Fingerprinting temperate <Emphasis Type="Italic">japonica</Emphasis> and tropical <Emphasis Type="Italic">indica</Emphasis> rice genotypes by comparative analysis of DNA markers

This paper describes the relative efficiency of three marker systems, RAPD, ISSR, and AFLP, in terms of fingerprinting 14 rice genotypes consisting of seven temperatejaponica rice cultivars, three indica near-isogenic lines, three indica introgression lines, and one breeding line of japonica type adapted to high-altitude areas of the tropics with cold tolerance genes. Fourteen RAPD, 21 ISSR, and 8 AFLP primers could produce 970 loci, with the highest average number of loci (92.5) generated by AFLP. Although polymorphic bands in the genotypes were detected by all marker assays, the AFLP assay discriminated the genotypes effectively with a robust discriminating power (0.99), followed by ISSR (0.76) and RAPD (0.61). While significant polymorphism was detected among the genotypes of japonica and indica through analysis of molecular variance (AMOVA), relatively low polymorphism was detected within the genotypes of japonica rice cultivars. The correlation coefficients of similarity were significant for the three marker systems used, but only the AFLP assay effectively differentiated all tested rice lines. Fingerprinting of backcross-derived resistant progenies using ISSR and AFLP markers easily detected progenies having a maximum rate of recovery for the recurrent parent genome and suggested that our fingerprinting approach adopting the ‘undefined-element-amplifying’ DNA marker system is suitable for incorporating useful alleles from the indica donor genome into the genome of temperate japonica rice cultivars with the least impact of deleterious linkage drag.     

Mapping of QTLs associated with cadmium tolerance and accumulation during seedling stage in rice (<Emphasis Type="Italic">Oryza sativa</Emphasis> L.)

Cadmium (Cd) is a non-essential element and toxic to plants. To investigate the genetics of Cd tolerance and accumulation in rice, quantitative trait loci (QTL) associated with Cd tolerance and accumulation at the seedling stage were mapped using a doubled haploid (DH) population derived from a cross between a japonica JX17 and an indica ZYQ8. A total of 22 QTLs were found to be associated with shoot height (SH), root length (RL), shoot dry weight (SDW), root dry weight (RDW), total dry weight (TDW) and chlorophyll content (CC), and 10 and 12 QTLs were identified under the control and Cd stress conditions, respectively. For Cd tolerant coefficient (CTC), 6 QTLs were detected on chromosomes 1, 3, 5, 8 and 10. Under Cd stress, 3 QTLs controlling root and shoot Cd concentrations were mapped on chromosome 6 and 7. One QTL for shoot/root rate of Cd concentration was identified on chromosome 3. The results indicated that Cd tolerance and accumulation were quantitatively inherited, and the detected QTLs may be useful for marker-assistant selection (MAS) and identification of the genes controlling Cd tolerance and accumulation in rice.     

Mechanisms of resistance to shoot fly, <Emphasis Type="Italic">Atherigona soccata</Emphasis> in sorghum

Summary Sorghum shoot fly, Atherigona soccata (Rondani) is an important pest of sorghum in Asia, Africa, and Mediterranean Europe, and host plant resistance is an important component for the management of this pest. The levels of resistance in the cultivated germplasm are low to moderate, and therefore, it is important to identify genotypes with different mechanisms of resistance to pyramid the resistance genes. We studied the antixenosis for oviposition, antibiosis, and tolerance components of resistance in a diverse array of shoot fly-resistant and -susceptible genotypes. The main plants and tillers of SFCR 151, ICSV 705, SFCR 125, and, IS 18551 experienced lower shoot fly deadhearts at 28 days after seedling emergence, produced more number of productive tillers. The insects fed on these genotypes also exhibited longer larval period (10.1–11.0 days compared to 9.3 days on Swarna), lower larval survival and adult emergence (54.7–67.8 and 46.7–52.2% compared to 73.3 and 60.6% on Swarna, respectively), and lower growth and adult emergence indices as compared to the susceptible check, Swarna. Physico-chemical traits such as leaf glossiness, trichome density, and plumule and leaf sheath pigmentation were found to be associated with resistance, and chlorophyll content, leaf surface wetness, seedling vigor, and waxy bloom with susceptibility to shoot fly and explained 88.5% of the total variation in deadhearts. Step-wise regression indicated that 90.4% of the total variation in deadhearts was due to leaf glossiness and trichome density. The direct and indirect effects, correlation coefficients, multiple and step-wise regression analysis suggested that deadhearts, plants with eggs, leaf glossiness, trichomes on the abaxial surface of the leaf, and leaf sheath pigmentation can be used as marker traits to select for resistance to shoot fly, A. soccata in sorghum.     

