F2 Plants Research Articles

Identification of novel sex determination loci in Japanese weedy melon

Japanese weedy melon exhibits unique sex expression with interactions between previously reported sex determination genes and two novel loci. Sex expression contributes to fruit quality and yield in the Cucurbitaceae. In melon, orchestrated regulation by sex determination genes explains the mechanism of sex expression, resulting in a great variety of sexual morphologies. In this study, we examined the Japanese weedy melon UT1, which does not follow the reported model of sex expression. We conducted QTL analysis using F2 plants for flower sex on the main stem and the lateral branch and mapped "occurrence of pistil-bearing flower on the main stem" locus on Chr. 3 (Opbf3.1) and "type of pistil-bearing flower" (female or bisexual) loci on Chr. 2 (tpbf2.1) and Chr. 8 (tpbf8.1). The Opbf3.1 included the known sex determination gene CmACS11. Sequence comparison of CmACS11 between parental lines revealed three nonsynonymous SNPs. A CAPS marker developed from one of the SNPs was closely linked to the occurrence of pistil-bearing flowers on the main stem in two F2 populations with different genetic backgrounds. The UT1 allele on Opbf3.1 was dominant in F1 lines from crosses between UT1 and diverse cultivars and breeding lines. This study suggests that Opbf3.1 and tpbf8.1 may promote the development of pistil and stamen primordia by inhibiting CmWIP1 and CmACS-7 functions, respectively, making the UT1 plants hermaphrodite. The results of this study provide new insights into the molecular mechanisms of sex determination in melons and considerations for the application of femaleness in melon breeding.

On the causes of gene-body methylation variation in Arabidopsis thaliana.

Gene-body methylation (gbM) refers to sparse CG methylation of coding regions, which is especially prominent in evolutionarily conserved house-keeping genes. It is found in both plants and animals, but is directly and stably (epigenetically) inherited over multiple generations in the former. Studies in Arabidopsis thaliana have demonstrated that plants originating from different parts of the world exhibit genome-wide differences in gbM, which could reflect direct selection on gbM, but which could also reflect an epigenetic memory of ancestral genetic and/or environmental factors. Here we look for evidence of such factors in F2 plants resulting from a cross between a southern Swedish line with low gbM and a northern Swedish line with high gbM, grown at two different temperatures. Using bisulfite-sequencing data with nucleotide-level resolution on hundreds of individuals, we confirm that CG sites are either methylated (nearly 100% methylation across sampled cells) or unmethylated (approximately 0% methylation across sampled cells), and show that the higher level of gbM in the northern line is due to more sites being methylated. Furthermore, methylation variants almost always show Mendelian segregation, consistent with their being directly and stably inherited through meiosis. To explore how the differences between the parental lines could have arisen, we focused on somatic deviations from the inherited state, distinguishing between gains (relative to the inherited 0% methylation) and losses (relative to the inherited 100% methylation) at each site in the F2 generation. We demonstrate that deviations predominantly affect sites that differ between the parental lines, consistent with these sites being more mutable. Gains and losses behave very differently in terms of the genomic distribution, and are influenced by the local chromatin state. We find clear evidence for different trans-acting genetic polymorphism affecting gains and losses, with those affecting gains showing strong environmental interactions (G×E). Direct effects of the environment were minimal. In conclusion, we show that genetic and environmental factors can change gbM at a cellular level, and hypothesize that these factors can also lead to transgenerational differences between individuals via the inclusion of such changes in the zygote. If true, this could explain genographic pattern of gbM with selection, and would cast doubt on estimates of epimutation rates from inbred lines in constant environments.

