Hybrids of <Emphasis Type="Italic">Passiflora</Emphasis>: <Emphasis Type="Italic">P. gardneri</Emphasis> versus <Emphasis Type="Italic">P. gibertii,</Emphasis> confirmation of paternity,morphological and cytogenetic characterization

Two new varieties of interspecific hybrids of Passiflora have been developed from the cross between P. gardneri versus P. gibertii, both registered under the Passiflora Society International. Twelve putative hybrids were analyzed. Hybridization was confirmed using RAPD and SSR markers. Primer UBC11 (5′-CCGGCCTTAC-3′) generated informative bands. Primer SSR Pe75 has amplified species-specific fragments and a heterozygote status was observed with two parent bands 300 and 350 bp. The molecular markers generated have been analyzed for the presence or absence of specific informative bands. Based on the morphological characterization, we have identified two hybrid varieties: P. ‘Gabriela’ and P. ‘Bella’. P. ‘Gabriela’ produced flowers in bluish tones, bluish petals on the adaxial and abaxial faces, light blue sepals on the adaxial and light green on the abaxial faces, corona with the base of filaments in intense lilac color and white apex. P. ‘Bella’ produced flowers in lilac tones, intense lilac petals on the adaxial and abaxial faces, dark lilac sepals with whitish edges on the adaxial and light green on the abaxial faces, corona with the base of filaments in intense lilac color and white apex. The cytogenetic analysis verified that the hybrids have the same chromosomal number as the parents (2n = 18); the formation of bivalents between the homeologous chromosomes (n = 9) was observad, leading to regular meiosis, which allows the sexual reproduction and use of these hybrids in breeding programs.     

Vitamin C,flower color and ploidy variation of hybrids from a ploidy-unbalanced <Emphasis Type="Italic">Actinidia</Emphasis> interspecific cross and SSR characterization

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.     

Creating novel chrysanthemum germplasm via interspecific hybridization and backcrossing

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.     

Production and characterization of amphihaploid hybrids between <Emphasis Type="Italic">Nicotiana wuttkei</Emphasis> Clarkson et Symon and <Emphasis Type="Italic">N. tabacum</Emphasis> L

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.     

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.     

Inheritance of resistance to <Emphasis Type="Italic">Fusarium oxysporum</Emphasis> f. sp. <Emphasis Type="Italic">melonis</Emphasis> races 0 and 2 in melon accession Tortuga

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.     

Assessment of the origin of new citrus tetraploid hybrids (2<Emphasis Type="Italic">n</Emphasis> = 4x) by means of SSR markers and PCR based dosage effects

We report the accurate determination of the allelic configurations of a total of eight new citrus tetraploid hybrids by means of SSR analysis, coupled with capillary electrophoresis, and PCR based dosage effects. Tetraploid hybrids were spontaneously obtained from different interploid crosses (2x × 4x) between diploid ‘Femminello’ lemon and the allotetraploid somatic hybrid (2n = 4x = 36) ‘Key’ lime + ‘Valencia’ orange, and between diploid ‘Wilking’ and ‘Fortune’ mandarins and an autotetraploid ‘Dancy’ mandarin (2n = 4x = 36). To understand the opportunity to employ them in further backcross programs, the cytological mechanisms underlying their ploidy level were unambiguously determined using six SSR primers. PCR conditions were optimized and skewness in template/product ratios were verified. Tetraploid allelic configurations were determined from PCR based dosage effects using electropherogram peak heights to estimate the copy number per allele. In all the tetraploid hybrids we found out that diploginy (2n eggs) has occurred, contributing the extra haploid genome in the tetraploids. According to the marker genotypes, it was further inferred that the 2n eggs in ‘Femminello’ lemon resulted from first division restitution (FDR), while in ‘Wilking’ and ‘Fortune’ mandarins 2n eggs occurred in second division restitution (SDR). These new genotypes, with their improved genetic female background, can be therefore considered very valuable in our citrus genetic improvement program as pollen donors in backcrosses suitable to eliminate negative traits.     

