Chance Seedlings Research Articles

Breeding approaches for improvement of temperate fruit crops and nuts - a review

Fruit breeding is an ancient technology with dynamic current technology and an exciting future (Janick and Moore, 1975, 1996). In its broadest sense, fruit breeding refers to the purposeful genetic improvement of fruit crops through various techniques including selection, hybridization, mutation induction, and molecular techniques. Its origins trace to the domestication process in prehistory and antiquity, where useful species were chosen and cultivated, and improved by continuous selection (Janick, 2005, 2011). Much of the world fruit industry is still based on grower selection from chance seedlings as well as mutations (sports) and as a result many fruit species are characterized by a narrow germplasm base. Spontaneous hybridization between wild plants and cultivated clones was critical to the early domestication of fruits. The lengthy juvenile period and the large field space required to grow temperate fruits have imposed major limitations on conventional breeding and various molecular biological techniques have been employed to make fruit breeding easier. (Igarashi et al.2016). Marker-assisted selection (MAS) uses DNA markers to provide an early DNA-based evaluation of genetic performance potential of seedlings, with the aim of improving cost and/or genetic efficiency of seedling selection (Ru, et al., 2015). Transgenic technology has facilitated the development of fruit trees with resistance to fungal or bacterial diseases, improved fruit quality, or root stocks with better rooting or dwarfing ability. In recent years, new technologies for genetic improvement, such as transgrafting, and genome-editing, have emerged. (Mudge, et al. 2009; Jia and Wang 2014). Using these techniques, no foreign genes are present in the final product, and some of them show considerable promise for application to apple breeding. Furthermore, genome editing, by which only the target gene can be accurately modified, is emerging as a novel breeding technology. These new technologies will undoubtedly facilitate fruit breeding, and yield novel and attractive fruit cultivars.

Morpho-chemical characterization of loquat (Eriobotrya japonica Lindl.) genotypes

Morphological and chemical characterization of loquat genotypes were carried out to select superior genotypes between 2018 and 2021 in the coastal region of the Black Sea. In the study, the description of 70 genotypes with 20 g and above fruit weight of loquat, which is grown as chance seedlings in the mentioned region, was done. From the study, it was found soluble solids content (SSC) between 6.95 and 18.30%, acidity (AC) 0.22–0.82%, SSC/acidity ratio (SSCAcR) 16.39–67.68%, pH 2.85–4.94, dry matter ratio 47.29–54.73%, fresh weight (FreWe) 35.13–103.76 g, and dry weight (DW) 20.78–85.59 g. Considering morphological characteristics, leaf width (LWi) was found between 5.41 and 12.71 cm, leaf length (LL) 15.63–41.22 cm, leaf length/width ratio (LLWR) 1.37–5.57%, petiole diameter (PD) 3.74–8.00 mm, petiole length (PL) 8.87–46.72 mm, and leaf area between 77.59 and 312.92 cm2. A strongly negative correlation was observed between SSCAcR and AC (0.836). In contrast, significant positive correlation was found between DW and FreWe (0.636), pH and SSCAcR (0.544). In the case of chemical characteristics, the percentage of variances of components 1 to 5 respectively observed (29.13%, 20.37%, 14.96%, 10.84%, and 10.22%), which cumulatively encompassed 85.54% of variances. In the case of morphological characteristics, the correlation between LWi and LLWR (− 0.670), LL and LLWR (0.597), LWi and PD (0.311), LLWR and PD (− 0.312), PD and PL (− 0.260) obtained significant at P < 0.05. The percentage of variance explained by each principle component from components 1 to 4 respectively observed (28.54%, 22.18%, 16.06%, and 10.70%), which cumulatively encompassed 77.50% of variances. Finally, five genotypes, including GN10, GN14, GN50, GN68, and GN69, were determined superior among 70 genotypes. Based on the high “Weighed Rating” scores they received, they were suggested for further consideration.

