RELEASE PROPOSAL FOR FOUR A/B SORGHUM PARENTAL LINES

Four sorghum [Sorghum bicolor (L). Moench] female parental lines have been evaluated in hybrid combinations over several environments for agronomic and yield traits. These lines were selected for release based on their agronomic desirability and unique combination of disease resistance and grain quality traits of importance to sorghum breeders. These characteristics and traits found in these lines should be of value to the sorghum breeding industry. Some of these lines may be useful directly as parents, while others maybe more useful as breeding stock. All four lines are in the A₁ cytoplasmic male-sterility system. Maintainer lines of all four females lines will be released as well.

PROPOSED NAMES AND SEED HANDLING

These lines were selected, increased and developed in the sorghum breeding program based at Lubbock, TX, but with selection and evaluation Statewide. The lines and their hybrids were evaluated in replicated yield and agronomic experimental trials in various locations in Texas and in Regional Yield Trials located in various states, and we propose that these lines should be released as parental lines. Using the numbering system of the Texas Agricultural Experiment Station sorghum improvement program, these parental lines should be designated as A/BTx642 through A/BTx645. Upon release, the lines will be registered in Crop Science and seed of these lines will be deposited at the National Seed Storage Laboratory in Fort Collins, Colorado. Seed will be maintained and distributed by the Texas Agricultural Experiment Station at the Texas A & M University Agricultural Research and Extension Center at Lubbock, Route 3, Box 219, Lubbock, Texas 79401-9757.

BREEDING HISTORY AND METHODOLOGY

All of these lines were developed from intentional crosses using the pedigree method of plant breeding. The pedigrees for the four parental lines are listed in Table 1. Most of the parents in the pedigrees of these germplasms are publicly released. Following is a more complete description of each line:

ATx642, tested as A35, was originally selected from a BC₁F₂ conversion population at Chillicothe, Texas. Selections in the F₃ to the F₁₀ generation that lead to the development of this line were made in one or more of the following locations; Lubbock (L) Texas, and Mayaguez (T) Puerto Rico. In the final generation of selection, 20 individual panicles of this line was self-pollinated and bulked to create the experimental line. Since that time, this line has been maintained by self-pollination. Male sterile (A-line) versions of this B-line were created via backcrossing with ATx623 as the source of A₁ cytoplasm. From 1991 to 2000, this line has been included in numerous replicated tests as an inbred line and in hybrid combination to determine the merits and weaknesses of each line for as many agronomic traits as possible.

ATx643, tested as A1, was originally selected from a F₂ population at Halfway, Texas. Selections in the F₃ to the F₁₀ generation that lead to the development of this line were made in one or more of the following locations; Lubbock (L), Beeville (B), Corpus Christi (CC), College Station (C) and Chillicothe (CV) Texas, and Mayaguez and Isabella (PR) Puerto Rico. In the final generation of selection, 20 individual panicles of this line was self-pollinated and bulked to create the experimental line. Since that time, this line has been maintained by self-pollination. Male sterile (A-line) versions of this B-line were created via backcrossing with ATx623 as the source of A₁ cytoplasm. From 1991 to 1999, this line has been included in numerous replicated tests as an inbred line and in hybrid combination to determine the merits and weaknesses of each line for as many agronomic traits as possible.

ATx644, tested as A807, was originally selected from a F₂ population at Halfway, Texas. Selections in the F₃ to the F₁₀ generation that lead to the development of this line were made in one or more of the following locations; Lubbock (L), Beeville (B), Corpus Christi (CC), College Station (C) and Chillicothe (CV), Orange Grove (OG) Texas, and Mayaguez and Isabella (PR) Puerto Rico. In the final generation of selection, 20 individual panicles of this line was self-pollinated and bulked to create the experimental line. Since that time, this line has been maintained by self-pollination. Male sterile (A-line) versions of this B-line were created via backcrossing with ATx623 as the source of A1 cytoplasm. From 1993 to 2000, this line has been included in numerous replicated tests as an inbred line and in hybrid combination to determine the merits and weaknesses of each line for as many agronomic traits as possible.

