Resistance Of Inbred Lines Research Articles

Evaluation of the lodging resistance and the selection of identification indexes of maize inbred lines

AbstractLodging is one of the main problems affecting the maize production. In this study, 220 maize inbred lines were used for determining the lodging resistance. Analysis methods such as the correlation analysis, the principal component analysis, the cluster analysis, the stepwise discriminate analysis, and the ridge regression analysis were deployed for data interpretation. The results of the correlation analysis showed that 17 characters were correlated with varying degrees. Strong and positive correlations between TID and FID (r = 0.910), TIL and FIL (r = 0.898), NSVB and NLVB (r = 0.775), ASVB and ALVB (r = 0.746), and LC and HC (r = 0.656) were observed. The first six principal components explained 79.13% of the phenotypic variation of the 17 characters, with the contribution rates being 20.77%, 18.12%, 14.09%, 11.17%, 8.66%, and 6.32%, respectively. Five categories were clustered in the 220 inbred lines. The result of stepwise discriminate analysis showed that 211 inbred lines were correctly discriminated and the identification rate was 95.91%, and 9 inbred lines were incorrectly discriminated and the identification rate was 4.09%, which meant that the result of cluster analysis was accurate and reliable. The stalk bending strength, ear height, cellulose content, number of small vascular bundles, and cross‐sectional area were selected, and the regression model of lodging resistance of inbred lines was established by using the ridge regression method. Thirty of the 220 inbred lines, including R1656, 4003, and LD61, showed the highest lodging resistance. The results provide a reference for the selection of lodging‐resistant germplasm resources in breeding for the lodging resistance hybrids.

Dose-dependent differential resistance of inbred chicken lines to avian pathogenic Escherichia coli challenge

ABSTRACTAvian pathogenic E. coli (APEC) cause severe respiratory and systemic disease. To address the genetic and immunological basis of resistance, inbred chicken lines were used to establish a model of differential resistance to APEC, using strain O1 of serotype O1:K1:H7. Inbred lines 72, 15I and C.B12 and the outbred line Novogen Brown were inoculated via the airsac with a high dose (107 colony-forming units, CFU) or low dose (105 CFU) of APEC O1. Clinical signs, colibacillosis lesion score and bacterial colonization of tissues after high dose challenge were significantly higher in line 15I and C.B12 birds. The majority of the 15I and C.B12 birds succumbed to the infection by 14 h post-infection, whilst none of the line 72 and the Novogen Brown birds developed clinical signs. No difference was observed after low dose challenge. In a repeat study, inbred lines 72 and 15I were inoculated with low, intermediate or high doses of APEC O1 ranging from 105 to 107 CFU. The colonization of lung was highest in line 15I after high dose challenge and birds developed clinical signs; however, colonization of blood and spleen, clinical signs and lesion score were not different between lines. No difference was observed after intermediate or low dose challenge. Ex vivo, the phagocytic and bactericidal activity of lung leukocytes from line 72 and 15I birds did not differ. Our data suggest that although differential resistance of inbred lines 72, 15I and C.B12 to APEC O1 challenge is apparent, it is dependent on the infectious dose.Research HighlightsLines 15I and C.B12 are more susceptible than line 72 to a high dose of APEC O1.Differential resistance is dose-dependent in lines 15I and 72.Phagocytic and bactericidal activity is similar and dose independent.

Effectiveness of quantitative resistance conferred by the genetic background of pepper in the control of root-knot nematodes and influence onto durability ofMe1-andMe3-resistant genes in greenhouse conditions

In pepper (Capsicum annuum), the major genes (R-genes) Me1 and Me3 confer resistance against root-knot nematodes (Meloidogyne spp.). The combination of R-genes and quantitative resistance factors in the same genotype is considered a good breeding strategy for increasing the durability of R-genes. To ascertain this hypothesis, five pepper inbred lines, differing in their quantitative resistance level, were combined with Me1 or Me3 genes in F1 hybrids. The resistance of inbred lines and F1 hybrids was evaluated in a greenhouse with soil naturally infected by M. incognita in two successive growing years. In both years, lines carrying Me3 were less infected by the nematode when combined with quantitative resistance. An increase in nematode infection was observed in the second growing year in lines carrying Me1 or Me3, independently of quantitative resistance. The infection level recorded in inbred lines without R-genes was similar in both years. The effectiveness of quantitative resistance controlling M. incognita is confirmed in greenhouse conditions, although the durability of Me1 and Me3 when combined with quantitative resistance factors was not seen to increase.

