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Crop Science 40:1555-1558 (2000)
© 2000 Crop Science Society of America

CROP BREEDING, GENETICS & CYTOLOGY

Total and Seasonal Distribution of Dry Matter Yields for Pearl Millet x Wild Grassy Subspecies Hybrids

Wayne W. Hanna

USDA-ARS, P O Box 248, Univ. of Georgia Coastal Plain Exp. Stn., Tifton, GA 31793 USA

whanna{at}tifton.cpes.peachnet.edu


   ABSTRACT
TOP
 ABSTRACT
INTRODUCTION
 Materials and methods
 Results and discussion
 REFERENCES
 
The wild grassy subspecies Pennisetum glaucum (L.) R. Br. subspecies monodii (Maire) Brunken has been used as a source of germplasm for improved disease resistance and cytoplasmic diversity for improving pearl millet [P. glaucum (L.) R. Br.] cultivars. The objective of this research was to evaluate a portion of the monodii germplasm to determine if this germplasm could be used to increase the dry matter yield and extend the growing period of pearl millet forage hybrids. Seventy-nine monodii accessions from Niger, Mali, Senegal, and Burkina Faso were crossed with Tift 85DA1, a cytoplasmic-nuclear-male-sterile (CMS) pearl millet used in commercial hybrid production. These hybrids along with `Tifleaf 2' (a popular commercial hybrid) and `Gahi 3' were tested for 2 yr on a fine, loamy, thermic Plinthic Kandiudult soil at Tifton, GA, latitude north 31.48° and longitude west 83.53°. The best experimental hybrid yielded up to 31% more dry matter than Tifleaf 2. A significant hybrid x year effect on total yield indicated that some of the hybrids showed a differential response during the 2 yr. Tifleaf 2 produced between 23 and 32% of its total yield in the last harvest, whereas a number of the experimental hybrids produced significantly more (up to 50%) of their dry matter in the last harvest. The experimental hybrids were consistent across years in their superior late-season production. Variation was also observed among hybrids for production of dry matter in the first harvest. Early production would be especially valuable in areas that have distinct wet and dry seasons. This research indicates that genes for enhancing level and distribution of yield in cultivated pearl millet are present in the wild grassy subspecies, monodii.

Abbreviations: CMS, cytoplasmic-nuclear-male-sterile


   INTRODUCTION
TOP
 ABSTRACT
 INTRODUCTION
Materials and methods
 Results and discussion
 REFERENCES
 
PEARL MILLET is an important summer annual forage crop in the USA that is used mainly for grazing and hay. It is also a major crop in India and Africa where an estimated 28 million hectares are grown for food, fodder, and fuel. Pearl millet will grow in areas where the environment is too harsh, such as low fertility and moisture, to grow most other grain crops. There is interest in developing pearl millet as a high quality grain crop in the USA.

Harlan and De Wet (1971) proposed an informal gene pool system to classify relatives of the cultivated species to categorize the ease with which subspecies and species in a genus will cross with the cultivated species. The primary gene pool consists of the wild weedy relatives or subspecies (Harlan, 1975) that usually cross easily with the cultivated species to produce fertile hybrids.

The wild subspecies, P. glaucum subsp. monodii, belongs to the primary gene pool of pearl millet and is a weedy plant that grows along farmer fields and roadsides, mainly in the Sahel region of Africa (Brunken, 1977). It usually has thinner stems and narrower leaves than the cultivated species but can be difficult to distinguish from the cultivated species in the vegetative stage. Seed head characteristics such as small inflorescences, loosely arranged florets, small seed, seed shattering, and seed dormancy distinguish monodii from the cultivated species. Subspecies monodii is vigorous and readily crosses with cultivated pearl millet. Bramel-Cox et al. (1986) reported that monodii had potential for increasing the growth rate in pearl millet. Hanna (1997) showed that hybrids with cytoplasms from different monodii accessions produced up to 17% more dry matter yield than Tifleaf 1, the commercial check, because of either cytoplasmic and/or cytoplasmic-nuclear effects.

Subspecies monodii has been an important germplasm source for improving pearl millet. Genetic resistance to rust (Puccinia substriata Ellis & Barth; var. indica Ramachar & Cummins), pyricularia leafspot [Pyricularia grisea (Cke) Sarc.], and smut [Moesziomyces penicillariae (Bref.) Vanky] (Wilson and Hanna, 1992) has been identified in monodii accessions and incorporated into inbred lines to develop and release commercial pearl millet forage (Hanna et al., 1988, 1997) and grain (Hanna, 1993) hybrids. Tift PS34 (Table 1) has contributed a large amount of this genetic resistance to pearl millet diseases. Tift PS34 has also contributed the stable A4 cytoplasm used to produce CMS Tift 85D2 A4 for commercial hybrid production (Hanna, 1996). The objective of this study was to evaluate a portion of the monodii germplasm in our collection and determine if this germplasm could be used to increase the dry matter yield and extend the growing period of pearl millet forage hybrids.


