Resistance Alleles Research Articles

Why some ‘inbreeder’ species among mostly outbreeders? conifer examples, a postulate, and research agenda

AbstractBreeding systems vary widely in plants, but mostly cluster towards outbreeding or inbreeding extremes. Conifers, which are woody and generally long-lived perennials, are almost all classical outbreeders, but include occasional species characterised as inbreeders. The latter include some very narrow endemics, but narrow endemics include outbreeders. The inbreeders show high self-fertility, minimal inbreeding depression, typically low DNA polymorphism, and modest functional genetic variation, but self-fertilisation rates can be low. Seven such species are reviewed. It is widely (if often tacitly) assumed that inbreeders arise through severe population bottlenecks. It is proposed, more specifically, that inbreeders could arise through recessive resistance alleles of large effects being expressed, during biotic crises, through some inbreeding in the typically mixed mating systems of outbreeders. Such a crisis might produce not only a population bottleneck but also the conditions for recessive alleles to operate beneficially to make inbreeding advantageous. Avenues for probing the recessive-alleles hypothesis are: quantitative modelling to identify what are plausible conditions, examining genomic signatures of inbreeders, and empirical observation. Appropriate modelling appears challenging, as does seeking informative genomic signatures. Empirical observation, however, may be facilitated by biotic crises promoted by current global migration of pathogens and animal pests.

Genetic dissection of resistance to Phytophthora sojae using genome-wide association and linkage analysis in soybean [Glycine max (L.) Merr.

Two novel and one known genomic regions associated with R-gene resistance to Phytophthora sojae were identified by genome-wide association analysis and linkage analysis in soybean. Phytophthora root and stem rot (PRR) caused by Phytophthora sojae is a severe disease that causes substantial economic losses in soybean [Glycine max (L.) Merr.]. The primary approach for successful disease management of PRR is using R-gene-mediated resistance. Based on the phenotypic evaluation of 376 cultivated soybean accessions for the R-gene type resistance to P. sojae (isolate 2457), a genome-wide association analysis identified two regions on chromosomes 3 and 8. The most significant genomic region (20.7-21.3 Mbp) on chromosome 8 was a novel resistance locus where no Rps gene was previously reported. Instead, multiple copies of the UDP-glycosyltransferase superfamily protein-coding gene, associated with disease resistance, were annotated in this new locus. Another genomic region on chromosome 3 was a well-known Rps cluster. Using the Daepung × Ilpumgeomjeong RIL population, a linkage analysis confirmed these two resistance loci and identified a resistance locus on chromosome 2. A unique feature of the resistance in Ilpumgeomjeong was discovered when phenotypic distribution was projected upon eight groups of RILs carrying different combinations of resistance alleles for the three loci. Interestingly, the seven groups carrying at least one resistance allele statistically differed from the other with none, regardless of the number of resistance alleles. This suggests that the respective three different resistance genes can confer resistance to P. sojae isolate 2457. Deployment of the three regions via marker-assisted selection will facilitate effectively improving resistance to particular P. sojae isolates in soybean breeding programs.

A single mutation G454A in the P450 CYP9K1 drives pyrethroid resistance in the major malaria vector Anopheles funestus reducing bed net efficacy.

Metabolic mechanisms conferring pyrethroid resistance in malaria vectors are jeopardizing the effectiveness of insecticide-based interventions, and identification of their markers is a key requirement for robust resistance management. Here, using a field-lab-field approach, we demonstrated that a single mutation G454A in the P450 CYP9K1 is driving pyrethroid resistance in the major malaria vector Anopheles funestus in East and Central Africa. Drastic reduction in CYP9K1 diversity was observed in Ugandan samples collected in 2014, with selection of a predominant haplotype (G454A mutation at 90%), which was completely absent in the other African regions. However, six years later (2020) the Ugandan 454A-CYP9K1 haplotype was found predominant in Cameroon (84.6%), but absent in Malawi (Southern Africa) and Ghana (West Africa). Comparative in vitro heterologous expression and metabolism assays revealed that the mutant 454A-CYP9K1 (R) allele significantly metabolises more type II pyrethroid (deltamethrin) compared with the wild G454-CYP9K1 (S) allele. Transgenic Drosophila melanogaster flies expressing 454A-CYP9K1 (R) allele exhibited significantly higher type I and II pyrethroids resistance compared to flies expressing the wild G454-CYP9K1 (S) allele. Furthermore, laboratory testing and field experimental hut trials in Cameroon demonstrated that mosquitoes harbouring the resistant 454A-CYP9K1 allele significantly survived to pyrethroids exposure (Odds ratio = 567, p < 0.0001). This study highlights the rapid spread of pyrethroid resistant CYP9K1 allele, under directional selection in East and Central Africa, contributing to reduced bed net efficacy. The newly designed DNA-based assay here will add to the toolbox of resistance monitoring and improving its management strategies.

