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Dep. of Plant Agriculture, Crop Science Building, Univ. of Guelph, Guelph, ON, Canada, N1G 2W1
* Corresponding author (lizlee{at}uoguelph.ca)
The 38 maize (Zea mays L.) populations described herein (Reg. no. GP-512–GP-549, PI613059–PI613096) are the result of over 30 yr of population development and improvement by the University of Guelph corn breeding program and were released by the University of Guelph in October 1999 (Table 1). They are adapted to short-season environments [<2800 Ontario Crop Heat Units (OCHU) (Brown and Bootsma, 1993)] [Note that 2800 OCHUs 
95-d relative maturity (RM) rating 350 FAO rating 2150 growing degree days (GDDs)]. The populations encompass 24 distinct genetic backgrounds, most of which, based on their initial composition, would be expected to represent extensive genetic diversity. Seven of the 38 populations have not undergone recurrent selection, i.e., are cycle 0 (C0) populations, although three (CG-SynA C0, CG-SynB C0, and CG-Syn C C0) underwent mild mass selection during their development. For 21 of the remaining 31 populations, various recurrent selection procedures were employed including selfed progeny (S), half-sib (HS), reciprocal recurrent selection (RRS), or combined S and RRS (COM) (Table 1). Selection was based on a performance index (PI) of grain yield/grain moisture which, beginning in the 1980s, included an adjustment for standability (Stoj
en and Kannenberg, 1994), although standability per se was also a selection criterion during the early years of the program as well. Visual selection of individual plants and lines was practiced during the development of each cycle. Depending on the response of the germplasm to the environmental conditions during a particular growing season, the number of lines tested per cycle varied from 37 to 100 and the number of selected genotypes to recombine to form the next cycle varied from eight to 30. Generally, higher numbers of lines were tested and recombined from the 1980s on. The objective was to have a selection intensity of around 20%. Also, beginning in the 1980s, the S and RRS procedures were changed to testing of S2 lines instead of S1 lines, and in addition, two generations of recombination were done to establish the subsequent cycle of the population. The half-sib procedure also was changing during this time from modified ear-to-row (ME) (Lonnquist, 1964) to half-sib progeny selection (HS) (Compton and Comstock, 1976). Detailed examples of the Guelph selection procedures can be found in Stojen and Kannenberg (1994) and Sullivan and Kannenberg (1987). The relative combining abilities, stabilities and performances of 12 of the populations are presented in Doersken et al. (2003) and Lee et al. (2003).
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Seed for these releases was produced through sib-mating the most recent completed cycle of the population. Twenty row nursery blocks were planted (15 plants per row). Approximately 100 to 120 ears were pollinated by bulking pollen from the first ten rows and pollinating ears in the other ten rows reciprocally.
CG-SYNA
Synthesis and Development of C0 (PI 613059)
CG-SynA is a 2600 OCHU population synthesized from 20 short-seasoned sources including eight populations or population crosses: Early Manitoba Cold Tolerant (EMCT)-6 (op), EMCT-2 (op), Golden Glow, Rutherford (op), Manitoba Cold Resistant Synthetic, Schindelmeiser F2, Manitoba Cold Resistant Synthetic x Northwestern Dent, and Northwestern Dent x Schindelmeiser; nine hybrids: Haapala 175, Pride 5, United 108, Ox303, CO168 x CO24, CO113 x W103, Pioneer experimental 1, KAS H1, and A498 x W103; and three inbred lines: CG6, MC101, and W9. All possible crosses were made between the 20 short-season sources. Equal quantities of seed from the crosses were bulked to form the base population.
CG-SynA was subjected to six generations of mass selection in high plant-density isolation blocks to establish the C0 population. For each generation, well-filled, disease-free ears from standing, competitive, smut-free plants were selected and approximately equal numbers of seeds were bulked from 144 to 350 ears. Following is the scheme used to develop CG-SynA C0:
Recurrently Selected Populations of CG-SynA
Three different recurrent selection (RS) strategies have been applied to the CG-SynA base population. Details of the recurrent selection programs and their genetic parameters can be found in Stojen and Kannenberg (1994).
CG-SynA (HS)C18 (PI 613061) Modified ear-to-row (ME) selection (Lonnquist, 1964) was used for the first six cycles of half-sib recurrent selection that was initiated in the base population, CG-SynA C0. In the subsequent 12 cycles, (C7 to C18, inclusive), half-sib progeny selection (HS) (Compton and Comstock, 1976) was employed. However, to simplify presentation, this release is identified as (HS)C18.
