Stalk Rot Resistance Research Articles

Gibberella stalk rot (Fusarium graminearum) resistance of maize inbreds and their F1hybrids and their potential for use in resistance breeding programs

With 1 table Abstract Fusarium graminearum Schwabe is one of the predominant fungal species responsible for stalk rot of maize in Canada and many other countries. Adapted sources of resistance to this disease are scarce but recently a few have been identified. To evaluate the usefulness of these sources in a breeding programme to improve stalk rot resistance, a complete diallel cross of five inbreds of varying susceptibility to stalk rot was conducted. Artificial inoculations of stalks were accomplished by injecting a conidial suspension into the first internode above the uppermost aerial root node. Stalk rot ratings, yield and lodging in the parents, crosses and reciprocals were evaluated over two field seasons. There were significant differences between inbred lines and hybrids for stalk rot ratings. Inbreds CM174 and CO325 were highly susceptible, whereas inbreds 73405 and 73353 were classified as resistant and both had good general combining ability. Those inbreds could be used as donors of favourable alleles in breeding programmes for Gibberella stalk rot resistance.

Molecular mapping of genomic regions harboring QTLs for stalk rot resistance in sorghum

Stalk rot, also called as charcoal rot in India, caused by Macrophomina phaseolina, is an economically important, soil borne disease in major sorghum growing areas across the world. A population of F9 generation recombinant inbred lines (RILs), derived from IS22380 (susceptible) × E36-1 (resistant), along with parents were phenotyped in sick plots at two locations (Dharwad and Bijapur, Karnataka, India). A total of 85 polymorphic marker loci (62 nuclear and 4 genic SSRs, 19 RAPDs) was available for the construction of genetic map, spanning 650.3 cM in all the ten linkage groups. Analysis with QTL Cartographer (2.5b), adopting composite interval mapping method (LOD > 2.0) at both locations, revealed 5 QTLs at Dharwad and 4 QTLs at Bijapur locations for the component traits of charcoal rot disease resistance. QTLs for number of internodes crossed, length of infection and per cent lodging accounted for 31.83, 10.76 and 18.90 per cent at Dharwad location and 14.87, 10.47 and 26.44 per cent phenotypic variability at Bijapur location, respectively. The QTLs for number of internodes crossed by the rot, length of infection and percent lodging were common across two locations. These QTLs, consistent over environments for the component traits, are likely to assist in marker-assisted selection (MAS) for charcoal rot resistance in sorghum.

Phenolics in Maize Genotypes Differing in Susceptibility to Gibberella Stalk Rot (Fusarium graminearum Schwabe)

The relationship between phenolic compounds and maize pith resistance to Fusarium graminearum, the causal agent of Gibberella stalk rot, was investigated. The phenolic acid profiles in the stalks of six maize inbred lines of varying susceptibility were evaluated from silking to grain maturity. Four different fractions of phenolic compounds were extracted from inoculated and non-inoculated (control) pith tissues: insoluble cell-wall-bound, free, soluble ester-bound, and soluble glycoside-bound phenolics. Analysis by HPLC revealed that p-coumaric acid and ferulic acid were the most abundant compounds in the soluble and cell-wall-bound fractions. The quantity of free, glycoside-bound, and ester-bound phenolics in the pith was lower than the level required for the inhibition of Fusarium growth or mycotoxins production; however, significant negative correlations between diferulic acid contents in the cell walls and disease severity ratings 4 days after inoculation were found. The results indicated that future studies should focus on the levels of diferulic acids during the early infection process. Diferulates may play a role in genotypic resistance of maize to Gibberella stalk rot as preformed barriers to infection.