Assessment of parental lines, F1 and F2 sunflower hybrids to Septoria leaf spot infection and some inheritance patterns

Abstract The foliar fungal disease Septoria leaf spot is economically important for sunflowers. It develops most intensively during the wet and warm season. However, the genetic nature of sunflower resistance to Septoria leaf spot is still not clear. The purpose of our work was to identify some inheritance patterns of sunflower resistance to this disease based on the assessment of lines and hybrids of the first and second generations. The studied material was sown in 2020 and 2021 and subsequently grown on a stationary artificial infectious plot enriched with Septoria helianthi pathogen. The frequency of infection and the severity of infection of each sample were taken into account. The two-factor variance analysis revealed a significant influence of genotype on the frequency of infection in six sunflower lines and confirmed the effect of individuality of the response of individual genotypes to disease damage. It was shown that about 65 % of the total variation of the trait is due to the genetic nature of the line, and only a little more than 20 % and about 11 % – to the influence of the environment and the “genotype × environment” interaction respectively. Based on disease damage data in 2020 and 2021, the lines were classified as susceptible, moderately susceptible, moderately resistant and resistant. Differentiation of lines according to sensitivity to Septoria leaf spot made it possible to obtain hybrids with different manifestations of the trait in their parents. The nature of inheritance of infection frequency in F1 sunflower hybrids was determined by the degree of dominance. As a result, it was revealed intermediate inheritance, as well as positive and negative overdominance of the trait. The severity of infection by S. helianthi pathogen in F1 hybrids was inherited according to the type of parental form with greater resistance to the disease. F2 populations were found to inherit infection frequency from the more resistant parent, showing a proportion of infected plants similar to that of the more resistant line from a given cross combination. It has been shown that the frequency of infection of the F2 population with Septoria leaf spot can be affected by the severity of infection of F1 plant with the pathogen S. helianthi.

Don't panic any more: MORE PANICLES 3 increases rice yield at elevated CO2 levels.

Don't panic any more: MORE PANICLES 3 increases rice yield at elevated CO2 levels.

Mapping and characterization of the recessive leaf rust resistance gene Lr83 on wheat chromosome arm 1DS

The leaf rust resistance gene in Thatcher wheat derivative 78-1 was mapped to chromosome 1DS with SNP markers and designated as Lr83. 'Thatcher' wheat near isogenic line RL6149, a putative derivative of Triticum dicoccoides, was previously determined to carry leaf rust resistance gene Lr64 on chromosome arm 6AL and a second gene temporarily named LrX on chromosome arm 1DS. The objective of this study was to map and characterize LrX in a population of recombinant inbred lines (RILs) that segregated for a single gene. Thatcher line 78-1 with LrX was crossed with Thatcher and individual F2 seedlings and F6 RILs were evaluated for leaf rust response. The 208 F2 plants segregated for a single recessive gene and 148 F6 lines for a single gene. The RILs and parents were characterized by genotyping by sequencing (GBS). Six GBS markers and five Kompetitive Allele-Specific PCR (KASP) markers were used to map LrX on the distal region of chromosome arm 1DS. LrX was 1 centiMorgan (cM) proximal to marker K-IWB38437 and 0.4cM distal to GBS marker 1D_9037138. Line 78-1 was crossed with Thatcher wheat lines with Lr21, Lr42, and Lr60 for allelism tests. LrX mapped 19.49cM from Lr21 and 11.93cM from Lr42. In the cross of line 78-1 with the Thatcher line with Lr60, one recombinant in 1,003 F2 plants was found. LrX and Lr60 are at tightly linked loci on the distal region of chromosome arm 1DS. The gene in line 78-1 was designated as Lr83. Cytological examination of RL6149 provided no evidence of transfer of a chromosome segment of an A- or B-genome chromosome to chromosome 1D.

Mapping a leaf rust resistance gene LrOft in durum wheat Ofanto and its suppressor SuLrOft in common wheat.