<Emphasis Type="Italic">Agrobacterium</Emphasis>-mediated transformation of faba bean <Emphasis Type="Italic">(Vicia faba</Emphasis> L.) using embryo axes

A system for the production of transgenic faba bean by Agrobacterium-mediated transformation was developed. This system is based upon direct shoot organogenesis after transformation of meristematic cells derived from embryo axes. Explants were co-cultivated with A. tumefaciens strain EHA105/pGlsfa, which harbored a binary vector containing a gene encoding a sulphur rich sunflower albumin (SFA8) linked to the bar gene. Strain EHA 101/pAN109 carrying the binary plasmid containing the coding sequence of a mutant aspartate kinase gene (lysC) from E. coli in combination with neomycinphosphotransferase II gene (nptII) was used as well. The coding sequences of SFA8 and LysC genes were fused to seed specific promoters, either Vicia faba legumin B4 promoter (LeB4) or phaseolin promoter, respectively. Seven phosphinothricin (PPT) resistant clones from Mythos and Albatross cultivars were recovered. Integration, inheritance and expression of the transgenes were confirmed by Southern blot, PCR, enzyme activity assay and Western blot.     

Evaluation of seedling and adult plant resistance in European wheat cultivars to Australian isolates of <Emphasis Type="Italic">Puccinia striiformis</Emphasis> f. sp. <Emphasis Type="Italic">tritici</Emphasis>

A set of 105 European wheat cultivars was assessed for seedling resistance and adult plant resistance (APR) to stripe (yellow) rust in greenhouse and field tests with selected Australian isolates of Puccinia striiformis f. sp. tritici (Pst). Twelve cultivars were susceptible to all pathotypes, and among the remainder, 11 designated seedling genes (Yr1, Yr3, Yr4, Yr6, Yr7, Yr9, Yr17, Yr27, Yr32, YrHVII and YrSP) and a range of unidentified seedling resistances were detected either singly or in combination. The identity of seedling resistance in 43 cultivars could not be determined with the available Pst pathotypes, and it is considered possible that at least some of these may carry uncharacterised seedling resistance genes. The gene Yr9 occurred with the highest frequency, present in 19 cultivars (18%), followed by Yr17, present in 10 cultivars (10%). Twenty four cultivars lacked seedling resistance that was effective against the pathotype used in field nurseries, and all but two of these displayed very high levels of APR. While the genetic identity of this APR is currently unknown, it is potentially a very useful source of resistance to Pst. Genetic studies are now needed to characterise this resistance to expedite its use in efforts to breed for resistance to stripe rust. Colin R. Wellings seconded from NSW Department of Primary Industries.     

Variation of <Emphasis Type="Italic">Wx</Emphasis> microsatellite allele,waxy allele distribution and differentiation of chloroplast DNA in a collection of Thai rice (<Emphasis Type="Italic">Oryza sativa</Emphasis> L.)