Comparing estimates of variances and correlations for two recurrent selection methods in the maize synthetic FAOSYNFR1B

The objective of this study was to compare estimates of variances and correlations for S1 and HSI methods in the second cycle of recurrent selection in the FAOSYNFR1B synthetic for stalk rot resistance and grain yield. We compared estimates of variance and correlations for S1 and HSI methods in the second cycle of recurrent selection in the maize synthetic FAOSYNFR1B for stalk rot resistance and grain yield when the components were re-estimated with restricted maximum likelihood (REML) method. There were some differences between variance components estimated by REML analysis and ANOVA due to adjusting of estimates in extended random model and by re-estimating the other variances because of some negative estimates. There was no either phenotypic or genotypic correlation between the two traits for the S1 method, while the both correlations for the HSI method were negative and very weak. The estimates of phenotypic and genotypic correlations were similar for both selection methods indicating that phenotypic correlations could alone accurately reflect expected correlated responses between the traits when sample size is relatively large.

Improvement of stalk rot resistance and grain yield in the maize synthetic FAOSYNFR1B by recurrent selection

Two cycles of simultaneous selection for stalk rot resistance and grain yield have been conducted in the FAOSYNFR1B population synthesized from Eastern European maize germplasm. The objectives of this study were: 1) to compare expected genetic gain from S 1 and HSI methods of selection in the second cycle and 2) to evaluate improvement (gain) of stalk rot resistance and grain yield in the population per se associated with two cycles of selection. In the first cycle of selection, S 1 method and HSI method (using an inbred tester) were combined (S 1 -HSI) to produce C1 population. In the second cycle of selection the S 1 and HSI methods were applied separately to produce C2(S 1 ) and C2(HSI) populations, respectively. In 1996, the C0, C1, C2(S 1 ), and C2(HSI) populations per se were evaluated at four locations in natural conditions and at one under artificial stalk infection. Combined S 1 -HSI method was successful in improving both stalk rot resistance and grain yield. In the second cycle, further improve...

Analysis of Stalk Rot Resistance and Genetic Diversity among Drought Tolerant Sorghum Genotypes

Forty‐five drought tolerant sorghum [Sorghum bicolor (L.) Moench] genotypes were screened for stalk rot resistance by artificial inoculation with Fusarium proliferatum in field trials near Manhattan, KS, in 2000. Four lines, SC134, SC1154, SC1039, and SC564, were identified with lesions that were smaller than the standard resistant check, SC599. These lines and four other checks were intercrossed in a Design II mating scheme with ‘AWheatland’ and ‘ARedlan’ to produce hybrids for further testing. The inbred parent lines and corresponding hybrids were evaluated for resistance to four major stalk rot pathogens, F. proliferatum, F. thapsinum, F. andiyazi, and Macrophomina phaseolina, using randomized complete block designs in field trials near Manhattan and Hesston, KS, in 2001. Significant differences in lesion length were detected among the inbred parent lines and their corresponding hybrids. Comparisons among entries indicated that crosses of SC701 and SC564 were susceptible and produced very large lesions following inoculation with each of the stalk rot pathogens evaluated in this study. Only small lesions were produced in SC599 and its hybrids following inoculation with either Fusarium species or M. phaseolina SC134 also exhibited high levels of resistance to Fusarium species and SC35 to M. phaseolina Comparisons among pathogens showed that inoculations with M. phaseolina produced larger lesions than the Fusarium species in most sorghum genotypes. The most resistant accessions in these studies were all from East Africa; therefore, an analysis of genetic diversity was conducted to evaluate the pattern of genetic relationships among the full set of drought tolerant lines. DNA fingerprinting followed by cluster analyses grouped the entries into five distinct clusters, mainly according to geographical origin. Three of the resistant lines grouped together in a cluster that contained mostly Ethiopian landraces while SC599 grouped in another cluster.

