Resistant Parent Research Articles

Improvement of three popular Indian groundnut varieties for foliar disease resistance and high oleic acid using SSR markers and SNP array in marker-assisted backcrossing

Foliar fungal diseases (rust and late leaf spot) incur large yield losses, in addition to the deterioration of fodder quality in groundnut worldwide. High oleic acid has emerged as a key market trait in groundnut, as it increases the shelf life of the produce/products in addition to providing health benefits to consumers. Marker-assisted backcrossing (MABC) is the most successful approach to introgressing or pyramiding one or more traits using trait-linked markers. We used MABC to improve three popular Indian cultivars (GJG 9, GG 20, and GJGHPS 1) for foliar disease resistance (FDR) and high oleic acid content. A total of 22 BC3F4 and 30 BC2F4 introgression lines (ILs) for FDR and 46 BC3F4 and 41 BC2F4 ILs for high oleic acid were developed. Recurrent parent genome analysis using the 58 K Axiom_Arachis array identified several lines showing upto 94% of genome recovery among second and third backcross progenies. Phenotyping of these ILs revealed FDR scores comparable to the resistant parent, GPBD 4, and ILs with high (~80%) oleic acid in addition to high genome recovery. These ILs provide further opportunities for pyramiding FDR and high oleic acid in all three genetic backgrounds as well as for conducting multi-location yield trials for further evaluation and release for cultivation in target regions of India.

Mapping and genetic analysis of QTLs for <italic>Fusarium</italic> head blight resistance to disease spread in Yangmai 16

Fusarium head blight (FHB) resistance of Yangmai wheat cultivars has been paid much attention, but the underlying genetic mechanism is unclear. In recent years, Yangmai 16 is a predominant wheat cultivar durably resistant to FHB in production. A population of 174 double haploid lines (DH) produced by crossing Yangmai 16 (YM16) with the susceptible cultivar Zhongmai 895 (ZM895) was evaluated for FHB response using point inoculation from 2017 to 2019. The DH population was genotyped with wheat 660K SNP array and a high-density genetic map was constructed. Six resistance QTLs were detected, and among them, five were from the resistant parent Yangmai 16 and one from Zhongmai 895. QFhb.yaas-4DS and QFhb.yaas-6AS were detected at least in two years, explaining 8.8% to 15.0% of the phenotypic variances, respectively. QFhb.yaas-2DL and QFhb.yaas-3BL were detected only in one year, accounting for 10.5% and 14.7% of the phenotypic variances. QFhb.yaas-5BL and QFhb.yaas-4BS were detected in one year, too, accounting for 6.4% and 8.3% of the phenotypic variances, respectively. Pyramiding of multiple resistant loci with large effects (>10%) is an effective approach to increase FHB resistance. The QTLs identified from Yangmai 16 in the present study will provide a starting point for genetic studies of other Yangmai cultivars, and the QTLs closely linked to markers will be useful for marker-assisted selection in wheat FHB improvement.

Identification of molecular marker associated with mungbean yellow mosaic virus resistance in mungbean [Vigna radiata (L.) Wilczek

Mungbean [Vigna radiata (L.) Wilczek] is an important legume which can be grown in varying environmental conditions, during all three crop seasons viz., kharif, rabi and spring/summer in India, as sole or inter crop for grain and green manure. It is an excellent source of easily digestible proteins with low flatulence, which complements the staple rice diet in Asia. Mungbean Yellow Mosaic Disease (MYMD) caused by whitefly (Bemisia tabaci) transmitted mungbean Yellow Mosaic Virus (MYMV) is an important constraint of mungbean. To fulfill future demands, there is a need to use molecular marker technology and other biotechnological interventions. Hence, Bulked Segregant Analysis (BSA) with a Random Amplified Polymorphic DNA (RAPD) marker technique was used to analyze the F2:3 individuals of Pusa Ratna (susceptible) × Meha (resistant) to identify the molecular marker linked to MYMV resistance in mungbean. Field screening of thirty-five mungbean genotypes against MYMV was carried out, prior to crossing program to identify the resistant and susceptible genotypes. The RAPD primer, OPP 07 showed the specific band of 895 bp in resistant parent and their bulks, but not in the susceptible parent and their bulks. Co-segregation analysis was performed in resistant and susceptible F2:3 individuals; it confirmed that OPP 07895 marker was associated with MYMV resistance in mungbean. The linked RAPD molecular marker OPP 07895, can be used for the identification of (Quantitative Trait Locus) QTL for MYMV resistance and marker assisted selection program in mungbean.