Interspecific hybrids between <Emphasis Type="Italic">Dendranthema morifolium</Emphasis> (Ramat.) Kitamura and <Emphasis Type="Italic">D. nankingense</Emphasis> (Nakai) Tzvel. achieved using ovary rescue and their cold tolerance characteristics

Ovary rescue was employed to create six interspecific hybrids from the cross between Dendranthema morifolium (Ramat.) Kitamura ‘rm20-12’ (2n = 54) and its wild diploid relative D. nankingense (Nakai) Tzvel. (2n = 18). The morphology of the hybrids differed from that of either parent. The leaf length and width of all three D. morifolium × D. nankingense hybrids exceeded that of the parents, as did the plant height of two and the inflorescence diameter of another of the hybrids. One of the reciprocal hybrids was heterotic for leaf length and width. All the hybrids bore yellow flowers. The cold tolerance of five hybrids was significantly superior to that of their D. morifolium parent. Interspecific hybridization clearly provides an effective means of cultivar improvement in chrysanthemum.     

Identification of citrus hybrids through the combination of leaf apex morphology and SSR markers

Citrus breeding programs normally face several biological obstacles such as apomixis and polyembryony that result in a cumbersome identification of hybrid seedlings. The main purpose of this work is to describe the combined use of visual selection based on the leaf apex morphology and SSR analysis to differentiate hybrid from nucellar seedlings derived from the cross between the ‘Murcott’ tangor [Citrus reticulata Blanco × Citrus sinensis (L.) Osb.] and ‘Pêra’ sweet orange [Citrus sinensis(L.) Osb.]. A new morphological variable named leaf apex morphometric index is also described as the quantitative basis of the visual selection. The efficiency of visual selection of hybrids was tested under two growth conditions, seedlings germinated in seedbeds and in plastic tubes. Putative hybrid seedlings were also confirmed through the analysis of simple sequence repeats (SSR). The visual selection of hybrid seedlings resulted in an increase of 87.2% (p < 0.01) and 202.2% (p <0.001) in the number of correctly identified hybrids when compared to the method of random picking of seedlings in seedbeds and plastic tubes,respectively. The results indicate that the combination of visual selection and SSR analysis for the identification of hybrids derived from the cross of polyembryonic citrus cultivars will improve the accuracy of the selection,save time, and reduce the costs involved in the use of molecular markers alone in citrus breeding programs. This revised version was published online in August 2006 with corrections to the Cover Date.     

Inheritance mode of male sterility in bunching onion (<Emphasis Type="Italic">Allium fistulosum</Emphasis> L.) accessions

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.     

Genome composition of ‘Elatior’-begonias hybrids analyzed by genomic in situ hybridisation

Interspecific hybridization of various tuberous Begonia species hybrids with Begonia socotrana results in so-called ‘Elatior’-begonias hybrids (B. × hiemalis Fotsch). In our study, genomic in situ hybridization (GISH) has been employed to assess the genome composition in eleven ‘Elatior’-begonias hybrids and their ancestor genotypes. Genomic DNA of tuberous Begonia was sonicated to 1–10-kb fragments, labelled by nick translation with digoxigenin-11-dUTP and used as a probe whereas B. socotrana DNA was autoclaved to 100 bp fragments and used as block. The genome of tuberous Begonia was clearly pronounced in ‘Elatior’-begonias when the probe concentration was ~3.75 ng/μl (150 ng/slide), with 30 times the excess of B. socotrana blocking DNA and stringency of post hybridization washings at 73% (0.1× SSC at 42°C). In ‘Elatior’-begonias hybrids GISH distinguished two groups comprising short (0.6–1.03 μm in length) and relatively longer chromosomes (1.87–3.88 μm) which represent B. socotrana and tuberous Begonia genomes, respectively. The number of chromosomes derived from tuberous Begonia ranged from 14 to 56 and for B. socotrana from 7 to 28 which suggest the presence of different ploidy levels in analyzed ‘Elatior’-begonia hybrids. Intergenomic recombination has not been detected through GISH in hybrids analyzed. Genomic in situ hybridization turned out to be useful to identify the genome constitution of ‘Elatior’-begonia hybrids and thus gain an insight into the origins of these cultivars. This knowledge on the ploidy level and genome composition is essential for further progress in breeding Begonias.     

