Cluster Analysis of Chinese Pumpkin Inbred Lines

A cluster analysis was carried out based on Euclidean genetic distances through UPGMA method in Chinese pumpkin inbred lines.7 important agronomic traits of 46 Chinese pumpkin inbred lines were investigated.The result indicated that 46 pumpkin inbred lines were clustered into 4 groups and the inter-groups distances was larger than that in intra-group.The genetic distances of parents were related to F1 performance and the results of cluster would increase effectiveness in the Chinese pumpkin crossing breeding.

Analysis on Combining Ability and Genetic Parameters of Main Agronomic Characters of 22 Maize Inbred Lines

The general combining ability（GCA）, special combining ability（SCA） and genetic parameter of ten characters of 22 maize inbred lines including plant height and ear height were analyzed using 10×12 through incomplete diallel cross（NC Ⅱ）.The results showed that：（1） Among the 22 maize inbred lines, the yield GCAs of11 HN 097, 11 HN 099, 11 HN 105 and 11 HN 110 were high, which were elite inbred lines to collocate hybridized combinations with strong heterosis. The yield of11 HN110 × 11 HN097, 11 HN110 × 11 HN105, 11 HN112 × 11 HN 097 and 11 HN 106 × 11 HN 104 were in the first four place. The yielding abilities, adaptabilities and yielding stabilities of the four combinations can be further identified by experiment. The heredities of the ten characters were mainly controlled by additive gene effect whereas the influence of non-addictive gene effect was small. The narrow heritabilities of plant height, ear height, ear rows, ear length, kernels per row,100-grain weight and seed-producing percentage were more than 50%. The variances were mainly caused by heredity and early-generation selection should be conducted. The narrow heritabilities of ear diameter, bare tip length and yield was low, which should not be selected in early-generation.

Combining Ability and Correlation of Ear Characteristics of Twenty Maize Inbred Lines

The combining ability and correlation of eight ear characteristics in 99 maize hybrids generated by crossing nine female parents with 11 male parents were analyzed by incomplete diallel cross （NC II ） design. The results showed that the line F6 had the highest general combining ability （GCA） for yield, followed by F7, M3, M4 and M8. All of the five lines have great potential in maize breeding. The cross combination M3xF10 had the highest specific combining ability （SCA） for yield, showing strong heterosis. Heritability analysis of ear characteristics showed that GCA variance was higher than SCA variance in ear diameter, number of rows per ear and seed rate, and they were mainly controlled by the additive gene effect, indicating that that the selections for these traits are effective at early generations. The other three traits had lower SCA, for which the selections should be carried out at late generations. The correlation analysis revealed that ear length, number of grains per row, ear diameter, number of rows per ear, 100-seed weight and seed rate had extremely significant positive correlations with grain yield per plant. Among them, number of grains per row had the most significant effect on yield per plant. Barren tip length had a significant negative correlation with grain yield per plant. Therefore, we concluded that the combinations with more grains per row and shorter barren tip should be selected to achieve high yield of maize.

Combining Ability Analysis on Yield Traits of Recombinant Inbred Lines in Hybrid Rice

A population of 140 recombinant inbred lines at F8 generation were obtained after seven successive generations of self-pollination using single seed descent（SSD） method from the F2 hybrids of three-line restorers Luhui 8258 with high combining ability and Yanghui 34. Then, the 140 inbred lines obtained above and their parents Luhui 8258 and Yanghui 34 were crossed with three different types of cyto-plasmic male sterile（CMS） lines（Gang 46 A, Ⅱ-32 A and Lu 98A） according to NCⅡ design. The resulting 426 combinations were planted at Deyang and Suining bases to test the combining ability and inheritance of five yield traits： yield per plant, panicle number per plant, filled grain number per panicle, seed setting rate and 1 000-grain weight. The results showed that the variances of both general and specific combining abilities of the five traits all reached a significant or extremely significant level at the two sites. The broad and narrow heritability of the yield traits（except 1 000-grain weight whose broad and narrow heritability were both over70%） were all below 50% at the two experimental bases, suggesting that the four traits were easily subjected to environment influence. Very significant positive correlation of general combining ability was found between yield per plant and other traits except 1 000-grain weight. The general combining ability variance showed a normal distribution among the recombinant inbred lines at two sites, right in line with inheritance of quantitative traits. So, the genes controlling rice general combining ability can be targeted by QTL mapping.