Epidemics of leaf rust (caused by the fungal pathogen Puccinia triticina Erikss., Pt) raise concerns regarding sustainability of wheat production. Deployment of resistant cultivars is the most effective and economic strategy for combating this disease. Ofanto is a durum wheat cultivar that exhibits high resistance to Pt race PHT throughout its entire growing period. In the present study, we identified a leaf rust resistance gene in Ofanto and temporarily designated it as LrOft. LrOft was mapped to a 2.5 cM genetic interval in chromosome arm 6BL between Indel markers 6B6941 and 6B50L24. During introgression of LrOft from Ofanto to common wheat it was observed that F1 plants of Ofanto crossed with Shi4185 exhibited leaf rust resistance whereas the F1 of Ofanto crossed with ND4503 was susceptible. In order to map the presumed suppressor locus, a Shi4185/ND4503//Ofanto three-way pentaploid population was generated and SuLrOft was mapped on chromosome arm 2AS. SuLrOft was mapped within a 2.6 cM genetic interval flanked by 2AS50L14 and 2AS50L6. Fine mapping using 2,268 plants of the three-way cross narrowed the suppressor locus to a 68.2-kbp physical interval according to IWGSC RefSeq v1.1. Sequence analysis of genes in the physical interval revealed that TraesCS2A02G110800 encoding an RPP-13-like protein with an NB-ARC domain was a potential candidate for SuLrOft.

Molecular Screening and Agronomic Trait Characterization of NLR 34449 X ISM Derived Population for their resistance against Bacterial Blight Disease

Bacterial Blight (BB) disease caused by Xanthomonas oryzae pv. oryzae (Xoo) is a major limiting factor amongst the diseases of rice in India. NLR34449 is a very popular high yielding variety. It is a popular variety not only in Andhra Pradesh but also in the neighbouring states of South India, but highly susceptible to the bacterial blight disease. A total of 802 BC1 F2 plants derived from the cross NLR 34449 and ISM were phenotypically screened for bacterial blight resistance, 687 were found to be resistant to BB. Genotyping of these plants revealed ten homozygous positive plants for all the three target BB genes viz., Xa21, xa13 and xa5. They were further assessed for key agro-morphological traits. viz., Days to 50% flowering, plant height, number of panicles per plant, thousand grain weight and grain yield per plant. Almost all the traits exhibited variation for key agronomic traits and among them, five plants were found to be performing well not only for bacterial blight resistance but also found to be superior in terms of key agronomic traits like thousand grain weight and single plant yield and flowered earlier than the parents as well. These identified plants will be advanced for further evaluation.

Multivariate Assessment of Genetic Relationships between Two Streptocarpus Cultivars and Their F1 Progenies Using Morphological Characteristics and SCoT Molecular Markers

Streptocarpus is a very popular houseplant with colorful flowers, and has thus piqued the curiosity of plant enthusiasts and breeders. In this study, “Natalie” and “Bristol’s Gum Drop” were artificially hybridized to study the influence of the parental reciprocal crosses (P1×P2 and P2×P1) on vegetative and generative morphological traits of F1 progeny. Mean comparisons for morphological characters of parents and F1 plants from both crosses revealed that F1 plants were able to express hybrid vigor for several valuable morphological characteristics. Pearson correlations showed both significant negative and positive correlations between morphological traits of F1 plants from P1×P2 cross, while in the case of P2×P1 no significant negative correlations were observed (p < 0.05). The Start Codon Targeted (SCoT) genetic profiles of the F1 plants with the identifiers P1×P2.19 and P1×P2.35 were remarkably similar, and they grouped with the maternal parent in a small group, supporting the findings of clustering based on morphological data. The parental combination P2×P1 revealed the presence of closely related progenies to the paternal parent, namely P2×P1.16 and P2×P1.5. Two F1 plants named P1×P2.33 and P2×P1.21 were selected based on their phenotypic characteristics and SCoT molecular fingerprinting. These selected genotypes will be tested in our future breeding programs with the aim to create and promote new valuable Streptocarpus cultivars.

Fine mapping of KLW1 that conditions kernel weight mainly through regulating kernel length in wheat (Triticum aestivum L.).