Mango seedling genotyping reveals potential self-incompatibility and pollinator behavior

Mango (Mangifera indica) is tropical fruit widely cultivated and appreciated for its sweet and aromatic fruit. There is great diversity among mango cultivars for important fruit quality and agronomic traits that could be leveraged as part of a mango breeding program. Historically, most genetic improvement of this species has been the result of chance seedlings. The recent publication of multiple mango genomes and availability of genomic resources is facilitating the efficient breeding of mango, but controlled pollination of mango is challenging with only a few out of thousands of panicle-borne flowers developing into fruit. Therefore, genotyping open-pollinated seedlings could be a labor-saving method to select favorable hybrids in a breeding program. An array of 384 single-nucleotide-polymorphism markers was used to genotype 140 mango cultivars and 575 mango seedlings from eleven open-pollinated populations in a mango diversity collection. Analysis of mango cultivars confirmed hybrid parentage in many instances and identified potential paternal parents for cultivars with unknown parentage. For the seedlings analyzed, the Dixon test of Gower's genetic dissimilarity (GD) values among identified triads revealed 161 significant triads (P≤0.05), indicating high confidence for paternal identification. The remaining triads had GD values less than 0.15 (n = 323), between 0.15 and 0.2 (n = 10), or between 0.2 and 0.3 (n = 5). In total, 70% of the hybrids were paired to a single paternal parent. Analysis of selfing rates indicated ‘Tommy Atkins’ had the highest selfing rate (40.4%) and ‘Glenn’ had the lowest (1.1%). Analysis of population structure and phylogeny divided the mango germplasm into three distinct clusters. The identified paternal pollen donors were mapped within a mango diversity collection and indicated mango pollinators can affect pollination beyond adjoining trees. This strategy can be used to aid mango breeding research and has identified intriguing hybrids for future evaluation.

New hyper-variable SSRs for diversity analysis in mango (Mangifera indica L.)

Whole genome sequence in mango offers unprecedented opportunities for genomics assisted crop improvement via enabling access to genome-wide genetic markers. In the present study, simple sequence repeats (SSRs) were predicted from genome sequence of mango. Based on the SSR length (? 50 bp), highly-variable mango SSRs (MSSRs) were sorted. A sub-set of 129 MSSRs was validated on a set of 24 diverse mango genotypes yielding marker validation and polymorphism of 88.96 and 85.27 per cent, respectively. One hundred and ten polymorphic markers were identified for the present set of mango genotypes. Polymorphic information content (PIC) ranged from 0.10 to 0.78 and the highest value was observed with MSSR133. The mean PIC value was 0.40 but 33 MSSR markers showed PIC values ? 0.5, suggesting that these markers can efficiently measure genetic diversity and serve for mapping of quantitative trait loci (QTLs) in mango. MSSRs data was further used for diversity analysis of mango genotypes belonging to different agro-ecological conditions including chance seedlings, landraces, exotic and indigenous germplasm and hybrids. Cluster analysis using UPGMA of 24 mango genotypes revealed that these MSSRs were informative in diversity analysis and distinguished mango genotypes based on their origin, parentage and embryo types. A novel set of 110 hyper-variable SSR markers have been added to the mango repository depicting usefulness in discriminating closely related mango germplasm and their use in mango improvement programme.

The \u2018Tommy Atkins\u2019 mango genome reveals candidate genes for fruit quality

BackgroundMango, Mangifera indica L., an important tropical fruit crop, is grown for its sweet and aromatic fruits. Past improvement of this species has predominantly relied on chance seedlings derived from over 1000 cultivars in the Indian sub-continent with a large variation for fruit size, yield, biotic and abiotic stress resistance, and fruit quality among other traits. Historically, mango has been an orphan crop with very limited molecular information. Only recently have molecular and genomics-based analyses enabled the creation of linkage maps, transcriptomes, and diversity analysis of large collections. Additionally, the combined analysis of genomic and phenotypic information is poised to improve mango breeding efficiency.ResultsThis study sequenced, de novo assembled, analyzed, and annotated the genome of the monoembryonic mango cultivar ‘Tommy Atkins’. The draft genome sequence was generated using NRGene de-novo Magic on high molecular weight DNA of ‘Tommy Atkins’, supplemented by 10X Genomics long read sequencing to improve the initial assembly. A hybrid population between ‘Tommy Atkins’ x ‘Kensington Pride’ was used to generate phased haplotype chromosomes and a highly resolved phased SNP map. The final ‘Tommy Atkins’ genome assembly was a consensus sequence that included 20 pseudomolecules representing the 20 chromosomes of mango and included ~ 86% of the ~ 439 Mb haploid mango genome. Skim sequencing identified ~ 3.3 M SNPs using the ‘Tommy Atkins’ x ‘Kensington Pride’ mapping population. Repeat masking identified 26,616 genes with a median length of 3348 bp. A whole genome duplication analysis revealed an ancestral 65 MYA polyploidization event shared with Anacardium occidentale. Two regions, one on LG4 and one on LG7 containing 28 candidate genes, were associated with the commercially important fruit size characteristic in the mapping population.ConclusionsThe availability of the complete ‘Tommy Atkins’ mango genome will aid global initiatives to study mango genetics.

