Germplasm Enhancement of Maize
- 1995 Public Cooperator's Report
Reaction of US GEM Temperate
Accessions to Cercospera zeae-maydis
John E Ayers
& Melvin W Johnson
Pennsylvania State University
Twenty-seven temperate accessions from the GEM collection were planted at two locations in Pennsylvania with a history of Gray Leaf Spot [GLS] caused by Cercospera zeae-maydis. Three check hybrids were added so the experiment could be designed as a 5x6 rectangular lattice; three replications were planted at each location. Lycoming Co. (LC) was planted on May 1 in a field that had been chisel plowed and disked one time prior to planting. Franklin Co. (FC) was planted with no prior tillage on May 8 in a field that had been in continuous no-till corn for several years. Growing conditions were very good at both locations until mid-July, when moisture and heat stress occurred. [GLS] appeared early at FC, but the drought and heat stress kept disease severities lower than anticipated based on the amount of disease seen in late June and early July. Entries at FC only were rated on Aug. 9 and 29 on a 0.5 to 5 scale where 0.5 equals few or no lesions and 5 equals plants prematurely dead. Average disease ratings on Aug. 29 ranged from 0.7 to 3.3 with the later maturing entries (higher grain moisture at harvest) showing the least amount of disease (r=-0.74). There were, however, some entries (ex, [UR10001], [UR11003], and [UR13088]) with slightly above average grain moistures and below average [GLS] ratings, suggesting there might be a potential for extracting some resistance factors without greatly increasing time to maturity. Other agronomic characteristics were measured.
Evaluation of Germplasm for
Resistance to Gray Leaf Spot (Cercospera
zeae-maydis) Under Inoculation Disease Pressure.
Charlie Martinson & Davy Simumba
Department of Plant Pathology, Iowa State
Sixty crosses were selected for study on the basis of disease severity. The mean Gray Leaf Spot [GLS] rating and standard deviations for the crosses are presented [see raw data] and range from 1.0 to 6.5. Out of sixty entries, more than half of the entries in the germplasm crosses have mean [GLS] ratings below 3.5 [0 = no lesions on the plant, 1 = a few restricted lesions on lower leaves and 9 = abundant lesions on all leaves]. Germplasm crosses [BR51501:S11a], [PRICGP3:N11a], [BR51403:N16], [CUBA164:S22], [CHIS775:S19] and [SCROGP3:N20] have mean ratings below 1.5. [CASH:N14] and [AR16035:S19] have the highest [GLS] rating of 6.5 followed by [AR01150:N04] with 6.0.
Accessions are significantly different
in their response to the disease inoculation, with mean Gray Leaf Spot
ratings ranging from 3.7 to 5.0. A comparison made in this case is the
variation between the accessions without necessarily looking at how each
individual ear performed within the accession. [Raw data] show the means
and standard deviations for each accession. The low [GLS] ratings for the
accessions clearly indicate that there is a high level of performance in
terms of resistance.
There were variations within each row
and averages are estimated from whatever number of plants existed in each
row. This is expected since these entries are not pure lines. However,
some of the plants had severe damage from Helminthosporium turcicum [NCLB]
which spread from the neighboring research plot, masking or hindering the
spread of [GLS]. Smuts and leaf spots were also observed.
Variability for Resistance to
Aspergillus flavus and Maize Weevil Feeding.
Department of Agronomy, Louisiana State
Sixty-one tropical x temperate crosses were planted at Baton Rouge, LA (three replications; randomized complete-block design). Fifteen days after midsilk, 10 ears/plot were inoculated with Aspergillus flavus [ASPER] spore suspension (20 million spores/ml) using the needle-in-silk-channel technique. The remainder of ears (second sub-sample) were used to obtain percent ear moisture loss/day during a 30-d post-midsilk and harvest period. Number of ears/plot and grain weight/ear for the second sub-sample were recorded at harvest. Variability among crosses for ear moisture loss rate (mean=0.8%/day; range=1.0 to 0.6%/day) and grain weight/ear (mean=118.7g; range=148.2 to 86.5g) was significant.
Percent kernel infection by Aspergillus flavus: All inoculated ears/plot were shelled and bulked. A sample of 156 kernels/plot is being used to obtain percent kernel infection. The procedure involves plating the surface-sterilized kernels on Czapek solution agar, incubating for 5-6 days and recording percentage of kernels showing infection. This work is expected to be completed by the end of February, 1996.