Knockdown resistance in Stomoxys calcitrans stable fly populations on German dairy farms: kdr alleles explain susceptibility of individual flies to deltamethrin

AbstractThe stable fly, Stomoxys calcitrans, is a globally important pest causing stress, economic losses and transmission of pathogens in livestock. Control on commercial farms relies predominantly on the use of insecticides, with pyrethroids being the most frequently used class of insecticides in industrialised countries. Here, laboratory isolates were obtained from four dairy farms in Brandenburg (Germany) and tested for phenotypic resistance to deltamethrin in comparison to a susceptible reference isolate using topical application. Individual flies were subsequently genotyped using allele-specific real-time PCRs. Phenotypic resistance was observed in all four field isolates with resistance ratios between 46 and 119 compared to the susceptible laboratory strain. At position 1014 of the voltage-sensitive sodium channel, allele-specific PCRs detected the wild-type, kdr-his and kdr genotypes encoding leucine, histidine and phenylalanine, respectively. In the susceptible laboratory isolate, only the wild-type was identified. On the farms with very high LD50 values, the kdr variant was most prevalent and logistic regression analysis revealed that the kdr variant increased the odds to survive exposure to deltamethrin more than the kdr-his genotype. Flies carrying two resistance alleles were less susceptible than flies that also carried one wild-type allele. In three out of four field isolates, the allele frequencies were significantly different from the expectations of the Hardy–Weinberg equilibrium suggesting ongoing selection. The data show that the phenotype can be largely explained by the kdr genotype and represent high frequencies of the L1014F kdr and L1014H kdr-his variants conferring high levels of resistance in northern Germany.

Applying a computer model to evaluate the evolution of resistance by western corn rootworm to multiple Bt traits in transgenic maize.

Western corn rootworm, Diabrotica virgifera virgifera (LeConte) (Coleoptera: Chrysomelidae), is a major pest of maize in the United States. Transgenic maize producing insecticidal toxins from the bacterium Bacillus thuringiensis (Bt) have been used to manage this pest since 2003. Refuges of non-Bt maize have been used to delay resistance to Bt maize by western corn rootworm, and are planted in conjunction with maize producing single or multiple (i.e., pyramids) Bt toxins. Two Bt toxins, Cry3Bb1 and Gpp34/Tpp35Ab1, were used individually before being combined as a pyramid, at which point resistance had already evolved to Cry3Bb1. Pyramids targeting western corn rootworm therefore contained at least one toxin to which resistance had evolved. Western corn rootworm has now evolved resistance to all four commercially available Bt toxins used for rootworm management. We used laboratory and field-generated data to parameterize a deterministic model to simulate the effectiveness of refuges and Bt pyramids to delay resistance to Bt maize in western corn rootworm. Resistance to the pyramid of Cry3Bb1 with Gpp34/Tpp35Ab1 evolved more rapidly when resistance to Cry3Bb1 was already present. This effect arose when model conditions affecting initial resistance allele frequency, inheritance of resistance, and fitness costs were varied. Generally, resistance evolved faster when initial resistance allele frequencies were higher, inheritance of resistance was nonrecessive, and fitness costs were absent, which is consistent with previous models that simulated resistance evolution. We conclude that new transgenic pyramids should pair novel, independently acting toxins with abundant refuges to minimize the risk of rapid resistance evolution.