Eighty-two varieties of rice from different regions in Thailand were selected to explore the Waxy (Wx)gene diversity and indica-japonica differentiation of chloroplast DNA. A comparison of the 5 splice site in the first intron was made between glutinous and nonglutinous rice. It revealed that non-glutinous with low-amylose content and glutinous rice were characterized as the Wx^b allele based on the G-to-T base substitution, whereas non-glutinous rice with intermediate and high amylose carried the Wx^a allele. Four Wx microsatellite alleles, (CT)_n repeat, (n = 16,17,18 and 19) were found in glutinous rice. In contrast, non-glutinous rice showed five Wx microsatellite alleles (n = 11, 16, 17, 18 and 19). The (CT)₁₇ allele was prominent allele in Thai population, while the (CT)₁₁ allele was found only in intermediate and high amylose rice varieties from southern Thailand. Almost all of upland rice grown by various ethnic groups in northern Thailand were characterized as japonica type based on their having the PstI-12 fragment in their cpDNA, whereas most of rainfed lowland varieties from other regions of Thailand were indica. This exploration of DNA-based genetic markers is important, as it enhances our ability to describe and manipulate sources of genetic variation for rice breeding programs.     

A cytoplasmic-nuclear male-sterility system derived from a cross between <Emphasis Type="Italic">Cajanus cajanifolius</Emphasis> and <Emphasis Type="Italic">Cajanus cajan</Emphasis>

Cytoplasmic-nuclear male-sterility is an important biological tool, which has been used by plant breeders to increase yields in cross-pollinated cereals and vegetables by commercial exploitation of the phenomenon of hybrid vigor. In legumes, no such example exists due to the absence of an economic way of mass pollen transfer from male to female parent. Pigeonpea [Cajanus cajan (L.) Millsp.], however, is a different legume where a moderate level of insect-aided natural out-crossing (25–70%) exists and it can be used to produce commercial hybrid cultivars, if an efficient and stable cytoplasmic-nuclear male-sterility (CMS) system is available. This paper reports the development of a stable CMS system (ICP 2039A), derived from an inter-specific hybrid of Cajanus cajanifolius, a wild relative of pigeonpea, with a cultivar ICP 11501. Using this genetic material, designated as the A₄ cytoplasm, a number of fertility restorers and maintainers have been developed. The best short-duration experimental pigeonpea hybrid ICPH 2470 produced 3205 kg ha⁻¹ grain yield in 125 days, exhibiting 77.5% advantage over the control cultivar UPAS 120. At present, all the important biological systems necessary for a successful commercial hybrid breeding program are available in pigeonpea and the package of this technology has been adopted by private seed sector in India for the production and marketing of hybrid varieties.     

Genetic and histological characterization of a novel recessive genic male sterile line of <Emphasis Type="Italic">Brassica napus</Emphasis> derived from a cross with <Emphasis Type="Italic">Capsella bursa</Emphasis>-<Emphasis Type="Italic">pastoris</Emphasis>

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.     

Evaluation of seedling and adult plant resistance to <Emphasis Type="Italic">Puccinia hordei</Emphasis> in barley

The responses of 92 barley genotypes to selected Puccinia hordei pathotypes were assessed in greenhouse tests at seedling growth stages and in the field at adult plant growth stages to identify known and/or unknown resistances. On the basis of multipathotype tests, 35 genotypes were postulated to carry Rph1, Rph2, Rph4, Rph5, Rph12, RphCantala, alone or in combination (Rph2 + Rph4 and Rph1 + Rph2), whereas 52 genotypes lacked seedling resistance to P. hordei to the pathotypes used. Five genotypes carried seedling resistance that was effective to all pathotypes, of which four were believed to carry uncharacterised resistance based on pedigree information. Field tests at adult plant growth stages indicated that while 28 genotypes were susceptible, 57 carried uncharacterised APR to P. hordei. Pedigree analysis indicated that APR in the test genotypes could have been derived from three different sources. The resistant responses of seven cultivars at adult plant growth stages were believed to be due to the presence of seedling resistance effective against the field pathotypes.     