Introgression of unique characteristics of floral initiation under 24 hour day-length of Fragaria chiloensis ‘CHI-24-1’ into F. × ananassa

A unique flower initiation of the wild Junebearing strawberry strain ‘CHI-24-1’ in Fragaria chiloensis occurs under 24 h DL and high temperature conditions. To introduce the floral initiation characteristics of ‘CHI-24-1’ into cultivated strawberries of F. × ananassa, a cross pollination was conducted between ‘CHI-24-1’ and the Japanese short-day type strawberry cultivar ‘Nyoho’. The floral initiation of ‘CHI-24-1’ was induced in both parent and daughter plants linked with runners under a 24 h DL and 23/20 ^∘C, but not 8 and 16 h DLs at the same temperatures. Of the 21 F1 hybrids grown under the 24 h DL, 12 showed flower truss production in the parent and/or daughter plants linked with runners. Among 64 F1 hybrids, 26 exposed to 8, 16 and 24 h DLs for 30 days produced no flower trusses. However, 32, one and five F1 hybrids produced flower trusses under the 24 h DL alone, 8 h DL alone and both the 8 and 24 h DLs, respectively. The results of the experiments indicated that none of the F1 hybrids were day-neutral plants, but approximately 60% had the characteristics of floral initiation under 24 h DL, which was inherited from the pollen parent of ‘CHI-24-1’. The importance of the unique floral initiation characteristics under 24 h DL with high temperature for strawberry breeding was discussed.     

Inheritance of red foliage in flowering dogwood (<Emphasis Type="Italic">Cornus florida</Emphasis> L.)

Flowering dogwood (Cornus florida L.) is an ornamental tree valued for its showy white, pink, or red spring bract display and red fall color. A “pseudo” F₂ flowering dogwood population was recently developed from a honeybee mediated cross of ‘Cherokee Brave’ × ‘Appalachian Spring’. The foliage color of 94 “pseudo” F₂ plants segregated into green- and red- leaved phenotypes and was visually rated for color on five spring dates over 3 years (2007–2009). Chi-square analyses of observed segregation of phenotypes indicated that a complementary gene interaction form of epistasis controls foliage color with a 9:7 two gene ratio. We propose the symbols rl ₁ and rl ₂ for the genes controlling this trait.     

Microsatellite mapping of complementary genes for purple grain colour in bread wheat (Triticum aestivum) L.

Complementary genes for purple grain colour Pp1, Pp2, Pp3 (now designated Pp1, Pp3b, Pp3a, respectively) were mapped using crosses between purple-grained hexaploid wheats ‘Purple Feed’ – Pp1Pp1/Pp2Pp2 (Pp1Pp1/Pp3bPp3b), ‘Purple’ – Pp1Pp1/Pp3Pp3 (Pp1Pp1/Pp3aPp3a) with non-purple-grained cultivars ‘Novosibirskaya 67’ (‘N67’) and ‘Saratovskaya 29’ (‘S29’). The genes Pp2 (Pp3b) and Pp3 (Pp3a) were inherited as monofactorial dominant when purple-grained wheats were crossed to ‘N67’. Both were mapped in the centromeric region of the chromosome 2A. Therefore, they were suggested being different alleles at the same locus and designated Pp3a and Pp3b. In the crosses between purple-grained wheats and ‘S29’ a segregation ratio of 9 (purple) to 7 (non purple) was obtained suggesting a complementary interaction of two dominant genes, Pp1 and Pp3. To map Pp1 as a single gene, the influence of the other Pp gene was taken into consideration by determining the Pp3 genotype of the F₂ plants. The gene was mapped on chromosome 7BL, about 24 cM distal to the centromere. The Pp1gene was shown to be non allelic to the Rc-1 (red coleoptile) and Pc (purple culm) genes, contrary to what was previously suggested. The colouration caused by the Pp genes has no effect on pre-harvest sprouting.     

High regeneration potential in vitro of sunflower (Helianthus annuus L.) lines derived from interspecific hybridization

Successful selection of interspecific hybrid progenies with superior ability to regenerate shoots from apical meristems was performed in sunflower which now allows for the development of lines for improved biotechnological applications. Early generations of interspecific hybrids originating from crosses between the two H. annuus CMS lines ‘HA89’ and ‘Baso’, and 9 wild species were screened for their ability to regenerate in vitro. Evaluation of 36 progenies allowed to identify seven progenies from crosses involving H. mollis, H. giganteus, H. strumosus, and H. decapetalus which showed a significantly higher regeneration potential than the commercial hybrid ‘Albena’ regarding the number of shoots per explant. Among these progenies, 47.2 to 62.4% of explants produced shoots with an average of 2.3 to 3.5 shoots per cultured explant. Regeneration in vitro was significantly determined by the genotype. More than half of the investigated interspecific hybrids performed better than the inbred ‘HA89’ demonstrating that the high regeneration potential available in the wild species can be efficiently transferred to cultivated sunflower. The seven progenies with high regeneration potential in vitro were characterised by agronomic performance in the field. Two of the interspecific hybrids derived from H. strumosus and H. decapetalus not only showed a superior regeneration potential but also proved to be competitive to commercial hybrids with regard to important agronomic traits, e.g. fat content and TGW. This revised version was published online in July 2006 with corrections to the Cover Date.     

