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Intersubspecific hybrids between Medicago sativa subsp. sativa and subsp. falcata show biomass yield heterosis in space planted plots. Relative biomass yield of alfalfa is known to differ in space planted versus sward plots, although the magnitude of the difference is variable. The objective of this study was to determine if and how much of the biomass yield heterosis observed in space planted alfalfa hybrids was retained in sward planted plots. Two falcata genotypes (WISFAL-6 and PI502453-1) and three elite sativa genotypes were crossed in a diallel mating design. Progeny were transplanted into space-planted plots and harvested three times per year or drilled into sward plots harvested four times per year. Hybrids of WISFAL-6 with the sativa genotypes produced as much first harvest biomass yield as intra-sativa hybrids in space-planted plots and more in sward plots. Yield in subsequent harvests was lower than intra-sativa hybrids in sward plots only. Hybrids of PI502453-1 with sativa were generally lower yielding than intra-sativa crosses. A moderate correlation was observed between biomass yield in space planted and sward plots. Heterosis expression in swards was lower than that in spaced planted nurseries for progeny of both falcata genotypes. The increased plant-to-plant competition in swards is the likely cause of the loss of heterosis. 相似文献
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Heathcliffe Riday 《Euphytica》2008,163(1):81-87
In the colder parts of the United States (north of 32° N latitude and east of 92° W longitude), in late winter after disappearance
of snow cover, red clover (Trifolium pratense) is often broadcast seeded into forage legume-depleted grass pastures to increase pasture forage quality. This method of
establishment is referred to as frost seeding. However, in an estimated 30–40% of frost seeded pastures in Wisconsin, USA
the legumes fail to establish. In this study 40 red clover halfsib families from one breeding population and ten check populations
were evaluated for spring frost-seeded establishment in three environments. Seedling establishment counts and plant heights
were measured 3 months after frost-seeded planting. One of the three environments experienced a stand establishment failure.
Narrow sense heritability estimates on a halfsib family basis for stand counts and heights were 0.07 and 0.63, respectively.
Seedling counts were greatly affected by environment with micro-environmental effects contributing to low heritability. Additive
by environment genetic variance was large, again leading to low seedling count heritabilities. These results, based on one
population, suggest that it may be difficult to select for increased frost-seeded seedling establishment and that many test
environments are needed to achieve genetic gains for this trait. In comparison, seedling height was very heritable with relatively
small additive by environment genetic variances. The genetic correlation between seedling count and height using frost-seeded
establishment was r
A = 0.42. 相似文献
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Semi-hybrid alfalfa cultivars offer the possibility of capturing non-additive genetic variation. Medicago sativa subsp. falcata and subsp.sativa have been shown to form a heterotic pattern for biomass yield. Objectives of this study were to examine morphological variation
in a broad range of falcate germplasm and to determine how falcate morphological variation per se is related to the performance of falcate germplasm in hybrid crosses with subsp. sativa. Falcata genotypes from 40 populations spanning the subspecies native range were selected and biomass yield, plant width,
plant height, growth angle, biomass density, plant maturity, and regrowth after cutting were measured on the genotypes and
their hybrid progeny three times throughout the growing season. In addition weekly plant heights were measured and growth
rates were determined with a Gompertz function. Falcata parental genotypes exhibited a full range of phenotypes for plant
width, plant height, growth angle, density, and maturity. Heterosis was not only observed for biomass yield but also for plant
width, plant height, and more erect growth habit. The top yielding sativa-falcata hybrids had increased plant width, plant
height, and plant density. European germplasm was taller and had faster regrowth than Asian material. Sativa-falcata hybrids
produced biomass yield superior to the mid-subspecies mean only after two to three weeks of growth prior to first and third
harvests. Prior to second harvest, biomass production was inferior to the mid-subspecies mean for 30 days. Hybrids using falcata
as one parent are not currently adapted to intensive harvest management due to their slower regrowth.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
4.