Combining Ability Analysis of Panicle Traits in Six CIMMYT Maize Inbred Lines

In this study, six CIMMYT maize inbred lines and five representative do- mestic maize inbred lines were used as parental lines. By using incomplete diallel cross design, 30 hybrid combinations were developed to analyze the general com- bining ability （GCA）, specific combining ability （SCA） and total combining ability （TCA） of seven panicle traits in six CIMMYT maize inbred lines. The results showed that CIMBL98 and GEMS13 were excellent inbred lines with good compre- hensive performance; CIMBL98 × 340 and GEMS13×Chang 7-2 were superior combinations.

Mapping of QTLs for Sheath Blight Resistance Using Recombinant Inbred Lines of Rice(Oryza sativa L.)

A recombinant inbred line （RIL） population composed of 157 lines derived from an inter-subspecific hybrid of Daguandao/IR28 by the single seed descent method was used as materials, and the quantitative trait loci （QTLs） coffering the resistance to sheath blight in the 157 RILs and the parents were detected using the toothpick inoculation method. The disease indexes of rice sheath blight in the two parents and 157 RILs were scored and the QTLs responsible for rice sheath blight resistance were detected accordingly by QTL Cartographer software. The results showed that a total of 4 QTLs （qsbl, qsb2, qsb5-1, qsb5-2） conferring sheath blight resistance were detected on chromosomes 1, 2 and 5, and their variance explained ranged from 10.41% to 36.92%. The additive effect of qsb5-1 was negative, indicat- ing that the QTLs derived from donor parent IR 28 could enhance the resistance to sheath blight. However, the additive effects of qsbl, qsb2 and qsb5-2 were positive, indicating that the QTLs derived from donor parent Daguandao weakened the resis- tance to sheath blight.

Selection of Maize Inbred Lines with High Regeneration and Susceptibility to Agrobacterium tumifacien

Ten-maize inbred lines of maize （Zea mays L.） with high-induction rate and proliferation ability of embryonic calli were selected from 70-maize inbred lines by immature embryo culturing. Some of the embryonic calli were transferred onto regeneration medium to examine the ability of regeneration, some were transformed via Agrobacterium tumifaciens C58 carrying intron-β-glucuronidase （gus） gene, and GV3301 carrying the green fluorescent protein （gfp） gene to study the susceptibility of different genotypes in maize to A. tumifaciens. All embryonic calli initiated from 10-maize inbred lines were able to regenerate into plantlets, and the regeneration frequencies of inbred lines 6010, 6038, 6015, 6051, and 6060 were 61.11%, 31.94%, 45%, 33.33%, and 56.94%, respectively, which were higher than that of other lines. Analysis of variance indicated that the susceptibility of the various genotypes in maize to A. tumifacien C58 showed a significant difference among each other, and the inbred lines 6010, 6015, 6051, 6050, 6058, 6060, 6069, 6077 were susceptible to A. tumifacien C58, of which frequency of gus expression were over 70%. Expression of GFP was observed in six-inbred lines （6050, 6015, 6051, 6058, 6069, 6077）. The inbred lines 6051, 6010, 6015, 6060, and 6050 had the high regeneration and the susceptibility to A. tumifaciens C58; and the inbred lines 6051, 6015, and 6060 had the high regeneration and the susceptibility to Agrobacterium tumifaciens GV3301.

Genetic Relation Analysis on Ramie[Boehmeria nivea(L.)Gaud.]Inbred Lines by SRAP Markers

The objective of this article is to reveal the variations of ramie inbred lines in DNA level and discuss their molecular background to provide a theoretical basis for ramie cross breeding. In the present study, the genetic relationships among 33 inbred line accessions and two wild types that originated from China and Brazil were estimated using sequence-related amplified polymorphism （SRAP） markers. The results showed that 33 out of 81 primer combinations turned out to be polymorphic and 332 polymorphism bands were obtained. On the basis of the appearance of the markers, the genetic relationships were analyzed using unweighted pair-group method of arithmetic average cluster analysis （UPGMA）, and the genetic Jaccard similarity coefficients were calculated. The inbred-lines originating from China and Brazil formed a cluster suggesting a possibility that the Brazilian cultivars could have developed from cultivars introduced from China. Within ramie inbred-lines, the groupings also indicated that the greatest genetic relationship among cultivars was correlated to the region of origin of cultivars. The results provided the evidence that SRAP was an efficient approach, suitable for taxonomic analysis of ramie inbred lines, To the authors＇ knowledge, this is the first application of SRAP marker on the systematics of ramie inbred lines.