Production of interspecific hybrids between <Emphasis Type="Italic">Lilium longiflorum</Emphasis> and <Emphasis Type="Italic">L. lophophorum</Emphasis> var. <Emphasis Type="Italic">linearifolium</Emphasis> via ovule culture at early stage

Interspecific hybridization was carried out between Lilium longiflorum and L. lophophorum var. linearifolium by using the cut style method of pollination, as a contrast, intraspecific hybridization between L. longiflorum ‘Gelria’ and L. longiflorum was also made, but no mature seeds and offspring were obtained from the two combinations under in vivo condition. Ovules excised from each carpel 5–35 days after pollination (DAP) were cultured on B5 or half-strength B5 medium containing sucrose at different concentrations in vitro. In L. longiflorum × L. lophophorum var. linearifolium, only 1.17% of ovules excised at 10 DAP developed into seedlings, and in L. longiflorum ‘Gelria’ × L. longiflorum, only 0.99% of ovules excised at 25 DAP developed into seedlings; none of the ovules excised at other different DAP in the two cross combinations produced any seedlings. The results showed that interspecific hybridization had a more serious post-fertilization barrier than the intraspecific hybridization, and that a lower concentration (3%) of sucrose led to better embryo development and higher percentage of seedlings in ovule cultures. All hybrid seedlings obtained were successfully transplanted to soil and grew normally. The progenies investigated were identified as true hybrids based on inter-simple sequence repeat (ISSR) analysis.     

Little heterosis for yield and yield components in hybrids of six cucumber inbreds

Heterosis and inbreeding depression for fruit yield has been reported for pickling cucumber (Cucumis sativus L.). However, cucumber inbreds often perform as well as hybrids, and there is little inbreeding depression. The objectives of this study were to reexamine the amount of heterosis and inbreeding depression for fruit yield and yield components in pickling cucumber, and to determine the relationship between yield components and yield for heterosis. Two pickling cucumber inbreds (M 12, M 20) and inbreds from four open-pollinated monoecious cultivars (‘Addis’, ‘Clinton’, ‘Wisconsin SMR 18’, ‘Tiny Dill’) were hybridized to form four F₁ hybrids (‘Addis’ × M 20, ‘Addis’ × ‘Wis. SMR 18’, ‘Clinton’ × M 12, M 20 × ‘Tiny Dill’). F₁ hybrids were then self-pollinated or backcrossed to generate F₂, BC_1A, and BC_1B progeny. Thirty plants of each generation within each hybrid family were grown in plots 3.1 m long with four replications in each of two seasons. Data were collected from once-over harvest for vegetative, reproductive, yield, and fruit quality traits. Heterosis and inbreeding depression for fruit yield and yield components were not observed in three of the hybrids. Only ‘Addis’ × ‘Wis. SMR 18’ exhibited high-parent heterosis and inbreeding depression for total, marketable, and early fruit weight. For ‘Addis’ × ‘Wis. SMR 18’, heterosis for fruit yield was associated with a decreased correlation between percentage of fruit set and fruit weight, an increased negative correlation between percentage of fruit set and both the number of branches per plant and the percentage of pistillate nodes, and an increased negative correlation between the number of nodes per branch and total fruit weight. Inbreeding depression was associated with a weakening of the strong negative correlations between percentage of fruit set and the number of branches per plant, and between the number of nodes per branch and total fruit weight. Those correlations were associated with high-parent heterosis and inbreeding depression only for one cross, and do not necessarily apply to future crosses in which heterosis may be observed for yield. We did not observe the heterosis or inbreeding depression for yield in cucumber in most of the crosses as was reported by Ghaderi & Lower (1979a; 1979c). This revised version was published online in August 2006 with corrections to the Cover Date.     

Resistance to <Emphasis Type="Italic">Meloidogyne incognita</Emphasis> race 1 in the lettuce cultivars Grand Rapids and Salinas-88

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.     

