Pairs Of Isogenic Lines Research Articles

Genetic diversity analysis in Bt introgressed and non-Bt lines of upland cotton (Gossypium hirsutum L.)

Diversity analysis of Bt lines, a prerequisite to heterosis breeding, are rarely published. Diversity analysis of 140 cotton genotypes comprising of BGI, BGII and Non-Bt lines resulted in the grouping of genotypes into 20 clusters among which five had multiple genotypes and 15 others were solitary. Specific clustering of genotypes of BGI and BGII was not observed which got distributed across the clusters. The maximum and minimum inter-cluster distances were observed between two solitary clusters XVI and XVIII (159.8) as well as clusters VII and XI (6.4), respectively, reflecting diverse and close relationship among the Bt genotypes of those clusters. Two pairs of isogenic lines were located in the same clusters as they shared the same genetic background. The genetic background played important role in the diversity rather than the Bt status of genotype. Also, the maximum genetic diversity (64%) was arising from traits which were not related to Bt genes such as plant height, boll weight, and ginning out-turn when compared to the characters related to Bt gnes such as seed cotton yield and boll number (33%). In general, for seed cotton yield, BGI outperformed BGII lines. The study helped in developing high yielding hybrids through diverse parental line selections. Key words: Bt cotton, Genetic diversity, Introgression, D2 analysis

Yield and Quality in Purple-Grained Wheat Isogenic Lines

Breeding programs for purple wheat are underway in many countries but there is a lack of information on the effects of Pp (purple pericarp) genes on agronomic and quality traits in variable environments and along the product chain (grain-flour-bread). This study was based on unique material: two pairs of isogenic lines in a spring wheat cv. Saratovskaya-29 (S29) background differing only in Pp genes and grain color. In 2017, seven experiments were conducted in Kazakhstan, Russia, and Turkey with a focus on genotype and environment interaction and, in 2018, one experiment in Turkey with a focus on grain, flour, and bread quality. The effect of environment was greater compared to genotype for the productivity and quality traits studied. Nevertheless, several important traits, such as grain color and anthocyanin content, are closely controlled by genotype, offering the opportunity for selection. Phenolic content in purple-grained lines was not significantly higher in whole wheat flour than in red-colored lines. However, this trait was significantly higher in bread. For antioxidant activities, no differences between the genotypes were detected in both experiments. Comparison of two sources of Pp genes demonstrated that the lines originating from cv. Purple Feed had substantially improved productivity and quality traits compared to those from cv. Purple.

Development of Molecular Markers Linked to Powdery Mildew Resistance Gene Pm4b by Combining SNP Discovery from Transcriptome Sequencing Data with Bulked Segregant Analysis (BSR-Seq) in Wheat.

Powdery mildew resistance gene Pm4b, originating from Triticum persicum, is effective against the prevalent Blumeria graminis f. sp. tritici (Bgt) isolates from certain regions of wheat production in China. The lack of tightly linked molecular markers with the target gene prevents the precise identification of Pm4b during the application of molecular marker-assisted selection (MAS). The strategy that combines the RNA-Seq technique and the bulked segregant analysis (BSR-Seq) was applied in an F2:3 mapping population (237 families) derived from a pair of isogenic lines VPM1/7∗Bainong 3217 F4 (carrying Pm4b) and Bainong 3217 to develop more closely linked molecular markers. RNA-Seq analysis of the two phenotypically contrasting RNA bulks prepared from the representative F2:3 families generated 20,745,939 and 25,867,480 high-quality read pairs, and 82.8 and 80.2% of them were uniquely mapped to the wheat whole genome draft assembly for the resistant and susceptible RNA bulks, respectively. Variant calling identified 283,866 raw single nucleotide polymorphisms (SNPs) and InDels between the two bulks. The SNPs that were closely associated with the powdery mildew resistance were concentrated on chromosome 2AL. Among the 84 variants that were potentially associated with the disease resistance trait, 46 variants were enriched in an about 25 Mb region at the distal end of chromosome arm 2AL. Four Pm4b-linked SNP markers were developed from these variants. Based on the sequences of Chinese Spring where these polymorphic SNPs were located, 98 SSR primer pairs were designed to develop distal markers flanking the Pm4b gene. Three SSR markers, Xics13, Xics43, and Xics76, were incorporated in the new genetic linkage map, which located Pm4b in a 3.0 cM genetic interval spanning a 6.7 Mb physical genomic region. This region had a collinear relationship with Brachypodium distachyon chromosome 5, rice chromosome 4, and sorghum chromosome 6. Seven genes associated with disease resistance were predicted in this collinear genomic region, which included C2 domain protein, peroxidase activity protein, protein kinases of PKc_like super family, Mlo family protein, and catalytic domain of the serine/threonine kinases (STKc_IRAK like super family). The markers developed in the present study facilitate identification of Pm4b during its MAS practice.