Genetic analysis in mango (Mangifera indica L.) based on fruit characteristics of 400 genotypes

&#x0D; &#x0D; &#x0D; The analysis of variance for 6 quantitative traits and 30 qualitative traits showed significant differences among the 400 genotypes of mango which indicates the existence of high heterozygosity. Among the 18 clusters formed, the highest fruit weight of 1404.27 g was recorded in cluster 10 followed by cluster 15 with 1280.67g whereas the lowest fruit weight was recorded in cluster 16 (30.94g). The highest fruit length (22.03 cm) was recorded in cluster 10 followed by 17.80 cm in cluster 14. Similarly, the fruit diameter was highest (12.18 cm) in cluster 10 followed by 12.03 cluster 4. The fruit thickness was highest (10.60 cm) in cluster 15 followed by cluster 4 with 9.96 cm. The pulp recovery was maximum (87.16%) in cluster-14 followed by clusters 4 and 18 with 79.28 and 78.41 %, respectively. Clusters 15 had the varieties meant for pickle making and possessed less TSS whereas the TSS of above 19°B was recorded in cluster 2. The maximum inter-cluster (D2) value was obtained between cluster 10 and cluster 11. These clusters may be used for hybridization programs due to wide variability and the possibility of transgressive sergeants. Estimates of phenotypic variance and genotypic variance had only a narrow difference for all six characters studied indicating that these characters are not much influenced by environmental factors and highly heritable which can be exploited by adopting clonal selection or selection of chance seedlings and selection as parents for breeding purpose.&#x0D; &#x0D; &#x0D;

Genetic analysis in mango (Mangifera indica L.) based on fruit characteristics of 400 genotypes

The analysis of variance for 6 quantitative traits and 30 qualitative traits showed significant differences among the 400 genotypes of mango which indicates the existence of high heterozygosity. Among the 18 clusters formed, the highest fruit weight of 1404.27 g was recorded in cluster 10 followed by cluster 15 with 1280.67g whereas the lowest fruit weight was recorded in cluster 16 (30.94g). The highest fruit length (22.03 cm) was recorded in cluster 10 followed by 17.80 cm in cluster 14. Similarly, the fruit diameter was highest (12.18 cm) in cluster 10 followed by 12.03 cluster 4. The fruit thickness was highest (10.60 cm) in cluster 15 followed by cluster 4 with 9.96 cm. The pulp recovery was maximum (87.16%) in cluster-14 followed by clusters 4 and 18 with 79.28 and 78.41 %, respectively. Clusters 15 had the varieties meant for pickle making and possessed less TSS whereas the TSS of above 19°B was recorded in cluster 2. The maximum inter-cluster (D2) value was obtained between cluster 10 and cluster 11. These clusters may be used for hybridization programs due to wide variability and the possibility of transgressive sergeants. Estimates of phenotypic variance and genotypic variance had only a narrow difference for all six characters studied indicating that these characters are not much influenced by environmental factors and highly heritable which can be exploited by adopting clonal selection or selection of chance seedlings and selection as parents for breeding purpose.