Molecular characterization of <Emphasis Type="Italic">Pina</Emphasis> and <Emphasis Type="Italic">Pinb</Emphasis> allelic variations in Xinjiang landraces and commercial wheat cultivars

Grain hardness plays an important role in determining both milling performance and quality of the end-use products produced from common or bread wheat. The objective of this study was to characterize allelic variations at the Pina and Pinb loci in Xinjiang wheat germplasm for further understanding the mechanisms involved in endosperm texture formation, and the status of grain texture in Chinese bread wheat. A total of 291 wheat cultivars, including 56 landraces, and 95 introduced and 140 locally improved cultivars, grown in Xinjiang, were used for SKCS measurement and molecular characterization. Among the harvested grain samples, 185 (63.6%), 40 (13.7%), and 66 (22.7%) were classified as hard, mixed and soft, respectively. Eight different genotypes for the Pina and Pinb loci were identified, including seven previously reported genotypes, viz., Pina-D1a/Pinb-D1a, Pina-D1a/Pinb-D1b, Pina-D1b/Pinb-D1a, Pina-D1a/Pinb-D1p, Pina-D1a/Pinb-D1q, Pina-D1a/Pinb-D1aa, Pina-D1a/Pinb-D1ab, and a novel Pinb allele, Pinb-D1ac. This new allele, detected in Kashibaipi (local landrace) and Red Star (from Russia) has a double mutation at the 257th (G to A substitution) and 382nd (C to T substitution) nucleotide positions of the coding region. Pina-D1b, Pinb-D1b, and Pinb-D1p were the most common alleles in Xinjiang wheat germplasm, with frequencies of 14.3%, 38.1% and 28.6% in hard textured landraces, 25.5%, 56.9% and 11.8% in hard introduced cultivars, and 24.8%, 47.8% and 26.5% in hard locally improved cultivars, respectively. The restriction enzymes ApaI, SapI, BstXI and SfaNI were used to identify Pinb-D1ab or Pinb-D1ac, Pinb-D1b, Pinb-D1e and Pinb-Dg, respectively, by digesting PCR products of the Pinb gene. The unique grain hardness distribution in Xinjiang bread wheat, as well as the CAPs markers for identification of the Pinb alleles provided useful information for breeding wheat cultivars with optimum grain textures. Liang Wang and Genying Li—contributed equally to this work.     

Identification of QTLs for the resistance to rice stripe virus in the <Emphasis Type="Italic">indica</Emphasis> rice variety Dular

The indica variety Dular has a high level of resistance to rice stripe virus (RSV). We performed quantitative trait locus (QTL) analysis for RSV resistance using 226 F₂ clonal lines at the seedling stage derived from a cross between the susceptible japonica variety Balilla and the resistant indica variety Dular with two evaluation criteria, infection rate (IR) and disease rating index (DRI). The experiments were performed in both 2004 and 2005. Based on IR, three putative QTLs were detected and had consistent locations in the 2 years, one QTL was detected in the RM7324–RM3586 interval on chromosome 3. The other two QTLs were linked and located in the RM287–RM209 and RM209–RM21 intervals on the long arm of chromosome 11, and accounted for 87.8–57.8% of the total phenotypic variation in both years. Based on DRI, three putative QTLs were also detected and had consistent locations in both years. One of them was located in the RM1124–SSR20 interval on the short arm of chromosome 11, while the other two linked QTLs had the same chromosomal locations on chromosome 11 as those detected by IR, and accounted for 55.7–42.9% of total phenotypic variation in both years. In comparison to the mapping results from previous studies, one of the two linked QTLs had a chromosomal location that was similar to Stv-b ⁱ , an important RSV resistance gene, while the other appeared to be a newly reported one.     

Expression of <Emphasis Type="Italic">Bruguiera gymnorhiza</Emphasis><Emphasis Type="Italic">BgARP1</Emphasis> enhances salt tolerance in transgenic <Emphasis Type="Italic">Arabidopsis</Emphasis> plants