Low validation rate of quantitative trait loci for Gibberella ear rot resistance in European maize.

Six quantitative trait loci (QTL) for Gibberella ear rot resistance in maize were tested in two different genetic backgrounds; three QTL displayed an effect in few near isogenic line pairs. Few quantitative trait loci (QTL) mapping studies for Gibberella ear rot (GER) have been conducted, but no QTL have been verified so far. QTL validation is prudent before their implementation into marker-assisted selection (MAS) programs. Our objectives were to (1) validate six QTL for GER resistance, (2) evaluate the QTL across two genetic backgrounds, (3) investigate the genetic background outside the targeted introgressions. Pairs of near isogenic lines (NILs) segregating for a single QTL (Qger1, Qger2, Qger10, Qger13, Qger16, or Qger21) were developed by recurrent backcross until generation BC3S2. Donor parents (DP) carrying QTL were backcrossed to a susceptible (UH009) and a moderately resistant (UH007) recurrent parent. MAS was performed using five SNP markers covering a region of 40cM around each QTL. All NILs were genotyped with the MaizeSNP50 assay and phenotyped for GER severity and deoxynivalenol and zearalenone content. Traits were significantly (P<0.001) intercorrelated. Out of 34 NIL pairs with the UH009 genetic background, three pairs showed significant differences in at least one trait for three QTL (Qger1, Qger2, Qger13). Out of 25 NIL pairs with the UH007 genetic background, five pairs showed significant differences in at least one trait for two QTL (Qger2, Qger21). However, Qger16, Qger10 and Qger13 were most likely false positives. The genetic background possibly affected NIL pairs comparisons due to linkage drag and/or epistasis with residual loci from the DP in non-target regions. In conclusion, validation rates were disappointingly low, which further indicates that GER resistance is controlled by many low-effect QTL.

Pollen–pistil interaction, pistil histology and seed production in A×B grain sorghum crosses under chilling field temperatures

SUMMARYSix pairs of isogenic lines of sorghum (Sorghum bicolor L. Moench) were sown in field plots in Montecillo, State of México (2240 m altitude), in 2005 and 2006. Crosses A (♀)×B (♂) were done in each pair. In A-lines, the length of pistil, stigma, style and ovary, as well as the ovary width, were measured. In B-lines, pollen diameter, viability (cytoplasm density) and production were evaluated. Pollen germination and pollen tube growth in the pistils of the A-lines, were quantified in vivo with aniline blue and epifluorescence 18 h after pollination (HAP), while fertilized pistils were counted at 96 HAP. Histological studies on both pollinated and non-pollinated pistils were performed in one male-sterile line. Seed yield, mean-seed weight, seeds per panicle and seed set (SS; seeds/flower/panicle) were determined at harvest. Pollen viability was the variable most related to pollen germination and pollen tube growth. Stigma receptivity was not associated with its morphology. Growth of the pollen tube in stigma, style and ovary was observed in the transmitting tissue 18 HAP, running parallel to the vascular tissue. Yield under chilling field temperatures (minimum average of 6 and 8°C) prevailing during flower development and pollination ranged from 7 to 12 g/panicle. The differences in seed production and SS among A×B crosses did not depend on the amount and viability of pollen.

Registration of Five Wheat Isogenic Lines for Leaf Rust and Stripe Rust Resistance Genes

Registration of Five Wheat Isogenic Lines for Leaf Rust and Stripe Rust Resistance Genes

Field assay of seedling and adult-plant resistance to southern leaf blight in maize

Resistance to southern corn leaf blight is under the control of a single recessive allele, rhm, and can be scored from lesion number, size, type and sporulation in the lesion, which are best expressed by plants growing under field conditions, although resistance also can be measured at the seedling stage. An assay procedure that can unequivocally score disease severity from the seedling stage to post-flowering in the field is desirable. We analysed pairs of isogenic lines H95/H95rhm and B73/B73Htrhm, the F 2 population of H95 × H95rhm consisting of a total of 687 individuals, and 120 F 3 families, which were inoculated with conidia of Bipolaris maydis race O. The disease ratings were also studied together with the segregation scores of a single copy DNA probe, agrP144. Among 687 F 2 plants derived from the cross H95 × H95rhm, 161 plants were rated as resistant and 526 susceptible, suggesting a 1: 3 ratio. Among the 120 F 3 families, there were 32 susceptible, 58 segregating and 30 resistant rows, fitting the expected 1: 2: 1 ratio for a single gene model. Using agrP144 as a marker, 99.5% restriction fragment length polymorphism (RFLP) allelic segregation scores corresponded to the disease ratings obtained from field data, indicating that the marker agrP144 is tightly linked to the rhm locus. Similarly, the amplified fragment length polymorphism (AFLP) marker p7m36 also is closely linked to the locus but on the opposite side of the marker agrP144.