Genome-wide analysis of detoxification genes conferring diamide insecticide resistance in Spodoptera exigua identifies CYP9A40

For over a decade, diamide insecticides have been effective against lepidopteran pests like beet armyworm, Spodoptera exigua (Hübner, 1808). However, the evolution of resistance poses a challenge to their sustainable use. We identified an I4790M mutation in the S. exigua ryanodine receptor (RyR) gene, but its correlation with resistance varied across the field-collected Korean populations of S. exigua. RNA sequencing and differential gene expression analysis were performed to investigate other resistance mechanisms. Diamide-resistant and susceptible strains and F1 hybrids were compared by mapping RNA-seq reads to the S. exigua reference genome. CYP9A40 was identified as a critical gene in diamide resistance due to its high expression in the resistant strains. Synergist bioassays with piperonyl butoxide supported the role of P450s in diamide metabolic resistance in S. exigua. A strong positive correlation between CYP9A40 over-expression levels (up to 80-fold) and diamide LC50 values was obtained for field-collected populations uniformly showing a 100% frequency of the RyR I4790M target-site resistance allele. To validate the function of CYP9A40 in diamide detoxification, we recombinantly expressed the gene and tested its ability to bind and degrade chlorantraniliprole as a substrate. The results confirmed its catalytic role in diamide metabolism. CYP9A40 has been identified and validated to confer metabolic resistance in Korean S. exigua populations. It works alongside the RyR target-site I4790M mutation to enhance diamide resistance. These mechanisms offer insights for resistance monitoring and support insecticide resistance management programs to improve control strategies for S. exigua.

Resistance of Anopheles gambiae s.s. against commonly used insecticides and implication of cytochrome P450 monooxygenase in resistance to pyrethroids in Lambaréné (Gabon)

BackgroundInsecticides are a crucial component of vector control. However, resistance constitute a threat on their efficacy and the gains obtained over the years through malaria vector control. In Gabon, little data on phenotypic insecticide resistance in Anopheles vectors are published, compromising the rational implementation of resistance management strategies. We assessed the susceptibility to pyrethroids, carbamates and organophosphates of Anopheles gambiae sensu lato (s.l.) and discuss the mechanisms involved in the pyrethroid resistance-phenotype.MethodsA. gambiae s.l. larvae were collected from breeding sites in Lambaréné. Emerging adults were used in WHO tube assays at an insecticide concentration that defines resistance (diagnostic concentration). Subsequently, deltamethrin and permethrin were used at 5x and 10x diagnostic concentrations and after preexposure with the cytochrome p450 (and glutathione S-transferase) inhibitor piperonyl butoxide (PBO). A subset of mosquitoes was typed by molecular methods and screened using Taqman assays for mutations conferring target site resistance at the Voltage-gated sodium channel 1014 (Vgsc-1014) locus and the acetylcholinesterase (Ace-1) gene.ResultsAll mosquitoes were A. gambiae sensu stricto (s.s.) and resistant to permethrin, deltamethrin and alphacypermethrin (mortality less than 98%). However, mosquitoes were susceptible to malathion but resistant to bendiocarb. The level of resistance was high for permethrin and at least moderate for deltamethrin. Pre-exposure to PBO significantly increased the mortality of resistant mosquitoes (P < 0.0001). They became fully susceptible to deltamethrin and permethrin-induced mortality increased 4-fold. The G119S Ace-1 resistance allele, which confers resistance to both organophosphates and carbamates, was not present. All sampled mosquitoes were either homozygous for the Vgsc-L1014F or heterozygous for Vgsc-L1014F/L1014S, a marker for resistance to pyrethroids and organochlorides.ConclusionThese findings demonstrate a role of cytochrome P450 monooxygenases in the pyrethroid-resistance of A. gambiae s.s. from Lambaréné. Combining PBO with pyrethroids, as done in second generation bednets, may be used to revert resistance. In addition, malathion could also be used in combination with pyrethroids-based methods for resistance management.

Identification of Genetic Loci for Grain Traits and Disease Resistance Reveals a Potential Trade-Off in Rice

Understanding how plants utilize limited resources for reproductivity and disease resistance can improve the efficiency of plant breeding. In the present study, we mapped genes for grain traits, including grain length and width and thousand grain weight (TGW). A previously constructed linkage map of a recombinant inbred line population (MHM) was used, which was derived from a cross between an indica restorer rice variety (Minghui 63) and a temperate japonica rice variety (M-202). The MHM population was grown in replicated field plots, and grain trait data were collected. Upon a 3-year field evaluation, a total of 16 loci were mapped on 9 of 12 chromosomes, including 7 for grain length, 4 for grain weight, and 5 for TGW. A TGW locus ( qTGW2) and a grain width locus ( qWIG2.2) were mapped at the known blast resistance locus qBLAST2 on chromosome 2 that harbors a major blast resistance allele Pi-b. Another TGW locus ( qTGW3.3) and a grain length locus ( qLNG3.3) were mapped at qBLAST3 on chromosome 3. These results reveal potential trade-offs between disease resistance and productivity, which are important for breeders to develop high-yielding and disease-resistant rice varieties. [Formula: see text] The author(s) have dedicated the work to the public domain under the Creative Commons CC0 “No Rights Reserved” license by waiving all of his or her rights to the work worldwide under copyright law, including all related and neighboring rights, to the extent allowed by law, 2024.