Şanlıurfa Yöresinde Selekte Edilen Bazı Badem (Prunus amygladus L.) Gen Kaynaklarının Meyve Özellikleri

Bu çalışma, 2017-2018 yılları arasında Şanlıurfa merkez ilçesi, Hilvan, Bozova ve Suruç ilçelerinde doğal olarak tohumdan yetişmiş çöğür badem ağaçlarının meyve özellikleri belirlenmesi amacıyla yürütülmüştür. Bölgede kendiliğinden yetişen doğal badem popülasyonu içerisinde seleksiyon kriterleri doğrultusunda ilk yıl 102 genotipin, ikinci yıl 43 genotipin bazı morfolojik ve pomolojik özellikleri tanımlanmıştır. Araştırma sonucunda tartılı derecelendirme yöntemi kullanılarak 21 genotip çiçeklenme ve kalite durumlarına göre ümitvar olarak seçilmiştir. Tam çiçeklenme dönemleri 2017 yılında 10 Mart-26 Mart tarihleri arasında gerçekleşirken; 2018 yılında 22 Şubat-21 Mart tarihleri arasında gerçekleşmiştir. Kabuklu meyve ağırlıkları 2.31-6.84 g, iç badem ağırlıkları 0.74-1.34 g, iç oranları %18.21-41.26 arasında değiştiği saptanmıştır. Kabuk kalınlıklarının 2.23-3.48 mm, çift ve ikiz iç oranının % 0, ve sağlam iç oranlarının % 60-100 arasında değiştiği tespit edilmiştir. Genotiplerin meyve şekli 18 genotipte, uzun oval, 2 genotipte kalp ve 1 genotipte elips grubunda yer almıştır. Genotipler iç rengi bakımından incelendiğinde ise l genotip açık, 7 genotip orta açık, 11 genotip koyu ve 2 ise çok koyu olarak değerlendirilmiştir.

Genotyping apple (Malus x domestica Borkh.) heirloom germplasm collected and maintained by the Regional Administration of Friuli Venezia Giulia (Italy)

This paper reports the genetic diversity of apple germplasm collected in the Friuli Venezia Giulia region (north-eastern Italy). The collection, maintained in three different locations, was represented by local cultivars which probably originated as chance seedlings together with cultivars introduced from neighbouring countries, the name and origin of most of which has been lost over time. A preliminary procedure described in the paper started with 469 molecular profiles analysed using 15 Simple Sequence Repeat (SSR) markers and allowed identification of the ‘true-to-type’ genotypes among those maintained in multiple locations. The set of the remaining 234 accessions was further reduced to 132 unique profiles by removing 102 synonyms, that is accessions with different name and the same molecular profile. Flow cytometry identified as many as 54 triploids (40.9%), whose status was confirmed by field observations on leaf size and the occurrence of triallelic profiles at several SSR markers. The remaining 78 diploid accessions were analysed for their genetic diversity, that is the number of alleles, observed and expected heterozygosity, polymorphism information content (PIC), the frequency of null alleles and the probability of identity for unrelated and full-sib genotypes. The paper provides a critical evaluation of the SSR markers adopted for the study, discusses the genetic diversity observed in the apple germplasm collection examined as well as its high frequency of triploids compared with other apple collections described in the literature.

Detection of diverse population of vegetative propagated Kinnow planting in western India

Genetic diversity in 20 accessions of kinnow collected (five each) from four orchards viz., Central Institute of Arid Horticulture (CIAH), Bikaner, Agricultural Research Station, (ARS) Bikaner, ARS, Sriganaganagar and Regional Research Station (RRS), Abhohar were evaluated through RAPD analysis. Each of the 11 primers tested generated amplicons and out of a total of 69 amplicons produced 66 were polymorphic, with an average polymorphism of 95.60%. Two primers (OPG 4 and 11) produced a maximum 10 amplicons each that were all polymorphic. The Jaccard’s similarity coefficient recorded an average similarity of 0.51, ranging from 40% (CIAH, Bikaner) to 52% (ARS, Sriganganagar). In the SAHN clustering based on UPGMA algorithms out of the 20 accessions, 17 accessions grouped in two major clusters, two accessions (C and F) together with a high level diversity (almost 50%) into a third cluster while accession H remained outlier. The poor clustering of accessions from the same location indicated diverse genotypes which could have come from diverse basic material or chance seedlings or accumulation of mutations. The presence of diversity in the orchards could hamper realization of potential yield and uniformity of produce. The study thus clearly suggests need for purification and multiplication of desired types from the presently growing kinnow plantation.

