Glenn W. Burton

Pearl Millet Breeding and Cytogenetics1

Publisher Summary Pearl millet, Pennisetum typhoides , a robust annual bunchgrass, occupies more than 45 million acres of the earths surface and occurs in every continent of the world. Although best adapted to the tropics, pearl millet also does well in hot areas of the temperate zone. It has many characteristics that make it an excellent tool for cytogenetic and breeding research. Yet it has been used very little for such studies. This chapter brings together widely scattered bits of information pertaining to the breeding and cytogenetics of pearl millet. It also includes unpublished information to make the treatment as complete as possible. Pearl millet has great economic potential for forage and grain production. Its unusual diversity, flexibility, and responsiveness suggest that its improvement as a useful crop for man has only begun. Few organisms of economic worth are very well suited to basic cytogenetic and plant breeding research. The knowledge of the karyotype of lines within species can give some indication of chromosome diversity and possible barriers to recombination. In pearl millet, the reports on karyotype have been divergent, yet the experience of breeding this species has uncovered no significant barriers to recombination. The chapter explains the cytogenetics of pearl millets and discusses the genetics of qualitative characters, genetics of quantitative characters, and details of breeding associated with pearl millets.

A search for the origin of Pensacola Bahia grass

Pensacola Bahia grass, Paspalum notatum Fluegge, received its coimmon namiie from county agent E. H. Finlayson, of Pensacola, Florida, in 1941 (3). Because it was distributed around the old Perdido Wharf (destroyed in 1926) and had not been observed in other places, he suggested that it had been introduced in ballast dumped in the low land adjacent to the wharf before it was destroyed. Believing that Pensacola Bahia grass had pasture potential, Finlayson and Paul Tabor, of the Soil Conservation Service, began to promote it as an improved pasture grass for the deep south. The excellent seeding habits, aggressiveness, persistence, and adaptation of Pensacola Bahia helped the Soil Conservation Service to spread it widely in Florida and the Coastal Plain of adjacent states. Today, it occupies well over a million acres, where it has been planted and hundreds of acres where it has been unintentionally spread by miian and beast. It is generally recognized as a good pasture grass, an excellent road-shoulder grass, and a serious pest in lawns and fine turf. There is good reason to believe that Pensacola Bahia grass is now so well distributed and so well adapted that it will soon be found wherever grass grows in the deep south, whether man plants it or not.

Breeding Pearl Millet

Pearl millet Pennisetum americanum (L.) Leeke, also called bulrush cattail or spiked millet in English, bajra in Hindi, kambu in Tamil, dukhn in Arabic, and mil de chandelles in West Africa, is the world’s most important cereal in the hot, arid sections of the world. It will grow and mature seed on sandy or rocky soils too acid, too dry, and too infertile for sorghum or maize. Yet it has great yield potential and can produce more forage than either sorghum or maize when grown in a favorable environment. In grain production, however, the best sorghum and maize hybrids outyield the top pearl millet hybrids under optimum growing conditions.

The Adaptability and Breeding of Suitable Grasses for the Southeastern States

Publisher Summary This chapter discusses the adaptability and breeding of suitable grasses for the southeastern states in the United States. Accurately evaluating grasses for pastures is a difficult and an expensive operation. Most agronomists begin the task by planting the grasses in rows or plots in pure stand. There they are allowed to grow undisturbed, and if they fail to survive the first 12 months, they are usually written off as having no value. Dallis grass, recognized as one of the best pasture grasses in the south, makes a poor showing in such a planting. Plantings of Dallis grass at Tifton, Georgia, which were never grazed or mowed, were found to make good growth during the first part of the summer, but died out by fall. The combined effect of the foliage diseases that build up in the accumulated mass of leaves and the heading process was thought to be responsible for these results. Tall fescue, another promising grass in the south, makes a poor record in such a planting if it is not well fertilized. This chapter describes the problem of evaluating grasses. Different types of grasses are discussed in detail in the chapter.