Genetic analysis and QTL mapping of stalk cell wall components and digestibility in maize recombinant inbred lines from B73 × By804

The cell wall composition and structure of the maize stalk directly affects its digestibility and in turn its feed value.Previous studies of stem quality have focused mostly on common maize germplasm,and few studies have focused on high-oil cultivars with high grain and straw quality.Investigation of the genetic basis of cell wall composition and digestibility of maize stalk using high-oil maize is desirable for improving maize forage quality.In the present study,a high-oil inbred line(By804)was crossed as male parent with the maize inbred line B73 to construct a population of 188 recombinant inbred lines(RILs).The phenotypes of six cell-wall-related traits were recorded,and QTL analysis was performed with a genetic map constructed with SNP markers.All traits were significantly correlated with one another and showed high broad-sense heritability.Of 20 QTLs mapped,the QTL associated with each trait explained 10.0%–41.1%of phenotypic variation.Approximately half of the QTL each explained over 10%of the phenotypic variation.These results provide a theoretical basis for improving maize forage quality by marker-assisted selection.

Determination of the Number of SSR Alleles Necessary for the Analysis of Genetic Relationships Between Maize Inbred Lines

The amount of molecular marker information has considerable impact on the results of studies of crop germplasm genetic relationships in crop. The number of alleles required to reveal genetic relationship in maize inbred lines is a theoretical issue that needs to be addressed. In this study, 112 pairs of SSR （simple sequence repeat） primers and 97 maize inbred lines were selected to study the relationship between the number of inbred lines and the number of SSR primers and alleles required for a stable cluster. The results showed that the number of SSR primers is not tightly associated with the stability of the cluster analysis results, while an increase in the number of alleles can significantly improve the stability of cluster analysis results. The number of inbred lines （X） is significantly associated with the number of alleles required for stable cluster analysis （Y）, and the regression equation is Y- 600.8xe（-15.9/x）. This equation can be used to calculate the number of SSR alleles required for a genetic relationship study of maize inbred lines. These results provide a reference for determining of SSR alleles number in genetic relationship analysis of maize inbred line and other crop germplasm.

Evaluation of Reproductive Characteristics of 21 Highly Inbred Lines of White Leghorns Divergently Selected for or Segregating in Tumor Resistance

Reproduction performance of 21 inbred experimental lines of White Leghorns was evaluated based on samples of reproduction records over a period of eight consecutive years. Two lines (63 and 72) have been extensively used in studies, especially in research seeking for genetic and epigenetic factors underlying resistance to avian tumor virus-induced diseases in chickens. The other 19 lines are recombinant congenic strains (RCS), which were generated by crossing lines 63 and 72 followed by two consecutive backcrosses to the line 63 and then full-sib mating. In theory, each RCS processes 7/8 of progenitor background line 63 genome and a random sample (1/8) of the progenitor donor line 72 genome. All 21 inbred lines share a common major histocompatibility complex haplotype, B*2. The estimated average fertility of the 21 inbred lines ranged from 72.9% (RCS-J) up to 96.8% (RCS-P). Both progenitor lines 63 and 72 were observed with lower average fertility (82.4% and 81.6%, respectively) in comparison with the RCS except the RCS-J, suggesting a substantial polygenic component underlying the fertility phenotype. The average embryo mortality rate ranged from 14.5% (RCS-P) up to 47.0% (RCS-M). The background line 63 fell at about the middle of the range (28.3%) significantly higher than the donor line 72 (15.7%), which was among the group with the lowest embryo mortality. By definition, hatchability of fertile eggs is reversely correlated with embryo mortality. The average hatchability ranged from 26.5% (RCS-M) up to 66.8% (line 72) while the background line 63 remained (46.6%) at about the middle of the range. The variability of the average embryo mortality and hatchability observed among the 21 inbred lines indicated the two correlated traits also follow polygenic models of inheritance. Findings from this study paves the way for further investigation on genetic and environmental influence over reproductive performance of inbred lines of chickens, and particularly in understanding and improving the reproduction fitness of invaluable genetic resources like these inbred lines.

Evaluation of drought tolerance in ZmVPP1-overexpressing transgenic inbred maize lines and their hybrids

The vacuolar proton-pumping pyrophosphatase gene(VPP)is often used to enhance plant drought tolerance via genetic engineering.In this study,the drought tolerance of four transgenic inbred maize lines overexpressing ZmVPP1(PH4CV-T,PH6WC-T,Chang7-2-T,and Zheng58-T)and their transgenic hybrids was evaluated at various stages.Under normal and drought conditions,the height and fresh weight were greater for the four transgenic inbred maize lines than for the wild-type(WT)controls at the germination and seedling stages.Additionally,the transgenic plants exhibited enhanced photosynthetic efficiency at the seedling stage.In irrigated and non-irrigated fields,the four transgenic lines grew normally,but with increased ear weight and yield compared with the WT plants.Moreover,the ear weight and yield of the transgenic hybrids resulting from the PH4CV-T×PH6WC-W and Chang7-2-T×Zheng58-W crosses increased in the non-irrigated field.Our results demonstrated that the growth and drought tolerance of four transgenic inbred maize lines with improved photosynthesis were enhanced by the overexpression of ZmVPP1.Moreover,the Chang7-2 and PH4CV transgenic lines may be useful for future genetic improvements of maize hybrids to increase drought tolerance.