Resistance to Maize Weevil [WEEVIL]: An aliquot of shelled grain (100 g/plot) was taken to evaluate differences among entries for resistance to weevil feeding. The samples are being evaluated in a free-choice environment. After 90-100 days of infestation by the weevils, grain weight will be recorded. This work is in progress and is expected to be completed by the end of February, 1996.
Evaluation of Anthracnose
Stalk Rot Resistance in Selected LAMP Accessions.
Smith & Lorraine Ericson
Department of Plant Breeding, Cornell University
We evaluated the levels of resistance
to Anthracnose Stalk Rot [ANTH], caused by Colletotrichum graminicola
(Ces.) G.W. Wils., in 30 GEM 50% exotic crosses together with the
susceptible (B73) and resistant (LB31) inbred checks and a commercial hybrid
(Mycogen 725cb). Each entry was planted in a two-replication randomized
complete block design at Aurora, NY. Ten competitive plants from each plot
[a single 20-plant row] were inoculated shortly after flowering...in the
first extended node above ground level. Stalks of 8 inoculated plants were
split open and rated for the lower 8 internodes [0=no tissue discolored;
1=1-5% discoloration; 2=6-25%; 3=26-75%; 4=76-99%; 5=100% discoloration].
Stalk rot pressure was generally quite high, with even resistant inbred check LB31 showing a rating of 35%. This rating may be partially an artifact of differences in maturity and vigor, as checks were small and severely shaded by tall and vigorous GEM crosses.
Several entries showed promising levels of
Anthracnose Stalk Rot resistance. [AR01150:N04], [GOQUEEN:N16], and
[FS8B(T):N18] all had mean severity ratings lower than that of the resistant
check; [FS8B(T):N18] also had good standability and relatively little
natural [ECB-] damage. [CH04030:S09], [FS8B(T):N11a], and [UR10001:N17]
showed Anthracnose severity similar to that of the resistant check;
[CH04030:S09] was the best of the entries involving a Stiff-Stalk parent.
In general, the non-Stiff Stalk parents showed better levels of resistance,
as might be expected. There appears to be good selection potential for
Anthracnose Stalk Rot resistance among the GEM crosses noted.
Evaluation of US GEM Project
Germplasm for Leaf Blights and Rind Puncture
Dudley & Donald G White
Department of Crop Sciences, University of
In 1995, 138 temperate accession x either B14/B73 or Oh43/Mo17 crosses were evaluated for Northern Corn Leaf Spot (races 2 and 3) [NCLS], Anthracnose Leaf Blight [ANTH], Nothern Corn Leaf Blight [NCLB], Southern Corn Leaf Blight [SCLB], and Gray Leaf Spot [GLS] resistance. In addition, flowering date, rind puncture resistance, plant height, and ear height data were obtained. For the leaf blights, data were obtained from one replication for each leaf blight. Rind puncture resistance readings, obtained using a rind penetrometer, on the internode below the ear-bearing node, were taken approximately three weeks following pollination on three replications of 10 plants each. Flowering date, plant height, and ear height were collected from three replications. Means by population cross are shown [see raw data]. On average, as expected, crosses to B14/B73 averaged lower in rind puncture resistance and had higher leaf blight ratings then crosses to Oh43/Mo17. Plant and ear heights were greater for the crosses to B14/B73. The crosses to B14/B73 also were slightly later than the crosses to Oh43/Mo17.
Accessions with greater rind puncture resistance tended to have lower leaf blight ratings [see raw data]. When population means averaged over testers were used, correlations of rind puncture readings with leaf blight ratings ranged from 0.08 to -0.42 [see raw data]. Correlations among leaf blight ratings were positive and ranged from 0.12 between Northern Corn Leaf Spot race 3 and Northern Corn Leaf Blight to 0.43 between Northern Corn Leaf Spot race 2 and Anthracnose Leaf Blight. Leaf blight ratings were negatively correlated to flowering date and plant height. Correlations among traits by individual testers [see raw data] were generally similar. However, the correlation of rind puncture resistance and anthracnose leaf blight for the B14/B73 tester was significantly positive (0.28) and was -0.21 for the Oh43/Mo17 tester.