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  		Table 1 Seasonal total dry matter yields and percent of total yields at Harvest 1 and 3 for Tift 85DA1 pearl millet x wild grassy subspecies hybrids

 

   Materials and methods
TOP
 ABSTRACT
 INTRODUCTION
 Materials and methods
Results and discussion
 REFERENCES
 
Seventy-nine monodii accessions were crossed as male parents with Tift 85D2A1, the CMS inbred used to produce the commercial single cross hybrid, Tifleaf 2. Subspecies monodii accessions were from Burkina Faso (1), Mali (30), Niger (27), and Senegal (21). Two commercial single-cross pearl millet forage hybrids were used as checks. Tifleaf 2 is a popular commercial semi-dwarf, leafy hybrid that is easy to manage for grazing and hay. Gahi 3 is a tall hybrid that was popular before the release of the `Tifleaf' series of hybrids. Although Gahi 3 usually produced more total dry matter than `Tifleaf' hybrids, it generally became stemmy reducing quality and complicating utilization.

Seventy-nine Tift 85D2A1 x monodii experimental hybrids, Gahi 3, and Tifleaf 2 were arranged in a 9 x 9 lattice-square design with five replications. Hybrids were planted on 14 June 1988 and 11 June 1989. Entries were planted as single row plots 4.8 m long with 1.8 m between centers to facilitate mechanical harvesting. Plot ends were separated by a 0.9 m alley. Trials received 28 kg ha-1 N, 56 kg ha-1 P and 84 kg ha-1 K at planting followed by 112 kg ha-1 N 30 d after planting. Plots were harvested 28 July, 25 Aug., and 17 Oct. 1988 and 29 July, 24 Aug., and 11 Oct. 1989. The shorter interval between the July and August harvests is due to the flush of growth that pearl millet makes during the middle of the summer. Plants were vegetative at the July and August harvests and past anthesis at the October harvests.

Forage was cut from each plot and weighed. Dry matter percentages were determined from subsamples of green forage dried in an oven at 70°C for 48 h and were used to convert fresh weights to dry weights. Dry forage yields were summed across harvests to obtain annual forage yields. Yields were analyzed by analysis of variance procedures (SAS Institute, Inc., 1985) to evaluate significance of hybrid, year, and hybrid x year interaction effects. Yields and distribution of production are reported by year because of a significant (P = 0.01) year x hybrid effect. Significance refers to P <= 0.05 if not indicated otherwise. Reference to a hybrid in RESULTS AND DISCUSSION refers to an experimental hybrid. To distinguish among hybrids in the following discussion, reference will be made to the male parent or PS number of the male parent.


   Results and discussion
TOP
 ABSTRACT
 INTRODUCTION
 Materials and methods
 Results and discussion
REFERENCES
 
Most monodii accessions have varying levels of day-length sensitivity and do not flower at Tifton, GA, until days are 11 h or less. Tift 85DA1 readily crosses with monodii and hybrids are relatively easy to obtain. Level of dry matter production and seasonal distribution of dry matter varied greatly among hybrids and between years (Table 1).

Dry Matter Yield
The number of hybrids yielding significantly more dry matter than Tifleaf 2 was four in 1988 and 15 in 1989 and more than Gahi was none and 41 for 1988 and 1989, respectively. In 1988 and 1989, the best hybrids yielded 31 (PS512) and 23% (PS143) more dry matter than Tifleaf 2, and 0 and 36% more dry matter than Gahi 3, respectively. The number of hybrids with yields that were not significantly less than the highest yielding hybrid were 43 and 29 for 1988 and 1989, respectively.

In general, most hybrids produced about the same or less dry matter in 1989 than in 1988. However, some hybrids such as PS464, PS470, PS592, PS636, PS648, and PS652 tended to produce higher dry matter yields in 1989 than in 1988. Other hybrids such as in the PS620 to 635 group produced more dry matter in 1988 than in 1989. The reason for the year x hybrid effect is attributed to higher rainfall during the last 2 wk of June in 1989 compared with 1988 (110 vs 43 mm). Observations (unpublished) on diverse pearl millet genotypes over the years indicate that some genotypes perform better under wetter soil conditions than others. This aspect deserves further study.