A single-nucleotide insertion in Rxp confers durable resistance to bacterial pustule in soybean.

The soybean Rxp gene, encoding a bHLH transcription factor and an ACT-like domain, has an rxp allele producing a truncated protein that confers resistance to pustule-causing Xanthomonas axonopodis pv. glycines. In soybean, bacterial pustules caused by Xanthomonas axonopodis pv. glycines lead to premature defoliation and decreased yield in warm, wet climates. In the USA, approximately 70years ago, bacterial pustules were eliminated by introducing a recessive resistance allele, rxp, of the Rxp gene, representing the first example of successful soybean breeding for durable disease resistance in North America. In this study, we isolated this historical Rxp gene from resistant soybean varieties using positional cloning. The 1.06Mb region where Rxp was reported to reside was narrowed down to an 11.1kb region containing a single gene, Glyma.17g090500. The resistance allele, rxp, contains a T insertion. A complementation test of the Rxp allele in resistant plants confirmed the identification of the Rxp gene. The product of the susceptible wild-type allele, Rxp, is presumed to be a basic helix-loop-helix (bHLH) transcription factor with an aspartate kinase, chorismate mutase, and TyrA (ACT)-like domain. This gene was mainly expressed in extended leaves, and its homologs were identified to be distributed in angiosperms. A total of six alleles were obtained: four from spontaneous variation, including the wild-type and three mutant alleles that encoded truncated proteins, and two from ethyl methanesulfonate mutants, including an allele that encoded a truncated protein and a missense allele. By evaluating the resistance of these six alleles, we found that the loss of function of RXP decreased the bacterial pustule lesions. This study provides important insights into the soybean rxp allele, which confers durable resistance to bacterial pustules.

DISTRIBUTION OF PLASMODIUM FALCIPARUM CHLOROQUINE RESISTANCE TRANSPORTER (PFCRT) AND PLASMODIUM FALCIPARUM MULTIDRUG RESISTANCE 1(PFMDR-1) GENES IN ILORIN NORTH-CENTRAL NIGERIA

Globally, malaria is a peculiar health challenge particularly in continent of Africa. The ease of developing resistance to anti-malaria drugs by Plasmodium falciparum is a serious impediment towards programs aim at control and elimination of malaria. Consequently, drug efficacy surveillance is desirable to institute adequate and effective treatment policies. In this study, distribution of these genes in Plasmodium falciparum isolates in Ilorin metropolis were investigated. One hundred and three samples collected randomly from 5 hospitals in Ilorin metropolis. The samples were amplified at codon 76 and 86 for Pfcrt and Pfmdr-1 respectively using PCR / Restricted Fragment Length Polymorphism (RFLP). The most prevalent alleles were drug susceptible alleles in the study area (K76 and N86) with 31% and 40% respectively, while drug resistance alleles (86Y) have 13% and the least prevalence 2% was the mixed alleles K76T. UITH has the highest number of susceptible alleles followed by CSC 38% and 46% for K76 and N86 respectively. There are significant differences in the distribution of these alleles and the study sites (P&lt; 0.05). The prevalence of resistance alleles in the area is a welcome development that can be employed for possibility of re-introduction of CQ for the treatment of malaria in the study area which will serve as an advantage over expensive ACT due to fact that it is safe cheap and readily affordable.

A major falling number locus on chromosome 4B governs resistance to pre-harvest sprouting in bread wheat line Soru#1