QTLs for cell membrane stability and flag leaf area under drought stress in a wheat RIL population

A population of 206 recombinant inbred lines (RILs F9–F10) derived from wheat cross WL711/C306 was phenotyped for morpho-physiological traits such as flag leaf area (FLA), flag leaf length (FLL), flag leaf width (FLW), and cell membrane stability (CMS) under water deficit stress (WDS) environment. High yielding cultivar, WL711 had higher FLA than the medium yielding cultivar C306 across trials under both environments. Parent cultivar C306 maintained membrane integrity while WL711 showed higher membrane damage under WDS. The RIL population showed considerable variation, normal distribution and transgressive segregation for FLA, FLL, FLW and CMS under WDS. The genetic linkage map of WL711/C306 RIL population was constructed comprising of 346 markers. The total map distance was 4526.8 cM with an averaged interval of 12.9 cM between adjacent markers. Major consistent QTL for FLA, FLL, FLW, and CMS were identified on chromosomes 2DS and 3BS respectively in the WL711/C306 RIL population under WDS. The major QTL for FLA, qFLAWD.2D.1 which expressed in multiple environments and for CMS, qCMSWD.3B.3 and qCMSWD.3B.4, accounted for a large proportion of phenotypic variance (PV) with positive allele being contributed by C306, a drought resistant (DR) parent. QTL qFLAWD.2D.1 for FLA co-located with QTL for grain number (GN) and days to flowering (DTF) while QTL qCMSWD.3B.3 and qCMS.3B.4 co-located with QTL for grain yield and its components, days to flowering, canopy temperature and coleoptiles length as reported in our previous publications on the WL711/C306 population (Shukla et al. in Euphytica 203:449–467, 2015; Singh et al. in J Plant Biochem Biotechnol 24:324–330, 2015). Two candidate genes Ghd7 for grain yield and heading date and OsCDK4 for calcium dependent protein kinases were identified in the 2DS and 3BS QTL regions respectively on comparison with gene content of rice chromosomes 7 and 1 respectively. Hence, QTLs qFLAWD.2D.1 and qCMSWD.3B.3 are potential target regions for fine mapping and marker assisted selection for FLA and CMS respectively in wheat under water deficit environments.

Diallel Analysis of Barley Resistance to Blumeria graminis

Powdery mildew, caused by Blumeria graminis f. sp. hordei (Bgh) is a common foliar disease of barley worldwide. The creation of new cultivars with durable resistance to Bgh is highly desirable. This work was undertaken to examine the resistance to Bgh in 10 genetically diverse barley parents, and to evaluate their general combining ability (GCA) and specific combining ability (SCA) effects toward determining the genetic basis of disease resistance. Two experiments, in a growth chamber on seedling and in the field on adult plant stages, were conducted using a randomized complete block design with three replicates. The parents expressing differences in their reactions to Bgh were crossed in a half-diallel mating design to generate 45 full-sib families. Genetic component analysis showed significant effects for both GCA and SCA under both experiments suggesting that additive as well as non-additive genetic mechanisms were involved in the expression of resistance in these parents. The estimate of narrow-sense heritability was 0.63 and broad-sense heritability was 98% indicating that selection for the disease resistance should be effective in these crosses. Resistant parents ‘Banteng, PK 30-136 and ‘Igri’ had significantly negative GCA effects, suggesting their prime suitability for use in barley breeding programs to improve resistance to Bgh.

