within the genus <Emphasis Type="Italic">Beta</Emphasis>

Phytophthora root rot caused by Phytophthora drechsleri Tucker is one of the most devastating sugar beet diseases in tropical areas. To identify genetic resources resistant to this disease, an aggressive isolate of P. drechsleri was selected. Then, a screening method was optimized based on the standard scoring scales of 1–9 (1: no symptoms, 9: complete plant death). Finally, 19 sugar beet lines, three cultivars, and 14 accessions of the wild species Beta vulgaris subsp. maritima, B. macrocarpa, B. procumbens, and B. webbiana were evaluated for resistance to the most aggressive isolate of P. drechsleri by using the optimized method (inoculum included 20 g of rice seed together with superficial wound creation). The isolates of P. drechsleri had significant variation in aggressiveness, and Kv10 was the most aggressive isolate on the susceptible variety Rasoul. The lines O.T.201-15, SP85303-0 (resistant check), and S2-24.P.107 had the lowest disease index with scores of 3.09, 3.13, and 3.27 respectively; they were categorized into the resistant group. The interaction between isolates and genotypes was not significant, which indicated the same response of each genotype to different isolates. Investigating the resistance of different generations of sugar beet revealed that progeny selection would be an effective method for increasing the resistance level of breeding materials to P. drechsleri. Among the wild species, the accession 9402 belonging to B. macrocarpa and the accession 7234 of B. vulgaris subsp. maritima had the lowest disease index (2.29 and 2.60, respectively) and were categorized into the resistant group.     

Mapping and use of seed protein loci for marker-assisted selection of growth habit and photoperiod response in <Emphasis Type="Italic">Nuña</Emphasis> bean (<Emphasis Type="Italic">Phaseolus vulgaris</Emphasis> L.)

The individual segregations of 14 seed protein loci named, SpA to SpM and Pha (phaseolin), were analyzed in a RIL population developed from the cross Xana × Cornell 49242. These seed protein loci were included in a genetic map previously developed in the same population. Protein loci, SpA, SpB, SpE, SpI, SpJ, and Pha, are organized in two different clusters, both located in linkage group (LG) 7; SpF, SpG, SpK, SpL, and SpM, form a single cluster in LG 4; SpC, is located in LG 3; and SpD, in LG 1. A close linkage was identified between the SpD seed protein locus, and the fin gene, controlling determinate growth habit. The usefulness of the SpD locus as a marker for the indirect selection of determinate growth habit and photoperiod insensitivity was checked in a F₂ population derived from the cross G12587 (an indeterminate and photoperiod sensitive nuña bean) × Sanilac (determinate and photoperiod insensitive) and in a set of Mesoamerican and Andean genotypes. Results indicate that SpD protein locus was useful to detect individuals having determinate growth habit and photoperiod insensitivity in the cross G12587 × Salinac although some recombinants were found. However, the linkage between the SpD locus and the genes controlling growth habit and photoperiod sensitivity should be checked before using the SpD locus for the indirect selection of these traits in different backgrounds.