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a USDA-ARS, P.O. Box 5367, Mississippi State, MS 39762
b Dep. of Plant and Soil Sciences, Mississippi State Univ., P.O. Box 5367, Mississippi State, MS 39762
c Dep. of Crop Science, North Carolina State Univ., Raleigh, NC 27695
d Mississippi Agriculture and Forestry Experiment Station, Mississippi State, MS 39762, current address: Oklahoma State Agricultural Experiment Station, Oklahoma State Univ., Stillwater, OK 74074
e Cotton Incorporated, 6399 Weston Pkwy., Cary, NC. Joint contribution of USDA, ARS, Mississippi State University, North Carolina State University, and Cotton Incorporated. Journal paper J-11289 of Mississippi Agricultural and Forestry Experiment Station. Mention of trademark or proprietary product does not constitute a guarantee or warranty of the product by the U.S. Department of Agriculture and does not imply its approval to the exclusion of other products that may also be suitable
* Corresponding author (johnie.jenkins{at}ars.usda.gov).
ABSTRACT
RMUP-C5 (Random Mated Upland Population Cycle 5) (Reg. No. GP-893, PI 652942) is a unique random mated germplasm population of Upland cotton (Gossypium hirsutum L.) involving six cycles of random mating beginning with an 11 parent half diallel. This germplasm was developed through cooperative research by the USDA-ARS, Mississippi Agricultural and Forestry Experiment Station, North Carolina State Agricultural Experiment Station, and Cotton Incorporated. Parents used in development represented nonrelated or distantly related cultivars or breeding lines from across the U.S. Cotton Belt. The bulked pollen method of pollination was used in the development, and there were six cycles of random mating, with intercrossing of the F1 considered cycle zero. Selfed seed of C5S1 has been released. Changes in correlations between traits among parents, C0, and C5 cycles show that after random mating, the C5 population has recombinations that should be useful for selection and cultivar development. Because this germplasm represents random mating among 11 very diverse breeding programs and includes parents from the major seed breeding companies, this population should be of value to breeders across the U.S. Cotton Belt.
The germplasm base of Upland cotton (Gossypium hirsutum L.) is narrow, and most cultivars are closely related (Calhoun et al., 1997, Bowman et al., 2006). Commercial companies generally cross among their elite germplasm and select for desired types in cultivar development. Genetic uniformity also increased considerably with the introduction in 1996 of transgenic cultivars, which generally relied on backcrossing in the early years to move the desired transgene(s) into currently available elite germplasm (Bowman et al., 2003). The most comprehensive sources of pedigree information available are Calhoun et al. (1997) and Bowman et al. (2006). These works trace pedigrees of cultivars developed between 1970 and 2005 and also provide some pedigree information on early foundation lines tracing as far back as the 18th century. Ware (1950) traced the origin of most of the cultivars in use in the mid–20th century and is also a valuable resource.
Random mating procedures have provided an important methodology to break undesirable associations and to form new combinations in several self-pollinated species, including tobacco (Nicotiana tabacum L.; Humphrey et al., 1969), sorghum (Sorghum bicolor L. Moench; Nordquist et al., 1973), soybean [Glycine max (L.) Merr.; Burton and Brim, 1981], and oats (Avena sativa; Frey and Holland, 1999). Random mating has previously been shown to reduce correlations between traits in cotton (Miller and Rawlings, 1967: Meredith, 1984: Meredith and Bridge, 1971). Random mating requires a considerable expenditure of time and energy. If one starts with a large diverse group of parental lines, it offers an opportunity to break up adverse linkage blocks and to form new recombinations, some of which should be superior.
RMUP-C5 (Random Mated Upland Population Cycle 5) (Reg. No. GP-893, PI 652942) is a unique random mated germplasm population of Upland cotton involving six cycles of random mating beginning with an 11 parent half diallel. This germplasm was developed through cooperative research by the USDA-ARS, Mississippi Agricultural and Forestry Experiment Station, North Carolina State Agricultural Experiment Station, and Cotton Incorporated. The methodology we used included bulked-pollen pollinations after the method of Miravalle (1964) and was shown to be effective as a random mating procedure by Gutierrez et al. (2006).
Methods
The aim of this project was to develop an elite breeding population of cotton through random mating. Eleven diverse Upland cotton lines from across the United States were chosen as parents for random mating so that the populations developed should have applicability to the entire U.S. Cotton Belt. Lines chosen were ‘Acala Ultima’, developed by California Planting Cotton Seed Distributors (Shafter, CA); ‘Tamcot Pyramid’, developed in the Multiple Adversity Resistant program by the Texas Agriculture Experiment Station, College Station. TX (Thaxton and El-Zik, 2004); ‘Coker 315’, developed by Coker Pedigreed Seed Co. (Hartsville, SC); ‘Stoneville 825’, developed by Stoneville Pedigreed Seed Co. (Stoneville, MS); ‘Fibermax 966’, developed by Bayer Crop Science (Lubbock, TX); M-240RNR, a root knot nematode resistant line developed by the ARS (Shepherd et al., 1996); ‘Paymaster HS-26’, a Texas High Plains cultivar developed by Paymaster Technologies, Inc. (Plainview, TX); ‘Deltapine Acala 90’, developed by Delta and Pine Land Co. (Scott, MS); ‘Suregrow 747’, developed by Sure-Grow Co. (Centre, AL); ‘Phytogen PSC 355’, developed by Mississippi Agriculture and Forestry Experiment Station (Mississippi State, MS) and licensed to Phytogen Seeds (Indianapolis, IN); and ‘Stoneville 474’, developed by Stoneville Pedigreed Seeds. These represent a diverse group of lines from major breeding programs. Pedigrees for all except M-240RNR can be found in Bowman et al. (2006).
