GEORGIA / FLORIDA
UNIVERSITY OF GEORGIA
Department of Agronomy, Griffin, GA 30212, USA.
J.W. Johnson, R.D. Barnett, B.M. Cunfer, and G.D. Buntin.
The 2003 Georgia winter wheat crop was grown on about 380,000 planted acres, 9 % more than last year. Oat acreage was 100,000 acres, 18 more than last year. Acres planted to rye, 270,000, were 8 % less than last year. The crop production for wheat resulted in a state average yield of 50 bu/acre. The autumn planting conditions were very wet, which delayed small grain planting. Most of the planting was delayed by at least 2 weeks past optimum. Overall, the season was characterized by a mild and wet winter conditions followed by a wet and mild spring. Wet conditions prevailed through the harvesting stage, which resulted in low test weight, severe sprout damage, and high incidence of Fusarium for 75 % of the crop. The average rainfall during the small grain growing season was 33 % more than normal.
Wheat. USG 3592 is a new cultivar developed by the University of Georgia and the University of Florida. The cultivar is derived from a single cross: Coker 9134/GA881502 (WM6525/GA821264//GA801468) and tested as GA 931241E16. USG 3592 is a medium-maturing, white-chaffed, medium-tall line that matures, on average, 2 days later than AGS 2000 in Georgia. The cultivar is resistant to currently predominant races of leaf rust and biotypes of Hessian fly in Georgia, moderately resistant to races of powdery mildew, and resistant to soilborne mosaic virus.
Oat. Horizon 314 is a new, full-season winter oat variety coöperatively released by the Florida and Georgia Agricultural Experiment Stations in 1999. Well suited as a winter grazing crop for beef or dairy producers, Horizon 314 will make an excellent grain, hay, or silage crop and is excellent for wildlife plots. In comparison to Chapman, Horizon 314 is higher yielding, has a heavier test weight, is 3-6 days later in heading, and 4 inches taller in height. Horizon 314 has good winter hardiness, good crown rust resistance, tillers well, and has a dark green plant color. Horizon 314 was tested experimentally as FL92OHR31,314 and as FLX499-1-B3-G6. The cultivar was selected from material donated by the Northrup-King Seed Company (Novartis Seeds) to the USDA-ARS when the Coker Pedigreed Seed Company oat-breeding program (owned by Northrup-King) was discontinued in 1989. A large number (25,000) of single-panicle selections that had been harvested from the 1988 nurseries of the Coker program were planted at Quincy, FL, for evaluation in 1992. Horizon 314 was a single row, designated 31,314, selected from that material and originated from the cross (X499) 'Coker 84-15/TX84AB2171'.
Triticale. Trical 342 is a new early maturing triticale cultivar for feed grain and silage production in the southeast U.S. Trical 342 was tested as FL91142-A19, which resulted from a cross made in 1991 at the North Florida Research and Education Center at Quincy, FL. The pedigree is 'Sunland/LAD 388'. LAD 388 is a winter triticale from Poland.
Stand reductions of double-cropped cotton following canola (Brassica napus L.) as compared to winter wheat have been observed in the coastal plain region of the southeastern United States. This investigation was conducted to evaluate these observed stand losses and to examine the role of tillage, planting time, and pesticide use on stand establishment of double-cropped cotton following winter wheat and canola. One field study conducted near Plains, GA, in 2 years examined the effect of at-planting insecticide, aldicarb (Temik), and in-furrow fungicide treatment, quintozene plus metalaxyl (Terrachlor plus Ridomil Gold EC), on cotton stand establishment, disease and insect incidence, and yield when double cropped. Winter crop treatments were canola, wheat, or fallow. A second study conducted near Plains and Tifton, GA, in 2 years examined in a strip split-plot design the effect of tillage (conventional verses strip-tillage) and planting time (immediately after winter-crop harvest or 10 days later) on double-cropped cotton.
In all trials in 1999, cotton stand and seed cotton yields were reduced following canola as compared with wheat and/or fallow. Seedling insect populations were affected by winter crop but were not the cause of significant cotton stand loss. In four of five comparisons, cotton seedling infection by R. solani was greater following canola than winter wheat or fallow. All R. solani isolates were anastomosis group AG-4, indicating that canola production did not selectively increase an unusual biotype of R. solani. In both years, R. solani AG-4 infection rates were enhanced by use of aldicarb granular insecticide regardless of the preceding winter crop. The fungicide treatment did not prevent seeding infection by R. solani but did reduce stand and yield losses in 1999. Tillage had no consistent affect on R. solani AG-4 infection, stand, or yield following any winter crop treatment. Delayed cotton planting also did not consistently affect R. solani AG-4 infection and stand loss, but reduced yield at Tifton. Thus, modified tillage practices and delayed cotton planting are not viable management tools for controlling R. solani AG-4 infection and minimizing stand losses of cotton when double cropped following canola. No significant problems occurred with double-cropped cotton planted following winter wheat.