Identifying markers for resistance to sugarcane orange rust (Puccinia kuehnii) via selective genotyping and capture sequencing

Sugarcane orange rust, caused by the fungus Puccinia kuehnii, is a serious disease of sugarcane. The most effective strategy to combat the disease is to develop resistant cultivars. Phenotypic screening for resistance is laborious, and breeders would benefit from molecular markers linked to the trait. The objective of this research was to identify, via association mapping, markers linked to resistance to orange rust. From the germplasm collection at Canal Point, Florida, 724 genotypes were screened for orange rust resistance via artificial inoculation of field-grown plants. A total of 38 susceptible and 37 resistant genotypes that were at or near the extremes of the population distribution were chosen for genotyping. Genotyping was accomplished via capture sequencing using 32,555 sugarcane probes anchored to the sorghum genome. Several methods were used to account for population structure and/or kinship. The most appropriate methods (determined by the genomic inflation factor) were mixed models and EIGENSTRAT. A total of 38 unique SNPs identified by these methods were then validated on 560 members of the population, using high resolution melting of PCR amplicons. Ten of these markers were statistically significant for the quantitative measure of rust severity, of which nine were also significant for the qualitative measure of ‘status’ (resistant/susceptible). The maximum amount of variation explained by any single marker was approximately 11%. This research has provided markers which can be deployed to help select superior parents for orange rust resistance, and also provided valuable insight for future research towards genetic control of orange rust in sugarcane.

Multiple quantitative trait loci contribute to resistance to bacterial canker incited by Pseudomonas syringae pv. actinidiae in kiwifruit (Actinidia chinensis)

Pseudomonas syringae pv. actinidiae (Psa) biovar 3, a virulent, canker-inducing pathogen is an economic threat to the kiwifruit (Actinidia spp.) industry worldwide. The commercially grown diploid (2×) A. chinensis var. chinensis is more susceptible to Psa than tetraploid and hexaploid kiwifruit. However information on the genetic loci modulating Psa resistance in kiwifruit is not available. Here we report mapping of quantitative trait loci (QTLs) regulating resistance to Psa in a diploid kiwifruit population, derived from a cross between an elite Psa-susceptible ‘Hort16A’ and a resistant male breeding parent P1. Using high-density genetic maps and intensive phenotyping, we identified a single QTL for Psa resistance on Linkage Group (LG) 27 of ‘Hort16A’ revealing 16–19% phenotypic variance and candidate alleles for susceptibility and resistance at this loci. In addition, six minor QTLs were identified in P1 on distinct LGs, exerting 4–9% variance. Resistance in the F1 population is improved by additive effects from ‘Hort16A’ and P1 QTLs providing evidence that divergent genetic pathways interact to combat the virulent Psa strain. Two different bioassays further identified new QTLs for tissue-specific responses to Psa. The genetic marker at LG27 QTL was further verified for association with Psa resistance in diploid Actinidia chinensis populations. Transcriptome analysis of Psa-resistant and susceptible genotypes in field revealed hallmarks of basal defense and provided candidate RNA-biomarkers for screening for Psa resistance in greenhouse conditions.

Gene pyramiding for elite tomato genotypes against ToLCV (Begomovirus spp.), late blight (Phytophthora infestans) and RKN (Meloidogyne spp.) for northern India farmers.

Mega variety with multiple disease and pest tolerance is one of the major research objectives to protect the crop from biotic stresses in current scenario of climate change. Three tomato leaf curl virus resistance genes (Ty-1, Ty-2 and Ty-3), two late blight resistance genes (Ph-2 and Ph-3) and one root knot nematodes resistance gene (Mi-1.2) were pyramided from different donor parents with the help of marker-assisted backcrossing followed by phenotypic selection. During 2016-2017 (August-March), 100 lines of BC1F4 mapping population were evaluated against these diseases and pest screening. Punjab Chhuhara (a popular north Indian tomato cultivar) was used as a recipient parent that is susceptible for all these diseases and pest. Whereas the resistant parents included CLN3022F2-154-11-11-0 for tomato leaf curl virus, LBR-15 for late blight and NR-5 for root knot nematodes. The study results evaluated, 13 advanced backcrossed lines which possessed multiple disease and pest resistance with better horticultural traits over the parents as well as checks. This investigation showed that the introgression of Ty-1, Ty-2, Ty-3, Ph-2, Ph-3 and Mi-1.2 genes significantly improved the resistance against leaf curl, late blight and root knot nematodes diseases in selected advanced backcrossed lines of tomato. These improved multiple diseases resistant lines may play an important role in future pre-breeding tomato improvement projects.