Genetic Diversity for Yield and Yield Contributing Characters of Short Statured Maize Inbred Lines

Genetic diversity is one of the useful tools to select appropriate lines for hybridization. Twenty short-statured maize inbred lines were taken for present study, which were collected from CIMMYT India and Mexico through Plant Breeding Division, Bangladesh Agricultural Research Institute (BARI), Gazipur. This experiment was conducted from November 2015 to April 2016 to identify parental lines to produce single cross short statured maize hybrids. From the genetic diversity studies, the importance of both additive and non-additive gene actions for the expression of yield and yield contributing characters were found. Values of vector I and II revealed that both the vectors had positive values for date of silking, plant height, rows/cob, grains/row and yield. These results indicated that these five characters had highest contribution towards divergence. Based on the relative magnitude of D2 values;20 inbred lines were grouped into five clusters. Seven inbred lines were selected on the basis of genetic diversity and per se performance which will be crossed separately in a half-diallel fashion to develop hybrids.

Analysis on Breeding Potential of 17 Maize Inbred Lines from Land Races

[Objective] The primary objective of this study was to estimate combining ability and genetic parameters of 17 new inbred lines.[Method] By using 11 commonly used maize inbred lines from Southwest China as testers and incomplete diallel cross design,combining ability and heterosis of 17 new inbred lines bred from the land races in Sichuan Basin and its surrounding areas were analyzed.In addition,the genetic parameters and heterotic groups were also investigated based on combining ability.[Result] P1-1,P1-16 and P1-14 with the better comprehensive characters can be directly used in maize breeding program.The SCA of P1-10×P2-4 was high in most traits.It is more possible to obtain high-yield hybrid combinations by the pattern Sipingtou × Lancaster.GCA variance was bigger than SCA variance in four traits such as rows per ear,grains per row,which were affected by the environments slightly and should be selected at early generations;while SCA variance was bigger than GCA variance in five traits such as 100-grain weight and plant weight,which were significantly influenced by environment and thus should be selected in later generations.[Conclusion] The paper will provide theoretical basis for further improvement of local maize varieties.

Evaluation of maize inbred lines for resistance to pre-harvest aflatoxin and fumonisin contamination in the field

Two important mycotoxins, aflatoxin and fumonisin, are among the most potent naturally occurring carcinogens, contaminating maize(Zea mays) and affecting crop yield and quality.Resistance of maize to pre-harvest mycotoxin contamination, specifically aflatoxin produced by Aspergillus flavus and fumonisin produced by Fusarium verticillioides, is a goal in breeding programs that screen for these important traits with the aim of developing resistant commercial hybrids. We conducted two years of field evaluations on 87 inbred lines originating primarily in China and Mexico and not previously screened for resistance.The objectives of our study were to identify resistant germplasm for breeding purposes and to examine possible relationships between resistances to the two mycotoxins. Aflatoxin and fumonisin were present in samples harvested from all lines in both years.Concentrations of total aflatoxin ranged from 52.00 ± 20.00 to 1524.00 ± 396.00 μg kg^(-1),while those of fumonisin ranged from 0.60 ± 0.06 to 124.00 ± 19.50 mg kg^(-1). The inbred lines TUN15, TUN61, TUN37, CY2, and TUN49 showed the lowest aflatoxin accumulation and CN1, GT601, TUN09, TUN61, and MP717 the lowest fumonisin accumulation. TUN61 showed the lowest accumulation of both mycotoxins. This study confirmed previous observations that high levels of aflatoxin can coexist with fumonisin, with 55 maize lines showing a positive correlation coefficient between the concentrations of aflatoxin and fumonisin and 32 lines showing a negative correlation coefficient. These selected lines,particularly TUN61, may provide sources of resistance to mycotoxin contamination in breeding programs. However, the mechanism of resistance in this germplasm remains to be identified. Future research should also address factors that influence the fungus–plant interaction, such as herbivory and environmental stress.