We have previously reported that expression of salt-responsive genes, including Bruguiera gymnorhiza ankyrin repeat protein 1 (BgARP1), enhances salt tolerance in both Agrobacterium tumefaciens and Arabidopsis. In this report, we further characterized BgARP1-expressing Arabidopsis to elucidate the role of BgARP1 in salt tolerance. BgARP1-expressing plants exhibited more vigorous growth than wild-type plants on MS plates containing 125–175 mM NaCl. Real-time PCR analysis showed enhanced induction of osmotin34 in the 2-week-old transformants under 125 mM NaCl. It was also showed that induction of typical salt-responsive genes, including RD29A, RD29B, and RD22, was blunted and delayed in the 4-week-old transformants during 24 h after 200 mM NaCl treatment. Ion content analysis showed that transgenic plants contained more K⁺, Ca²⁺, and NO₃ ⁻, and less NH₄ ⁺, than wild-type plants grown in 200 mM NaCl. Our results suggest that BgARP1-expressing plants may reduce salt stress by up-regulating osmotin34 gene expression and maintaining K⁺ homeostasis and regulating Ca²⁺ content. These results indicate that BgARP1 is functional on a heterogeneous background.     

Germination characters and early seedling growth of wheat (<Emphasis Type="Italic">Triticum aestivum</Emphasis> L.) genotypes under salt stress conditions

Screening of wheat genotypes as salt tolerance through seed germination and early seedling growth is crucial for their evaluation. Seeds of 20 wheat genotypes were germinated in Petri dishes on a sand bed irrigated with saline (15 dS m_-1) and control solutions for 10 days and also tested at different salinity levels (control, 4, 6, 8, and 10 dS m^-1) which were artificially developed in the soil for 30 days. At 10 days, germination percentage, rate of germination, co-efficient of germination, germination vigor index, shoot length, root length, and seedling dry weight were found to be affected due to salinity. Salt tolerance index (STI) for seedling dry weight maintained a significant positive correlation with rate of germination, germination vigor index, shoot length, and root length, which indicates that these parameters could be used as selection criteria for screening wheat genotypes against salt stress. Significant differences in shoot length, root length, and seedling dry weight in 30-day-old seedlings were observed among selected wheat genotypes as well. From the overall observation of germination characters and early seedling growth, it was concluded that the wheat genotypes including Gourab, Shatabdi, Bijoy, Prodip, BARI Gom 26, BAW 1186, and BAW 1189 showed better salt tolerance as compared to others.     

Genetic analysis of resistance to <Emphasis Type="Italic">soil-borne wheat mosaic virus</Emphasis> derived from <Emphasis Type="Italic">Aegilops tauschii</Emphasis>

Genetic Analysis of Resistance to Soil-Borne Wheat Mosaic Virus Derived from Aegilops tauschii. Euphytica. Soil-Borne Wheat Mosaic Virus (SBWMV), vectored by the soil inhabiting organism Polymyxa graminis, causes damage to wheat (Triticum aestivum) yields in most of the wheat growing regions of the world. In localized fields, the entire crop may be lost to the virus. Although many winter wheat cultivars contain resistance to SBWMV, the inheritance of resistance is poorly understood. A linkage analysis of a segregating recombinant inbred line population from the cross KS96WGRC40 × Wichita identified a gene of major effect conferring resistance to SBWMV in the germplasm KS96WGRC40. The SBWMV resistance gene within KS96WGRC40 was derived from accession TA2397 of Aegilops taushcii and is located on the long arm of chromosome 5D, flanked by microsatellite markers Xcfd10 and Xbarc144. The relationship of this locus with a previously identified QTL for SBWMV resistance and the Sbm1 gene conferring resistance to soil-borne cereal mosaic virus is not known, but suggests that a gene on 5DL conferring resistance to both viruses may be present in T. aestivum, as well as the D-genome donor Ae. tauschii.     