Estimation of Combining Ability for Resistance to Fusarium Stalk Rot in Grain Sorghum

Fusarium stalk rot (caused by Fusarium spp.) is an important disease of grain sorghum [Sorghum bicolor (L.) Moench]. The objectives of this study were to identify genetic sources of Fusarium stalk rot resistance and estimate combining ability. Six sorghum R‐lines, representing commercial parent lines and potential sources of stalk rot resistance, Tx2737, Tx435, SC33, SC35, SC599 and SC1158, and three standard seed parents, ASA3042, AWheatland, and ARedlan, were intercrossed in a Design II mating scheme. The inbred parent lines and corresponding hybrids were evaluated in field trials at Manhattan and Hesston, KS, in 1999 and 2000. Three randomly selected plants in each plot were artificially inoculated in the pith tissue of the basal stalk with liquid cultures of F proliferatum at 14 d after flowering. One additional plant in each plot was inoculated with distilled water as a control. At 28 d after inoculation, plants were harvested and scored for disease severity. Significant differences in disease reactions were noted among parent lines and hybrids. Among hybrids, significant male and female parent effects and interactions were detected. SC599 consistently had very low mean disease scores, followed by SC1158. Hybrids produced with SC599 were also highly resistant, indicating that genes for resistance had a dominant mode of inheritance in this genotype. SC599 represents an excellent source of resistance to F. proliferatum for use in breeding programs.

Resistance of Maize Inbreds and their Hybrids to Fusarium Stalk Rot

 The resistance of 35 inbred lines and their 70 hybrids with two testers to stalk rot is described and the results of natural and artificial stalk infection are compared. A mixture of Fusarium spp. spores was used for artificial infections. The disease was scored for two years. Inbreds and hybrids differed significantly in resistance and infection types in both years. Generally, disease scores of hybrids were lower than of inbreds. No close association was found between lines and their testcross hybrids (r = –0.06 to 0.29) and between hybrids with the two testers (r = –0.04 to 0.38). The correlation coefficients of disease scores after natural and artificial infection were in inbreds and in hybrids highly significant (r = 0.45–0.87). The results suggest, that Fusarium stalk rot resistance should be tested in both inbreds and hybrids. We recommend for maize breeding, that tests with artificial infection should be followed by tests under natural infection.  

Cytogenetic study of Helianthus laevigatus and its F1 and BC1F1 hybrids with cultivated sunflower, Helianthus annuus

AbstractAlthough the wild sunflower species Helianthus laevigatus has not been extensively studied it may be considered for sunflower breeding as a potential source of desirable genes for Sclerotinia stalk rot resistance and high contents of proteins and linoleic acid in the seed.A set of six H. laevigatus populations was crossed to cultivated sun~ower lines and produced nine F1 (2‐14 plants) and 66 BC1F1 hybrid combinations (1‐13 plants). Male sterility occurred in F1 and BC1F1 hybrid combinations and pollen viability was lower in the progenies than in the parents (51.6‐77.2%in F1 and in F1 and 4.8‐34.0% in BC1F1). Meiosis was normal in the H. laevigatus populations It was found that this tetraploid species also occurred in a hexaploid form Numerous irregularities were observed in the meiosis of the F1 interspecific hybrids During diakinesis, quadrivalents and hexavalents were recorded in addition to bivalents Dislocated chromosomes and chromosome bridges were present in the other phases The chromosome number in F1 was 68 (tetraploid). Irregularities in chromosome pairing were observed in the interspecific hybrids at BC1F1. There were many univalents, and trivalents quadrivalents and hexavalents were also present The chromosome number in the BC1F1 generation ranged from 34 to 60. The occurrence of meiotic irregularities in the F1 and BC1F1 interspecific hybrids indicates that H. laevigatus and the cultivated sunflower differ in genome constitution.

Estimation of Genetic Variances for Ear and Stalk Rot Resistance in Two Romanian Maize Populations

Estimation of Genetic Variances for Ear and Stalk Rot Resistance in Two Romanian Maize Populations

Evaluation of Methods for Identification of Corn Genotypes with Stalk Rot and Lodging Resistance

Methods of evaluating corn (Zea mays) stalk quality at or near anthesis and stalk rot susceptibility following inoculation were examined for 3 yr to identify those most effective in predicting premature death of plants and stalk lodging in multiple environments. Stalk quality measurements, including rind puncture, rind thickness, stalk push test, pith density or pith moisture, and susceptibility to the stalk rotting fungi Stenocarpella maydis and Colletotrichum graminicola, were determined on eight single-cross hybrids grown in Urbana, Illinois. Data on premature death of plants and lodging were collected from the same hybrids grown near Urbana in 1984 and at 16 locations throughout the midwestern United States in 1985 and 1986 [...]