Analysis of quantitative adult plant resistance to blackleg in Brassica napus

Leptosphaeria maculans L. causing blackleg is a highly evolved fungal pathogen that damages the rapeseed industry in Canada, Australia, and Europe. Advanced backcross populations segregating for intermediate resistance (BLMR2) and susceptible (blmr2) alleles were planted and inoculated using cotyledons. Near iso-genic lines (NILs) containing the intermediate blackleg resistance locus along with the parent lines and other controls were planted in a blackleg nursery at the University of Manitoba. ANOVA indicated a correlated significant difference between the genotypes with BLMR2 and blmr2 alleles at the seedling and adult plant stages. Heterozygous plants with both BLMR2 and blmr2 alleles showed relatively lower disease severity index (DSI) while other plants with only the blmr2 allele induced a higher DSI at seedling and adult plant stages, respectively, on a scale of 0–9. In the field, the NILs with the BLMR2 alleles consistently showed lower stem canker severity index similar to the resistant parent Surpass 400 in three consecutive years. In comparison, lines with known R genes (BLMR1 and Rlm2) showed relatively higher DSI in the field test. This demonstrated that the intermediate resistance locus performed well under severe blackleg disease pressure in the field while the NIL lines with single dominant R genes were ineffective. Because a group of isolates carrying various Avr/avr alleles was used in the field evaluation, our results suggest that the intermediate resistance locus confers horizontal resistance and has excellent potential in blackleg management in western Canadian canola production regions.

Meta-analysis of QTL for Fusarium head blight resistance in Chinese wheat landraces

Epidemics of Fusarium head blight (FHB), incited by Fusarium graminearum Schwabe, in wheat cause significant reductions in grain yield and quality. Numerous quantitative trait loci (QTL) for FHB resistance have been reported from Chinese sources. However, the relationships among QTL from different landraces have not been characterized. We earlier mapped QTL for FHB resistance using low-density maps developed from five recombinant inbred line (RIL) populations involving Chinese landraces ‘Haiyanzhong’ (HYZ), ‘Wangshuibai’ (WSB), ‘Baishanyuehuang’ (BSYH), ‘Huangfangzhu’ (HFZ), and ‘Huangcandou’ (HCD) as FHB resistant parents. In this study, we used maps of single nucleotide polymorphisms (SNP) developed from the five populations and identified 31 QTL on 16 chromosomes; 10 QTL were new. We constructed a consensus map and identified six meta-QTL (MQTL) and SNP within the MQTL regions using meta-analysis. Two of the MQTL were on chromosome 3BS (3BSd and 3BSc), and one on each of chromosomes 3A, 2D, 3D, and 4D. Twenty-two SNP closely linked to MQTL were converted into breeder friendly Kompetitive Allele Specific Polymerase Chain Reaction (KASP) assays, which should be useful for marker-assisted selection in breeding programs.

Screening of Polymorphic SSR Molecular Markers Between Resistant and Susceptible Parents for Localization of Brown Rust Resistance Gene

Sugarcane brown rust induced by Puccinia melanocephala is an important global disease. Exploring novel resistance genes and breeding varieties with durable resistance is the most economical and effective way of controlling brown rust. The establishment of complete and high-density molecular genetics maps is a key prerequisite for the discovery and location of sugarcane brown rust resistance genes. To obtain more polymorphic simple sequence repeat (SSR) markers for the construction of genetic linkage maps, six highly resistant varieties and six highly susceptible varieties were used as parents to screen the primers with clear bands, obvious polymorphism, and good repeatability. The highest numbers of polymorphic primers were obtained from the parental group of Liucheng 03-1137 × Dezhe 93-88 (52.38%). Ten pairs of primers including mSSCIR34 exhibited high polymorphism in the parental group of Liucheng 03-1137 × Dezhe 93-88. Here, we recommend ten SSR pairs of polymorphic primers including mSSCIR34 to use in the mapping populations of Liucheng 03-1137 × Dezhe 93-88. The polymorphic primers could facilitate the construction of genetic maps and lay an appropriate foundation for the localization of brown rust resistance genes and development of molecular genetics linkage markers.

