Inheritance of parthenocarpy in summer squash (Cucurbita pepo L.)

The inheritance of the tendency to set parthenocarpic fruit in the summer squash (Cucurbita pepo L.) line Whitaker was studied. Two parental lines, Whitaker (parthenocarpic) and Caserta (non-parthenocarpic), and the F1 and F2 generations and backcrosses to both parents were tested. The parthenocarpic tendency of individual plants was scored on a scale from 1 (non-parthenocarpic fruit) to 5 (parthenocarpic fruit). The Whitaker line produced parthenocarpic fruit and had a mean score of 4.2, whereas Caserta did not set parthenocarpic fruit and had a score of 1.55. The heritability estimates indicated that genetic gains from selection were feasible. The additive-dominant model showed a good fit, with epistasis being negligible or nonexistent. The hypothesis of monogenic inheritance with incomplete dominance was not rejected within the degree of dominance range from 0.2 to 0.5. These results indicate that parthenocarpy is controlled by a single locus, with incomplete dominance in the direction of parthenocarpic expression.     

Determination of the composition and the allelic state of disease and pest resistance genes in potato parental lines using DNA markers

The allelic dosage of disease and pest resistance genes was determined in 11 prospective potato varieties and hybrids by means of detecting the corresponding PCR DNA markers in their progeny from crosses with specially selected testers. It was revealed that most (65%) resistance genes in the analyzed parental lines were present as a single dominant allele (simplex). Nevertheless, we were able to find some multiplex lines valuable for breeding. The Yanka variety and the clone 52-03-16 had one triplex and one duplex of resistance genes, the Lilea and Charaunik varieties and the clone 106-04-17 had two resistance genes in duplex, and the Uladar and Falvarak varieties and the clone 45-04-24 were duplex for some single genes. The highest number of multiplex lines was detected for the genes Ry_sto, H1, and Sen1. Only simplex genotypes were revealed for the Gro-1-4 and PLRV1 genes.     

吉林爆玉米遗传距离与杂种优势关系的研究

根据吉林省80个爆玉米自交系数量性状的表现,估算了它们之间的遗传距离。又估算了这80个自交系间随机组配的67个杂交组合F1代小区产量、爆粒率和膨胀倍数的杂种优势。相关和回归分析表明,F1代产量的对照优势与其双亲之间的遗传距离呈显著的二次曲线关系,而F1代品质特性爆粒率和膨胀倍数的对照优势与其双亲之间的遗传距离无确定性关系。因此,可以根据亲本间数量性状的综合遗传差异——遗传距离来预测吉林省爆玉米杂种一代的产量优势。 An experiment was conducted in 1990 to 1991 at the university,to study the relationships between genetic distance,cluster analysis and heterosis in popcorn(Zea mays var.everta).Results showed that there is no sense in cludtering parental lines for prediction of yield heterosis,but blood pedigree can beidentifed from cluster analysis.The relation between genetic divergence or distance and yield heterosis of F1 hybrids can be predicted from the genetic distances of their parental lines according to this model,but no definite relation could be found between parental genetic divergence and the quality heterosis of F1 hybrids.     

Molecular expression of genes involved in parthenocarpic fruit set in tomato

To characterize the phenomenon of natural parthenocarpy in tomato ( Lycopersicon esculentum Mill.) two different approaches have been followed. At a developmental level, the ovary weights of three non-parthenocarpic lines and three near-isogenic parthenocarpic ( pat-2 ) lines were compared. Four developmental stages were considered: flower bud, preanthesis, anthesis and 4 days after anthesis. The parthenocarpic lines displayed ovary weights higher than their respective non-parthenocarpic lines from preanthesis to 4 days after anthesis. A molecular approach involved comparison of in vitro translation products from flower RNAs taken from the same developmental stages of non-parthenocarpic and near-isogenic parthenocarpic ( pat-2 and pat-3/pat-4 ) lines. Analysis by two-dimensional polyacrylamide gel electrophoresis showed the differential expression of a 30-kDa product in parthenocarpic materials from preanthesis to anthesis. These results suggest that the physiological and molecular events responsible for parthenocarpy begin at the preanthesis stage, before the flower is completely mature and receptive to pollination. The differential expression of this in vitro translation product in pat-2 and pat-3/pat-4 genotypes also suggests a common or confluent molecular basis in genetically controlled parthenocarpy.     

