Heathcliffe Riday

Morphological variation of Medicago sativa subsp. falcata genotypes and their hybrid progeny

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.

Correlations between visual biomass scores and forage yield in space planted red clover (Trifolium pratense L.) breeding nurseries.

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-R2 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.

Intercropping Tropical Vine Legumes and Maize for Silage in Temperate Climates

ABSTRACT Maize silage is used extensively in American dairy rations. Increasing protein content would enhance maize silage quality. This study examined nine forage legume species (Austrian winter pea, common bean, cowpea, lablab, scarlet runner bean, sesbania, sunn hemp, tropical kudzu, and velvet bean) grown in mixture with maize plants in Wisconsin, in the U.S. Plants were evaluated for growth throughout the growing season, harvest forage dry matter content, total dry matter yield, and forage mixture components. Of the forage legumes tested, common bean, lablab, scarlet runner bean, sunn hemp, and velvet bean were most successfully intercropped with maize. The common bean entry was the most aggressive forage legume, comprising 23% on a dry-matter basis of the final harvested forage mixture. The lablab entry, despite a slow start, became more productive during the late growing season and comprised 7.4% on a dry-matter basis of the final harvested forage mixture. Harvested forage moisture ranged from 299 g kg−1 to 364 g kg−1 of dry matter. Except for the common bean mixture, which had a lower forage dry-matter yield, the mixtures did not differ from one another or the pure maize control for dry-matter accumulation per unit area. Similar to forage dry-matter yields, stover forage mixture fractions were not significantly different among entries, except for the common bean-maize mixture. Grain yields were inversely proportional to the amount of legume present.

Alfalfa Subsp. Sativa by Falcata Intersubspecific Semi-Hybrid Seed Production Using Alfalfa Leafcutter Bees

ABSTRACT Intersubspecific sativa by falcata alfalfa (Medicago sativa L.) hybrids offer a means of improving alfalfa dry-matter yields. The alfalfa leafcutter bee (Megachile rotundata F.) is a major pollinator used in alfalfa seed production in North America. Alfalfa leafcutter bees have a pollinator preference for purple-flowered subsp. sativa plants over the yellow-flowered subsp. falcata plants. This study was conducted to quantify the pollinator preference by observing the amount of hybrid seed produced using alfalfa leafcutter bees. Two pollination environments and three different proportions of falcata parents in pollination cages (50%, 75%, and 90%) were included to determine shifts in quantities of hybrid seed produced due to environment and/or pollinator subsp. falcata flower availability. Total and hybrid seed amounts and seed size differed between environments. Seed size differences were observed between subspecies. Hybrid seed yields were 57% of expected hybridity on an experiment mean basis. In crossing cages with higher subsp. falcata parent proportions, a decreased amount of observed percent hybridity compared with expected hybridity was observed (i.e., 50% subsp. falcata = 72%, 75% subsp. falcata = 59%, and 90% subsp. falcata = 39% of expectation). Seed yield per plant and seed size did not differ between cages with differing subsp. falcata parent proportions. Plant-to-plant variation for seed yield and seed weight was observed; however, no plant-to-plant variation for observed percent hybridity of expected hybridity was found. This study suggests using 50% subsp. falcata plants to 50% subsp. sativa plants will produce 36% hybrid seed (or 72% of expectation) in alfalfa seed production fields using alfalfa leafcutter bees as pollinators and suggests increasing percent subsp. falcata parentage will decrease the percent of hybrid seed observed compared with expectation.