Genetic Diversity and Responses of Some Selected Yellow Maize Genotypes to Stem Borer (Sesamia calamistis Hampson) Infestation

Aims: Identification of promising resistant parents against stem borer infestation for the development of high yielding maize hybrids.
 Study Design: Ten yellow maize genotypes selected for yield potential and durable level of tolerance to stem borer infestation were used in this study. A stem borer resistant yellow maize variety was crossed with nine stem borer (not necessarily resistant) maize varieties in a top-cross mating design.
 Place and Duration of Study: The study was conducted in 2017 and 2018 at the Institute of Agricultural Research and Training, OAU, Ibadan, Nigeria.
 Methodology: The resulting nine F1 hybrids along with the ten parents were evaluated under irrigation using a Randomized Complete Block Design (RCBD) with three replications in a stem borer endemic area. Data collected were subjected to combined analysis of variance (ANOVA), principal component analysis (PCA) and hierarchical clustering analyses.
 Results: Results obtained showed significant differences for year and genotype, as well as their interaction for some traits measured. Maize varieties were delineated into three groups. The first two PCA with Eigen values greater than 1.0 accounted for 73.0% of the variation; where PC1 was responsible for 52.5% of the variation and was associated with percentage stem borer infestation, leaf damage, plant aspect, stem tunneling ratio and dead heart. PC2 accounted for 20.5% and associated with only grain yield (GY). Also, maize hybrids had higher GY and better resistance to stem borer than their parents by 24.3% and -14.3%, respectively. BR9928-DMR-SR-Y was identified as resistant to stem borer with high GY in hybrid combinations. Positive and significant correlation was obtained among infestation parameters.
 Conclusion: Genes from promising donor parents may be introgressed into other desirable maize germplasm for the development of stem borer resistant maize hybrids.

Selection and Inheritance of Tomato Resistance against Ralstonia solanacearum

Ralstonia solanacearum is a plant pathogen causes wilting which is a major obstacle in the cultivation of tomato plants. In plant breeding, knowledge of the source of resistance genes and inheritance patterns is important in the development of bacterial wilt resistant varieties. This study aimed to obtain bacterial wilt resistant lines and to find out the inheritance pattern of tomato resistance to bacterial wilt. Selection of resistant plant involved the selected breeding lines from irradiation and crossing collections of the Genetic Laboratory, Faculty of Agriculture, Universitas Gadjah Mada. Introduced lines of H-7996 and F1 Permata and Timoti were used as a control. H-7996 as resistant parents and GM2 as susceptible parents, and their offspring include F1 GM2 x H-7996, F1 reciprocal, F2, Back Cross 1 (F1 x GM2), and Back Cross 2 (F1 x H-7996) used in testing inheritance patterns. Inoculation was carried out 1 week after planting by pouring 100 ml of water suspension of R. solanacarum (108 cfu/ml) on the roots. Completely Randomized Design (CRD) was used in this experiment. The scoring observation was carried out every week for one month. This study showed that Permata as a control was the most resistant, while Timoti and H-7996 were medium resistant. The CLN, G6, G8, and G7 lines were susceptible medium, yet only G8 and G7 with the smallest percentage of disease intensity and not significantly different than Timoti. The resistance gene to bacterial wilt on H-7996 was controlled by genes in the cell nucleus with additive-dominant gene action. Resistance to bacteria has a moderate level of heritability.

Genetic parameters and selection of sugarcane in early selection stages for resistance to sugarcane borer Diatraea saccharalis

Abstract A T1 (sugarcane population originating from true seeds) and T2 (first sugarcane clonal stage) population were used to estimate genetic parameters and compare selection strategies for Diatraea saccharalis (Lepidoptera: Crambidae) resistance in sugarcane. In the T1 stage, heritability at the family mean level (h²=0.77) was higher than individual genotype heritability (h²=0.16), and the additive genetic effect was more important for sugarcane borer resistance than non-additive effects. In addition, there was high genotypic variance among and within full-sib families. In the T2 population, genotypic variance was high, and heritability at the clone mean level was moderate (h²=0.61). We can conclude that family experiments enable selection of more promising families and parents for borer resistance. However, due to high genotypic variance within families, family selection at the T1 stage must be followed by clone selection at the T2 stage.