Pre-harvest sprouting (PHS) is a serious threat to wheat quality and occurs when maturing seeds on plants encounter substantial rain before harvest. In the present study, the genetics of PHS resistance were studied using a population of 131 recombinant inbred lines (RILs) from a cross between Soru#1 and Naxos. The population was genotyped with the Illumina 90 K and Axiom 35 K wheat SNP arrays and tested in field trials across two locations in Norway and one in China. Seed dormancy as a measure of sprouting damage was evaluated using germination index (GI) and falling number (FN). Days to heading, days to maturity, and plant height were also recorded to evaluate their potential impact on PHS. Thirteen PHS-related quantitative trait loci (QTL) were detected. The most consistent QTL for FN, contributed by Soru#1, on the long arm of chromosome 4B explained 10.0–19.2% of the phenotypic variation across trials. Other important PHS resistance QTL from Soru#1 detected on chromosome arms 2AL, 2BL, and 4BS, affected both GI and FN. Naxos carried favorable QTL alleles for PHS resistance on chromosome arm 4AS and the Phs1 allele on 4AL. The reduced height Rht-D1 and vernalization Vrn-A1 alleles were the major determinants of plant height and earliness; however, these traits had minimal impact on the genetic control of PHS resistance in this population. Thus, both parents contributed valuable alleles for improving PHS resistance in breeding programs.

Allelic interactions defining Raphanus raphanistrum AHAS resistance level: strong vs weak target-site AHAS resistance alleles.

Chlorsulfuron resistance and genetic dominance was evaluated in Raphanus raphanistrum genotypes homozygous (122-RR, 376-RR), heterozygous (122-RS, 376-RS) and compound heterozygous (122-R/376-R) for the target-site resistance mutations Ala-122-Tyr and Asp-376-Glu in the AHAS (acetohydroxyacid synthase) gene. At the AHAS level, 122-RR and 122-RS plants exhibited significantly higher I50 values than 376-RR and 376-RS plants, respectively. However, plants of the compound heterozygous genotype (122-R/376-R), showed no difference in AHAS activity compared to the 122-RS genotype but lower activity than the 122-RR genotype, and showed a nearly 400-fold greater I50 value than both genotypes (376-RR and 376-RS) carrying the 376-Glu allele. At the whole-plant level, 100% survival was observed for 122-RR plants at the highest chlorsulfuron dose of 640 g ha-1, yet 376-RR plants showed no survival at 380 g ha-1. Thus, this survival difference resulted in different median lethal dose (LD50) estimates [>640 (122-RR) versus 330 g ha-1(376-RR)]. The effect of chlorsulfuron in reducing aboveground growth of surviving plants also was markedly lower for the homozygous 122-RR (GR50 = 566 g ha-1) than for 376-RR plants (GR50 = 66). Heterozygous plants carrying the 122-Tyr allele (122-RS) exhibited two- and five-fold higher LD50 values than both homozygous and heterozygous plants carrying the 376-Glu allele (376-RR, 376-RS), respectively. Along the difference in plant survival, 122-RS plants also showed four-fold higher GR50 than both 376-RR and 376-RS plants. Survival of plants with the compound heterozygous genotype (122-R/376-R) under increasing chlorsulfuron doses was similar to 122-RR or 122-RS genotypes. However, this compound heterozygous genotype showed two- and six-fold higher LD50 values than 376-RR or 376-RS genotypes, respectively. However, both resistance 122-Tyr and 376-Glu alleles were dominant or nearly dominant over the wild-type susceptible alleles (ALA-122 and ASP-376), and the resistance 122-Tyr allele was dominant over the 376-Glu allele. These results broaden our understanding of AHAS target-site resistance in R. raphanistrum and strengthens the hypothesis that the AHAS 122-Tyr allele corresponds to a stronger target-site resistance allele than the 376-Glu allele. © 2024 Society of Chemical Industry.

Identification of genetic loci for powdery mildew resistance in common wheat.

Powdery mildew (PM) poses an extreme threat to wheat yields and quality. In this study, 262 recombinant inbred lines (RILs) of Doumai and Shi 4185 cross were used to map PM resistance genes across four environments. High-density genetic linkage map of the Doumai/Shi 4185 RIL population was constructed using the wheat Illumina iSelect 90K single-nucleotide polymorphism (SNP) array. In total, four stable quantitative trait loci (QTLs) for PM resistance, QPm.caas-2AS, QPm.caas-4AS, QPm.caas-4BL, and QPm.caas-6BS, were detected and explained 5.6%-15.6% of the phenotypic variances. Doumai contributed all the resistance alleles of QPm.caas-2AS, QPm.caas-4AS, QPm.caas-4BL, and QPm.caas-6BS. Among these, QPm.caas-4AS and QPm.caas-6BS overlapped with the previously reported loci, whereas QPm.caas-2AS and QPm.caas-4BL are potentially novel. In addition, six high-confidence genes encoding the NBS-LRR-like resistance protein, disease resistance protein family, and calcium/calmodulin-dependent serine/threonine-kinase were selected as the candidate genes for PM resistance. Three kompetitive allele-specific PCR (KASP) markers, Kasp_PMR_2AS for QPm.caas-2AS, Kasp_PMR_4BL for QPm.caas-4BL, and Kasp_PMR_6BS for QPm.caas-6BS, were developed, and their genetic effects were validated in a natural population including 100 cultivars. These findings will offer valuable QTLs and available KASP markers to enhance wheat marker-assisted breeding for PM resistance.