Genetics of resistance to <Emphasis Type="Italic">Cucumber mosaic virus</Emphasis> in <Emphasis Type="Italic">Cucumis sativus</Emphasis> var. <Emphasis Type="Italic">hardwickii</Emphasis> R. Alef

The genetics of resistance to Cucumber mosaic virus (CMV) in Cucumis sativus var. hardwickii R. Alef, the wild progenitor of cultivated cucumber was assessed by challenge inoculation and by natural infection of CMV. Among the 31 genotypes of C. sativus var. hardwickii collected from 21 locations in India the lowest mean percent disease intensity (PDI) was recorded in IC-277048 (6.33%) while the highest PDI was observed in IC-331631 (75.33%). All the four cultivated varieties (DC-1, DC-2, CHC-1 and CHC-2) showed very high PDI and susceptible disease reaction. Based on mean PDI, 8 genotypes were categorized as resistant, 13 as moderately resistant, 9 as moderately susceptible and one as susceptible. A chi-square test of frequency distribution based on mean PDI in F₂ progenies of six resistant × susceptible crosses revealed monogenic recessive Mendelian ratio 1(R):3(S) to be the best fit. This monogenic recessive model was further confirmed by 1(R):1(S) ratio as the best fit for back cross with resistant parent and no fit for either 3:1 or 1:1 in the back cross with the susceptible parent. The results revealed that CMV resistance in C. sativus var. hardwickii was controlled by a single recessive gene. Considering the cross compatibility between C. sativus var. hardwickii and cultivated cucumber, the resistance trait can be easily transferred to cultivated species through simple backcross breeding.     

Ploidy level studies on the <Emphasis Type="Italic">Dioscorea cayenensis</Emphasis>/<Emphasis Type="Italic">Dioscorea rotundata</Emphasis> complex core set

The Guinea yams, Dioscorea cayenensis Lam. and D. rotundata Poir. (D. cayenensis–D. rotundata complex), represent a highly important crop, widely distributed in the humid and semi-humid tropics. The ploidy levels of 170 accessions of the core set of Guinea yams from West African countries was determined using flow cytometry with propidium iodide staining. One hundred and eight of the genotypes were found to be tetraploid, 47 were hexaploid and five were octoploid. One mixoploid individual containing tetraploid and hexaploid nuclei was also detected. A deeper analysis considering each separate taxon revealed that while for D. rotundata the majority of individuals were tetraploid, for D. cayenensis this ploidy level was not detected in any of the accessions. Also, no association between ploidy level and place of cultivation was found for the evaluated germplasm. The obtained data is highly valuable for breeding programs of Guinea yam, especially for the optimization of future hybridization experiments directed to the genetic improvement of this economically important crop.     

Production and characterization of inter-sectional hybrids between <Emphasis Type="Italic">Kalanchoe spathulata</Emphasis> and <Emphasis Type="Italic">K. laxiflora</Emphasis> ( = <Emphasis Type="Italic">Bryophyllum crenatum</Emphasis>)

The genus Kalanchoe is currently divided into section Kalanchoe and section Bryophyllum, and there has been no successful report on the production of inter-sectional hybrids. Therefore, reciprocal crosses were made between Kalanchoe spathulata (sect. Kalanchoe) and K. laxiflora (sect. Bryophyllum) in order to obtain basic information on the reproductive barriers between these two sections. The seeds were aseptically germinated in vitro and the plants were grown in greenhouse till flowering. When K. spathulata was used as a maternal donor, 39 out of 80 plants showed intermediate characteristics between K. spathulata and K. laxiflora. In contrast, no plants were obtained in the reverse crosses. Hybridity of these plants was confirmed by flow cytometric analysis, chromosome numbers and RAPD analysis. Bulbil formation on the leaf margin as one of the conspicuous characteristics of K. laxiflora was not observed in the hybrids. Some of the hybrid lines showed some pollen fertility, but failed to yield viable seeds by self-pollination or backcross-pollination. Successful production of the inter-sectional hybrid between the two species suggests that they are not so distantly related as considered previously.     