Although the results obtained from the two testers were similar, correlations between testers, using the 66 populations crossed to both testers, were relatively low except for flowering date [see raw data]. Of the leaf blight ratings, only the correlation for southern corn leaf blight was significant and it was low (0.30).
When ratings were taken, a high degree of segregation for disease reaction within plots was noted. None of the population crosses evaluated appeared to have extremely high levels of resistance. Based on rind puncture resistance and leaf blight resistance, 12 accessions were selected to be entered into a study evaluating the potential of these accessions for improving elite germplasm. The accessions selected [and currently in use by GEM] are: [AR16026] and [AR16035]. In our proposed work for 1996, we plan to include these accessions along with the tropical accessions crossed to either B73 or Mo17 and the tropical hybrids crossed to either B73 or Mo17. The objective is to evaluate these materials for their potential to improve an elite hybrid for grain yield, leaf blight resistance, and rind puncture resistance.
1995 Evaluations of Maize for
Resistance to Corn Rootworm Larvae.
Tollefson & Xiaoling Wang
Department of Entomology, Iowa State University
All 57 original GEM accessions were
evaluated for resistance to Corn Rootworm larvae [RTWORM]. The experiment
was conducted at three locations that had a high probability of natural Corn
Rootworm infestation. The experimental design was a randomized complete
block with three replications. Treatments consisted of paired rows, 5 m in
length [overplanted and thinned]. Vertical root-pull resistance was
measured with a recording dynamometer. Washed roots were evaluated for
rootworn larval damage [1=no damage or few scars; 2=feeding scars evident,
no roots eaten off to within 1 1/2 in. of plant; 3=several roots eaten to
within 1 1/2 in. of plant; 4=one node of roots completely destroyed; 5=two
nodes destroyed; 6=three or more nodes destroyed], degree of secondary root
development [1=smallest roots, 6=largest and most vigorous secondary roots],
and root size [1=smallest roots, 6=largest and most vigorous roots].
Results show significant differences
among germplasms for all traits studied. There was a significant germplasm
* location interaction for both plant lodging and root-pull resistance.
Root damage was related to plant lodging. Correlations between root size,
root-pull resistance, and root damage were negative. High, positive
correlations were observed between root size and secondary root development
and root-pull resistance. Data indicate that germplasms with high root-pull
resistance are most tolerant of Corn Rootworm feeding damage.
[CHIS775] and [BR51403] exhibited the
least amount of root damage in the test, comparable to the resistant check
(NGSDCRW1) and significantly less than the susceptible check (B73xMo17).
[CHIS775] also had the largest root size and highest root-pull strength of
all entries tested. [BR52060] and [FS8A(T)] had high levels of
secondary-root development, with [FS8B(S)] the best for all entries and
significantly better than NGSDCRW1. [XL212] exhibited the least amount of
lodging by a wide margin.
Resistance to First and Second Brood
European Corn Borer & Corn Rootworm
Genetics Research Unit, USDA-ARS (Columbia, Missouri)
Original GEM accessions were evaluated
for resistance to European Corn Borer first generation [ECB1] and second
generation [ECB2]. Two locations were utilized with three replications
each. Resistance to Corn Rootworm [RTWORM] was also noted. [ECB1] was
rated on a scale of 1 to 6 with 1 indicating more resistance and 6
indicating less resistance. [ECB2] was rated as length of stem tunneling in
inches. [DREP150], [GUAD05], [BARBGP2], and [DK212T] appear to have fared
well at all locations/reps for European Corn Borer. [AR16035], [FS8A(T)],
[CHIS740], and [DKB830] were selected to be retested for Corn Rootworm [RTWORM].
Additional data found no GEM accessions better than NGSDCRW1(C4)S2 for
resistance to [RTWORM], however.
Evaluation of GEM Accessions for Resistance to Fall
Southwestern Corn Borer.
W Paul Williams & Frank M Davis
Plant Resistance Research Unit, Mississippi State University
Fifty maize accessions and seven
hybrids were evaluated for resistance to leaf feeding by Fall Armyworm,
Spodoptera frugiperda (JE Smith) [FAWORM], and Southwestern Corn Borer,
Diatraea grandiosella Dyar [SWCB], at Mississippi State, MS. These
genotypes and known resistant and susceptible checks were grown in
single-row, 20-plant plots arranged in a randomized complete block design
with three replications for each insect.