Development and identification of Verticillium wilt-resistant upland cotton accessions by pyramiding QTL related to resistance

Cotton Verticillium wilt is a serious soil-borne disease that leads to significant losses in fiber yield and quality worldwide. Currently, the most effective way to increase Verticillium wilt resistance is to develop new resistant cotton varieties. Lines 5026 and 60182 are two Verticillium wilt-resistant upland cotton accessions. We previously identified a total of 25 quantitative trait loci (QTLs) related to Verticillium wilt resistance from 5026 and 60182 by assembling segregating populations from hybridization with susceptible parents. In the current study, using 13 microsatellite markers flanking QTLs related to Verticillium wilt resistance, we developed 155 cotton inbred lines by pyramiding different QTLs related to Verticillium wilt resistance from a filial generation produced by crossing 5026 and 60182. By examining each allele's effect and performing multiple comparison analysis, we detected four elite QTLs/alleles (q-5/NAU905-2, q-6/NAU2754-2, q-8/NAU3053-1 and q-13/NAU6598-1) significant for Verticillium wilt resistance, pyramiding these elite alleles increased the disease resistance of inbred lines. Furthermore, we selected 34 elite inbred lines, including five lines simultaneously performing elite fiber quality, high yield and resistance to V. dahliae, 14 lines with elite fiber quality and disease resistance, three lines with high yield and disease resistance, and 12 lines with resistance to V. dahliae. No correlation between Verticillium wilt resistance and fiber quality traits/yield and its components was detected in the 155 developed inbred lines. Our results provide candidate markers for disease resistance for use in marker-assisted breeding (MAS), as well as elite germplasms for improving important agronomic traits via modern cotton breeding.

Confirmation of QTL Reducing Aflatoxin in Maize Testcrosses

ABSTRACTAflatoxins, produced by the fungus Aspergillus flavus Link:Fr, constrain maize (Zea mays) production in some regions. Difficulties in breeding resistance to this toxin make it a good target for quantitative trait locus (QTL) identification and molecular‐assisted breeding. Multiple QTL have been identified for aflatoxin resistance in inbred lines per se; however, it has not been determined if aflatoxin resistance QTL would be useful in hybrids or have deleterious pleiotropic effects. The objectives were to confirm the presence, in testcrosses, of QTL estimates previously identified in lines per se; estimate new QTL for reducing aflatoxin accumulations and agronomic traits in hybrids; and evaluate co‐localization of QTL that suggest pleiotropic effects with measured traits. Plant height, flowering time, starch, oil, and protein were also included in the analysis. Significant environment and genetic × environment interaction were detected for most traits. Heritability estimates were equivalent to those previously reported, and no meaningful correlations were detected between aflatoxin accumulation and other traits. Ninety‐three QTL were detected across 14 traits measured in five environments. Aflatoxin‐reducing QTL detected in per se analyses were detected in testcrosses on chromosome 1, with new QTL detected on chromosomes 3, 4, 8, and 9. Co‐localization of aflatoxin‐reducing QTL detected on chromosome 9 with QTL for silking date suggests a pleiotropic effect based on avoidance or agronomics and not a resistance QTL.

Diallel analysis of grain yield and resistance to seven diseases of 12 African maize (Zea mays L.) inbred lines

Maize (Zea mays L.) is grown on 15 million ha in eastern and southern Africa. Several diseases are of common occurrence in the region and regularly result in significant yield losses. A collaborative regional disease nursery (REGNUR) project was initiated in 1998 to identify and increase access to disease resistant germplasm, generate and disseminate information on disease and insect resistance sources, and facilitate the development of resistant cultivars by project partners. A diallel among 12 elite inbred lines was formed with the specific objective of evaluating the combining ability of these inbred lines for grain yield and resistance to seven diseases. The trial was grown at six sites in 2001. Results showed that both general (GCA) and specific combining ability effects were significant for most diseases. On the average, GCA accounted for 69% of resistance to diseases and only 37% of variation for grain yield. Correlations between GCA effects for disease scores were generally non-significant, implying that it is possible to pyramid genes for disease resistance in inbred lines. This underscores the need for screening for resistance to prevailing diseases using artificial inoculation or reliable hot-spots. Based on GCA effects for grain yield and across diseases, P12 and P6 were the best inbred lines. The crosses P4 × P9 (6.7 t ha−1) and P4 × P12 (6.9 t ha−1) were the best hybrids in the earlier maturity group, while P3 × P9 (8.3 t ha−1) and P2 × P8 (7.4 t ha−1) were the best hybrids in the late maturity group.

An Evaluation of Quantitative Traits Related to Drought Resistance in Inbred Lines of Maize in Stress and Non-Stress Conditions

An Evaluation of Quantitative Traits Related to Drought Resistance in Inbred Lines of Maize in Stress and Non-Stress Conditions

Induced responses in Ipomoea hederacea: simulated mammalian herbivory induces resistance and susceptibility to insect herbivores

Multispecies interactions between plants and natural enemies are ubiquitous, and often lead to diffuse interactions between plants and their herbivores. Non-specific induced responses, where responses induced by one species affect other species, are one potential mechanism generating diffuse interactions. Using 57 inbred lines of the Ivyleaf morning glory, Ipomoea hederacea, in a greenhouse experiment, we examined whether simulated mammalian herbivory induced responses that could affect plant resistance to the generalist insect herbivore, Spodoptera exigua. Inbred lines were highly variable for induced responses, ranging from induced resistance to induced susceptibility, with the rank-order for resistance in inbred lines changing between clipping and control treatments. We failed to detect significant genetic correlations between induced responses and trichome density, or that clipping modified the negative relationship between trichome density and Spodoptera exigua consumption and biomass. Our results suggest that non-specific induced responses can mediate the diffuse evolutionary relationship between I. hederacea and its herbivores, and that genetic variation in induced responses are an important component of this interaction.