Do rice hybrids have heterosis for insect resistance? A study with Nilaparvata lugens (Hemiptera: Delphacidae) and Marasmia patnalis (Lepidoptera: Pyralidae)

Antibiosis-based resistance to two insect pests of rice, Nilaparvata lugens (St?l) (Hemiptera: Delphacidae) and Marasmia patnalis Bradley (Lepidoptera: Pyralidae), was compared in 11 F1 hybrids and their parental lines. Our objective was to determine whether hybrids show heterosis (hybrid vigor) for insect resistance or susceptibility. Heterosis is defined as the amount by which a hybrid exceeds its midparent value or its better parent. Overall, we did not find evidence of heterosis or heterobeltiosis (a type of heterosis in which a hybrid exceeds its better parent) for antibiosis-based resistance or susceptibility to either of the insects. One hybrid, IR64616H, seemed more resistant to M. patnalis than its better parent but none of the other hybrids showed heterobeltiosis for resistance or susceptibility to either insect. Three hybrids had resistance to N. lugens that exceeded their midparent value, possibly due to dominant resistance in one of the parents. The increased frequency and severity of insect outbreaks on hybrid rice that have been reported in China may be attributable to factors other than diminished antibiosis in hybrids, such as greater attractiveness of hybrids to migrating or dispersing insects or differences in agronomic practices applied to hybrids and inbred rice cultivars.     

Contributions of heterosis and epistasis to hybrid fitness

Early-generation hybrid fitness is difficult to interpret because heterosis can obscure the effects of hybrid breakdown. We used controlled reciprocal crosses and common garden experiments to distinguish between effects of heterosis and nuclear and cytonuclear epistasis among morphotypes and advanced-generation hybrid derivative populations in the Piriqueta caroliniana (Turneraceae) plant complex. Seed germination, growth, and sexual reproduction of first-generation hybrids, inbred parental lines, and outbred parental lines were compared under field conditions. Average vegetative performance was greater for hybrids than for inbred lines, and first-season growth was similar for hybrids and outbred parental lines. Hybrid survival surpassed that of inbred lines and was equal to or greater than outbred lines' survival, and more F(1) than parental plants reproduced. Reductions in hybrid fitness due to Dobzhansky-Muller incompatibilities (epistasis among divergent genetic elements) were expressed as differences in vegetative growth, survival, and reproduction between plants from reciprocal crosses for both F(1) and backcross hybrid generations. Comparing performance of hybrids against parental genotypes from intra- and interpopulation crosses allowed a more robust prediction of F(1) hybrids' success and more accurate interpretations of the genetic architecture of F(1) hybrid vigor.     

Analysis of Indian Sorghum [Sorghum bicolor (L) Moench] Cultivars and Lines Using RAPD Markers

Random Amplified Polymorphic DNA (RAPD) analysis was performed for the identification and assessment of genetic relationships in Indian sorghum comprising released varieties, hybrids and their parental lines (A, B and R-lines). Twenty-three random decamer primers generated 151 amplicons, of which 87 were found to be polymorphic (57.6%). The primer OPL-03 was the most informative as it could alone discriminate 13 accessions out of the 37 studied. The accessions 27B, C 43, CSV 14R and HC 6 were found to have specific bands. Four of the male sterile (27A, 296A, 2219A and AKMS 14A) lines and their respective maintainer (27B, 296B, 2219B and AKMS 14B) lines could be easily differentiated with thirteen random primers (OPA-09, OPC-02, OPD-07, OPE-04, OPE-16, OPG-09, OPL-01, OPL-03, OPL-05, OPL-15, OPL-18, OPV-01 and OPX-12). Based on Jaccard’s similarity coefficient values, the most distant two accessions were CS 3541 and CSV 14R and the closest were 104A and 104B, with similarity values of 0.64 and 1.00 respectively. The average Jaccard’s similarity coefficient of 0.78 revealed low level of genetic diversity in the investigated material. The dendrogram generated by UPGMA could group all the accessions into distinct clusters consistent with established classification viz. grain and forage sorghum and known pedigree information.     