Most of the hybrids with lower dry matter yields in 1989 compared with 1988 were in the PS628 to PS652 group (Table 1). This group was collected from a region represented by the triangle formed by the cities of Gao, Kidal, and Meneka in eastern Mali. Other accessions from Mali (most collected west of Gao), such as PS131, PS132, PS296, and PS512, showed higher and more consistent yields in 1988 and 1989. Although a group of accessions produced low dry matter yields, they should not be discounted as a valuable germplasm source. For example, PS34 was not one of the top dry matter producers in this experiment, but it has been a valuable source of germplasm for disease resistance and new CMS to produce new commercial forage and grain hybrids (Hanna, 1993, 1996; Hanna, et al., 1988; Hanna, et al., 1997). No significant differences were detected for dry matter yields among means of hybrids from Niger (13.7), Senegal (14.2), and Mali (12.8) in 1988. However, in 1989, hybrids from Mali (10.1) yielded significantly less than hybrids from Senegal (12.6) and Niger (12.1). Burkina Faso (15.9 and 12.7, respectively, for 1988 and 1989) was not included because we had only one accession from this country and each of the other countries had one or more accession that equaled its yield.

Dry Matter Distribution
Many parts of the world have distinct wet seasons followed by drought. Hybrids that produce most of their dry matter early in the growing season would have an advantage in these areas. Greatest percentage of total seasonal dry matter produced in the first harvest for seven hybrids (PS426, 445, 512, 576, 582, 620, and Gahi 3) in 1988 and four hybrids (PS634, 635, 637, and 640) in 1989 were not significantly different from the hybrid that produced the highest percentage of forage in the first harvest in 1988 (PS620, 59%) and 1989 (PS640, 72%). None of the hybrids in this group were in common between 1988 and 1989 as opposed to the more repeatable response observed in the third harvest. This differential response of the hybrids between years may be due to both a genetic effect and to rainfall as discussed earlier for differences in total dry matter production.

One of the greatest forage needs for warm-season grasses is improved quantity and quality of late summer and fall production. Tifleaf 2, a widely used hybrid, produced 23 and 32% of its dry matter in the third harvest in 1988 and 1989, respectively. Twenty-six and 37 of the experimental hybrids in 1988 and 1989, respectively, produced significantly more dry matter than Tifleaf 2 in the third harvest. Fifteen and 10 of the hybrids produced from 35 to 42% and from 45 to 50% of their dry matter in the third harvest in 1988 and 1989, respectively. Percentage distribution of forage by these latter hybrids in the third harvest was not significantly different from that of the hybrid that produced the highest percentage of forage in the third harvest, PS292 and 433 (42%) in 1988 and PS433 (50%) in 1989. The consistency of PS433 to produce both high total dry matter yields and high third harvest yields in both years make it a good source of germplasm for improving pearl millet hybrids. Nine (PS134, 138, 292, 296, 428, 433, 434, 438, and 439) of the 10 hybrids that produced the highest percentage of dry matter yield in the third harvest in 1989 were also found in the highest percentage producing group in 1988. This distribution of dry matter production in commercial forage hybrids would be favorable for providing forage in the late summer and fall. Later production could result from later maturity of hybrids and/or better regrowth potential.

Data from this experiment indicate that genes for enhancing level and distribution of yield in cultivated pearl millet are present in the wild grassy subspecies monodii. The ease with which monodii germplasm can be used to improve pearl millet may depend on the recurrent parent of the cultivated species. Roberts and Sarr (1992) reported that while F2 plants from the `Thiotande' x wild cross favored the wild type, F2 plants from the `Souna' x wild cross favored the cultivated type. Poncet et al. (1998) showed that although a high level of recombination occurred between the genomes, the existence of preferential associations between some characters preserved the cultivated-like phenotype in some crosses. We have successfully used the backcrossing method in previous research to transfer cytoplasms and disease resistance from monodii to cultivated pearl millet and the potential for transferring genes to increase dry matter yield and extend the growing period appears promising (Wilson and Hanna, 1992).


   ACKNOWLEDGMENTS
 
This study was supported, in part, by U.S. Department of Energy Contract No. DE-FG02-93ER20099. The author thanks P.A. Diop, G.B. Ingram, L. Marchais, Mr. and Mrs. A. Lambert, International Research Institute for the Semi-Arid Tropics, and the International Board of Plant Genetic Resources for providing the seed of the accessions used in this study.

Received for publication January 24, 2000.


   REFERENCES
TOP
 ABSTRACT
 INTRODUCTION
 Materials and methods
 Results and discussion
 REFERENCES
 




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This Article
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