Development and validation of microsatellite markers linked to the rice blast resistance gene <Emphasis Type="Italic">Pi-z</Emphasis> of Fukunishiki and Zenith

Rice blast resistance gene ‘Pi-z’ present in rice genotypes, Zenith and Fukunishiki, represents a potential source of blast resistance for the north-western Himalayan region of India. We tested the reliability of microsatellite markers linked to Pi-z for assessing blast resistance phenotype in crosses of commercial importance. A new set of microsatellite markers linked to Pi-z was also developed by exploiting the publicly available marker and genomic resources of rice. Of the three previously reported markers for Pi-z, only MRG5836 was suitable for the marker assisted selection of Pi-z. Among the 17 microsatellites selected from the putative region of Pi-z locus, two, RM8225 and RM8226 cosegregated with MRG5836 and were located at distance of 1.2–4.5 cM from the gene. A new microsatellite marker ‘SSR236’ was developed from the (CT)₁₆ repeat of PAC clone P0502B12, which exhibited closer linkage (0.6–1.2 cM) to Pi-z. Survey of the allelic diversity at the loci of the Pi-z linked microsatellite markers revealed that the Fukunishiki and Zenith type alleles were not present in majority of the local indica rice genotypes. As these markers are polymorphic between the Pi-z donors and a great majority of local indica rices tested, they can be used as a selection tool in rice breeding programs aimed at improving the blast resistance of local rices.     

Resynthesizing <Emphasis Type="Italic">Brassica napus</Emphasis> from interspecific hybridization between <Emphasis Type="Italic">Brassica rapa</Emphasis> and <Emphasis Type="Italic">B. oleracea</Emphasis> through ovary culture

Using three varieties of Brassica rapa, cv. Hauarad (accession 708), cv. Maoshan-3 (714) and cv. Youbai (715), as the maternal plants and one variety of B. oleracea cv. Jingfeng-1 (6012) as the paternal plant, crosses were made to produce interspecific hybrids through ovary culture techniques. A better response of seed formation was observed when ovaries were cultured in vitro at 9–12 days after pollination on the basal MS and B5 media supplemented with 6-benzylaminopurine (BA) and naphthylacetic acid (NAA). The best response was observed for cross 714×6012 with the rate of seeds per ovary reaching 43.0%. Seeds for cross 715×6012 showed the best germination response (66.7%) on the regeneration medium (MS+1.0 mg l^–1 BA+0.05 mg l^–1 NAA). In all three cross combinations, good response in terms of root number and length of plants was observed on the root induction medium (MS+1.0 mg l^–1 BA+0.1 mg l^–1 NAA). A better response was observed for the regenerated plants cultured for 14 days than for 7 days. The ovary-derived plants with well-developed root system were hardened for 8 days and their survival rate reached over 80%. Cytological studies showed that the chromosome number of all plants tested was 19 (the sum of both parents), indicating that these regenerated plants were all true hybrids of B. rapa (n = 10) × B. oleracea (n = 9). The regenerated plants were doubled with colchicine treatment, and the best response in the crosses 708×6012, 714×6012 and 715×6012 was observed when treated with 170 mg l^–1 colchicine for up to 30 h and their doubling frequency reached 52, 56 and 62%, respectively.     

Genetic diversity evaluation of a loquat (<Emphasis Type="Italic">Eriobotrya japonica</Emphasis> (Thunb) Lindl) germplasm collection by SSRs and <Emphasis Type="Italic">S</Emphasis>-allele fragments

Loquat (Eriobotrya japonica (Thunb.) Lindl.) is a minor Rosaceae fruit of growing interest as an alternative to the main fruit crops. In this context, the selection of new cultivars to satisfy the market demand will request the suitable characterization of the available germplasm. In this work, genetic relationships among 83 loquat accessions from different countries belonging to the European loquat germplasm collection, held at the Instituto Valenciano de Investigaciones Agrarias (IVIA) in Moncada (Spain) were evaluated using microsatellites and S-allele fragments. A total of nine single sequence repeats (SSRs) from Malus and Eriobotrya genera revealed 53 informative alleles and the S-RNases consensus primers detected 11 self-incompatibility putative alleles. The combined data allow to distinguish unambiguously 80 out of the 83 accessions studied. Unweighted pair-group method (UPGMA) cluster and principal coordinates analysis (PCoA), based on Dice’s genetic distance, generally grouped genotypes according to their geographic origins and pedigrees. Discrepancies and similarities of the results obtained with other variability analysis, based on pomological traits or molecular markers, on the same loquat collection are discussed.