The 11 lines were crossed in a half diallel to produce 55 half-sib families. Random mating of the F1 from the half diallel was designated Cycle 0, (C0). These 55 families were kept separate in the mating process. The half diallel crosses, the C1, C3, and C5 cycles were made at Mississippi State, MS, where approximately 80 plants of each half-sib family were grown. The C0, C2, and C4 cycles were made at the Cotton Winter Nursery in Tecoman, Mexico, where 15 hills (approximately 60 plants) of each half-sib family were grown.
Random mating was accomplished in each cycle by mixing pollen from an equal number of blooms, bagged as candles the previous day, from each of the 55 half-sib families each day of pollination and using this bulked pollen to pollinate 10 emasculated and protected flowers per day on each of the 55 lines. Pollination did not start until at least 12 blooms in each half-sib family were available. This process was repeated until approximately 100 emasculated flowers were pollinated on each half-sib family. The bulked pollen methodology was described in detail by Gutierrez et al. (2006) and followed the methodology of Miravalle (1964). Each cycle of random mating thus resulted in approximately 75 crossed bolls harvested from each half-sib family. Approximately two weeks were involved in pollination for each cycle. After each cycle of random mating, a random sample of crossed seed within each half-sib family was planted in individual plots (approximately 60 plants in Mexico and approximately 80 plants in Mississippi), and the next cycle of random mating was made. Following each cycle of random mating, an equal number of crossed seed from each of the 55 families was bulked, and a random sample was planted and self-pollinated to produce enough seed to represent the first selfed (S1) generation of that cycle of random mating in field evaluations. Random mated seed and S1 seed from each cycle of random mating were kept in storage. The seed being registered (RMUP-C5) are C5S1 bulked seed. These are a bulk sample of equal number (1000) of seed from each of the 55 families in the C5S1 generation.
Because of the expected usefulness of this random mating population to the cotton breeding community, two sets of reference data are provided for the seed being registered. Set 1 is composed of C0S1 through C5S1, plus the 11 parents. To provide planting seed for data set 1 (evaluated as experimental numbers 06.8.06 and 06.8.07), an equal number of seed from each of the 55 families from C0S1 was bulked and called C0S1, and an equal number of seed from each of the 55 families from C2S1 was bulked and called C2S1. The same procedure was followed for each random mating cycle to provide seed for planting. Set 2 is composed of the C0S1 and C5S1 within each of the 55 families, plus the 11 parents. To provide planting seed for data set 2, (evaluated as experimental number 06.8.01), seed of C0S1 and C5S1 for each of the 55 families was used.
Seed for data set 1 was planted as four replications in a randomized complete block at two locations on the Plant Science Research Farm at Mississippi State, MS, in 2006, and yield and HVI fiber data were obtained. Boll weight was determined by weighing 25 hand-harvested boll samples. Boll samples were ginned on a 10-saw laboratory gin, and fiber samples were used for fiber analyses. Data are presented in Table 1 . These data can be used to compare yield and fiber properties of C0S1 through C5S1 with that of the parental lines. Seed for data set 2 were planted as a split-plot randomized complete block experiment with the 55 half-sib families being whole plots and cycles of random mating being the subplots on the Plant Science Research Farm at Mississippi State, MS, in 2006. Using data set 2, Pearson correlation coefficients were estimated (see Table 2 ).
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The data given in Tables 1 and 2 show the diversity among the parents and provide evidence that RMUP-C5 is a unique population that should be useful for breeding. Only Phytogen PSC 355 produced more lint than RMUP-C5, the C5 random mated population (Table 1). Detailed data for yield and fiber properties of the families of cycles C0 to C3 are given in McCarty et al. (2008). Comparisons among Pearson correlations coefficients between traits of parents, C0 and C5 are shown in Table 2. The changes in the correlation coefficients show that we are breaking up and/or recombining linkage blocks by the random mating process. Changes may also be caused by pleiotrophy as well as some natural selection and interactions among new combination of genes. Correlations between fiber strength and lint yield, elongation and fiber length, micronaire and fiber length, and micronaire and seed cotton yield were negative in parents and were nonsignificant in C5. Correlations between fiber length and uniformity as well as micronaire and seed cotton yield were positive in parents and nonsignificant in C5. New positive correlations between uniformity and elongation, as well as strength and elongation, and a new negative correlation between elongation and lint yield were present in C5 but not in parents. Changes in correlations among traits show that after random mating, the C5 population has recombinations that should be useful for selection and cultivar development.
We suggest that this population can be used for direct plant-to-row selection or that one boll or lock could be bulk harvested from each plant and planted and individual plant selections made in the S2 or later generations. We further suggest that breeders who plant this population harvest a large random sample of bolls and maintain this bulk for further research and cultivar development.
Availability
Until seed supply is exhausted, seed (100 g) from C5S1 are available to cotton breeders, geneticists, and other research personnel on written request to the corresponding author. It is requested that appropriate recognition of the source be given when this germplasm contributes to the development of a new breeding line, hybrid, or cultivar. Genetic material of this released population has been deposited in the National Plant Germplasm System.
Acknowledgments
Partial funding for the development and evaluation of this population was furnished by Cotton Incorporated.
Footnotes
All rights reserved. No part of this periodical may be reproduced or transmitted in any form or by any means, electronic or mechanical, including photocopying, recording, or any information storage and retrieval system, without permission in writing from the publisher. Permission for printing and for reprinting the material contained herein has been obtained by the publisher.
Received for publication February 5, 2008.
References
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| Soil Science Society of America Journal | Journal of Environmental Quality |
The Plant Genome | |||
in families in C0S1, C5S1, and parents of Upland cotton germplasm population RMUP-C5.