The impact of lethal and sub-lethal exposure of emamectin benzoate on populations of Spodoptera litura (Lepidoptera: Noctuidae) under laboratory conditions

Emamectin benzoate is an avermectin bio-insecticide commonly used for managing several insect pests including Spodoptera litura (Fabricius) (Lepidoptera: Noctuidae), a major polyphagous pest of many cultivated crops. The current study was conducted to evaluate the effects of emamectin benzoate on the fitness of S. litura populations exhibiting differential susceptibility to insecticide. The selection process and all the bioassays were carried out using 6-day-old 2nd instar larvae of S. litura. A field-collected population of S. litura was divided into two groups: one selected with emamectin benzoate for eight generations (EB-Sel) and the other kept unexposed (Unsel-Lab) to insecticide in the laboratory. An increase in resistance ratio from 1.71-fold in the F1 generation to 22.54-fold in the F8 generation of the EB-Sel population was observed compared to the Unsel-Lab (F8) population. The EB-Sel and Unsel-Lab populations were treated with their respective lethal and sub-lethal concentrations which resulted in an extended development period, decreased larval survival, and adult emergence along with increased morphological abnormalities in adults. Significant reductions were observed in both male and female longevity, fecundity, egg hatching, net reproductive rate (R0), intrinsic rate of increase (rm), and finite rate of increase (λ) in EB-Sel and Unsel-Lab populations. Higher concentrations of the insecticide also reduced the relative fitness (Rf) of S. litura larvae, with maximum effect at LC50 of the EB-Sel population where the Rf value was 0.32 compared to the Unsel-Lab population. Both populations have been affected by emamectin benzoate exposure, however, the impact was more pronounced in the EB-Sel population indicating fitness costs. Our results suggested the fitness cost linked to emamectin benzoate resistance in S. litura which might favor managing insecticide resistance by reducing the frequency of resistant alleles by removing selection pressure. Consequently, our research provides significant insights to devise better pest management strategies for S. litura.

Molecular diversiry studies among blackgram genotypes for yellow mosaic virus resistance

Yellow mosaic disease (YMD), incited by a geminivirus. Mungbean Yellow Mosaic Virus (MYMV), is transmitted by whiteflies, poses a significant threat to various leguminous crops in India. This study focuses on identifying resistant sources and validating molecular markers for their efficacy in detecting YMV resistance in blackgram. In the present study, 150 blackgram genotypes were evaluated to identify resistant sources for YMD under natural field conditions and through molecular markers. Among the 150 genotypes, 22 (both resistant and susceptible) were selected based on field screening. These genotypes were validated using 15 molecular markers, including 8 simple sequence repeats (SSRs) and 7 gene-specific markers linked to MYMV resistance. The markers amplified a total of 48 alleles, with polymorphic information content (PIC) values ranging from 0.82 (CEDG67) to 0.21 (HSP), with an average value of 0.55. The highest PIC values were exhibited by markers CEDG67 (0.82), CEDG115 (0.81), and CEDG20 (0.74). Cluster analysis using DARWIN revealed that most phenotypically resistant genotypes grouped together, while susceptible genotypes formed separate clusters. The genotypes LBG 904, LBG 932, LBG 884, PU 1815, PU 1808, PU 1803, MASH 1008, MASH 114, VBN 10, and PU 31 exhibited resistance to YMV phenotypically. Among these, LBG 904, LBG 932, PU 1815, PU 31, and MASH 1008 produced a 162 bp resistant allele using the marker CEDG180. Similarly, the gene-specific marker DEF produced a 190 bp resistant allele in all the resistant genotypes, whereas the susceptible genotypes produced both 190 and 250 bp alleles. These identified genotypes can serve as valuable sources for MYMV resistance in blackgram breeding programs. Keywords: SSR markers, Blackgram, Diversity, MYMV