甘蔗优良品种材料抗高粱花叶病毒鉴定与评价

采用生长期人工切茎接种和RT-PCR检测相结合方法,于2011—2012年2次对国家甘蔗体系近年选育的49份优良新品种(系)和19份云蔗系列优良中间材料进行由高粱花叶病毒(SrMV-HH,GenBank登录号DQ530434)引起的甘蔗花叶病的抗性鉴定与评价。结果表明,49份优良新品种(系)中,1级高抗到3级中抗的有29份,占59.18%。其中粤甘40号、粤甘42号、粤糖55号、云蔗03-194、云蔗99-596、云瑞06-189、桂糖30号、德蔗03-83、闽糖01-77等9份材料表现1级高抗,占18.37%;福农0335、柳城05-129、粤糖96-86、云蔗01-1413、云蔗03-258、云蔗06-80、桂糖02-351等7份材料表现2级抗病,占14.29%。19份云蔗系列优良中间材料中,1级高抗到3级中抗的有13份,占68.42%。其中云蔗04-622、云蔗05-197、云蔗06-267、云蔗05-194、云蔗06-160、云蔗07-2384、云瑞05-704等7份材料表现1级高抗,占36.84%;云蔗06-362表现2级抗病,占5.26%。研究结果为深入开展甘蔗抗花叶病育种,选育和推广优良抗病品种,有效防控甘蔗花叶病提供了科学依据和优良抗源材料。     

Heterosis breeding in rice (Oryza sativa L.)

Summary Studies conducted at the International Rice Research Institute (IRRI) during 1980 and 1981 have shown up to 73% heterosis, 59% heterobeltiosis and 34% standard heterosis for yield in rice. The latter was estimated in comparison to commercial varieties: IR36 and IR42 (yield 4–5 t/ha in wet season trials and 7–8 t/ha in dry season trials). Generally speaking, absolute yield was lower and extent of standard heterosis was higher in wet season than in dry season with some exception. Yields up to 5.9 t/ha (22% standard heterosis) in the wet season and 10.4 t/ha (34% standard heterosis) in the dry season were obtained. Most of the hybrids performed better in some season while some performed better in both seasons. Hybrids showed better lodging resistance although they were 5–10 cm taller. F₁ hybrids had significant positive correlations with the parental traits viz., yield (r = 0.446), tillering (r = 0.746), height (r = 0.810) and flowering (r = 0.843). Selection of parents among elite breeding lines on the basis of their per se yield performance, diverse origin and resistance to insects and diseases should give heterotic combination. Yield advantage of hybrids was due primarily to increase in number of spikelets per unit area even though tiller number was reduced. Grain weight was either the same or slightly higher. High yielding hybrids also showed significant heterosis and heterobeltiosis for total dry matter and harvest index. For commercial utilization of heterosis in rice, effective male sterility and fertility restoration systems are available and up to 45% natural outcrossing on male sterile lines has been observed. Consequently, F₁ rice hybrid have been successfully developed and used in China. Prospects of developing hybrid rice varieties elsewhere appear bright especially in countries that have organized seed production, certification and distribution programs and where hybrid seed can be produced at a reasonable cost.     

Genetic Variation and Combining Ability Analysis of Bruising Sensitivity in Agaricus bisporus

Advanced button mushroom cultivars that are less sensitive to mechanical bruising are required by the mushroom industry, where automated harvesting still cannot be used for the fresh mushroom market. The genetic variation in bruising sensitivity (BS) of Agaricus bisporus was studied through an incomplete set of diallel crosses to get insight in the heritability of BS and the combining ability of the parental lines used and, in this way, to estimate their breeding value. To this end nineteen homokaryotic lines recovered from wild strains and cultivars were inter-crossed in a diallel scheme. Fifty-one successful hybrids were grown under controlled conditions, and the BS of these hybrids was assessed. BS was shown to be a trait with a very high heritability. The results also showed that brown hybrids were generally less sensitive to bruising than white hybrids. The diallel scheme allowed to estimate the general combining ability (GCA) for each homokaryotic parental line and to estimate the specific combining ability (SCA) of each hybrid. The line with the lowest GCA is seen as the most attractive donor for improving resistance to bruising. The line gave rise to hybrids sensitive to bruising having the highest GCA value. The highest negative SCA possibly indicates heterosis effects for resistance to bruising. This study provides a foundation for estimating breeding value of parental lines to further study the genetic factors underlying bruising sensitivity and other quality-related traits, and to select potential parental lines for further heterosis breeding. The approach of studying combining ability in a diallel scheme was used for the first time in button mushroom breeding.     

Parthenocarpic fruit development in tomato

Abstract: Parthenocarpic fruit development is a very attractive trait for growers and consumers. In tomato, three main sources of facultative parthenocarpy, pat, pat-2, pat-3/pat-4, are known to have potential applications in agriculture. The parthenocarpic fruit development in these lines is triggered by a deregulation of the hormonal balance in some specific tissues. Auxins and gibberellins are considered as the key elements in parthenocarpic fruit development of those lines. An increased level of these hormones in the ovary can substitute for pollination and trigger fruit development. This has opened up genetic engineering approaches for parthenocarpy that have given promising results, both in quality and quantity of seedless fruit production.     