Plant breeding of some tropical fruits in Thailand; durian, mango, rambutan, tangerine, pummelo and papaya

Until recently, most Thai fruit cultivars were improved by chance seedlings and selected by Thai farmers. However, some commercial cultivars were selected and improved by plant breeders. A durian breeding program was commenced by the Department of Agriculture in 1956. Eighteen cultivars were selected to be parent plants for 55 reciprocal crosses and produced 7,634 F1 hybrid seedlings. Three promising lines were selected as commercial cultivars, namely, 'Chanthaburi 1', '2' and '3' in 2006 and characterized by DNA fingerprinting. Subsequently, 253 lines of F2 generation, 4,278 F1 lines from 51 new crosses between 1998 and 2002, 110 interspecific hybrids from 45 crosses between 1988 and 1992 and 21 crosses in 2000 are being investigated for high tolerance to Phytophthora palmivora, high yield and good fruit quality. Between 2006 and 2016, three lines were released namely, 'Chanthaburi 4', '5' and '6' in 2013 and another three will be released namely, 'Chanthaburi 7', '8', '9' in 2016. Exploration, collection, conservation, characterization, documentation and utilization of mango and rambutan species were studied in 2000-2003. Two lines of mango (CB0007 and CB0010) and one line of rambutan (CB0023) 'Thong Muang Trat' with long shelf life were selected. A mango breeding project was conducted on 60 crosses and 2 hybrids namely, 'Chanthaburi 1' and '2' were released with early maturity. In addition, the commercial cultivars 'Nam Dok Mai', 'Nam Dok Mai Si Tong' are exported. From 1974-1983, rambutan cultivar improvement was achieved by reciprocal crossing between five parents and 'Plew#3' was released to farmers. Acute and chronic gamma irradiation for mutation induction in tangerine (C. reliculata) and pummelo (C. grandis) to produce seedless cultivars or those containing fewer seeds were conducted between 2000-2006. Two seedless M1V4 pummelo 'Kao Thong Dee' resulted. Moreover, 8 promising lines were further investigated and one of them, A4V3-22-2 has good eating quality, 0-2 seeds fruit-1 and high yield namely, 'Phare 1'. Pummelo cultivar improvement has been conducted from 2006-2010 for high yield, high quality. Evaluation of 425 F1 hybrid pummelos showed that some have good growth, have started to set fruit and are being evaluated. In addition, 2 citrus species ('Thabtim' and 'Cleopatra') used as rootstocks have good compatiblity and result in good growth of cultivar 'Kao Thong Dee'. DOA papaya breeding was commenced in 1984. The DOA approved 'Khaek Dam Si Sa Ket' was selected as a new cultivar in 1994. 'Khaek Dam' was crossed to 'Coimbatire No. 2' (CO2) and 'Phichit' line was approved in 1997. A cross between the 'Khaek Dam' and the 'Florida Tolerant' cultivar, resulted in new cultivars, 'Khaek Dam Tha Phra' and 'Khon Kaen 80' which were approved in 1997 and 2010, respectively. In addition, genetic engineering was undertaken by the DOA in collaboration with Cornell University. The coat protein gene (CP gene) of PRSV was transferred into Thai papaya, 'Khaek Dam' and 'Khaek Nuan' cultivars. Currently, one cultivar 'Khaek Dam' (R3 300KD) and two 'Khaek Nuan' (R3 319-1KN-180 and R3 319-1KN-181) cultivars were selected for the R3 PRSV resistance. However, GMO research is still limited at the present in Thailand.

Volatile metabolite profiling reveals the changes in the volatile compounds of new spontaneously generated loquat cultivars