ATx645, tested as A803, was originally selected from a F₂ population at Halfway, Texas. Selections in the F₃ to the F₁₀ generation that lead to the development of this line were made in one or more of the following locations; Lubbock (L), Beeville (B), Corpus Christi (CC), College Station (C) and Chillicothe (CV), Texas, and Mayaguez and Isabella (PR) Puerto Rico. In the final generation of selection, 20 individual panicles of this line was self-pollinated and bulked to create the experimental line. Since that time, this line has been maintained by self-pollination. Male sterile (A-line) versions of this B-line were created via backcrossing with ATx623 as the source of A₁ cytoplasm. From 1992 to 1997, this line has been included in numerous replicated tests as an inbred line and in hybrid combination to determine the merits and weaknesses of each line for as many agronomic traits as possible.

LINE DESCRIPTION AND PERFORMANCE (in hybrid combinations)

Any gene symbols used in the description of these lines are those recommended by Schertz and Stephens (1966). All of these parental lines are in the A₁ cytoplasmic genetic male sterility system. The A-lines are 100% male sterile. All four parental lines are three dwarf lines (dw₁Dw₂ dw₃dw₄). The lines are purple plant color, with various pericarp color. These lines were developed in the drought resistance breeding program of the Texas Agricultural Experiment Station and posses various combinations of pre and post-flowering drought resistance. These lines should prove useful in the development of drought and lodging resistant hybrids for commercial release. None of these lines have a pigmented testa. A brief description explaining why each line is proposed for release follows:

ATx642, tested as A35, is a lemon-yellow pericarp, purple plant colored line. The panicle of B35 is semi-compact, erect, elliptic, 6-8” in length (Durra head type). Rachis branches are short, stiff. The grain is nearly round, only slightly pointed and covered with hairy glumes. The line is slightly later and similar in height to ATx2752, but earlier and shorter than BTx631. It possesses excellent post-flowering drought tolerance (known as stay-green), charcoal rot resistance, and lodging resistance, and produces hybrids with excellent stay-green, charcoal rot resistance, and lodging resistance. In all hybrid combinations tested, the stay-green reaction expresses itself well in the F₁. In most hybrid combinations, it will produce a light red pericarp grain. It is resistant to head smut and head blight, but susceptible to downy mildew, anthracnose, most leaf diseases, and is tolerant to MDMV. The line expresses a physiological leaf spot reaction close to maturity, but should not affect performance. The line combines well with certain pollinators, such as RTx430, but does not perform well with certain other R-lines. Hybrids of A35 have produced above average yields, especially under late season drought conditions, but has somewhat limited yield potential under high yield or fully irrigated conditions (Tables 2-4).

ATx643, tested as A1 (this code does not designate sterility system), is a white, translucent pericarp, purple-red plant colored line. The panicle of B1 is semi-loose, long, and rectangular in shape. Rachis branches are moderately long and erect. The grain is slightly oval and slightly turtle shaped with glabrous glumes. The line is slightly later and taller in height to ATx2752, and similar in maturity but shorter than BTx623. It possesses good post-flowering drought tolerance, charcoal rot resistance, and lodging resistance. The stay-green in A1 is not as dominant as in ATx642 (A35) and in some combinations is completely recessive. Hybrids will vary in their expression of stay-green from very good, to intermediate, to poor depending on the male parent. It is very susceptible to head smut and head blight, and anthracnose. It is moderately resistant to downy mildew, tolerant to MDMV and highly resistant to fusarium head blight. The line has excellent sterility (similar to ATx623) and has excellent general combining ability. It has moderate resistance to grain mold/weathering. Hybrids of A1 are shorter, more open-headed and much more attractive in appearance than ATx623 hybrids. Depending upon the male parent, hybrids have produced above average yields, especially under dry-land, limited moisture conditions and has good yield potential under high yield or fully irrigated conditions (Tables 5-7).

