K. H. Quesenberry

Nitrogen Fixation in Grasses Inoculated with Spirillum lipoferum.

Field-grown pearl millet (Pennisetum americanum) and guinea grass (Panicum maximum), lightly fertilized and inoculated with Spirillum lipoferum, produced significantly higher yields of dry matter than did uninoculated controls. Up to 42 and 39 kilograms of nitrogen per hectare were replaced by inoculation for pearl millet and guinea grass, respectively. The data demonstrate that nitrogen fixation by these grass-Spirillum systems is efficient and is achieved at a reasonable energy cost to the plant.

Fluorescent antibody technique to identify Azospirillum brasilense associated with roots of grasses

Abstract Bacteria associated with roots of grasses from Florida, Ecuador and Venezuela were isolated and their N 2 -fixing ability was demonstrated by C 2 H 2 reduction assay. The bacterial isolates have been classified as Azospirillum brasilense (formerly Spirillum lipoferum ). These N 2 -fixing isolates have been compared with several Brazilian strains. Fluorescent antibody (FA) techniques were used to assist identifying isolates of N 2 -fixing bacteria from grass roots. Tests with antisera prepared against four strains of Azospirillum were used to define serological groups. Antigen-antibody specificity was demonstrated using both Azotobacter and Azospirillum antisera against known species of other soil microorganisms and numerous unidentified soil bacteria. Several applications of the FA technique are suggested to identify N 2 -fixing bacteria associated with grass roots.

Cluster analysis of a world collection of red clover germplasm

SummaryGermplasm evaluation data on more than 800 accessions of red clover (Trifolium pratense L.) representing 41 countries of origin were examined from the Germplasm Resource and Information Network of the National Plant Germplasm System. Large variations exist for most characters over all origins. Clustering accessions using standardized values of 15 morphological and physiological descriptors produced three distinct groups that correspond to early, medium, and late maturity groups. Within each maturity group, different similarity groups were produced. The analysis revealed a large range of diversity among the red clover accessions over all origins with the most diversity occurring in accessions from Eastern and Northern Europe. Accessions with similar attributes often were from countries with contrasting agroecological conditions. Categorizing red clover accessions into similarity groups provided a structure for sampling a limited number of entries to represent the diversity of the germplasm into a core collection. The utilization of this core collection should facilitate genetic resource management and identification of genotypes for breeding and other agronomic uses.

Red Clover ( Trifolium pratense )

Genetic modification of plants by the insertion of transgenes can be a powerful experimental approach to answer basic questions about gene product function. This technology can also be used to make improved crop varieties for use in the field. To apply this powerful tool to red clover, an important forage legume, a population of red clover with a high potential for regeneration in tissue culture has been developed. Here we provide a detailed procedure for Agrobacterium-mediated transformation of genotypes derived from this regenerable population. We have successfully used this methodology to express a beta-glucuronidase (GUS) reporter gene and to silence an endogenous polyphenol oxidase gene in red clover.

Genetic diversity for root-knot nematode resistance in white clover and related species

AbstractA total of 237 Plant Introduction in eleven Trifolium species were evaluated for resistance to Meloidogyne arenaria (Neal) Chitwood race 1, M. hapla Chitwood, M. incognita (Kofoid & White) Chitwood race 3, and M. javanica (Treub) Chitwood. Plants were infected with 1500 nematode eggs collected from Rutgers tomato (Lycoperiscon esculentum Mill.) roots with 0.5% NaOCl. Ratings of galling severity and egg mass production were assigned to each plant 8 wk after inoculation. Host plant reaction was classified as immune, highly resistant, resistant, moderately resistant, intermediate, moderately susceptible, susceptible, and highly susceptible according to the resistance index n

Collection of Trifolium sp. and other forage legumes in Bulgaria

RI{text{ = }}sqrt {{text{(gall}}^{text{2}} {text{ + egg}}^{text{2}} {text{)}}}

Selection for Tolerance to Root-Knot Nematodes in Red Clover

n. More than 95% of 171 white clover accessions were moderately to highly susceptible to all four nematodes species. The best white clover accessions were only moderately resistant to either M. arenaria (PI 291843 and PI 306286) or M. hapla (PI 100250 and PI 204930). Accessions with moderate resistance or resistance to root-knot nematodes were found among relatives of white clover, with T. ambiguum M. Bieb. exhibiting the greatest resistance level. Among the other Trifolium species evaluated, T. carolinianum Michx. PI 516273 was immune or highly resistant to all four nematode species while accessions of T. hirtum All. showed a wide range of reaction to root-knot nematodes. Identified germplasm of white clover relatives with resistance to root knot nematodes should be useful for the selection of parents in white clover breeding programs.

Registration of Cherokee' red clover

A germplasm collection of red clover (Trifolium pratense L.) and seven related species was evaluated in greenhouse tests for resistance to Meloidogyne arenaria (Neal) Chitwood, M. hapla Chitwood, M. incognita (Kofoid & White) Chitwood, and M. Javanica (Treub) Chitwood. Plants were rated for root galling severity and nematode egg production at eight weeks after inoculation with 1500 nematode eggs. A resistance index, RI = √(gall2; + egg2;), was generated to assess the plants reaction to nematode infection as immune, highly resistant, resistant, moderately resistant, intermediate, moderately susceptible, susceptible, or highly susceptible. More than 98% of red clover accessions were intermediately to highly susceptible to all four root-knot nematode species. Only one accession, PI 271627 introduced from India, had a moderate resistance level to the four nematodes tested. About one third of the T. medium accessions were resistant or highly resistant to M. arenaria, M. incognita, and M. javanica whereas more than 50% of the T. alpestre accessions were highly resistant or immune to all four nematodes species. Genetic factors for resistance to root-knot nematode could be introduced into T. pratense through interspecific hybridization with T. medium and/or T. alpestre