CG-SynA (S)C7 (PI 613060) Selfed progeny recurrent selection was initiated in the ME C2 population. In the first three cycles S1 lines were selected and recombined to form the next cycle; in the subsequent four cycles, S2 lines were used.
CG-SynA (RRS)C7 (PI 613062) Reciprocal recurrent selection was initiated in the ME C4 population. The reciprocal population was CG-Wigor (describe below). The reciprocal testers for CG-SynA (RRS) C0 were inbred lines derived from CG-Wigor; subsequently, S4 or S5 lines from the previous cycle of CG-Wigor (RRS) were used as testers. For all cycles, S2 lines were selected and recombined to form the next cycle.
CG-SynB
Synthesis and Development of CG-SynB C0
CG-SynB is a 2600 OCHU population that is later maturing than CG-SynA and is less tolerant to high plant densities. CG-SynB was synthesized from F2s of crosses between high altitude races from the Colombian Andes (Rocamex V7, Blanco Rubi, and Cundinarmarca 410) and short-season inbreds (W103, V3, CO113, ND203, A498, and CO106). The F2s were inter-pollinated in isolation. Equal quantities of seed from each plant were bulked to form the initial starting population. CG-SynB was initially subjected to six generations of mass selection in isolation blocks at a plant density of 86 000 plants ha–1 to establish the C0 population. For each generation of mass selection, well-filled, disease-free ears from standing, competitive, smut-free plants were harvested, and approximately equal numbers of seeds were bulked from 74 to 150 selected ears.
Recurrently Selected Populations of CG-SynB
Two different RS strategies have been applied to the CG-SynB base population. Details of the recurrent selection programs and their genetic parameters can be found in Stojen and Kannenberg (1994).
CG-SynB (HS)C18 (PI 613064) As with CG-SynA (HS) (above), the first six cycles of half-sib selection used ME, followed by HS for C7 to C18, inclusive. However, to simplify presentation, the release is identified as (HS)C18.
CG-SynB (S)C7 (PI 613063) As with CG-SynA (S) (above), S was initiated in the ME C2 population; the first three cycles of S used S1 lines and the subsequent four cycles S2 lines were used.
CG-SYNC
(S)C3 (PI 613065)
CG-SynC is a 2700 OCHU population that tillers heavily. Cycle 0 was from the fifth recombination of a population developed at The Pennsylvania State University in 1961 by Dr. R.G. Creech at the Horticultural Research Farm, University Park, Pennsylvania. Approximately 1400 accessions from the Plant Introduction Station in Ames, Iowa were used as male parents in crosses with Golden Cross Bantam sweet corn. Around 5000 crosses were made and ten kernels from each cross were bulked and planted in an isolation block. The synthetic was formed by inter-pollinations among five row blocks that had been planted on three different dates. The center row from each block was detasseled before pollen shed. Ten kernels from each ear in the detasseled row were bulked and planted the following year. This pattern of intermating continued for five cycles.
CG-SynC was initially subjected to six generations of mass selection at high plant density (86 000 plants ha–1). For each generation of mass selection, well-filled, disease-free ears from standing, competitive, smut-free plants were harvested. The number of ears harvested each generation ranged from 40 to 200. Approximately equal numbers of seed were bulked from each ear. During the three cycles of the CG-SynC recurrent selection program, only S1 lines were tested and recombined to form the next cycle. Depending on the seasonal environment, 40 to 50 S1 lines were evaluated in each cycle; a selection intensity of about 20% was imposed.
CG-Wigor
C0 (PI 613066), (S)C3 (PI 613067) and (RRS)C7 (PI 613068)
CG-Wigor is a 2550 OCHU population with excellent general combining ability. Wigor is an early European dent variety that may have originated from the Wisconsin 25 population (L.W. Kannenberg, personal communication, 1999). CG-Wigor (S) has undergone three cycles of selfed progeny selection with S1 lines selected and recombined to form the next cycle. CG-Wigor (RRS) has undergone reciprocal recurrent selection with CG-SynA (RRS) (see above), with the first cycle of RRS originating in CG-Wigor C0. The reciprocal tester for CG-Wigor (RRS) C0 were inbred lines from CG-SynA; subsequently, S4 or S5 lines from the previous cycle of CG-SynA (RRS) were used as testers. For all cycles, S2 line topcrosses were evaluated, and the selected S2 lines were recombined by two generations of intermating to form the next cycle. Details and genetic parameters of the RRS program for CG-SynA (RRS) and CG-Wigor (RRS) can be found in Stojen and Kannenberg (1994).