Residual macronutrient concentration and follower maize (<Emphasis Type="Italic">Zea mays</Emphasis>) crop performance in soilless growth medium previously cropped with six <Emphasis Type="Italic">Musa</Emphasis> genotypes

The nutrient mining abilities of six Musa genotypes: ‘Agbagba’, ‘PITA 22’, ‘Nsukka Local’, ‘FHIA 17’, ‘Fougamou’, and ‘BITA 7’, grown in organic medium formulated by decomposing rice husks with poultry manure in volume proportions of 3:2, were determined at the Teaching and Research Farm of the Department of Crop Science, University of Nigeria, Nsukka, Nigeria. Results indicated significant variation in nutrient mining with respect to Musa genotype and duration of growth. The medium previously cropped with ‘Agbagba’ recorded highest residual mean values for P and Ca, while the medium cropped with ‘Fougamou’ had the highest residual concentration of Mg and S. Residual amount of K was highest in the medium where ‘PITA 22’ and ‘Nsukka Local’ were previously grown. Peak residual concentration of P and K occurred in the medium in which Musa plants were grown only for 4 months, decreasing thereafter, in contrast to Ca, Mg, and S. Residual N tended to increase with longer growth duration of the Musa crops. Follower crop of maize grown in the medium previously cropped with Musa genotypes showed variable performance. While medium previously cropped with ‘PITA 22’ and ‘BITA 7’ favored growth attributes and leaf greenness of the follower maize plant, ‘Fougamou’ favored maize fresh weight attributes. Ectomycorrhiza association was observed in medium previously cropped to ‘BITA 7’ and ‘PITA 22’. Generally, ‘Agbagba’ and ‘Fougamou’ seemed to be the most reticent nutrient miners while uptake of P and K appeared to be low 4 months after planting (MAP) in contrast to Ca, Mg, and S uptake. However, substrate previously cropped with ‘PITA 22’, ‘BITA 7’ and ‘Fougamou’ gave rise to superior growth and fresh weight attributes, respectively, of the maize, the follower crop. A prospect of utilizing the ectomycorrhiza association observed with some genotypes to upgrade Musa yields and those of associated or follower crops exist.     

Association of fruit traits and aril browning in pomegranate (<Emphasis Type="Italic">Punica granatum</Emphasis> L.)

Pomegranate cultivation is one of the most attractive farming enterprises in the Indian arid tropics. However, the quality of the fruit is often severely affected by a physiological disorder called ‘aril browning’ in which a part or all the arils show discolouration (browning) and such fruits are unfit for consumption. This has become a serious concern to consumers, growers and researchers in the recent times. In order to understand the genotypic variation for aril browning and its association with other fruit traits, 158 progenies obtained by selfing two pomegranate multiple hybrids viz., {(‘Ganesh’ × ‘Kabul’) × ‘Yercaud’} × {(‘Ganesh’ × ‘Gulsha Rose Pink’)-F₂} and {(‘Yercaud’ × ‘Jyothi’) × (‘Ganesh’ × ‘Gulsha Rose Pink’)-F₂} × {(‘Ganesh’ × ‘Kabul’) × ‘Yercaud’} were studied. Because of heterozygous nature of the crop and diverse genetic base of parents, a wide array of recombinants were produced which were scored for aril browning, fruit skin colour, aril colour, total soluble solids (TSS) and seed mellowness. Results of Spearman’s correlation analysis revealed that aril browning is inversely related with aril colour (r = −0.41). A statistical model constructed to study the reasons for the observed variation in aril browning showed that about 82.9% of it was accounted collectively by skin colour, aril colour, TSS and seed mellowness. Further, a refined model represented by Y (aril browning severity) = 0.78 − 0.52 X₁ (aril colour) + 0.23 X₂ (TSS) was found to contribute to 73.5% of the observed variability in aril browning with least error in prediction. Analysis of data further showed that every unit increase in intensity of aril colour amounted to decrease in severity of aril browning by 0.52 units. However, for every unit increase in TSS there was an increase of 0.23 units in severity of aril browning. Thus, with the increase in intensity of aril colour there was a reduction in severity of aril browning while with raise in TSS, aril browning incidence was higher, an association often not favourable in selection of desirable genotypes. The results of the present study suggested that while developing varieties free from aril browning it is important to strike a balance between aril colour and TSS level.