Antibiosis of maize inbred lines to the carmine spider mite, tetranychus cinnabarinus

The antibiosis of tenZea mays L. inbred lines to the carmine spider mite,Tetranychus cinnabarinus (Boisduval) (Acari: Tetranychidae), was evaluated. Two maize inbred lines previously reported as resistant to this spider mite and a susceptible inbred line were compared with B96 (formerly called 41:2504B), reported as being resistant to the two-spotted spider mite T. urticae and to the European corn borer (Ostrinia nubilalis Hubner). Other lines were derived from B96. All lines originated in the U.S.A. and were tested in Israel at two different growth stages. Four days after inoculation of detached leaf squares with adult mites, significant differences in susceptibility were observed among lines. At the 3-leaf stage lines B68, B96, B79, A619, B65, B49 and B64 reduced the average mite daily fecundity by 43%, 64%, 66%, 67%, 77%, 81% and 87%, respectively, as compared with the most susceptible line, B52. At the flowering stage, the average reduction in mite daily fecundity was much lower: inbred lines B64, A619 and B96 reduced the average mite daily fecundity by 48%, 51% and 86%, respectively, whereas the seven other genotypes had an intermediate or a susceptible reaction to the carmine spider mite, with A661 being the most susceptible. Our results show that B96 could be used as a source of resistance in developing improved resistance of inbred lines of maize to carmine spider mites.

Breeding wheat and rye for resistance to Fusarium diseases

Abstract Fusarium culmorum and F. graminearum Groups 1 and 2 cause seedling blight, crown rot, foot rot and head blight in wheat and rye that may affect grain yield and quality for baking and feeding. This review starts with an analysis of Fusarium populations with regard to their genetic variation for aggressiveness, mycotoxin production, and isolate‐by‐host genotype interaction. To assess resistance in the different host growth stages, quantitative inoculation and disease assessment techniques are necessary. Based on estimated population parameters, breeding strategies are reviewed to improve Fusarium resistance in wheat and rye. Epidemiological and toxicological aspects of Fusarium resistance that are important for resistance breeding are discussed. F. culmorum and F. graminearum display large genetic variation for aggressiveness in isolate collections and in naturally occurring populations. The production of mycotoxins, especially deoxynivalenol and its derivatives, is a common trait in these populations. Significant isolate‐by‐host genotype interactions were not found across environments in wheat and rye.Artificial infections in the field are indispensable for improving Fusarium crown rot, foot rot and head blight resistance in wheat and rye. For a reliable disease assessment of large populations, disease severity ratings were found to be the most convenient. The differentiation of host resistance is greatly influenced by an array of nongenetic factors (macro‐environment, microclimate, host growth stage, host organ) that show significant interactions with host genotype. Selection for environmentally stable resistance has to be performed in several environments under a maximum array of different infection levels. Selection in early growth stages or on one plant organ does not in most cases allow prediction of resistance in adult‐plant stages or another plant organ.Significant genetic variation for resistance exists for all Fusarium‐incited diseases in breeding populations of wheat and rye. The patho‐systems studied displayed a prevalence of additive gene action with no consistent specific combining ability effects and thus rapid progress can be expected from recurrent selection. In wheat, intensive testing of parental genotypes allows good prediction of the mean head blight resistance after crossing. Subsequent selection during selfing generations enables the use of transgression towards resistance. In hybrid breeding of winter rye, the close correlation between foot rot resistance of inbred lines and their GCA effects implies that selection based on the lines per se should be highly effective. This is not valid for F. culmorum head blight of winter rye caused by a greater susceptibility of the inbred lines compared to their crosses.For both foot rot and head blight resistance, a high correlation between the resistance to F. graminearum and F. culmorum was found in wheat and rye. Mycotoxin accumulation occurs to a great extent in naturally and artificially infected plant stands. The correlation between resistance traits and mycotoxin contents are medium and highly dependent on the environment. Further experiments are needed to clarify whether greater resistance will lead to a correlated reduction of the mycotoxin content of the grains under natural infection.

Effects of Temperature and Illuminance on Resistance of Inbred Lines of Corn to Isolates ofBipolaris maydis

Effects of Temperature and Illuminance on Resistance of Inbred Lines of Corn to Isolates of<i>Bipolaris maydis</i>

Effect of Illuminance on the Resistance of Inbred Lines of Corn to Isolates ofColletotrichum graminicola

Effect of Illuminance on the Resistance of Inbred Lines of Corn to Isolates of<i>Colletotrichum graminicola</i>