CG-Schindelmeiser
(S)C4 (PI 613086)
CG-Schindelmeiser is a 2700 OCHU population. Schindelmeiser is an open-pollinated flint population from Germany with good first brood corn borer resistance but poor stalk quality. It has undergone selfed progeny (S) selection at Guelph. Depending on the seasonal environment, 44 to 50 S1 lines were evaluated, 10 to 12 lines were selected for a single generation, with two generations of recombination to establish the subsequent cycle. Details and genetic parameters of the RRS program for CG-SynA (RRS) and CG-Wigor (RRS) can be found in Stojen and Kannenberg (1994).
CG-HOPE Elite A (RRS)C6 (PI 613069)
The Hierarchical Open-ended Population Enhancement (HOPE) breeding system (Kannenberg and Falk, 1995) is designed to develop inbred lines with commercial potential through increasingly stringent selection in a hierarchical series of extraordinarily broad-based 2650 OCHU populations. The HOPE germplasm is divided into A and B sets, each with four populations. CG-HOPE Elite A is the highest performing population in the A set and is undergoing RRS with its counterpart CG-HOPE Elite B (see below) of the B set of populations. Cycle 0 of CG-HOPE Elite A was synthesized by intercrossing five S2 lines from three full-sib families selected from the High population of the HOPE A set; the High populations of the HOPE system are the next "best" in performance to the Elite populations. The Elite A C1, S1 lines from C0 were testcrosses and the selected S1 lines were intermated to form C1. In subsequent cycles, S2 lines were testcrossed and recombined with two generations of intermating to form the next cycle. For C1 to C3, ten lines were selected for recombination, but this was increased to 20 lines from C4 on. Because the HOPE breeding system is open-ended, germplasm can be advanced as S2 lines from the High performance level to the Elite level; through C6 of Elite A two lines have been introgressed into Elite A from the High A population. Information on the HOPE breeding system, its genetic diversity and performance can be found in Cramer and Kannenberg (1992), Kannenberg and Falk (1995), Popi et al. (2000), and Popi and Kannenberg (2001).
CG-HOPE Elite B (RRS)C6 (PI 613070)
Elite B represents the highest performing level of the B set of populations in the HOPE breeding system. CG-HOPE Elite B is the RRS partner of CG-HOPE Elite A and the procedures are the same as those described for CG-HOPE Elite A (above). Through C6 of Elite B, one line has been introgressed from the High B population.
CG-Stiff Stalk
Synthesis of CG-Stiff Stalk C0 (PI 613071)
CG-Stiff Stalk is a 2700 OCHU population synthesized from 18 elite inbred lines from the BSSS heterotic pattern (A632, A634, A635, A664, A665, A669, B14A, B37, B73, CH586–12, CH591–23, CH591–36, CM105, CM174, H84, MS153, N28, and SD24). Crosses among the 18 lines were set up as a partial diallel such that each line was crossed with at least five other lines, so that the crosses were roughly on an "early maturing" line by a "late maturing" line basis. Each line was also crossed to CO263, the inbred parent of a very early maturing three-way hybrid (CO263 x OX553) developed by the Agricultural and Agri-Foods Canada Ottawa research station. CO263 was the source of earliness for CG-Stiff Stalk. Each single-cross from the partial diallel was crossed to a single-cross involving CO263, in such a pattern that the same inbred was not repeated in each cross and that the early by late pattern was maintained. The double-cross hybrids so formed were planted in separate rows. Pollen was bulked from half of the double-crosses and used to pollinate the other half of the double-crosses and vice versa. This initial intercrossing was followed by three additional intercrossings, with the C0 of CG-Stiff Stalk being the product of the fourth intercrossing.
Recurrently Selected Populations of CG-Stiff Stalk
CG-Stiff Stalk (RRS)C5 (PI 613072) In each cycle, 100 S2 lines were testcrossed to S4 or S5 lines from the previous cycle of CG-Lancaster (RRS) (see below), the reciprocal population in this RRS breeding program. Twenty selected S2 lines were recombined for two generations to form the next cycle of the CG-Stiff Stalk (RRS) population. For development of C1, the same 100 S2 lines from C0 were evaluated in both the RRS and S (see below) programs.