Effect of pattern and severity of moisture-deficit stress on stalk-rot incidence in sorghum. II. Effect of source/sink relationships

Stalk-rot of grain sorghum [ Sorghum bicolor (L.) Moench] is most commonly associated with weakly parasitic root and stalk-rot fungi when the host plants are subjected to environmental stresses. The incidence of rots is generally more in high-grain-yield environments associated with high plant density or fertilizer application. The effects of time of occurrence and degree of moisture deficit stress (moisture stress) on grain and biomass yields, and the natural incidence of stalk-rots were studied. Stress during grain-filling had a greater effect on incidence of rots than stress at earlier stages. Grain-yield and disease incidence were differently affected by timing and severity of moisture stress. Stalk-rot incidence was most commonly and strongly associated with moisture stress at the terminal stage of growth. However, stress during panicle development induced changes in the sink size (grain number) or root-growth pattern, which in turn influenced both the timing and extent of stalk-rot incidence. The amount of biomass produced during the later part of the grain-filling period was positively correlated with lower disease susceptibility. The distribution index (i.e., the ratio of grain-yield to biomass produced after flowering) could be generally used to predict disease susceptibility. There were no simple correlations between biomass, grain-yield or yield components, and stalk-rot. Implications of these findings for sorghum production and for stalk-rot resistance screening are discussed.

Distributions Among S1Lines for European Corn Borer (Lepidoptera: Pyralidae) and Stalk Rot Resistance Ratings in Two Maize Synthetics Improved by Recurrent Selection

Four cycles of recurrent selection were used to reduce leaf-feeding damage caused by first-generation European corn borer (ECB), Ostrinia nubilalis Hubner, and pith decay associated with Diplodia, Diplodia maydis (Berkeley) Saccardo, stalk rot (DSR) in two maize, Zea mays L., synthetics, BSAA and BSBB. Recurrent selection was based on the evaluation of SI progenies. For this study, 100 unselected Illines from each of the original (CO) and improved (C4) populations of BSAA and BSBB were evaluated for ECB resistance, DSRresistance, and stalk rind puncture. The distributions of S,1 lines for the three traits and the genetic relationships among traits were evaluated to determine the effectiveness of the recurrent selection programs. The C4s of both synthetics were more resistant than the COs to ECB leaf feeding after artificial infestations, were more resistant to D5R after artificial inoculations, and possessed harder stalks. The differences between the CO and C4 means were highly significant (P < 0.01) in all instances. Reductions in genetic variation were observed in BSAA for ECB ratings and in BSBB for all three traits. The reductions in genetic variation were especially dramatic for ECB ratings, indicating that relatively few gene pairs were segregating for leaf-feeding resistance in BSAA and BSBB. Low and generally nonsignificant correlations between DSR ratings and rind puncture readings indicated that selection for both traits would be justified to improve field stalk lodging resistance.

Improvement of Resistance to Ear and Stalk Rots and Agronomic Traits in Tropical Maize Gene Pools