Distribution of Plasmodium falciparum Chloroquine Resistance Transporter (Pfcrt) and Plasmodium falciparum Multidrug Resistance 1(Pfmdr-1) Genes in Ilorin North-central Nigeria

Malaria remains a major health problem globally, especially in Sub-Saharan Africa. The ease of developing resistance to anti-malaria drugs by Plasmodium falciparum is a serious challenge to malaria control and elimination programs. Consequently, continuous monitoring of drug efficacy is necessary to ascertain effective treatment policies. The study investigated the distribution pattern of these genes in Plasmodium falciparum isolates in Ilorin metropolis. One hundred and three samples were collected randomly from 5 hospitals in Ilorin metropolis. The samples were amplified at codon 76 and 86 for Pfcrt and Pfmdr-1 respectively using PCR/Restricted Fragment Length Polymorphism (RFLP). Drug susceptible alleles were most prevalent in the study area (K76 and N86) with 31% and 40% respectively, followed by drug resistance alleles (86Y) with 13%, and the least prevalent (2%) was the mixed alleles K76T. UITH has the highest number of susceptible alleles followed by CSC 38% and 46% for K76 and N86 respectively. There are significant differences in the distribution of these alleles and the study sites (P55&lt; 0.05). The prevalence of resistance alleles in the area is a welcome development that can be employed for the possible re-introduction of CQ to treat malaria in the study area. It will be an advantage over expensive ACT because it is safe, cheap, and readily affordable.

Marker Assisted Selection (MAS) and It's Application in Vegetable Crop Improvement

Vegetable crop breeding has changed dramatically since the early 1980s due to technological breakthroughs, especially high-throughput sequencing and molecular marker technologies, which have made it possible to sequence many plant genomes, create dense genetic maps, and identify important genes and QTLs linked to traits like yield and disease resistance. ..These instruments have expedited genetic research and breeding programs in crops including tomato, pepper, eggplant, and cucumber, establishing marker-assisted selection (MAS) as a crucial component of contemporary breeding. The use of these technologies has improved crop characteristics significantly and is still influencing the development of vegetable crops in the future. .. For instance, in the majority of private and public tomato breeding projects, major-gene disease resistance traits like verticillium wilt and anthracnose are selected for using PCR-based markers such as SCAR and CAPS.Bs5 and Bs6 have broad-spectrum resistance against Xanthomonas spp. against chilli leaf spot thanks to marker-assisted gene pyramiding. Major QTLs associated to SSR marker CAMS451 on chromosome 1 (from Capsicum accession LS2341) and marker ID10-194305124 on chromosome 10 (from C. annuum BVRC1) have been mapped for resistance to Ralstonia bacterial wilt.Constantly searching crop germplasm for new resistance genes or alleles is essential to diversify the gene pool and stop resistance from breaking down. By using marker-assisted selection (MAS), it is possible to combine genes for resistance to different pathogens or several sources of resistance to the same pathogen to create novel cultivars.

Genetic diversity of naked barley accessions from the VIR collection for resistance to powdery mildew in the North-West Region of the Russian Federation

BACKGROUND: Barley is an important grain crop characterized by adaptability to various growing conditions. In recent years close attention has been paid to groups of naked barley which compared to covered barley is more susceptible to the influence of pathogens, that decreases the yield and quality of grain. Powdery mildew is the most harmful diseases of barley (caused by the biotrophic fungus Blumeria graminis (DC.) Golovin ex Speer f. sp. hordei Marchal). The search for new promising sources of resistance to powdery mildew is necessary for barley breeding. AIM: The aim is studying the powdery mildew resistance of naked spring barley accessions from the world collection of VIR and identifying promising sources for economically valuable traits. MATERIALS AND METHODS: In field and laboratory conditions 271 of naked barley accessions of different ecological and geographical origin were studied for powdery mildew resistance and other economically valuable traits (lodging resistance, duration of the vegetative period, yield). The pathogen inoculum for laboratory work was represented by the north-western population of the pathogen. The resistance of barley samples was assessed in the field using the VIR point scale, in the laboratory using the E.B. Mains, S.M. Dietz point scale. The highly effective to powdery mildew resistance allele mlo11 was identified using PCR. RESULTS: The diversity of barley of different origins in resistance to powdery mildew is shown. 16 samples mainly from Europe, local forms from Ethiopia, Japan and India, were found to be resistant in field condition. According to the results of the assessment at the juvenile stage, 1 highly resistant sample k-31058 and 5 moderately resistant (k-20923, k-25801, k-27165, k-29911, k-30231) were identified. The naked forms k-20923 from Germany and k-29911 from Poland were resistant at all stages of plant development. The mlo11 allele was detected in the Arabische variety (k-20923) and heterogeneous pathogen resistance accessions k-20921, k-25793, k-27080, k-29440, k-29820. CONCLUSIONS: As a result of the work the sources of resistance to powdery mildew with a complex of economically valuable traits were identified, which can be involve in the breeding.