In recent years, the advantageous traits of three new loquat cultivars have drawn the attention of breeders and growers. All three have spontaneously arisen from the ‘Algerie’ cultivar: the new ‘Xirlero’ cultivar is a bud mutant of ‘Algerie’, while ‘Amadeo’ and ‘Raúl’ arose as chance seedlings. Following a non-targeted approach based on HS-SPME-GC–MS, the volatile compounds profile of the fruits from the new cultivars were obtained and compared to the original ‘Algerie’ cultivar. Carboxylic acids clearly dominated the volatile profile of all the loquat cultivars, but esters, aldehydes, ketones and alcohols were also predominant compounds. Interestingly when the bud mutant event did not lead to marked changes in the volatile compounds complement, pronounced changes in the volatile composition of chance seedling-generated cultivars ‘Amadeo’ and ‘Raúl’ were observed. ‘Amadeo’ fruits showed lower levels of 2-methyl butanoic acid and much higher levels of methylhexanoate, methylbutanoate and 2-hydroxy-5-methylacetophenone. The ‘Raúl’ cultivar also had a distinctive volatile profile characterised by high levels of C6-aldehydes, (E)-2-hexanal, 2-hexenal, (Z)-3-hexenal and hexanal, and several carotenoid-derived volatiles; e.g. 2-pentene-1,4-dione 1-(1,2,2-trimethylcyclopentyl), (S)-dihydroactinidiolide, isodurene, cis-geranyl acetone, β-damascenone, β-ionone, α-ionone and 3,4-dehydro-β-ionone. These changes in volatiles were associated with a more intense flavour in cultivars ‘Amadeo’ and ‘Raúl’, according to the sensory evaluation of the flavour intensity carried out by a semi-trained panel. A metabolomic correlation network analysis provided insights as to how volatiles were regulated, and revealed that the compounds modified in ‘Amadeo’ were uncoupled from the rest of the volatilome, while the volatiles modified in ‘Raul’ changed according to specific groups. To conclude, this work provides a holistic view of how the loquat volatilome was affected, and this information was integrated with the physical-chemical-sensory attributes to understand the changes that occur in the new cultivars.

Clone identification in Japanese flowering cherry (&lt;i&gt;Prunus&lt;/i&gt; subgenus &lt;i&gt;Cerasus&lt;/i&gt;) cultivars using nuclear SSR markers

Numerous cultivars of Japanese flowering cherry (Prunus subgenus Cerasus) are recognized, but in many cases they are difficult to distinguish morphologically. Therefore, we evaluated the clonal status of 215 designated cultivars using 17 SSR markers. More than half the cultivars were morphologically distinct and had unique genotypes. However, 22 cultivars were found to consist of multiple clones, which probably originate from the chance seedlings, suggesting that their unique characteristics have not been maintained through propagation by grafting alone. We also identified 23 groups consisting of two or more cultivars with identical genotypes. Most members of these groups were putatively synonymously related and morphologically identical. However, some of them were probably derived from bud sport mutants and had distinct morphologies. SSR marker analysis provided useful insights into the clonal status of the examined Japanese flowering cherry cultivars and proved to be a useful tool for cultivar characterization.

Oryzalin-induced Tetraploidy in Cryptomeria japonica (Cupressaceae)

Japanese-cedar [Cryptomeria japonica (L.f.) D. Don] represents an alternative to leyland cypress [×Cuprocyparis leylandii (A.B. Jacks. &amp; Dallim.) Farjon] as an evergreen screen or specimen plant for landscapes. It performs well under a range of soil and environmental conditions but has been underused attributable, in part, to unsightly winter browning caused by photoinhibition. In previous studies, chance seedlings that did not exhibit winter browning were identified as tetraploids. The current study was conducted to induce polyploidy in japanese-cedar. Approximately 600 seedlings were sprayed with 150 μM oryzalin + 0.1% SilEnergy™ for 30 consecutive days under laboratory conditions. Two hundred thirty-seven seedlings with thickened and twisted leaves were selected, transplanted, and grown in a glasshouse for 120 days. Seedling ploidy levels were analyzed using flow cytometry 180 days after treatment (DAT), identifying 197 (83.1%) tetraploids, 22 (9.3%) cytochimeras, and 18 (7.6%) diploids. Morphology of induced tetraploids was similar to that previously described and provided a phenotypic marker during selection that was over 92% accurate. A random subset of 20 tetraploid individuals was analyzed 270 DAT and were found to contain only tetraploid cells in the leaves analyzed, confirming stability over this period. This study demonstrated the use of oryzalin for inducing tetraploids in japanese-cedar, which we predict will be effective in other gymnosperms.