Ear and stalk rots of maize (Zea mays L.) caused by Fusarium moniliforme (Sheldon) limit maize production in the lowland tropics. A modified ear‐to‐row (MER) selection scheme was used, with minor changes, to improve resistance to these diseases and five agronomic traits in eight tropical maize gene pools. Six pools were selected for stalk‐rot resistance (SRR) and two for ear‐rot resistance (ERR). Each pool included approximately 500 half‐sib (HS) families, and the selection intensity among and within families was adjusted so as to maintain this population size during each cycle of selection. Family selection was based on single‐row plots of 16 to 21 plants in one or two environments. Data on grain yield, plant and ear height, days to 50% silking (DS), lodging, disease and insect reaction, and plant and ear uniformity were recorded at appropriate stages of plant development. One cycle of selection was completed season−1. Selection for disease resistance was practiced under artificial inoculation. Averaged over pools, progress from selection (linear response) was 2.50** (significant at the 0.01 probability level), −0.15**, −0.35**, −1.66**, and −0.90% cycle−1** for yield, DS, plant height, SRR, and ERR, respectively. Yield improvement (linear response) averaged higher in pools selected for SRR (3.02% cycle−1**) than in those selected for ERR (1.38% cycle−1**). In the reduction of DS and plant height, however, greater progress was made in pools selected for ERR (−0.50** and −0.75% cycle−1**, respectively) than in those selected for SRR (−0.04** and −0.25% cycle−1**, respectively). Results indicate that the MER selection scheme employed by the International Maize and Wheat Improvement Center (CIMMYT) was effective in increasing grain yield, SRR, and ERR; and in reducing DS and plant height in maize.

Response of Two Maize Populations to Reciprocal Recurrent Selection in a High-yield Environment

A selection program using reciprocal recurrent selection procedures in maize (Zea mays L.) was developed. Intra-and interpopulation selection procedures were used for two maize populations BS10 and RSSSC. Intrapopulation selection procedures included phenotypic mass selection for multiple leaf and multiple stalk-rot disease resistance and S1 family selection for grain yield in a high-yield environment. Interpopulation improvement involved selection of testcrosses of S1 family×inbred tester in a high-yield environment. Evaluations of populations per Se, population crosses and populations×testers for response to three cycles of selection for grain yield were conducted at four environments. Evaluation of populations per se and population crosses for response to three cycles of selection for multiple leaf disease and multiple stalk-rot resistance was conducted at disease nursery in 1985. The results indicate that selection response was consistent among environments. Gain from selection was satisfactory in populations per Se, population crosses and populations x testers for grain yield, multiple leaf disease resistance and multiple stalk-rot resistance. Linear response to three cycles of selection for grain yield for BS10, RSSSC, BS10×RSSSC, BS10×B37, and RSSSC×B79 were: 0.95, 0.69, 0.65, 0.65 and 0.24 Mg/ha/cycle, respectively. The rates of gain for grain yield obtained in the present study compare favorably with published reports. Linear response for stalk lodging for BS1O, BS10×RSSSC and BS10×B37 were: -9.0, -5.4 and -3.5%/cycle, respectively. All populations per Se, population crosses and populations×testers showed significant increase in penetrometer reading. Increase in plant height and ear height were observed for RSSSC, BS10×RSSSC and RSSSC×B79. Population BS10 showed an increase in 300-kernel weight and kernel number per ear, and a decrease in ear number per 100 plants. Population RSSSC only showed an increase in 300-kernel weight. Three cycles of selection slightly increased grain moisture in BS10 and BS10×B37. This result indicates the procedures of selection in a high-yield environment are beneficial in improving grain yield, multiple disease resistance and stalk lodging resistance in maize populations per se and their hybrids.

Moisture Stress in the Screening of Maize Cultivars for Stalk Rot Resistance and Yield

Moisture Stress in the Screening of Maize Cultivars for Stalk Rot Resistance and Yield

Stalk Quality and Stalk Rot Resistance of Tropical Hybrid Maize Derivatives

Stalk Quality and Stalk Rot Resistance of Tropical Hybrid Maize Derivatives

General and specific combining ability estimates for pith cell death in stalk internodes of maize

Stalk rot and associated stalk lodging in maize ( Zea mays L.) continue to be major production problems. The inheritance of several stalk traits that contribute to stalk strength has been studied previously. However, inheritance of pith (parenchyma) cell death, an important stalk quality trait, has not been thoroughly investigated. The objective of this study was to estimate general and specific combining ability effects for pith cell death through a diallel mating design. All possible crosses among six inbred lines (C103, Mo17, B14A, W64A, Wf9, and B37) were evaluated at two locations and analyzed according to Griffing's method 2, model 1 (fixed effects for genotypes). General combining ability effects were found to be more important than specific combining ability effects. Heritability of F 1 hybrid means was estimated to be 86%. A cyclic selection program might be effective in reducing pith cell death. A reduction in pith cell death would result in stalk-rot resistance which is positively correlated to the presence of living cells in the stalk.