KLW1 was localized to a 0.6 cM interval near the centromere of chromosome 4B and found to be dominant in conditioning longer kernels and higher kernel weight. Kernel weight is a major wheat yield component and affected by kernel dimensions, filling process and kernel density. Because of this complexity, the mechanism underlying kernel weight is still far from clear. Qtgw.nau-4B or KLW1 was a major kernel weight QTL identified in the Nanda2419 × Wangshuibai population. We showed that introduction of the Nanda2419 allele into elite cultivar Wenmai6 resulted in longer kernels as well as higher kernel weight, without affecting other traits such as spike number per plant, plant height, spike length, spikelet number per spike, and kernel number per spike. KLW1 was dominant in conditioning higher kernel weight and functioned mainly through affecting kernel length. Using F2 plants derived from KLW1 NIL, a high-density genetic map covering the QTL was constructed. KLW1 was consequently confined to the 0.6cM Xwgrc4219-Xwgrc4067 interval by evaluating the recombinant lines in three field trials. KLW1 is complementary to KT1, the QTL on chromosome 5A of Nanda2419 for thicker and heavier kernels, in producing larger kernels with higher commercial value, augmenting its usefulness in wheat breeding.

Integrated analysis of biparental and natural populations reveals CRIB domain-containing protein underlying seed coat crack trait in watermelon.

The scc locus of the watermelon seed coat crack trait was fine mapped on chromosome 3. Cla97C03G056110 (annotated as CRIB domain-containing protein) was regarded as the most likely candidate gene Seed coat crack (scc) is a special characteristic of watermelon compared with other cucurbit crops. However, information regarding the genetic basis of this trait is limited. We conducted a genetic analysis of six generations derived from PI 192938 (scc) and Cream of Saskatchewan (COS) (non-scc) parental lines and found that the scc trait was regulated by a single recessive gene through two years. Bulk segregant analysis sequencing (BSA-seq) and initial mapping placed the scc locus into an 808.8kb region on chromosome 3. Evaluation of another 1152 F2 plants narrowed the scc locus to a 277.11kb region containing 37 candidate genes. Due to the lack of molecular markers in the fine-mapping interval, we extracted the genome sequence variations in this 277.11kb region with in silico BSA among seventeen re-sequenced lines (6 scc and 11 non-scc) and finally delimited the scc locus to an 8.34kb region with only one candidate gene Cla97C03G056110 (CRIB domain-containing protein). Three single nucleotide polymorphism loci in the promoter region of Cla97C03G056110 altered cis-acting elements that were highly correlated with the nature watermelon panel. The expression of Cla97C03G056110 in seed coat tissue was higher in non-scc than in scc lines and was specifically expressed in seed coat compared with fruit flesh.

Identification of simple sequence repeat markers linked to heat tolerance in rice using bulked segregant analysis in F2 population of NERICA-L 44 × Uma.

The damage caused by high temperature is one of the most important abiotic stress affecting rice production. Reproductive stage of rice is highly susceptible to high temperature. The present investigation was undertaken to identify polymorphic microsatellite markers (SSR) associated with heat tolerance. The rice cultivars NERICA- L 44 (heat tolerant) and Uma (heat susceptible) were crossed to generate F1 and F2 populations. The F2 population was subjected to heat stress at >38°C and the 144 F2 plants were evaluated for their tolerance. The results note that the mean of the F2 population was influenced by the tolerant parent with regards to the traits of plant height, membrane stability index, photosynthetic rate, stomatal conductance, evapotranspiration rate, pollen viability, spikelet fertility and 1000 grain weight. Ten each of the extremely susceptible and tolerant plants were selected based on the spikelet fertility percentage. Their DNA was pooled into tolerant and susceptible bulks and Bulked Segregant Analysis (BSA) was carried out using 100 SSR markers to check for polymorphism. The survey revealed a polymorphism of 18% between the parents. RM337, RM10793, RM242, RM5749, RM6100, RM490, RM470, RM473, RM222 and RM556 are some of the prominent markers that were found to be polymorphic between the parents and the bulks. We performed gene annotation and enrichment analysis of identified polymorphic markers. Result revealed that the sequence specific site of that chromosome mostly enriched with biological processes like metabolic pathway, molecular mechanism, and subcellular function. Among that RM337 was newly reported marker for heat tolerance. Expression analysis of two genes corresponds to RM337 revealed that LOP1 (LOC_Os08g01330) was linked to high temperature tolerance in rice. The results demonstrate that BSA using SSR markers is useful in identifying genomic regions that contribute to thermotolerance.