Broad-sense Heritability Estimates for Fruit Color and Morphological Traits from Open-pollinated Half-sib Mango Families

The visual appearance of mangos is a primary factor in determining consumer acceptance and sale, similar to other fruit and vegetable commodities. Even if the appeal of visual appearance is based on consumer perception rather than on established quality factors, breeders must usually select within the range of acceptance, at least in some countries. Mango selection using multiyear breeding programs is slowly replacing the former method by which most earlier cultivars were selected, namely from chance seedlings either from planned or unplanned crosses. The knowledge of heritability of traits as they are controlled by genetics and experimental design and the effects and interaction of these two sets of factors on achieved gain have become more critical. The use of portable colorimeters has been shown to give repeatable scores in a quantitative, three-dimensional space for fruits and vegetables. In this experiment, we calculated broad-sense heritability estimates for five color traits, three morphological fruit traits, and one disease resistance trait (anthracnose expressed on the fruit). Estimates were found to be relatively high, indicating good potential for improvement through breeding. For nearly all traits measured, variance within families was greater than that among families, illustrating the likely importance of heterozygosity, dominance, and epistasis in these crosses. The careful estimation of heritability and repeatability will help prioritize and increase the efficiency of trait improvement as breeding methods become more sophisticated and competition for funding increases.

Selection of the chance seedlings of `Mézes körte' (Pyrus communis L.) from the gene bank of Keszthely

We have concluded the selection tests of the `Mézes körte' seedlings planted in the spring of 2006, with special emphasis on the cotyledonary, foliage leaf and the height of plant. Out of the 75 seeds planted in rows, there were 40-45 pieces growing out, so during the first cotyledonary test we had to calculate with almost 40% decay. On 12th April 2006, we recorded some of the important characteristics of the seedlings in their cotyledonary stage which characteristics were important from the point of view of selection (cotyledonary form, cotyledonary length, cotyledonary thickness, cotyledonary colour, cotyledonary petiole length, cotyledonary petiole thickness, cotyledonary petiole colour). The above morphological characteristics are shown in Table No. 1-6. We have also tested the seedling in foliage leaf state, paying special attention on the development stage of the plants (colour of foliage leaf , height of plant). We have completed statistical calculations of the two above mentioned characteristics. The result of that is summarised in Table No. 8-9. The variation coefficient show smaller value in the case of the foliage leaf number (15-32%), while the wider range of spread of the data referring to the height of the plant is shown by the 33-61% CV values. On charts No 4-9. we present the relationship between the height of the plant and the number of foliage leaf, as well as the differences between the two graphs. Based on the above charts and graphs it can be defined that the 40% destruction of the developing seedlings during the period till the next measurement reached 70-80% level. In spite of this however some seedlings showed strong and balanced growth (A44, B42, C25, D16, E5, E39, F38), the further testing and selection of those is to be completed in the future.

MOLECULAR AND GENETIC REGULATION OF SENSORY QUALITY OF CLIMACTERIC FRUIT

The sensory quality of fruit has become a major criterion in making the purchasing decision by consumers. Breeding programs have mainly been directed, from the post-harvest stand point, towards improving shelf-life. Chance seedlings or mutants with improved agronomic traits and/or extended shelf-life have been used for introgressing the long shelf-life character and eventually improved sensory quality traits in commercial genotypes of apple, melon or tomato. Because the plant hormone ethylene plays a central role in both storability and ripening of climacteric fruit, the generation by biotechnology of ethylene-inhibited fruit has offered a powerful tool to better understand, at the molecular and genetic level, the interrelations between storability and sensory quality. In the melon, inhibition of ethylene synthesis results is a strong inhibition of the synthesis of aroma volatiles while the accumulation of sugars is not affected or is even improved. The softening of the flesh is strongly affected but not abolished. Mid or long shelf-life melons generated by classical breeding present the same behavior. The generation of recombinant inbred lines by crossing a typical climacteric melon (Cantaloupe Charentais of the cantalupensis group) with a non climacteric melon (PI161375 of the agrestis chinensis group) allowed to demonstrate that the climacteric character is conferred by 2 duplicated loci only, which are of great importance for the regulation of storability and sensory quality. Due to the importance of aroma volatiles in sensory quality and to the strong negative correlation between aroma production and ethylene synthesis, we have developed a research program aimed at isolating genes involved in the synthesis of aroma volatiles. We will report on the recent advances in the field with special emphasis on the characterization of genes responsible for the synthesis of esters, a family of compounds crucial for the flavor of many fruit.

Parentage Analysis in Japanese Peaches using SSR Markers.