SSR heterogenic patterns of parents for marking and predicting heterosis in rice breeding

The most important concerns of hybrid rice breeders are selection of donors to improve parental lines and prediction of hybrid performance. In this study, SSR molecular marker technology and a half-diallel method were used to address these related hybrid production issues. The results show that genetic diversity among the parental lines is certainly related to heterosis. The heterozygosity of each parental pair is significantly associated with the general combining ability, not with the specific combining ability. However, neither genetic diversity nor heterozygosity is a good indicator for predicting heterosis. From these results, it is suggested that donors for improving parents of hybrids be selected from the improved inbred lines by conventional breeding programs. In this investigation, we also discovered that four favorable alleles and six favorable heterogenic patterns on the parental lines significantly contribute to the heterosis of their hybrids in grain yield, whereas six unfavorable alleles and six unfavorable heterogenic patterns significantly reduce heterosis. These noticeable findings could be, in practice, useful for hybrid rice breeding programs with SSR marker-assisted selection. It is suggested that the optimal combinations with the superior grain yield could be bred out by assembling those favorable alleles into their parental lines and by removing the unfavorable alleles from the parental lines. This study also indicates that there is still a great heterosis potential to be exploited in indica/indica hybrids by the same strategy. In indica/japonica hybrid breeding programs, it may also be important to remove unfavorable alleles rather than broaden genetic diversity or heterozygosity of the parents.     

Genetic Analysis of Growth-Regulator-Induced Parthenocarpy in Arabidopsis

In Arabidopsis, seedless silique development or parthenocarpy can be induced by the application of various plant growth regulators (PGRs) to unfertilized pistils. Ecotype-specific responses were observed in the Arabidopsis ecotypes Columbia and Landsberg relative to the type of PGR and level applied. The parthenocarpic response was greatest in ecotype Landsberg, and comparisons of fruit growth and morphology were studied primarily in this ecotype. Gibberellic acid application (10 micromol pistil(-1)) caused development similar to that in pollinated pistils, while benzyladenine (1 micromol pistil(-1)) and naphthylacetic acid (10 micromol pistil(-1)) treatment produced shorter siliques. Naphthylacetic acid primarily modified mesocarp cell expansion. Arabidopsis mutants were employed to examine potential dependencies on gibberellin biosynthesis (ga1-3, ga4-1, and ga5-1) and perception (spy-4 and gai) during parthenocarpic silique development. Emasculated spy-4 pistils were neither obviously parthenocarpic nor deficient in PGR perception. By contrast, emasculated gai mutants did not produce parthenocarpic siliques following gibberellic acid application, but silique development occurred following pollination or application of auxin and cytokinin. Pollinated gai siliques had decreased cell numbers and morphologically resembled auxin-induced parthenocarpic siliques. This shows that a number of independent and possibly redundant pathways can direct hormone-induced parthenocarpy, and that endogenous gibberellins play a role in regulating cell expansion and promoting cell division in carpels.     

利用SSR标记鉴定西瓜杂交种纯度的研究

以2个西瓜杂交品种(系)的种子黑公子和04-17及其亲本为材料,用SSR标记技术研究杂种与其双亲之间的扩增谱带多态性,以甄别真假杂种.结果发现,所试验的52对SSR引物中有13对引物分别在2个西瓜杂交种和其双亲之间存在扩增条带的多态性,表现为:多数SSR引物对自交系的扩增只出现1条带,但部分引物在某些自交系中扩增出2条带,杂交种条带均为父母本的互补型,很适合做杂交种纯度鉴定.用引物CMCT134b对黑公子和引物CMGA165对04-17进行了各100粒单种子SSR鉴定,所测纯度分别为96%和100%,与田间纯度95.6%和99.7%非常接近,表明SSR标记技术在西瓜杂交种子纯度室内快速检测中的应用前景.     

The dual role of the potyvirus P3 protein of Turnip mosaic virus as a symptom and avirulence determinant in brassicas

Two isolates of the potyvirus Turnip mosaic virus (TuMV), UK 1 and CDN 1, differ both in their general symptoms on the susceptible propagation host Brassica juncea and in their ability to infect B. napus lines possessing a variety of dominant resistance genes. The isolate CDN 1 produces a more extreme mosaic in infected brassica leaves than UK 1 and is able to overcome the resistance genes TuRB01, TuRB04, and TuRB05. The resistance gene TuRB03, in the B. napus line 22S, is effective against CDN 1 but not UK 1. The nucleic acid sequences of the UK 1 and CDN 1 isolates were 90% identical. The C-terminal half of the P3 protein was identified as being responsible for the differences in symptoms in B. juncea. A single amino acid in the P3 protein was found to be the avirulence determinant for TuRB03. Previous work already has identified the P3 as an avirulence determinant for TuRB04. Our results increase the understanding of the basis of plant-virus recognition, show the importance of the potyviral P3 gene as a symptom determinant, and provide a role in planta for the poorly understood P3 protein in a normal infection cycle.     