A comparative study between trait selections and marker‐assisted selections to improve fiber strength in upland cotton

AbstractA determination of efficiency in the use of marker‐assisted selection (MAS) for improving cotton (Gossypium hirsutum L.) fiber quality is critical for a successful utilization of MAS in cotton breeding. This study was designed to determine selection responses and realized heritability (h2) of fiber strength selected by MAS in comparison with phenotype selections by traditional breeding. Previously identified single‐sequence repeats markers, CGR6764 and DPL0852, flanking a fiber strength quantitative trait locus on chromosome A07 were used in MAS. Two genetic populations, MD15/TAM98D‐99ne (Pop 1) and TAM98D‐99ne/UA48 (Pop 2), were developed. F2 plants were selected by three methods based on (1) phenotype, (2) combined marker‐genotype and phenotype (MAS‐1), and (3) marker‐genotype alone (MAS‐2) in Pop 1 and two methods based on phenotype and MAS‐1 in Pop 2. F3 progeny rows derived from the selected F2 plants were planted with two replicates in 2019. In Pop 1, the fiber strength mean of the selected F3 progenies was in an order of MAS‐1 > MAS‐2 > phenotype selection. In Pop 2, there was no significant difference in strength between F3 progenies derived from selections by MAS‐1 and phenotypic breeding. In Pop 1, h2 of MAS selections was higher than phenotype selections. In Pop 2, h2 of MAS selections was similar to the phenotype selections. The results indicate that selection efficiency by MAS for fiber strength is better than or equivalent to phenotype selection.

Knockout of elF4E using CRISPR/Cas9 for large-scale production of resistant cucumber cultivar against WMV, ZYMV, and PRSV.

CRISPR/Cas9 is one of the most robust technologies for plant breeding enabling precise and efficient modifications in a genome. This technology is being used for the manipulation of target genes in a host to develop resistance against the plant pathogens. Cucumis sativus elF4E is one of the target genes playing a key role in viral infection during interaction with potyvirus viral proteins genome linked (VPg). Nevertheless, the allelic and positional effect of elF4E mutations in C. sativus is to be clarified in elF4E-VPg interaction. In addition, there are entanglements in the massive production of pathogen-resistant cultivars suitable for commercial production using CRISPR/Cas9 technology. Therefore, we targeted different positions of the elF4E in G27 and G247 inbred lines, using specific gRNA1 and gRNA2 for the first and third exons, respectively, and 1,221 transgene-free plants were selected in segregated T1 generation, where 192 G27 and 79 G247 plants had the least mutation at Cas9 cleavage site of gRNA1 or gRNA2. Crossing was performed to see allelic effects of elfF4E mutations in F1 populations, which were homozygous and heterozygous single (elF4E_1DEL or elF4E_3DEL) and double (elF4E_1-3DEL) mutants. Disease symptoms of watermelon mosaic virus (WMV), papaya ringspot virus (PRSV), and zucchini yellow mosaic virus (ZYMV) were evaluated in both non-edited and edited F1 plants, and we did not observe any symptom in homozygous elF4E_1-3DEL and elF4E_1DEL mutants. However, homozygous elF4E_3DEL was positive in reverse transcription polymerase chain reaction (RT-PCR), even if there were no significant symptoms on the inoculated leaves. ELISA and qRT-PCR indicated lower viral accumulation in homozygous elF4E_3DEL than heterozygous and non-edited plants. Regeneration and transformation protocols were also optimized comprehensively for both the genotypes. The average number of shoots/100 explants was determined for both G27 and G247 as 13.6 and 18.0, respectively. We could not detect any distinguishing difference between the non-edited and edited F1 plants for yield and morphology. Our results demonstrate an effective route for mass production of viral resistant cultivars of cucumber to WMV, ZYMV, and PRSV. In this way, the pathogen-resistant cultivars could be generated to reduce the losses caused by these pathogens in cucumber production.