The experiment for evaluating Fall
Armyworm resistance was planted 6 April 1995, and the experiment for
evaluating Southwestern Corn Borer resistance was planted 10 April. In both
experiments, plants were infested with 30 neonates each on 19 May. Leaf
feeding damage for each insect was visually rated 14 days later using a
scale of 0 (no damage) to 9 (heavy damage) (Williams, Buckley, & Davis.
1989. Crop Science 29:913-915).
Most genotypes sustained heavy damage
from both insects; a few accessions appeared to exhibit low levels of
resistance and did not differ significantly from MpSWCB-4, a resistant
check. Those accessions showing less damage to Fall Armyworm also exhibited
lower levels of damage to Southwestern Corn Borer. Among the accessions
that may be potentially useful as sources of resistance to these insects
are: [CUBA117], [DREP150], [SCROGP1], [ANTIG03], [GUAD05], and [SCROGP3].
Maize Plant Resistance to Fall
Armyworm Larvae & Corn Earworm Larvae
Biology & Population Management Rsch Lab, Coastal Plain Expt Sta, USDA-ARS
Fifty-four Plant Introductions from
the US GEM Project plus a resistant and a susceptible check were evaluated
in the field at Tifton, GA, for leaf-feeding resistance against the Fall
Armyworm [FAWORM]. The experiment was arranged as a randomized complete
block design with 3 replications. At the 8-leaf stage, 2 applications of 20
Fall Armyworm larvae were introduced into the whorls of 10 plants per
plot/replication. Plots were rated for leaf feeding by the larvae at 7 and
14 days after inoculation on a 0-9 rating scale where 0=no damage and
9=severe damage to the whorl.
[CUBA117] had the lowest ratings (most
resistant) of the accessions for 7 and 14-day ratings. [PRICGP3],
[UR01089], and [DREP269] were also rated well.
Fifty-three Plant Introductions from the US GEM Project plus a resistant and a susceptible check and regular bean diet and a bean diet plus celufil checks were evaluated as oven-dried silks mixed into pinto bean-diets at Tifton, GA, for resistance against larvae of the Corn Earworm [CEW]. The experiment was arranged as a randomized complete block design with 30 replications. When silks had emerged two days, they were excised to the ear-tip, brought to the laboratory, oven dried at 41 C for 10 days, ground with a Cylotec 1093 sample mill and mixed into pinto bean diets at 50 mg/ml. Diet mixtures were dispensed into plastic cups and 1 neonate earworm was placed onto the diet/cup. Weight of larvae were recorded 8 days after infestation.
[CUBA117] showed the least weight gain
for all accessions. [FS8B(S)], [UR05017], [DK212T], [UR13061] also showed
low weight gains (in increasing order).
Value-Added Properties of GEM Material
A Johnson & Suvrat Singh
Center for Crops Utilization Research, Iowa
Fifty-three Latin American (LA) accessions along with two commercial dent corn hybrids and two inbreds were evaluated for their compositions, physical properties, and wet-milling characteristics, and evaluation of the functional properties of starches recovered from them was begun.
Wide variations in compositional properties were observed among the LA accessions. Kernels of the LA accessions had a wide range in starch content (70.9 to 75.1% versus 73.3% for commercial dent hybrids). On average, protein (9.9%) and oil (4.8%) contents were higher in the LA accessions than in commercial dent hybrids (8.4 and 4.0%, respectively).
There were wide ranges in test weights (52.4 to 68.2 lb/bu) and 1000 kernel weights (240 to 316 g) among the LA accessions, but, on average, were comparable to commercial hybrids. Absolute densities were consistently higher for the LA accessions (1.32 versus 1.29 g/cc). Absolute density is highly correlated with protein content and kernel hardness. US dent corn in general is quite soft, while the LA accessions are much harder, making them less susceptible to breakage and more suitable for dry milling.
The wet-milling properties of the LA accessions were not nearly as good as for the commercial dent corn hybrids (starch yields averaged only 54.4% for the LA accessions versus 64.8% db for the commercial dent hybrids). Gluten yields were much greater for the LA accessions than for the commercial dent hybrids, which was attributed to starch ending up in the gluten fraction (increasing starch loss and reducing the protein content of the gluten). Occasionally, high fiber yields were also obtained for the LA accessions, indicating that the starch did not separate well from the fiber.
