Clarification of relationships among species in mixed stands is essential to enlightened management of forage mixtures. During 1976–1979, we evaluated several grass‐legume mixtures in a field study in eastern Kansas. Grasses were: commercial smooth brome, Bromus inermis Leyss.; ‘Regar’ Turkish brome, B. biebersteinii Roem. &Schult.; ‘Kentucky 31’ tall fescue, Festuca arundinacea Scbreb.; and ‘Ioreed’ reed canarygrass, Phalaris arundinacea L. Legumes were: ‘Kanza’ alfalfa, Medicago sativa L.; ‘Kenstar’ red clover, Trifolium pratense L.; ‘Dawn’ birdsfoot trefoil, Lotus corniculatus L.; and ‘Emerald’ crownvetch, Coronilla varia L. Each grass was grown in a two‐species mixture with each legume, and in a pure stand with 0 and 90 kg N ha‐1 as NH4NO3. Mixtures were obtained by alternating all‐grass and all‐legume drill rows. Legumes were grown in pure stands in an adjacent planting. Both plantings were on a Woodson silt loam of the fine, mixed, thermic family in the Abruptic Argiaquolls subgroup of the Mollisols. Dry matter (DM) yields were obtained from all plots. Proportion of grass in mixtures was determined from hand‐harvested samples. Dry matter yield of the grass component of each mixture was computed as the product of the DM yield of the whole stand and the proportion of grass in the mixture. Crude protein (CP) contents of whole stands and grass components of mixtures were computed as 6.25 times N. Although comparisons varied across years, mixtures averaged as much grass DM (3.21 Mg ha‐1) as unfertilized all‐grass stands (3.07 Mg ha‐1) during the 4‐year period. Crude‐protein contents of grass components of mixtures consistently ranked above those of unfertilized all‐grass stands; differences usually were significant (P < 0.05) but varied in magnitude with year and type of stand. Legumes differed significantly (P < 0.05) every year in DM yield and every year except 1979 in CP content. Over the 4‐year period, however, no legume was clearly superior in either variable.

Chromosome number, meiotic behavior, and pollen stainability were studied in switchgrass plants originating mainly in Kansas and Oklahoma. Tall, coarse, glabrous plants, referred to as “lowland”, were tetraploid (2n =36). Shorter, finer plants, featuring varying amounts of leaf blade pubescence and referred to as “upland,” were mostly octoploid. One upland plant was hexaploid, however, and four were aneuploid near the 72‐chromosome level.Tetraploids were more regular meiotically and exhibited a higher frequency of well‐stained pollen than either octoploids or aneuploids. Octoploids and aneuploids were similar in meiotic behavior, but the former exhibited a higher frequency of well‐stained pollen.Genetic distinctness of upland and lowland populations was suggested. Asexual reproduction seemed unlikely in tetraploids. It appeared more likely at higher levels of polyploidy where extreme meiotic irregularity suggested materially reduced sexual fertility in occasional plants.

Twenty-five inbred lines, including grain and forage types from the USA and China, two hybrids, one Sorghum almum, and one Parasorghum (S. versicolor) were tested for their response to anther culture . Three nutrient media were effective in inducing anther calli from six cultivars (Xin White, TX 403-TSB, DDY Sommer Milo, TX 2779, Brawley, and Spur Federal) and one was effective for plant regeneration for one cultivar, Xin White . Averaged over media, callus induction frequency (number of calli per 100 anthers) was highest in cultivars Xin White and TX 403-TSB (6 .7 and 3 .9%, respectively) . The means of cultivars for media C17-2 and Ms-t-z-2, 4 .3 and 3 .2%, respectively, were superior to that for medium 85D3-2 (0 .1%) . Expressed as an average of the six cultivars and three media the mean calli induction frequency was 2 .6% ; however, differential responses of genotype and medium were noted . Among the 10 regeneration media tested, medium MS-d-4 containing Murashige and Skoog basal components plus 2 .0 mg/1 indole-3-acetic acid (IAA) and 2 .5 mg/l kinetin was the most effective for plant regeneration . Numbers of albino plants and calli developing only roots increased directly with callus-induction time, whereas the frequency of plant regeneration decreased . Regenerated plants had varied numbers of chromosomes in root tip cells : 10, 15, 20, 40, and 60. The 29 regenerated plants that reached maturity, however, were highly fertile and contained only 10 bivalents in pollen mother cells . Normal chromosome number and behavior for the regenerated plants suggest that induced calli originated from cells other than microspores . However, spontaneous chromosome doubling in microspore-derived haploids may occur . The appearance of albinos also implies that haploids may have been produced from anther culture .

No abstract

No abstract