Study on the cross-resistance of Aedes albopictus (Skuse) (Diptera: Culicidae) to deltamethrin and pyriproxyfen

BackgroundInsecticide resistance poses a significant challenge in the implementation of vector-borne disease control strategies. We have assessed the resistance levels of Aedes albopictus to deltamethrin and pyriproxyfen (PPF) in Fujian Province (China) and investigated the correlation between these resistance levels and mutations in the voltage-gated sodium channel (VGSC).MethodsThe WHO bioassay protocol was used to evaluate the resistance coefficient of Ae. albopictus to deltamethrin and PPF, comparing a susceptible population from the Foshan (FS) area with wild populations from the Sanming (SM), Quanzhou (QZ), Zhangzhou (ZZ), Putian (PT) and Fuzhou (FZ) areas in Fujian Province. Genomic DNA was analyzed by PCR and sequencing to detect knockdown resistance (kdr) in the VGSC, specifically at the pyrethroid resistance alleles V1016V, I1532I and F1534F. Molecular docking was also performed to analyze the binding interactions of PPF and its metabolite 4'-OH-PPF to cytochrome P450 (CYP) 2C19, 2C9 and 3A4 and Ae. albopictus methoprene-tolerant receptors (AeMet), respectively.ResultsThe analysis of resistance to deltamethrin and PPF among Ae. albopictus populations from the various regions revealed that except for the sensitive population in FS and the SM population, the remaining four regional populations demonstrated resistance levels ranging from 4.31- to 18.87-fold for deltamethrin and from 2.85– to 3.62-fold for PPF. Specifically, the FZ and PT populations exhibited high resistance to deltamethrin, whereas the ZZ and QZ populations approached moderate resistance levels. Also, the resistance of the FZ, PT and ZZ populations to PPF increased slowly but consistently with the increasing trend of deltamethrin resistance. Genomic analysis identified multiple non-synonymous mutations within the VGSC gene; the F1534S and F1534L mutations showed significant resistance to deltamethrin in Ae. albopictus. Molecular docking results revealed that PPF and its metabolite 4'-OH-PPF bind to the Ae. albopictus AeMet receptor and CYP2C19.ConclusionsThe wild Ae. albopictus populations of Fujian Province showed varying degrees of resistance to deltamethrin and PPF and a trend of cross-resistance to deltamethrin and PPF. Increased vigilance is needed for potential higher levels of cross-resistance, especially in the PT and FZ regions.Graphical

Improvement of Quality and Disease Resistance for a Heavy-Panicle Hybrid Restorer Line, R600, in Rice (Oryza sativa L.) by Gene Pyramiding Breeding.

The utilization of heavy-panicle hybrid rice exemplifies the successful integration of architectural enhancement and heterosis, which has been widely adopted in the southwest rice-producing area of China. Iterative improvement in disease resistance and grain quality of heavy-panicle hybrid rice varieties is crucial to promote their sustainable utilization. Here, we performed a molecular design breeding strategy to introgress beneficial alleles of broad-spectrum disease resistance and grain quality into a heavy-panicle hybrid backbone restorer line Shuhui 600 (R600). We successfully developed introgression lines through marker-assisted selection to pyramid major genes (Wxb + ALKA-GC + Pigm + Xa23) derived from three parents (Huanghuazhan, I135, I488), which significantly enhance grain quality and confer resistance to rice blast and bacterial blight (BB). The improved parental R600 line (iR600) exhibited superior grain quality and elevated disease resistance while maintaining the heavy-panicle architecture and high-yield capacity of R600. Moreover, the iR600 was crossed with male sterility line 608A to obtain a new heavy-panicle hybrid rice variety with excellent eating and cooking quality (ECQ) and high yield potential. This study presents an effective breeding strategy for rice breeders to expedite the improvement of grain quality and disease resistance in heavy-panicle hybrid rice.