Steer Gains under Six Systems of Coastal Bermudagrass Utilization

Highlight: Steer gains on ‘Coastal’ Bermudagrtzss (Cynodon dactylon (L.) Per-s.), utilized by continuous, weekly rot(ation, or daily strip grazing, or green chop, dehydrated hay, or pellet feeding, were studied for 3 years. Previous studies had included fewer methods of utilization, or had run for only a short time. Average daily gains and gains per hectare were: continuous, 594 g and 600 kg; rotation, 449 g and 469 kg; strip, 392 g and 487 kg; green chop, 369 g and 647 kg; hay, 671 g and 971 kg; and pellets, 800 g and 967 kg. Diferences among grazing methods in average daily gain were largely accounted fQr by differences in grazing pressure. DifSerences among feeding methods reflected diflerences in forage intake and lignin content of the forage. Seasonal changes in gain andforage intake were influenced by seasonal changes in lignin content and increasing #steer weights. ‘Coastal’ Bermudagrass (Cynodon dactylon (L,.) Pers.), released in 1943, quickly became one of the most important pasture grasses in the southeastern United States and in other areas with similar climate. Continuous grazing, the most

Effect of recurrent mutagen seed treatments on mutation frequency and combining ability for forage yield in pearl millet (Pennisetum americanum (L.) K. Schum.)

The effects of 3 cycles of recurrent seed treatment with thermal neutrons (TN), ethyl methane sulfonate (EMS), and diethyl sulfate (DS) on mutant frequency and combining ability in pearl millet ( Pennisetum americanum (L.) K. Schum., formerly P. typhoides ) were studied for eleven years. TN seed treatments gave the highest percentages of M 1 striped plants, the lowest percentage of M 1 selfed seed set, and the highest M 2 frequency of chlorophyll-deficient seedlings of the mutagens tested. Combining a low dose of EMS or DS with high and low TN treatments generally increased these effects. Normal lines, which looked like the controls, selected from lines subjected to 3 cycles of mutagen treatment, were compared with controls in 3 × 3 or larger Design II hybrid matings in 9 × 9 forage-yield trials. The 1,637 singlecrosses between normal lines from mutagen treatment failed to exceed the 825 control singlecrosses in average forage yield or highest forage yield. These results suggest that pearl millet has many specific-yield genes, none of which exerts a very great effect on yield. Genetic variances estimated from the Design II diallels were not significantly altered by mutagen seed treatment. EMS treatments increased the percentage of non-additive genetic variance over that in the control and TN treatments, but the failure of any of the 486 hybrids from EMS lines to outyield the best control hybrid suggested that these variance estimates might not be significant. The study suggests that attempts to improve the combining ability of inbred lines of pearl millet by mutagen treatment without several cycles of recurrent selection are not likely to succeed.

An induced mutant of coastcross 1 bermudagras with improved winterhardiness

Abstract Coastcross 1 bermudagrass, a sterile F 1 hybrid, (Coastal × PI 255445 from Kenya) establishes faster, yields as much dry matter, is 12% more digestible, and gives 30–35% better daily gains and liveweight gains per ha when fed to cattle than does the Coastal clone but fails to develop rhizomes and lacks the winterhardiness of Coastal. To create a winterhardy mutant, some 500,000 green stems (each containing several dormant buds) were exposed to 7000 rad of 60 -Co rays at Oak Ridge. TN June 21, 1971 and were immediately planted at Blairsville, GA where relatively severe winters occur frequently. One of 4 plants surviving the 1971–1972 winter was like Coastcross 1 in yield, in vitro dry matter digestibility and appearance in a 3-yr test during mild winters at Tifton, GA. In the growing season following the moderate winter of 1976–1977, Coastcross 1-M3 yielded more than Coastcross 1 but only about half as much as Coastal. The severe winter of 1977–1978 destroyed about 98% of the plants in the clipped plots of Coastcross 1 and Coastcross 1-M3 but reduced the stand of Coastal very little. The small gain in winterhardiness by Coastcross 1-M3 suggests that several genes control the winterhardiness of well-established Coastal bermudagrass.

FORAGE PRODUCTION OF PEARL MILLET HYBRIDS GROWN FROM SEED EXPOSED TO LOW DOSES OF GAMMA RAYS.