ATx644, tested as A807, is a dark red, translucent pericarp, purple-red plant colored line. The panicle of B807 is rectangular to slightly oval and long (10-13”) and is semi-loose at maturity. The rachis branches are moderately long, erect, and not stiff. Glumes are slightly pointed and slightly hairy. The line is slightly earlier and similar in height to ATx2752, but earlier and shorter than BTx631. The line tends to be later in south Texas and gets progressively earlier in more northern latitudes. The dark red grain has a moderately high level of grain mold/weathering resistances that transfers well into the F₁ hybrids, resulting in high test-weight grain. The panicle is moderately loose as are its’ hybrids. The line and its’ hybrids possess excellent pre-flowering drought tolerance, but no stay-green. It is very susceptible to head smut, moderately resistant to downy mildew, tolerant to MDMV, and moderately resistant to leaf diseases. The line has excellent combining ability. Hybrids of A807 have produced above average yields under a wide range of conditions (Tables 8-10).

ATx645, tested as A803, is a light red (slightly orange tint) translucent pericarp, purple plant colored line. The panicle of B803 is erect angular to slightly oval and long (8-12”), moderately open and somewhat drooping at maturity. The rachis branches are moderately long, not stiff. The grain is slightly pointed with glabrous glumes. The line is slightly earlier and similar in height to ATx2752, but earlier and shorter than BTx631. It possesses excellent pre-flowering drought tolerance and a slight degree of stay-green with some lodging resistance. In most hybrid combinations, it will produce a light red pericarp grain. It is moderately resistant to head smut and head blight, and downy mildew, and most leaf diseases, and is tolerant to MDMV. The grain is rounder in shape and slightly smaller than grain of ATx 643 and ATx 644. The line combines well with many pollinators. Hybrids of A803 have produced above average yields under dry-land conditions, but generally yield slightly less than ATx 643 and ATx644 hybrids under higher yield potential conditions (Tables 11-13).

ACKNOWLEDGEMENTS

The early stages in the development of these lines were supported by the International Sorghum/Millet Collaborative Research Support Program (INTSORMIL) which is funded by the United States Agency for International Development (USAID). I would also like to acknowledge the numerous scientists who contributed to the development and testing of these lines from Weslaco, Corpus Christi, College Station, Chillicothe, and Lubbock.

SCIENTISTS and TECHNICAL SUPPORT CONTRIBUTING TO THIS RELEASE

L. E. Clark, Retired Professor, TAES, Vernon

F. R. Miller, Retired Professor, Dep. Of Soil & Crop Sciences, College Station

R.A. Frederiksen, Retired Professor, Dep. of Plant Pathology and Microbiology, College Station

G.N. Odvody, Associate Professor, TAES-AREC, Corpus Christi

G. C. Peterson, Professor, TAES, Lubbock

L.W. Rooney, Professor, Dep. of Soil & Crop Sciences, College Station

C.A. Woodfin, Research Scientist, Lubbock

S.D. Collins, Research Associate, Dep. of Soil & Crop Sciences, College Station

K Schaefer, Research Associate, TAES, Corpus Christi

A. Hamburger, Research Associate, TAES, Chillicothe

Table 1. Designation, evalution codes, grain and plant descriptor, and pedigrees of the sorghum breeding lines proposed for release.

Designation	Evaluation Code	Pericarp Color	Plant Color	Pedigree
ATx642	A35	LY	P	[(BTx406*IS12555(SC35)F3)*IS12555]
ATx643	A1	W	P	(BTx625*B35)-HL19-HL9
ATx644	A807	R	P	(BTx623*(BTx625*B35))-37B-2
ATx645	A803	R	P	BTx3042*(BTx625*B35)

LY =Lemon Yellow; W = White; R = Red; P = Purple; HL = Halfway Limited

Table 2. Descriptive plant and grain characteristics of the sorghum breeding lines proposed for release.