Evaluation of Four Maize Populations Containing Different Proportions of Exotic Germplasm1

Introgression of exotic maize (Zea mays L.) germplasm into adapted U.S. breeding populations has been proposed as a means for increasing useful genetic variability of quantitatively inherited traits and for enhancing response to selection. However, it is not clear what proportion of exotic germplasms most favorable. The present study was conducted to assess the relative breeding value of four populations with different proportions of exotic germplasm. Two maize populations, Illinois Stiff Stalk Synthetic Composite (RSSSC; adapted to the central Corn Belt) and South African Photoperiod Insensitive Composite II (PIC2;t ropical origin) were crossed and the F1 was backcrossed once to RSSSCT. he F1 and BC1 were randommated to produce the F2, and BC1‐F2 generations, respectively. Random sets of at least 80 to 100 S1 families were derived from the RSSSC, BC1‐ F2, F2, and PIC2 populations (with 0, 25, 50, and 100% exotic germplasm, respectively). These were grown in 1983 and 1984 in replicates‐in‐block designs with two replications at one location. Grain yield, pollen‐shed date, rind puncture resistance, stalk rot and leaf blight severity, and other agronomic traits were evaluated. Genetic variance and covariances were estimated for all traits and all pairs of traits, respectively.M eagnr ain yields for RSSC, BC1‐F2, F2, and PIC2 were 3.31, 3.08, 2.88, and 1.96 t ha−1, respectively. In both years, highest genetic variance estimates for yield were obtained in BC1‐F2. Pollen‐shed in RSSSCw as 10 days earlier than in PIC2 and percentage grain moisture increased linearly with increasing proportion of exotic germplasm. In trogression of PIC2, as expressed in BC1‐F2 and F2, improved stalk rot, leaf blight, and rind puncture resistance of RSSSCP. redictions of gain from selection for grain yield, per se, indicated that the BC1‐F2 would be the most favorable foundation population. However, A desired gain performance index including grain yield, grain moisture, rind puncture resistance, and stalk rot and leaf blight ratings favored the F2 if little weight was given to yield, but ranked RSSSC,BC1‐F2, and F2 as equally valuable foundation of pulations if considerable weight as assigned to yield. The PIC2 population was markedly less valuable mainly due to its lack of adaptiveness.

A comparative study of pith cell death in stalk internodes of corn grown on organic and conventional fields

AbstractA few farmers in the Midwest produce corn (Zea mays L.) commercially by using organic methods, i.e., use no synthetic fertilizers or pesticides. Studies have been conducted previously on organic vs. conventional fields to compare yield, soil properties, stalk lodging and rot, and crude protein. However, pith cell death in stalk internodes, an important trait related to stalk lodging and stalk rot, has not been studied previously under organic and conventional management systems. Fertility differences exist between organically-managed and conventionally-managed fields which can influence pith cell death and related traits. This study was conducted to compare pith cell death in corn stalks on matched pairs of organic and conventional fields (2 in Illinois, 2 in Iowa, and 1 in Minnesota). For the four lowermost consecutive internodes above the brace roots examined in this study, there was no consistent pattern for pith cell death differences among pairs. In three of five pairs, the second internode pith cell death was higher on organic fields than on conventional fields. The same pattern was observed for the third stalk internode. Numbers of European corn borer (Ostrinia nubilalis Hübner) were less in the stalks on organic plots, a plausible cause for greater stalk lodging and rot resistance on organically-managed fields. Further study of pith cell death and stalk rot relationship under organic and conventional managements is needed to elucidate fertility relations and other unique factors at work on organic and conventional fields. It appears that while there are some factors that affect pith cell death, stalk rot, and stalk lodging similarly, there may be other factors that affect these three traits differentially.