CG-Stiff Stalk (S)C5 (PI 613073) In each cycle, 100 S2 lines were evaluated and 20 selected S2 lines were recombined for two generations to form the next cycle. For C1, the same 100 S2 lines from C0 were evaluated in both the S and RRS (see above) programs.
CG-Stiff Stalk (combined RRS & S)C4 (PI 613074) In each cycle, the same 100 S2 lines were evaluated in S2 progeny trials and also in testcross trials with CG-Lancaster S4 or S5 lines from the previous cycle of CG-Lancaster (combined RRS &S) (see below) as the tester. The S2 lines to form the C1 of the combined RRS and S program were selected on the basis of data from the evaluation trials of the C0 S2 lines for the RRS and S program described above. In subsequent cycles, the S and RRS evaluations involved only S2 lines from the combined RRS and S population. The number of S2 lines recombined to form C1 and C2 were 10 and 15, respectively, but 20 in subsequent cycles.
CG-Lancaster
Synthesis of CG-Lancaster C0 (PI 613075)
CG-Lancaster is a 2700 OCHU population synthesized from 26 elite inbred lines from the Lancaster heterotic pattern (A619, A661, A662, A663, A666, A667, A668, CH24, CH661–17, CH663–8, CH671–7, CH671–28, H99, Mo17Ht, MS71, Oh545, Oh551, Pa762, SD23, SDp310, Va26, Va35, W117HHt, W153RHt, W406, and W64AHt). Crosses among the 26 lines were set up as a partial diallel such that each line was crossed with at least six other lines, so that the crosses were roughly on an "early maturing" line by a "late maturing" line basis. Each line was also crossed to OX553, the single-cross parent of a very early maturing three-way hybrid (CO263 x OX553). Developed by the Agriculture and Agri-foods Canada Ottawa research station OX553 was the source of earliness for CG-Lancaster. The parental lines of OX553 are proprietary information. Each single-cross from the partial diallel was crossed to a three-way cross involving OX553, in such a pattern that the same inbred was not repeated in each cross and that the early by late pattern was maintained. The modified double-cross hybrids so formed were planted in separate rows. Pollen was bulked from half of the double-crosses and used to pollinate the other half of the double-crosses and vice versa. This initial intercrossing was followed by three additional intercrossings, with the C0 of CG-Lancaster being the product of the fourth intercrossing.
Recurrently Selected Populations of CG-Lancaster
CG-Lancaster (RRS)C5 (PI 613076) The partner population in the RRS program is CG-Stiff Stalk (RRS) and the RRS procedures were the same (see above under CG-Stiff Stalk RRS).
CG-Lancaster (S)C5 (PI 613077) The procedures for CG-Lancaster (S) were the same as for CG-Stiff Stalk (S) (see above).
CG-Lancaster (combined RRS & S)C4 (PI 613078) The procedures employed for the combined RRS and S program in CG-Lancaster were the same as those described above for its partner population, CG-Stiff Stalk (combined RRS & S). The number of S2 lines recombined to form C1 and C2 were 14 and 15, respectively, but 20 in subsequent cycles.
CG-CBI
CBI (RRS)C5 (PI 613079)
CBI (Corn Borer I) is a 2900 OCHU population, synthesized from six inbred lines {F120, CG6, [CO113(CO113 x (R x BR)-1) CO113–3-1–1], Przy Bioia (1468), Malapolanka (1488), and Bodenii 1–2-2 (1500)}. The six lines were selected on the basis of reduced susceptibility to first brood European corn borer (Ostrinia nubilalis Hübner) and heterotic performance (grain yield) when crossed with the 11 inbred lines used to form CBII (see below). Twenty 3-way crosses were made with the six inbred lines with the restriction that an inbred could only appear once in a three-way cross. The single crosses involving Przy Bioia (1468) were not used in this scheme; only crosses of Przy Bioia (1468) with other single crosses were used. The three-way crosses were intermated by making all possible crosses. Equal quantities of seed from the crosses were bulked to form the C0. CBI has undergone five cycles of RRS with it partner population CG-CBII (RRS) (see below). CBI (RRS) possesses excellent resistance to both leaf feeding and stalk tunneling by first brood European corn borer (Hudon and Chiang, 1991).