	Pericarp color, visual appearance	Pericarp color, genetics	Mesocarp thickness	Plant color	Glume color	Awns	Midrib	Glume coverage
B35	Lemon-yellow chalky	rrYY	thick	purple	lite-reddish purple	present	dry	40%
B1	White, pearly	RRyy	thin	red	red	absent	juicy	30%
B807	Dark red, pearly	RRYY	thin	red	purple-red	absent	juicy	35%
B803	Red, rather pearly	RRYY	moderately thin	purple	purple	absent	juicy	35%

Table 3. Performance (% of checks) of hybrids using A35 as the female relative to the performance of 3 common checks, ATx399*RTx430, ATx378*RTx430, ATx2752*RTx430, and the overall test mean where the experimental hybrids and the checks were evaluated in the same enivironment.

			Yield of A35 hybrids relative to:
		ATx399		ATx378	ATx2752
		*		*	*	Test
		RTx430		RTx430	RTx430	Mean
Location	Year	%		%	%	%
Gregory	1994	88.9		79.8	79.4	90.0
Thrall	1993	102.8		108.0	108.6	110.0
Granger	1997	99.7		81.0	89.5	101.0
	1998	86.4		77.2	92.3	97.1
	1999	105.9		86.6	101.2	106.0
	2000	106.8		94.1	97.1	103.9
Prosper	1998	79.1		87.6	118.6	100.7
	2000	102.2		101.0	106.1	108.9
Lubbock	1993	111.7		100.4	92.7	112.7
	1994	118.3		108.7	118.5	123.7
	1997	112.8		122.0	109.0	97.0
	1998	105.0		95.5	91.1	113.1
	1999	78.9		63.8	72.2	66.4
Halfway Dryland	1994	152.7		.	.	.
Halfway	1997	152.3		166.6	159.5	136.9
	1998	114.5		106.7	101.0	112.2
	1999	101.1		109.2	109.7	128.4
	2000	95.4		89.9	90.3	99.2
Dumas	2000	155.4		156.4	142.4	135.2
Average		108.9		101.9	104.4	107.9

Table 4. Agronomic performance data from replicated tests for hybrids using the new female A35 and appropriate checks in 39 locations over various years.

Location	Year	Hybrid	Days to anthesis	Plant height (cm)	Exsertion (cm)		Test weight (lbs/bu)	Grain yield (lbs/acre)
Gregory^1	1994	A35*(430*9188)	82	50	13		56.5	4250g-n
		ATx399*RTx430	75	49	10		57.2	4779a-j
		ATx378*RTx430	76	59	10		57.2	5325a-c
		ATx2752*RTx430	75	53	9		56.3	5354a-b
						Test mean (62)		4720
							LSD(0.05)	633.7
Thrall^1	1993	A35*88BE2668	92	53	10		62.0	6556a-g
		A35*89CC443	94	53	10		63.3	6378a-j
		ATx399*RTx430	92	47	6		59.3	6291a-m
		ATx378*RTx430	93	54	5		60.5	5988a-o
		ATx2752*RTx430	93	50	5		61.6	5955a-o
						Test mean (66)		5901
							LSD(0.05)	775.5
Granger^1	1997	A35*88V1080	100	51	9		60.2	5948
		A35*89CC445	101	52	11		60.3	6067
		ATx399*RTx430	101	47	7		56.5	6025
		ATx378*RTx430	101	60	8		56.9	7421
		ATx2752*RTx430	101	54	6		59.4	6710
						Test mean (71)		5973
							LSD(0.05)	847.0
	1998	A35*88V1080	87	45	6		58.8	4206
		A35*89CC445	85	45	6		59.2	5028
		ATx399*RTx430	84	42	4		57.0	5343
		ATx378*RTx430	86	48	3		58.4	5402
		ATx2752*RTx430	85	44	5		60.0