Spontaneous Brassinolide-insensitive Barley Mutants &amp;lsquo;&lt;i&gt;uzu&lt;/i&gt;&amp;rsquo; Adapted to East Asia

The uzu gene shows typical semi-dwarf plant type and has resulted in lodging resistance and improved canopy structure in barley (Hordeum vulgare L.). The geographic distribution of ‘uzu’ lines is limited in East Asia including Japan, Korean peninsula and China. For many years, majority of cultivated six-rowed barley varieties in southern Japan were ‘uzu’ type. Inheritance of the uzu gene, located on chromosome 3H, is monogenic recessive and the expression is pleiotropic during developmental process. In cereal crop plants, several semi-dwarf genes have been widely used in breeding programs to increase productivity and it is known that several of these semi-dwarf genes were derived from gibberellin (GA)-related mutations. The barley dwarfing gene uzu is independent to GA. This characteristics are known earlier. In this study, we characterized uzu gene in molecular aspects. As the result of comprehensive study using several pairs of isogenic lines, we found the morphological and physiological similarities of barley uzu gene to rice dwarf mutant, d61. D61 encodes OsBRI1, which is homologous gene for Brassinosteroid insensitive 1 in Arabidopsis. We also found that ‘uzu’ lines specific single nucleotide polymorphism (SNP) contributed for amino acid substitution in barley homologous sequence of OsBRI1, HvBRI1. Linkage analysis using a segregating population for uzu showed the co-segregation between uzu and HvBRI1. Furthermore, as the results of derived cleaved amplified polymorphic sequences (dCAPS) marker analysis using more than 260 ‘uzu’ landraces and the genomic sequencing analysis of HvBRI1 gene derived from 19 barley accessions, all the ‘uzu’ lines investigated in this study had the same SNP in putative kinase domain of HvBRI1. On the basis of these findings, we discussed the phylogeny of ‘uzu’ landraces in East Asia.

Phenotypic effect of substitutions of short chromosomal segments containing different alleles of histone HI genes in garden pea (Pisum sativum L.)

SummaryA hypothesis has been tested that alterations in the molecule of histone H1 are capable of influencing quantitative traits of an organism. Two pairs of isogenic lines were constructed by selfing of plants kept heterozygous either for allelic variants of histone H1 subtype 1 (His1 gene) or for allelic combinations (haplotypes) of closely linked genes of H1 subtypes 3, 4, 5 and 6 (gene clusterHis(2–6)). After 19 and 15 generations of selfing, respectively, expectation of the length of chromosome which remained heterozygous has comprised 2·6 cM nearHisl and 3·5 cM nearHis(2–6). The third pair of isogenic lines was obtained as a result of two successive intracluster cross-over events bordering the gene of the subtype 5 (His5). In each pair of isogenic lines there have been revealed some statistically significant differences between mean values of a number of quantitative traits.

Role of gravitropic response in the dry matter production of rice (Oryza sativa L.): An experiment with a line having lazy gene

Role of gravitropic response in the dry matter production was explored using a near isogenic line pair of rice; Kamenoo and lazy-Kamenoo. Productive structures were quite different in plant with a lazy gene, lazy-Kamenoo from in Kamenoo. Heads were oriented in the surface of canopy in Kamenoo, while they distributed in all zones from the soil surface to the top of canopy in lazy-Kamenoo. The value of SLA, ratio of leaf area to leaf weight, was the same at the early stage of growth between Kamenoo and lazy-Kamenoo. However the value rapidly decreased in lazy-Kamenoo indicating that the thickness of leaves increased more rapidly with the advance of growth in plants with the lazy-gene. Tiller shoots of lazy-Kamenoo, showed prostrate or spreading growth pattern. This is probably due to the inability or reduced responsibility to gravity since they showed only reduced response to gravistimulation in 12-and 13-leaf stage and almost no response was detected in 14-leaf stage. On the other hand, Kamenoo well responded to gravistimulation in all growth stages tested. Thus, the difference in productive structure in two near isogenic lines was explained, at least in part, by their difference in gravitropic response.