Heathcliffe Riday E. Charles Brummer T. Austin Campbell Diane Luth Patricia M. Cazcarro 《Euphytica》2003,131(1):37-45
Biomass yield heterosis has been shown to exist between Medicago sativasubsp. sativa and Medica gosativa subsp. falcata. The objective of this study was to gain a better understanding of what morphological and genetic factors were most highly
correlated with total biomass yield heterosis. We calculated genetic distances among nine sativa and five falcate genotypes
based on amplified fragment length polymorphism (AFLP) and simple sequence repeat (SSR) DNA markers. Genetic distance did
not correlate with specific combining ability (SCA) or mid-parent heterosis. In contrast, a morphological distance matrix
based on seventeen agronomic and forage quality traits was significantly correlated with heterosis; the agronomic traits of
maturity, midseason regrowth, and autumn regrowth showed strong association with heterosis. Heterosis was also correlated
with subspecies. We suggest that in many cases progeny heterosis can be accounted for by the interaction of genes controlling
morphologically divergent traits between the parents. In other cases, progeny heterosis could also be due to divergence between
the parents at particular genetic loci that do not control field-level phenotypic differences. Genetic distanceper se between parental genotypes, based on neutral molecular markers, however, does not reflect the potential of individual genotypes
to produce heterosis in their progeny.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
5.
Heathcliffe Riday 《Euphytica》2009,170(3):339-345
Red clover (Trifolium pratense L.) forage yield remains a prime breeding target for improved variety development. In a world of decreasing forage legume
breeding resources, rapidly and cheaply phenotyping plants for the highly quantitative trait of forage yield is vital. Many
red clover selection programs are based on space planted nurseries. The objectives of this study were to determine: (1) the
accuracy of visual forage yield scores in predicting actual forage yield; (2) the nature of the relationship between visual
scores and actual measurements; and (3) The repeatability of visual scores between different evaluators. Twenty-seven halfsib
families were transplanted at two locations in three replicates of six plant plots. Individual plant fresh weights and visual
scores, by two evaluators, for forage yield were taken. On an individual plant basis visual forage yield scores showed an
exponential relationship with actual fresh weights. Individual plant visual scores were very accurate with a pseudo-R
2 of 0.79 observed for the exponential model. On an entry mean basis using a linear model, visual scores could explain 90%
of the variation of actual fresh weights. Agreement among evaluators scoring the same plants was very high with coefficients
of determination at 0.84 for individual plants and as high as 0.96 on an entry mean basis. This study suggests that visual
scores of plants in space planted red clover breeding nurseries are basically as accurate as measuring actual yields and that
plants can be consistently scored the same by different evaluators. 相似文献
6.
Heathcliffe Riday David W. Johnson Karolina Heyduk John A. Raasch Mark E. Darling Jay M. Sandman 《Euphytica》2013,194(3):335-349
Determining unknown parentage in autotetraploid alfalfa (Medicago sativa L.) (2n = 4x = 32) can improve breeding gains. An exclusion analysis-based paternity testing SAS code, amenable to genotyping errors, is presented for autotetraploid species utilizing co-dominant molecular markers with ambiguous dosage. To demonstrate the paternity testing SAS code, 19 SSR loci were genotyped and analyzed on 1,107 progeny from a commercial, isolated, clonally replicated, 16-parent alfalfa breeding polycross which was pollinated by leafcutter bees (Megachile rotundata F.). Paternal assignment success rate was over 90 %. Among typed progeny, 45 % were the result of self-fertilization. Significant differences were detected between the 15 parents that produced seed and were observed as fathers for (1) total fertilizing pollen contribution (% deviation from expectation), (2) self-fertilization rates (%), and (3) outcrossing fertilizing pollen contribution (% deviation from expectation). Physical within-cage distance between parental plants was correlated with outcrossing fertilizing pollen frequency (negative power function). Parental seed yield was positively correlated with total fertilizing pollen contribution, particularly with self-fertilization rates (42 % self-fertilization and 17 % outcrossing). These correlations suggest that selecting for increased seed yield may result in indirect selection for increased self-fertilization rates. Parental total fertilizing pollen contribution was 62 % determined by outcrossing and 35 % by self-fertilization. This study cautions alfalfa breeders that heretofore unconsidered sources of inbreeding could be present in some breeding materials. This study also provides cost effective and easy to use molecular genetic tools for detecting, managing, and/or selecting against (through breeding) those sources of inbreeding. 相似文献
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