The two most widespread and damaging diseases in Georgia and the Southeast in 2003 were caused by stripe rust and wheat soilborne mosaic virus. The largest outbreak of stripe rust ever recorded from Texas to the northern Great Plains occurred in 2003. Predominated sources of resistance to stripe rust were from cultivars and lines with Yr17 and Yr18. Yr9 was affected in combination with Yr18. Cold, early-season temperatures also favored SBWMV. Plants were stunted by late winter and had leaves with a yellow mottled appearance. Several cultivars and lines were identified with resistance to SBWMV (Crawford, GA931241E16, PIO 26R61, USG 3209). Two new experimental lines (GA951079-2E31, GA951395-2E19) were resistant to both diseases.
Powdery mildew adult plant resistance. The cultivar Knox 62 is known to have adult-plant resistance to powdery mildew, but the relationship between the genes conferring its resistance and corresponding chromosomes has not been documented. To determine the chromosomal locations of adult-plant resistance genes, Knox 62 was crossed with the susceptible disomic Chinese Spring and a full set of Chinese Spring monosomic lines. The adult plants of F2 populations and their parents were evaluated for resistance to powdery mildew in a condition of polycyclic infection, based on their infection type (IT), infected leaf area (ILA), area under disease development curve (AUDPC), and daily disease increase index (DDII) controlled in the glasshouse. Results indicated that the resistance genes in Knox 62 are mainly additive, and seven chromosomes were involved in the adult-plant resistance of this cultivar. Chromosomes 5A, 7A, 4B, and 5D carry genes showing positive effects on resistance, whereas chromosomes 3A, 1B, and 1D have factors increasing susceptibility. The segregation of the disomic F2 populations and noncritical crosses fit a four-gene model, suggesting that chromosomes 5A, 7A, 4B, and 5D each contain one gene or one cluster of tightly-linked genes. The interactions between resistance genes and susceptibility genes seem to be in a complex epistatic manner.
Effect of rye chromatin in soft wheat. The effect of introgression of rye chromatin arm from the absence of a corresponding wheat chromatin arm has not been fully studied. The agronomic and milling and baking quality effects of the individual wheat and rye chromosome 1 arms in translocations, substitutions, and nontranslocation lines were determined. Chromosome arm 1RS significantly increased grain yield that was depended upon the source of rye chromatin. All translocations and substitutions involved with 1RL had a negative effect on agronomic performance and had significantly higher protein content. The 1RS translocations increased alkaline water retention capacity. The baking quality did not depend on the 1RS source in wheat-rye translocations but was depended upon the wheat chromatin, which was replaced by the rye chromatin. The 1RS translocations can be used to improve grain yield when the source is carefully selected from different wheat genetic background. The translocation T1RS·1BL gave the optimum for agronomic performance, whereas the T1RS·1AL was the best for milling and baking quality.
Effect of the T1D·1RS translocation. The influence of the T1DL·1RS genotype on agronomic performance and end-use quality was determined in two crosses. Grain yield and test weight of the Kanto/Gabo (T1DL·1RS) were significantly lower than nonsiblings, but no significant differences were observed in the other cross (Jaypee/Gabo). The effect of the translocation for quality traits were undesirable for cookie quality. The effects of the translocation on agronomic performance were modified by wheat genetic background, whereas milling and baking qualities were less affected.
Waxy wheat. The effect of starch amylose concentration
on pasting properties and milling and baking quality was studied
in eight granule-bound starch synthase (GBSS: waxy protein) genotypes
in a soft wheat background. Double null lines showed lower amylose
concentration than single null lines and wild-type lines. Milling
and baking quality traits were clearly different between waxy
(nil amylose) and the other genotypes. Waxy lines showed the lowest
flour yield of 69.5 %. The typical A-type patterns of x-ray diffractograms
were observed for all starches. No intensity peak at 2q
= 23^o^ was observed for waxy starch. Waxy starch showed higher
crystallinity than nonwaxy starch. Analysis by rapid viscoanalyzer
showed distinctive differences among the eight genotypes. The
peak viscosities of waxy starches were higher than those of all
other genotypes. Breakdown and setback also differed.