Identification of QTLs for Blast, Bacterial Blight, and Planthopper Resistance Using SNP-Based Linkage Maps from Two Recombinant Inbred Rice Lines

Rice is the most significant global food security. Several biotic factors limit rice production, breeding biotic-resistant rice has, therefore, become an increasingly important goal. Two elite rice lines, IR71033-121-15 (IR71033) and IR57514-PMI-5-B-1-2 (IR57514), provide potential genes for biotic stress resistance traits. In this study, genotyping by sequencing (GBS) for single nucleotide polymorphism (SNP)-based linkage map construction was used to detect quantitative trait loci (QTLs) for blast (BL), bacterial blight (BB), whitebacked planthopper (WBPH), and brown planthopper (BPH) resistance. IR71033 was derived from Oryza minuta and carried BL, BB, WBPH, and BPH resistance QTLs. IR57514 is a well-adapted rainfed lowland line that carries BL and BB resistance QTLs. Two sets of recombinant inbred line (RIL) populations derived from crosses of KDML105 × IR71033 and KDML105 × IR57514 were used to dissect the genetic basis of disease and insect pest resistance. The RIL populations were evaluated for BL, BB, WBPH, and BPH resistance from 2016 to 2018 at four rice research centers in Thailand. From these, we identified a large number of SNPs through GBS and constructed high-resolution linkage maps. By combining phenotypic evaluation with the GBS data, a total of 24 QTLs on four chromosomes were detected that confered pest resistance and explained 7.3% - 61.4% of the phenotypic variance. These findings should facilitate identifying novel resistance genes and applying marker-assisted selection for resistance to the four major rice pests investigated here. These strategies will improve the resilience and reliability of rice varieties adapted to the low-yielding environment of rainfed lowland areas worldwide.

Factors influencing seed reserve utilization during seedling establishment in maize inbred lines

Strong seedlings are essential for high yield.To explore the foundation of strong seedlings,we investigated various factors influencing the conversion and distribution of seed storage reserves during seedling establishment in maize inbred lines.Three maize inbred lines were used to explore the effects of seed size,seed vigor,illumination duration,temperature,water content,and salt concentration of the seedling medium on the utilization of seed storage reserves during seedling establishment.The results showed that the conversion rate of small seeds was 3.69 to 17.71%higher than that of large seeds.Moreover,prolonged illumination time was conducive to the formation of strong seedlings.However,low temperature,drought stress and salt stress reduced the conversion rate of seed storage reserves and increased the root/shoot ratio.These results could be used to guide field management during seedling emergence and develop improved germplasm with a high conversion rate of seed storage reserves.

Genetic Diversity Analysis of 13 Maize Inbred Lines by SSR Molecular Markers

This paper used SSR molecular markers to perform the genetic diversity analysis on 13 ordinary inbred lines of maize of different sources in order to divide heterotic groups of maize inbred line and predict heterosis. Using 12 pairs of SSR primers,a total of 47 allelic variants were detected in 13 inbred lines,2-5 alleles were detected for each pair of primers,an average of 3. 9,and polymorphism information content varied from 0. 379 to 0. 828. According to the cluster analysis,the 13 inbred lines could be divided into 5 groups.

Comparative evaluation of maize inbred lines (zea mays l.) according to dus testing using morphological, physiological and molecular markers

A major challenge facing those involved in the testing of new plant varieties for Distinctness, Uniformity and Stability (DUS) is the need to compare them against all those of 'common knowledge'. A set of maize inbred lines was used to compare how morphological, physiological characterization and RAPD molecular marker described variety relationships. All the inbred lines were confirmed as morphologically and physiologically distinct. At morphological level the maximum genetic distance (10.8) and least genetic distance (1.6) were found. For physiological characters distance varied from 0.35 to 1.92 and results from dendrogram, which was made on the basis of dissimilarity matrix, were grouped into five major clusters. From RAPD, random primers provide polymorphic amplification products;the distance varying 0.42 to 0.65 and dendrogram showed that these lines formed close clusters due to the less variation in these lines at molecular level. In the present study, the molecular markers also exposed useful genetic diversity and the visual displays appeared to disperse the lines somewhat more evenly over the plot than the morphological and physiological methods.

Application of Genetic Rules of Quality Traits in the Selection of Watermelon Inbred Lines

On the basis of ascertaining the dominant and recessive relationship and separation ratio of quality traits such as leaf type and peel stripes,the separation of dominant and recessive traits was studied to infer whether the genes of the previous generation were homozygous.Individuals with homozygous recessive traits can be confirmed in F2 generation,and homozygous single lines with dominant traits can be confirmed in F3 generation,which speeds up the breeding process of watermelon inbred lines.