Genetic Improvement for Grain Yield under Heat Stress Conditions in Bread Wheat (Triticum aestivum L.)

Extreme temperature is one of the abiotic stresses that causes significant yield reductions in wheat. Therefore, the current study aims to create heat-tolerant wheat plants with superior grain yield productivity by using traditional breeding. Two cycles of phenotypic directional selection for grain yield per plant were applied in two F2 populations. These populations were derived from crosses among four local wheat varieties. In the first cycle, a directional selection for grain yield per plant was performed under both the favorable environment (optimal sowing date) and heat stress environments (late sowing date). Under the favorable conditions, the responses of F3 plants to selection for grain yield per plant were positive and significantly higher (averaged 7.71%) than under heat stress conditions (averaged 8.20%). Moreover, the average of the concurrent response to selection for grain yield per plant in grain yield per spike had a positive and high percentage under the favorable (7.00%) and the heat stress environment (8.84%). Highly significant and positive responses were observed within the F3 plants of the two populations. The value of the average was greater under favorable (6.85%) than under the heat stress conditions (7.20%). Additionally, the 1000 kernel weight was highly significant and positive responses (5.35% and 6.11%) in both favorable and heat stress environments, respectively. Generally, the observed results indicating the F4 plants could be a promising source to introduce yield related traits to develop high-yielding wheat cultivars for heat-stressed environments.

GENETIC ANALYSIS OF WHEAT ACCESSIONS FOR YIELD CONTRIBUTING TRAITS UNDER WATER DEFICIT CONDITION

Current research was conducted in the field area of Department of Plant Breeding and Genetics, University of Agriculture Faisalabad during 2018-19. Six parents were used as female lines and three parents as male testers. F1 along with their parents were sown under drought and normal conditions in a randomized complete block design. Data were recorded for flag leaf area, chlorophyll contents, plant height, spike length, spikelets per spike, grains per spike, grain weight per spike, relative water contents, spike density, weight of 1000-grain, grain yield from each plant and tillers per plant. F1 plants and their parents were evaluated for general as well as for specific combining ability. The SSR marker-based screening of parental genotypes was also conducted using 4SSR markers related to drought tolerance. Under normal water conditions, parent Chakwal-50 was a good general combiner for plant height and 1000 grain weight, 9774 perform best for spike length and grain weight per spike. Line BARS-2009 performed best for tillers per plant, number of spikes per plant. In drought conditions, for plant height parent AAS11, Chakwal-50 and 10137 gave significant results. Line BARS-2009 and 9774 gave desirable results for number of tillers per plant. Under normal water condition, cross 9774 × Kohistan 97, Chakwal-50 × Sialkot-13, Chakwal-50 × 9733, BARS-2009 × 9496 and Punjab 2011 × Sialkot-13 performed well for chlorophyll content, flag leaf area, 1000-grain weight and tillers/plant. In drought conditions, crosses 9774 × Kohistan 97, AAS-11 × Sialkot-13, 10137 × Sialkot-13 and 10137 × 9496 performed good for plant height, grain weight per spike, flag leaf area and yield per plant. So, it was concluded from physiological and molecular analysis results that among parents Chalwal-50, BARS-2009, 9496 and 10137 were better performing for drought and can be included in future breeding program.