Up-regulation of microRNA-136 induces apoptosis and radiosensitivity of esophageal squamous cell carcinoma cells by inhibiting the expression of MUC1

ObjectiveThis present study is performed to figure out the role of microRNA-136 (miR-136) in radiosensitivity of esophageal squamous cell carcinoma (ESCC) cells through the regulation of MUC1. MethodsSeventy-four ESCC patients were divided into radiotherapy sensitive group and radiotherapy resistance group. Colony formation assay and flow cytometry were used to test the radiosensitivity of radiotherapy resistant strain and parent strain. The expression of miR-136 between radiotherapy resistant strain and parent strain was detected by RT-qPCR, and the expression of miR-136 in Eca109 and TE-1 cells as well as Eca109-R and TE-1-R cells was detected after different doses of X-ray irradiation. Eca109 and TE-1 cells as well as Eca109-R and TE-1-R cells with overexpression of miR-136 or co-overexpression of miR-136 and MUC1 were constructed. Cell proliferation, colony formation and apoptosis was detected by CCK-8 assay, colony formation assay, and flow cytometry, respectively. ResultsThe expression of miR-136 in ESCC tissues was lower and MUC1 mRNA and protein expression was higher than that in adjacent normal tissues. The expression of miR-136 was negatively correlated with the expression of MUC1 mRNA in ESCC. Low expression of miR-136 and high expression of MUC1 were associated with tumor size, lymph node metastasis and distant metastasis. The expression of miR-136 increased while the expression of MUC1 decreased in the radiotherapy sensitive group of ESCC patients relative to the radiotherapy resistant group. The colony formation ability of radiation resistant cell line was stronger than that of parent cell line, and the apoptosis rate showed an opposite trend. Up-regulation of miR-136 reduced the survival rate, suppressed colony formation ability and induced apoptosis of ESCC cells under irradiation, which was reversed by upregulated MUC1. ConclusionThis study demonstrates that up-regulation of miR-136 induces apoptosis and radiosensitivity of ESCC cells by inhibiting the expression of MUC1.

Genetics and gene action for resistance to leaf curl disease in chilli (Capsicum annuum)

Leaf curl disease of chilli has become a big menace and destroys the crop every year during kharif season because of which the farmers have abandoned growing the crop in kharif which is the main season of cultivation. Resistance breeding is the only safe and economical solution for this problem. WBC-Sel-5 was identified as a resistant genotype to ChiLCV after 4 seasons of rigorous field evaluation. This resistant line was used to generate F1 and F2 generations with susceptible recipient parent (Phule Mukta). F2 population raised from a cross of susceptible parent Phule Mukta and resistant parent WBC-Sel-5 was screened against chilli leaf curl virus along with parents and F1 in both natural and challenged inoculation using viruliferous white flies carrying chilli leaf curl virus. All the F1 plants were susceptible to leaf curl disease and the F2 population showed susceptible and resistant individuals segregating in 3:1 ratio under both natural and artificial epiphytotic conditions indicating monogenic recessive genetic control of resistance to chilli leaf curl virus disease.

Mapping quantitative trait loci (QTLs) associated with resistance to major pathotype-isolates of pearl millet downy mildew pathogen

Downy mildew (DM) caused by Sclerospora graminicola is the most devastating disease of pearl millet. It may lead to annual grain yield losses of up to ~80% and substantial deterioration of forage quality and production. The present study reports construction of the linkage map integrating simple sequence repeat (SSR) markers, for detection of quantitative trait loci (QTLs) associated with DM resistance in pearl millet. A mapping population comprising of 187 F8 recombinant inbred lines (RILs) was developed from the cross (ICMB 89111-P6 × ICMB 90111-P6). The RILs were evaluated for disease reaction at a juvenile stage in the greenhouse trials. Genotyping data was generated from 88 SSR markers on RILs and used to construct genetic linkage map comprising of 53 loci on seven linkage groups (LGs) spanning a total length of 903.8 cM with an average adjacent marker distance of 18.1 cM. Linkage group 1 (LG1; 241.1 cM) was found to be longest and LG3 the shortest (23.0 cM) in length. The constructed linkage map was used to detect five large effect QTLs for resistance to three different pathotype-isolates of S. graminicola from Gujarat (Sg445), Haryana (Sg519) and Rajasthan (Sg526) states of India. One QTL was detected for isolate Sg445 resistance, and two each for Sg519 and Sg526 resistance on LG4 with LOD scores ranging from 5.1 to 16.0, explaining a wide range (16.7% to 78.0%) of the phenotypic variation (R2). All the five co-localized QTLs on LG4 associated with the DM resistance to the three pathotype-isolates were contributed by the resistant parent ICMB 90111-P6. The QTLs reported here may be useful for the breeding programs aiming to develop DM resistant pearl millet cultivars with other desirable traits using genomic selection (GS) approaches.