Integration of the genetic and physical maps of the chicken macrochromosomes

A large amount of genetic mapping information has been obtained in the chicken from the East Lansing, Compton and Wageningen reference populations. Physical mapping information has however, been more limited. We have mapped 14 new clones, both genetically and physically, and all 14 have been assigned to macrochromosomes. The orientation of linkage groups E01C01C11W01 (Chr 1), E06C02W02 (Chr 2), E02C03W03 (Chr 3), E05C04W04 (Chr 4), E07E34C05W05 (Chr 5), E11C10W06 (Chr 6), E45C07W07 (Chr 7) and E43C12W11 (Chr 8) has been established. Here we present integrated maps of the eight macrochromosomes and the Z chromosome of the chicken and correlate genetic with physical distances for chromosomes 1-3 and the Z sex chromosome.     

Differential gene expression in liver of inbred chickens and their hybrid offspring

Differential display of mRNA was used to analyse the differences of gene expression in liver between chicken hybrids and their parents in a 4 x 4 diallel crosses in order to study the molecular basis of heterosis in chickens. The results indicated that patterns of gene expression in hybrids differ significantly from their parents. Four patterns of differential gene expression were revealed, which included: (i) bands only detected in the hybrid F1s (UNF1); (ii) bands only absent in the hybrid F1s (ABF1); (iii) bands only detected in the parental P1 or P2 lines (UNP1 and UNP2) and (iv) bands absent in the parental P1 or P2 lines (ABP1 and ABP2). In addition, correlations between patterns of gene expression and heterosis percentages of nine carcass traits of 8-week-old chickens were evaluated. Statistical results showed that negative correlations between heterosis percentages and the percentage of F1-specific bands (UNF1) were significant at P < 0.01 for breast muscle yield, leg muscle yield, wing weight, eviscerated weight and eviscerated weight with giblet of 8-week-old chickens, and at P < 0.05 for intermuscular fat width. Heterosis percentage was negatively correlated with ABP (bands present in the hybrid F1s and one parental line but absent in the other parental line, ABP1 and ABP2) for breast muscle yield, leg muscle yield, wing weight, eviscerated weight and eviscerated weight with giblet of 8-week-old chickens (P < 0.01). Bands detected only in the hybrid F1s but not in either of the parental lines (UNF1) and bands absent in parental P1 or P2 lines (which includes ABP1 and ABP2) may play important roles in chicken heterosis.     

Heterotic patterns in rapeseed (<Emphasis Type="Italic">Brassica napus</Emphasis> L.): I. Crosses between spring and Chinese semi-winter lines

Chinese semi-winter rapeseed is genetically diverse from Canadian and European spring rapeseed. This study was conducted to evaluate the potential of semi-winter rapeseed for spring rapeseed hybrid breeding, to assess the genetic effects involved, and to estimate the correlation of parental genetic distance (GD) with hybrid performance, heterosis, general combining ability (GCA) and specific combining ability (SCA) in crosses between spring and semi-winter rapeseed lines. Four spring male sterile lines from Germany and Canada as testers were crossed with 13 Chinese semi-winter rapeseed lines to develop 52 hybrids, which were evaluated together with their parents and commercial hybrids for seed yield and oil content in three sets of field trials with 8 environments in Canada and Europe. The Chinese parental lines were not adapted to local environmental conditions as demonstrated by poor seed yields per se. However, the hybrids between the Chinese parents and the adapted spring rapeseed lines exhibited high heterosis for seed yield. The average mid-parent heterosis was 15% and ca. 50% of the hybrids were superior to the respective hybrid control across three sets of field trials. Additive gene effects mainly contributed to hybrid performance since the mean squares of GCA were higher as compared to SCA. The correlation between parental GD and hybrid performance and heterosis was found to be low whereas the correlation between GCA_{(f + m)} and hybrid performance was high and significant in each set of field trials, with an average of r = 0.87 for seed yield and r = 0.89 for oil content, indicating that hybrid performance can be predicted by GCA_{(f + m)}. These results demonstrate that Chinese semi-winter rapeseed germplasm has a great potential to increase seed yield in spring rapeseed hybrid breeding programs in Canada and Europe.