Causal Analysis of the Difference in Crude Protein Content of Barley Kernels between Two-rowed and Six-rowed Forms

TAKAHASHI, HAYASHI and MORIYA (1975) have demonstrated in their studies with a large number of V-v isogenic line pairs that the two-rowed strains were about two percent higher in general in crude protein content of the grain than the corresponding six-rowed strains. This study was planned to approach the underlying cause of the difference in crude protein content (%) between two types of isolines. In the first experiment change of crude protein content with the progress of the kernel growth was investigated using a six-rowed late cultivar (Kikai Hadaka) and a two-rowed early cultivar (Seijo 17). Seed samples were taken from 17 days after anthesis to maturity at 6-day intervals. The result indicated that percentage of crude protein accumulated in the kernels was not so much different between varieties at any stage of kernel growth (Fig. 1). Next, crude protein content of the central and lateral kernels was compared in the second experiment with three six-rowed varieties, which showed no appriciable difference existing between central and lateral kernels (Table 2). Finally, effects of removing lateral kernels of six-rowed strain at different times of kernel growth on final protein content of central kernel was studied in the third experiment. Three pairs of V-v isogenic paired lines (KA-26, KT-16 and GT-17) which had been produced by TAKAHASHI et al. were used. The removal of lateral kernels was made firstly on one or two days before anthesis, and repeated five times at 5-day intervals after anthesis (from 5th to 25th days). In KA-26 and KT-16, one-half of the spikes within plant was used for treatment and remaining half for untreated control. In GT-17, treatment was made within population regardless of the plant. The removal of lateral kernels resulted generally in an increase in crude protein content of remaining central kernels, and the increasing effect of the removal was most evident when the treatment was made before anthesis (Figs. 2 and 3). However, the increase of crude protein content became smaller and smaller with the later date of the treatment, and the treated spikes reached the same crude protein percent as the intact plot on 25th day after anthesis. Removal of laterals affected a little on 1000 kernel weight. From this study, the cause of difference of protein content between two-rowed and six-rowed isolines may be explained as follows : Protein is mainly synthesized in leaves from nitrogen absorbed from the roots, and is distributed almost uniformely to central and lateral kernels in intact six-rowed spike. But when lateral kernels have been removed from the spike, the protein which ought to be allotted to the lateral kernels will be distributed to and accumulated excessively in the central kernels. Consequently, if so-called source size is not different between two-rowed and six-rowed types, crude protein percent of the kernels will be higher in two-rowed type with small size of so-called sink than those of six-rowed ones.

EFFECT OF UZU (UZ) GENE ON THE LEVEL OF ENDOGENOUS GIBBERELLINS IN BARLEY

A near isogenic line pair which differs only in the Uz and uz alleles was used for investigating the effect of uzu (uz) gene on the level of endogenous gibberellins in barley. Amounts of endogenous gibberellins in uzu plants were found to decrease in about a half to that of nami (normal) plants. Application of gibberellin A3 to uzu plants stimulated seedling growth and that of 2-chloroethyl trimethylammonium chloride, an inhibitor of gibberellin biosynthesis, to corresponding normal (nami) plants reduced both of stem length and endogenous gibberellin production.

Weight Gain of Cereal Leaf Beetle Larvae on Normal and Induced Leaf Pubescence1

Seeds of wheat (Triticum aestivum L.) germinated and grown in closed petri dishes consistently produced leaves with more pubescence than those grown under natural conditions. Weight gain and percent survival of freshly emerged cereal leaf beetle larvae were measured on seedling plants with increased amounts of pubescence and control plants with normal pubescence.Larval weight gain on plants of cultivars susceptible and resistant to the cereal leaf beetle with increased densities of pubescence were significantly lower than the weight gain of larvae grown on control plants. These results make it possible to examine the contribution of pubescence to resistance within a single genotype in a manner similar to those comparisons in which pairs of isogenic lines are used.

Isogenic Analysis of Strontium‐89 Accumulation in Barley1

The effect of short segments of chromosomes on Sr‐89 accumulation in barley, Hordeum vulgate L., was studied by comparing Sr‐89 accumulation in pairs of isogenic lines. The members of each isogenic pair differed by segments of chromosome estimated to be less than 6 recombination units in length.Six of the 11 chremosome segments studied influenced Sr‐89 accumulation in grain, stems, or leaves of mature plants or in shoots of seedling plants. In three of the segments the marker gene that served to identify the segment appeared to effect the differential accumulation of Sr‐89. The three genes were those that control hoods vs. awns, long vs. short awn, and naked vs. covered caryopsis. In addition, the chromosome segments identified by the genes controlling two vs. six rows of kernels, black vs. white lemma and pericarp, and purple vs. nonpurple lemma and pericarp had a significant effect on Sr‐89 accumulation.The study leads to the conclusion that the genetic basis for differences in Sr‐89 accumulation involves a number of genes and is highly dependent on the genetic stocks involved.