Genetic and physiological requirements for high-level sesquiterpene-production in tomato glandular trichomes.

Type-VI glandular trichomes of wild tomato Solanum habrochaites PI127826 produce high levels of the sesquiterpene 7-epizingiberene and its derivatives, making the plant repellent and toxic to several pest insects and pathogens. How wild tomato trichomes achieve such high terpene production is still largely unknown. Here we show that a cross (F1) with a cultivated tomato produced only minute levels of 7-epizingiberene. In the F2-progeny, selected for the presence of the 7-epizingiberene biosynthesis genes, only three percent produced comparable amounts the wild parent, indicating this trait is recessive and multigenic. Moreover, trichome density alone did not explain the total levels of terpene levels found on the leaves. We selected F2 plants with the "high-production active-trichome phenotype" of PI127826, having trichomes producing about 150 times higher levels of terpenes than F2 individuals that displayed a "low-production lazy-trichome phenotype". Terpene quantities in trichomes of these F2 plants correlated with the volume of the storage cavity and shape of the gland. We found that trichome morphology is not a predetermined characteristic, but cavity volume rather depended on gland-cell metabolic activity. Inhibitor assays showed that the plastidial-precursor pathway (MEP) is fundamental for high-level production of both cytosolic as well as plastid-derived terpenes in tomato trichomes. Additionally, gene expression profiles of isolated secretory cells showed that key enzymes in the MEP pathway were higher expressed in active trichomes. We conclude that the MEP pathway is the primary precursor-supply route in wild tomato type-VI trichomes and that the high-production phenotype of the wild tomato trichome is indeed a multigenic trait.

Evaluation of Cowpea F2 Population for Resistance to Flower Bud Thrips (Megalurothrips sjostedti)

A study to screen F2 populations obtained from IT10K-837-1 x Sanzi for resistance to M. sjostedti. A total of 351 F2 plants were screened under field conditions and each line rated visually for thrips damage score, flower abortion rate, number of pods per plant and number of thrips per flower. The study was conducted during the 2020 cropping seasons where F2 seeds were planted under field conditions. Thrips damage score, flower abortion rate, number of pods per plant, and number of thrips per bloom was all visually scored for each accession. The data from the field and laboratory were analyzed using GENSTAT edition 12 to determine if there were any major variations among the cowpea genotypes. The approximate correlations among all measured parameters, including damage scores at 45 DAP, 55 DAP, 65 DAP, using were established using Breeding View software and heritability values were also calculated. There was a strong and significant correlation between thrips population and damage rating during the planting season. Thrips resistance levels identified in most genotypes in this study are interesting compared to the resistant check Sanzisabinli and can be further exploited for future studies to develop resistant varieties to improve cowpea yields.

Panicle formation order influence in rice Oryza sativa L in vitro androgenesis

A comparative analysis of rice Oryza sativa L. main and lateral panicles in androgenesis in vitro on F1 plants of two hybrid combinations: L×3P and K×3P to increase the number of cultivated anthers during the season was carried out. Donor plants were grown on the growing area in metal vessels filled with soil. The main panicle was used from three L×3P hybrids and one K×3P hybrid, single lateral panicle was cut from six L×3P plants and three K×3P plants. The genotypes number was calculated as the product of the calli number with doubled haploids by 1.25. In vitro culture 2050 anthers were introduced. According to the intensity of callus formation, the number of green regenerants per callus, and the doubled haploids proportion, there were no statistically significant differences between the main and lateral panicles in the L×3P combination. In total, 215 doubled haploids lines of twenty nine genotypes were obtained, which is theoretically sufficient for breeding a new variety. On the hybrid combination K×3P, 120 doubled haploids of five genotypes were formed from one donor plant with the main panicle. There were no statistically significant differences between the main and lateral panicles. It is concluded that it is expedient to use lateral rice panicles in vitro androgenesis to create the initial breeding material. Their use makes it possible to distribute labor force over time and increase the total volume of anthers cultivated in vitro, and, ultimately, the doubled haploids number and variability of one sample. In the time absence and other restrictions, it is preferable to use the main panicle.