The evaluation of starch functional properties has not yet been completed, but preliminary evidence indicates there are considerable differences in starch properties among the LA accessions that may be worth exploiting. On average, starches from LA accessions gelatinized at lower temperatures (70.0 versus 71.3 C) and over narrower ranges (7.9 versus 10.5 C) than did the starches from the commercial dent hybrids. On average, heats of gelatinization (enthalpy) were similar for starches from the LA accessions and commercial dent hybrids.
Physical and Compositional
Horticulture and Crop Science Department, Ohio State University
Twenty-nine temperate accession x Corn
Belt crosses plus two checks were planted near Wooster, Ohio, on 16 May
1995, in a replicated randomized complete block design according to standard
agronomic practices. Plots were harvested on 20 November 1995. A high
level of stalk lodging (72% average) occurred in the plot. Average yield
[YIELD] and harvest moisture [MOIST] values of the plot were 8.21 Mg/ha
[~130.9 bu/ac] and 24.1%, respectively. One GEM entry, [FS8A(S)], displayed
noticeably superior performance. Many other GEM entries were not
statistically different than the check hybrids.
Grain samples were harvested and dried
in a low-temperature, forced-air drying oven. Ear samples were also taken
from all entries planted at another location and low-temperature dried. Ear
and grain physical compositional testing has commenced and will take some
time to complete.
UW GEM Project -
Silage Potential of GEM Populations
Department of Agronomy, University of Wisconsin
In 1995, the
UW GEM project analyzed 29 breeding populations (50% exotics) for silage
nutritive value. These populations were evaluated at two locations, Madison
and Arlington, WI using two-row plots with three replications/location. Ears
were removed from one row, which was then harvested as stover alone. The
other row was harvested as whole-plant silage. Fresh weights were recorded
and 1,000 g samples collected for dry matter determination and laboratory
analyses. Samples were analyzed for stover neutral detergent fiber [NDF-ST],
stover acid detergent fiber [ADF-ST], stover lignin [LIG-ST], stover protein
[CP-ST], stover in vitro dry matter digestibility [IVD-ST], stover cell wall
digestibility [CWD-ST], whole-plant neutral detergent fiber [NDF-WP],
whole-plant acid detergent fiber [ADF-WP], whole-plant lignin [LIG-WP],
whole-plant protein [CP-WP], whole-plant in vitro dry matter digestibility [IVD-WP],
whole-plant cell wall digestibility [CWD-WP]. All chemical and digestibility
constituents are reported as percentages on a dry matter basis. Near infra
red reflectance [NIR] was used to predict all constituents. An internal
calibration set was developed for NDF-ST, ADF-ST, LIG-ST, NDF-WP, ADF-WP,
and LIG-WP. Other constituents were predicted using our global NIR
calibration set developed over the past four years. Agronomic traits that
were evaluated included days from July 1 to mid-pollen [FLOWER], stover and
whole-plant % moisture [H2O-ST and H2O-WP], stover and whole-plant dry
matter yield in tons/acre [YLD-ST and YLD-WP] and percent ear [%EAR].
the populations were not adapted to conditions in Wisconsin. This was
reflected in either the FLOWER or %EAR values. We established a cutoff for
future work by deciding to drop all populations with %EAR less than 40%.
Because of the large range in FLOWER or %EAR values across populations, we
were also concerned that maturities and ear percentages were confounded with
our laboratory assessments of nutritive value. We therefore decided to
resample the following 11 populations in 1996: AR16021:S9, AR16035:S19,
AR17026:N10, AR17056:S12, CH05015:N15, UR10001:N17, UR13085:S19, UR13085:N2,
AR01150:N4, CH04030:S9, and GOQUEEN:N16. These populations and 21 related
25% exotic populations will be reanalyzed in Wisconsin during the current
season. The populations will be stagger planted according to their
maturities so that all will be at a relatively similar physiological stage
Of the 11 selected populations, one in particular, UR10001:N17, had notably higher nutritive value, particularly on a stover basis. It had low NDF, ADF, and lignin concentrations, and high protein. On a whole-plant basis, most quality components were average, however protein was again relatively high. The protein concentration in adapted U.S. hybrids averages approximately 7% for stover and 8% for whole plants. Among the more adapted selected populations, UR10001:N17, had markedly higher protein concentrations on both a stover and whole-plant basis. Its low NDF, ADF, and lignin concentrations also indicate that it may have high intake potential.
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