Genetic characterization of Gossypium arboreum accession PI 529740 for reniform nematode resistance

AbstractBreeding for reniform nematode (Rotylenchulus reniformis) resistance is hindered by the lack of resistance in upland cotton (Gossypium hirsutum) cultivars. Resistance has been frequently identified in accessions from the Gossypium arboreum germplasm collection with accession PI 529740 rated as highly resistant. Accession PI 529740 was crossed with the susceptible G. arboreum accession PI 529729 to develop an F2 population for genetic characterization. The population showed quantitative variation suggesting multiple genes conferred the resistant phenotype. Thirteen of the 216 F2 plants showed resistance similar to the resistant parent and these data supported a two recessive gene model. Sixty plants were classified as resistant or moderately resistant, indicating a single recessive gene conferred the moderately resistant phenotype. The classification of 24 F2:3 families for nematode resistance generally supported the classification of the corresponding F2 plants; however, most families were highly variable for infection with no families rated as resistant. This information will aid in the introgression of resistance into upland cotton as larger populations will be required to successfully recover resistance conferred by multiple recessive genes.

Diversity analysis of mungbean [Vigna radiata (L.) Wilczek] genotypes for bruchid resistance

Mungbean [Vigna radiata (L.) Wilczek] is one of the most important pulse crops in the tropical and sub-tropical areas. Although the total production of mungbean is not enough to supplement the nutritional requirement, an additional issue further augments the concern of its use: the post-harvest damage in the storage condition. Bruchids (Callosobruchus chinensis) are major polyphagous storage pest that causes substantial losses, both quantitatively and qualitatively. The objective of the current study was to classify the fifty-two mungbean genotypes into groups based on their bruchid resistant and susceptibility by using multivariate statistical analysis. Since the present study emphasizes the progressive breeding program, the multivariate analysis is expected to effectively demonstrate the diversity of bruchid attack and therefore identify and ensures the correct representation of the resistant genotypes. The Principal Component Analysis (PCA) displays the correlation of bruchid morpho-physiological traits and the diversity analysis groups the considered genotypes into four clusters (I-IV). The cluster III contains seven genotypes which are observed most effective against bruchid attack. The PC1 shows 70.83% of variability where PC2 shows 29.17% of variability. PCA picturize the most positive correlation between the number of egg laid (NOEL-0.922) and percentage of seed damage (POSD-0.975) among all the morpho-physiological traits. The cluster III thus helps selecting resistant parents for hybridization in future crop improvement program.

Caffeic Acid and α-Chaconine Influence the Resistance of Potato Tuber to Phthorimaea operculella (Lepidoptera: Gelechiidae)

Host plant quality can influence insect larval performance and subsequent adult fitness. Advanced hybrid potato clones (donor species: Solanum berthaultii Hawkes) and their parents were evaluated for resistance to the potato tuber moth (PTM) and examined for several biochemical, molecular and physical traits in order to investigate the mechanisms which underlie PTM-resistance. Resistant parent recorded 57% of mortality of pupae in comparison to the 23% observed in the susceptible parent. Expression patterns of specific genes involved in the phenolic biosynthetic pathway show that hydroxycinnamoyl-CoA quinate hydroxycinnamoyl transferase (HQT) and cinnamate-4-hydroxylase (C4H) reflect chlorogenic and caffeic acid levels in the skin of all the genotypes (0.7 ≤ r ≤ 1.0). Skin α-chaconine and skin caffeic acid strongly and significantly related with PTM larval mortality (r2 = 0.99 and r = 0.90, respectively). This study suggests that skin α-chaconine and skin caffeic acid could play a defensive role against PTM and proposes a PTM resistant clone with high level of these bio-compounds, useful in breeding projects for plant defense and nutritional value purposes.