Characterization and Molecular Mapping of a Gene Conferring High-Temperature Adult-Plant Resistance to Stripe Rust Originally from Aegilops ventricosa.

Wheat near-isogenic line AvSYr17NIL carrying Yr17, originally from Aegilops ventricosa for all-stage resistance to Puccinia striiformis f. sp. tritici, also shows nonrace-specific, high-temperature adult-plant (HTAP) resistance to the stripe rust pathogen. To separate and identify the HTAP resistance gene, seeds of AvSYr17NIL were treated with ethyl methanesulfonate. Mutant lines with only HTAP resistance were obtained, and one of the lines, M1225, was crossed with the susceptible recurrent parent Avocet S (AvS). Field responses of the F2 plants and F3 lines, together with the parents, were recorded at the adult-plant stage in Pullman and Mount Vernon, WA under natural P. striiformis f. sp. tritici infection. The parents and the F4 population were phenotyped with a Yr17-virulent P. striiformis f. sp. tritici race in the adult-plant stage under the high-temperature profile in the greenhouse. The phenotypic results were confirmed by testing the F5 population in the field under natural P. striiformis f. sp. tritici infection. The F2 data indicated a single recessive gene, temporarily named YrM1225, for HTAP resistance. The F4 lines were genotyped with Kompetitive allele-specific PCR markers converted from single-nucleotide polymorphism markers polymorphic between M1225 and AvS. The HTAP resistance gene was mapped on the short arm of chromosome 2A in an interval of 7.5 centimorgans using both linkage and quantitative trait locus mapping approaches. The separation of the HTAP resistance gene from Yr17 should improve the understanding and utilization of the different types of resistance.

QTL mapping and BSA-seq map a major QTL for the node of the first fruiting branch in cotton.

Understanding the genetic basis of the node of the first fruiting branch (NFFB) improves early-maturity cotton breeding. Here we report QTL mapping on 200 F2 plants and derivative F2:3 and F2:4 populations by genotyping by sequencing (GBS). BC1F2 population was constructed by backcrossing one F2:4 line with the maternal parent JF914 and used for BSA-seq for further QTL mapping. A total of 1,305,642 SNPs were developed between the parents by GBS, and 2,907,790 SNPs were detected by BSA-seq. A high-density genetic map was constructed containing 11,488 SNPs and spanning 4,202.12 cM in length. A total of 13 QTL were mapped in the 3 tested populations. JF914 conferred favorable alleles for 11 QTL, and JF173 conferred favorable alleles for the other 2 QTL. Two stable QTL were repeatedly mapped in F2:3 and F2:4, including qNFFB-D3-1 and qNFFB-D6-1. Only qNFFB-D3-1 contributed more than 10% of the phenotypic variation. This QTL covered about 24.7 Mb (17,130,008-41,839,226 bp) on chromosome D3. Two regions on D3 (41,779,195-41,836,120 bp, 41,836,768-41,872,287 bp) were found by BSA-seq and covered about 92.4 Kb. This 92.4 Kb region overlapped with the stable QTL qNFFB-D3-1 and contained 8 annotated genes. By qRT-PCR, Ghir_D03G012430 showed a lower expression level from the 1- to 2-leaf stage and a higher expression level from the 3- to 6-leaf stage in the buds of JF173 than that of JF914. Ghir_D03G012390 reached the highest level at the 3- and 5-leaf stages in the buds of JF173 and JF914, respectively. As JF173 has lower NFFB and more early maturity than JF914, these two genes might be important in cell division and differentiation during NFFB formation in the seedling stage. The results of this study will facilitate a better understanding of the genetic basis of NFFB and benefit cotton molecular breeding for improving earliness traits.