CG-CBII
CG-CBII (RRS)C5 (PI 613080)
CBII (Corn Borer II) is a 2700 OCHU population, synthesized from 11 inbred lines (CM169, CM139, RB262, RC150, CG11, CG13, A385, CM40–3, A498, Wigor-2–1-2, and 3W-775–127-sib-7–6-1). These lines were selected on the basis of reduced susceptibility to first brood European corn borer and heterotic performance (grain yield) when crossed with the six inbred lines that formed CBI (see above). One hundred twenty three-way crosses were made with the 11 inbred lines with the restriction that an inbred could only appear once in a three-way cross. The single crosses involving CG11 were not used; only crosses of CG11 with other single crosses were made. The three-way crosses were intermated by making all possible crosses. Equal quantities of seed from the crosses were bulked to form the C0. CBII is undergoing RRS with CG-CBI (RRS) (see above). CBII (RRS) possesses good resistance to both leaf feeding and stalk tunneling by first brood European corn borer (Hudon and Chiang, 1991).
CG-Cross-Canada Gene Pool (CCGP)
CCGP C0 (PI 613081), CCGP A (RRS)C3 (PI 613082), CCGP B (RRS)C3 (PI 613083) CCGP was synthesized from 12 commercial hybrids that exhibited drought tolerance: PAG SX 111, Pioneer 3949, Pioneer 3859, Pioneer 3978, Pioneer 3975A, Pioneer 3950, Pickseed 2599, Pickseed 2550, Martyn 8061, First Line 1626, First Line 1636 (OX713), and Rothwell OX715. The hybrids were intermated by making all possible crosses (66 crosses). Seventeen seeds from each cross were bulked, planted in a 50 row block, and selected plants were intermated. After two cycles of recombination, 17 seeds from each cross were bulked to form CCGP C0. After the C0 was established, the population was divided into an A and B side for reciprocal recurrent selection by crossing 50 S1 lines onto the inbred tester CO265. Based on performance index, lines that combined favorably with CO265 were used to form the A side and the other lines were used to form the B side. CCGP A (RRS) is a 2650 OCHU population and CCGP B (RRS) is a 2700–2800 OCHU population.
CG-SynGA
CG-SynGA C0 (PI 613084)
CG-SynGA is a 2650 OCHU population synthesized from 15 elite Guelph inbred lines (CG33, CG36, CG39, CG55, CG56, CG58, CG59, CG61, CG62, CG66, CG69, CG76, CG82, CG83, and CG85) and one advanced line (94ET13). The 16 lines were crossed in pairs to form eight single crosses. The single crosses were then mated in a diallel to form double-crosses. The double-cross hybrids were planted in separate rows. Pollen was bulked from half of the double-crosses to pollinate, reciprocally, the other half of the double-crosses. This initial intercrossing was followed by two additional intercrossings, with the C0 of CG-GA being the product of the third intercrossing.
CG-SynGB
CG-SynGB C0 (PI 613085)
CG-SynGB is a 2650 OCHU population synthesized from 14 elite Guelph inbred lines (CG40, CG42, CG44, CG57, CG63, CG64, CG65, CG67, CG68, CG70, CG71, CG72, CG80, and CG87). The 14 lines were crossed in pairs to one another to form seven single crosses. The single crosses were then mated in a diallel to form double-crosses. The double-cross hybrids were planted in separate rows. Pollen was bulked from half of the double-crosses to pollinate, reciprocally, the other half of the double-crosses. This initial intercrossing was followed by two additional intercrossings, with the C0 of CG-GB being the product of the third intercrossing. CG-SynGB was designed to be complementary to CG-SynGA (see above) for a RRS program.
Populations Involving CG SynA-NL
CG-SynA-NL (ME) C11 is a 2300 OCHU population that is an early version of CG-SynA (see above) developed initially by mass selection for earliness for seven cycles at New Liskeard, ON (1900 OCHU). Later cycles used a form of modified ear-to-row selection; individual ears visually selected from ear-to-row plots grown at New Liskard with final selections based on replicated performance trials at the Elora ON research station (2600 OCHU).
CG-[OhS4 (S) C1 x CG-SynA-NL] (PI 613087) is a 2650 OCHU population. OhS4(S)(C1) was developed from BS4 (Gerdes et al., 1993) at the Ohio Agricultural Research and Development Center. Approximately 100 plants of OhS4(S)(C1) were crossed onto CG-SynA-NL, and for five generations about 60 early flowering segregants of good agronomic type were sib mated out of a population of approximately 200 plants. It has good agronomic performance.