Seeds of three pearl millet varieties (Gahi 1, Millex 22 and Tift 23 × 186) received gamma ray dosages of 0, 150, 300, 600, 1200, 2400, 4800, 9600 and 19,200 R just before planting in 1969 and 1970. Repeating 3 times each variety-treatment combination in a 9 × 9 lattice square field test gave coefficients of variability (CVs) of 8·0 and 8·2 per cent for total 1969 and 1970 yields and made average dosage effects 3·4 per cent different than the control—significant ( P =0·05). Millex 22 and Tift 23 × 186 yielded 5·1 and 15·9 per cent more forage respectively than Gahi 1. Exposing seeds to gamma rays ranging from 150 to 9600 R failed to significantly increase forage yields in either year. Exposing seeds to 19,200 R reduced forage yields 9·5 per cent ( P > 0·01). Dry matter yields of 9-day-old seedlings grown in growth chambers tended to parallel field results. Dry weights of 8-day-old seedlings decreased from 1·50 to 0·10g as seed exposure to gamma rays increased from 6 to 54 kR. Gahi I was most tolerant of heady gamma ray seed treatment. No evidence of radiation-induced stimulation was observed.

Inheritance of height and maturity in crosses between pearl millet landraces and inbred Tift 85DB.

SummaryOver 300 landraces of pearl millet were collected in Burkina Faso and grown at the Coastal Plain Experiment Station in Tifton/GA. At Tifton, these landraces are predominantly tall and late-maturing. The photoperiod requirements of these landraces hinder evaluation of their performance in the field and their use in breeding programs. A conversion program has been initiated to transfer genes for dwarf stature and early flowering into the tall, late-maturing landraces. The inbred Tift 85DB is being used as a donor of genes for the dwarf and early characteristics, and was crossed to nine randomly selected landraces from Burkina Faso. The parents, F1, F2, and backcrosses to each parent were grown in the field and evaluated for plant height at anthesis and time in days from planting to anthesis. In general, plant height of F1s was taller than the tallest parent, and in all crosses the maturity of F1s was intermediate between the parents. Numbers of loci conferring height varied among crosses, ranging from 0 to 9.6, and averaged 1.6. Estimated numbers of loci conferring maturity ranged from 0 to 12.8 and averaged 3.4. Broad-sense heritability estimates for height and maturity averaged 60.2 and 65.7%, respectively. Corresponding narrow-sense estimates averaged 23.8 and 48.2%. Joint scaling tests revealed that additive-genetic effects were highly significant for both traits, but dominance and epistatic-genetic effects contributed to the inheritance of each trait in some crosses. The low gene numbers, high heritability estimates, and preponderance of additive-genetic effects suggest that selection for these traits should be effective.

Silage production and quality of pearl millet, sorghum, and corn hybrids grown from seed exposed to low doses of gamma rays

Just before planting, seeds of pearl millet, Pennisetum americanum (L.) K. Schum., (formerly P. typhoides ) hybrid, “Tift 23 × li”, and corn, Zea mays L., hybrids “Coker 71”, “DeKalb 1214”, and “Pioneer 3030” were exposed to gamma ray dosages of 0, 0·15, 0·3, 0·6, 1·2, 2·4, 4·8, 9·6, and 19·2 kR. “FS26” hybrid sorghum, Sorghum bicolor (L.) Moench., seeds were exposed to gamma ray dosages of 0, 0·2, 0·4, 0·8, 1·6, 3·2, 6·4, 12·8, and 25·6 kR. In one 2-yr. experiment, pearl millet, sorghum, and Coker 71 corn gave respective dry matter yields of 12, 166, 6, 993, and 6,306 kg/ha and in vitro dry matter digestibility (IVDMD) percentages of 45·7, 52·8, and 59·9. The heaviest exposures of gamma rays generally reduced yields of all species, and lighter exposures failed to increase yield significantly. Seed irradiation did not affect the quality (IVDMD) of the forage. In a 2-yr. corn hybrid experiment, DeKalb 1214 yielded 24% more dry matter and tolerated the heavy exposures of gamma rays better than Pioneer 3030 and Coker 71. None of the lower exposures increased yield significantly.