Parentage of 16 peach cultivars, including 9 cultivars bred by controlled hybridization, 2 from bud sport mutations and 5 from chance seedlings, was analyzed using 17 SSR markers. The parent-offspring relationships of 9 crossbreeding cultivars were confirmed because SSR alleles were transmitted to offspring cultivars from their parents without discrepancy at all the used loci. ‘Akatsuki’ and ‘Gyousei’ showed identical SSR genotypes, which suggested that ‘Gyousei’ was derived from a bud sport mutation. In contrast, another bud sport cultivar, ‘Hikawa Hakuhou’, showed different SSR genotypes from those of the original cultivar ‘Hakuhou’ at 12 SSR loci, indicating that ‘Hikawa Hakuhou’ was not a bud sport mutant of ‘Hakuhou’. Four cultivars that presumably originated from chance seedlings, i.e., ‘Abe Hakutou’, ‘Kawanakajima Hakutou’, ‘Kouyou Hakutou’ and ‘Shimizu Hakutou’, shared one allele with their putative parent ‘Hakutou’ at each SSR locus. SSR analysis suggested that these 4 cultivars were not bud sport mutants, but offsprings of ‘Hakutou’. It was concluded that SSR markers could be effectively utilized for parentage analysis in Japanese cultivated peaches.

Shanhai Suimitsuto, One of the Origins of Japanese Peach Cultivars

Almost all peaches grown in Japan supposedly originated from 'Hakuto' by crossbreeding, so that they are closely related to it. For example, 'Hakuho' and 'Akatsuki', offsprings of 'Hakuto', were obtained by controlled hybridization. There is a possibility that many cultivars are chance seedlings or bud sports of 'Hakuto'. However, the genetic origin of 'Hakuto' has not yet been identified. In this study, genetic relationships between 'Hakuto' and other peaches with different origins were analyzed, using 10 SSR markers. The results indicate that a close relationship exists between 'Shanhai Suimitsuto' and 'Hakuto' as well as a possible parent-offspring relationship. Contrarily, the peach 'Kinto' showed a close relationship to 'Hakuto' but not that of a parent-offspring because of a discrepancy of genotypes for the SSR loci. Parentage analysis of 'Hakuto' and 'Shanhai Suimitsuto' that was analyzed by 43 SSR loci, revealed that all SSR alleles were inherited by 'Hakuto' without any discrepancy from the putative parent 'Shanhai Suimitsuto'. These results indicate the very high possibility that 'Shanhai Suimitsuto' is a parent of 'Hakuto' and one of the original germplasm of the Japanese peaches.

Release of Five Sweetpotato Cultivars in Uganda

‘Bwanjule’, ‘New Kawogo’, ‘Tanzania’, and ‘Wagabolige’ are superior Ugandan farmers’ cultivars selected from a collection of 380 landrace accessions assembled at Namulonge Agricultural and Animal Production Research Institute (NAARI) in 1987 and subsequently evaluated in trials at NAARI and elsewhere in Uganda. Pedigrees of these landrace cultivars are not known, but they are assumed to be chance seedlings selected by farmers. On the basis of numbers of landrace cultivars, and the adaptation of these cultivars to local conditions, including diseases and pests, eastern Africa is considered to be a secondary center of sweetpotato genetic diversity. ‘Sowola’, designated NIS/90/389a during testing, is a seedling selection from the sweetpotato breeding program at NAARI, and was selected from bulked seed from a polycross of 18 parents made from 1989 to 1990. The progenitors in this polycross block were popular farmers’ cultivars from various parts of Uganda as follows: ‘Odeyo cani’, ‘Bwom dege’, and ‘Cwara opoko’, from Gulu District; ’Tanzania’, from Soroti District; ‘Siliki’, ‘Mpaeifumbiro’, and ‘Wagabolige’, from Jinja District; ‘Katalaako’, from Iganga District; ‘Tororo 1’, ‘Tororo 2’, and ‘Tororo 3’, from Tororo District; ‘Nylon’, ‘Bugerere’, ‘Sukali’, and ‘Mwezigumu’ from Nakasongola District; and ‘Nantongo’, ‘Kawogo’, and ‘Mwezigumu’ from Mpigi District. Because of the open-pollinated and bulk nature of the