CG-[OhS3 (S)C1 x CG-SynA-NL] (PI 613088) is a 2650 OCHU population. OhS3 (S)(C1) was developed from BS3 (Gerdes et al., 1993) at the Ohio Agricultural Research and Development Center and released to the public in 1975 (Pratt et al., 1994). Approximately 100 plants of OhS3 (S)(C1) were crossed onto CG-SynA-NL, and for four generations about 60 early flowering segregants of good agronomic type were sib-mated out of a population of 200 plants. It has good agronomic performance.
CG-[BS2 x CG-SynA-NL] (PI 613089) is a 2650 OCHU population. BS2 was developed at Iowa State University from ETO Composite (a Colombian composite) and six early Corn Belt inbred lines (Gerdes et al., 1993). Ten early flowering segregants out of 200 plants of BS2 were crossed onto CG-SynA-NL, and for four generations ten early flowering segregants of good agronomic type were sib mated out of a population of 200 plants. It has good agronomic performance.
CG-[BS16 x CG-SynA-NL] (PI 613090) is a 2650 OCHU population. BS16 was developed at Iowa State University by mass selection for adaptation in ETO Composite (a Colombian composite) (Gerdes et al., 1993). Ten early flowering segregants of BS16 were crossed onto CG-SynA-NL from a population of 200 plants of BS16, and for four generations ten early flowering segregants of good agronomic type were sib mated out of a population of 200 plants. It has good agronomic performance.
CG-[Mexican Dent x CG-SynA-NL] (PI 613091) is a 2650 OCHU population. The Mexican Dent population was developed by Cargill and is primarily of Latin American germplasm (Gerrish, 1980). The F1 (Mexican Dent x CG-SynA-NL) was crossed with the BC1 (CG-SynA-NL recurrent parent) and for four generations 60 early flowering segregants of good agronomic type were sib mated out of a population of 200 plants. The final population is approximately 37.5% exotic germplasm.
CG-[Cateto Flint x CG-SynA-NL] (PI 613092) is a 2650 OCHU population. The Cateto Flint population was developed by Cargill and is primarily of Latin American germplasm (Gerrish, 1980). The F1 (Cateto Flint x CG-SynA-NL) was crossed with the BC1 (CG-SynA-NL recurrent parent) and for four generations 60 early flowering segregants of good agronomic type were sib mated out of a population of 200 plants. The final population is approximately 37.5% exotic germplasm.
POPULATIONS FROM GERRISH (1980), ADAPTED TO SOUTHWESTERN ONTARIO
CG-Coroico Flour (PI 613093) is a 2700 OCHU population. It was originally developed by Cargill and released publicly as Cargill North Temperate Zone Coroico (PI 451692) (Gerrish, 1980). The CG version underwent four generations of sib mating for earliness, in which about 60 out of 200 plants were selected.
CG-Cuzco Flour (PI 613094) is a 2650 OCHU population. It was originally developed by Cargill and released publicly as Cargill North Temperate Zone Cuzco (PI 451693) (Gerrish, 1980). The CG version underwent four generations of sib mating for earliness, in which about 60 out of 200 plants were selected.
CG-Cateto Flint (PI 613095) is a 2650 OCHU population. It was originally developed by Cargill and released publicly as Cargill North Temperate Zone Cateto (PI 451693) (Gerrish, 1980). The CG version underwent four generations of sib mating for earliness, in which about 60 out of 200 plants were selected.
CG-Caribbean Flint (PI 613096) is a 2600 OCHU population. It was originally developed by Cargill and released publicly as Cargill North Temperate Zone Caribbean Flint-Dent (PI 451690) (Gerrish, 1980). The CG version underwent eight generations of sib mating for earliness, in which about 60 out of 200 plants were selected.
Breeder seed for these populations can be obtained through requests to the National Seed Storage Laboratories in Fort Collins, CO, or from the Plant Introduction Station in Ames, IA. Recipients of seed are asked to make appropriate recognition of the originator of the seed (Department of Plant Agriculture, University of Guelph, Guelph, Ontario, Canada) if it is used to develop a new population or parental line, or in published scholarly work.
NOTES
Financial support, in part, from the Ontario Ministry of Agriculture and Food, Natural Science and Engineering Research Council, Canadian Foundation for Innovation, Ontario Innovative Trust, and Ontario Corn Producers, Association. Registration by CSSA.
Received for publication October 4, 2005.
REFERENCES
en, D., and L.W. Kannenberg. 1994. Genetic changes associated with different methods of recurrent selection in five maize populations: I. Directly selected traits. Crop Sci. 34:1466–1472.
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