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An improved solid semiselective medium (M-SSM) for isolation of Xanthomonas campestris pv. phaseoli was developed by the addition of starch, dyes, and agar to a liquid semiselective medium. The solid medium was equal or superior to two other semiselective media for isolation of X. c. phaseoli from diseased bean (Phaseolus vulgaris) tissues. The medium was easy to prepare, and it remained stable in cold storage over a 45-day period. Each of 19 strains of the pathogen grew on the medium; the colonies appeared earlier, and grew larger, than those of nontarget bacteria(.)

Of 16 weed species belonging to 10 families, only Neonotonia wightii served as a perennial reservoir of Pseudomonas syringae pv. phaseolicola, the cause of halo blight. The weed survived dry periods along fences and hedgerows, by roadsides, on ditch banks, and in corners of farmers' fields. Only race 1 of P. s. phaseolicola was recovered from N. wightii. With artificial inoculation, however, all three races of the bacterium caused lesions in the weed. Because race 1 of P. s. phaseolicola was not seedborne in N. wightii, the weed cannot spread the pathogen into new areas by means of seed dispersal

The pathogenic variation among 118 isolates of Pseudomonas syringae pv. phaseolicola associated with halo blight of bean (Phaseolus vulgaris) in the Arusha and Kilimanjaro regions of northern Tanzania from November 1988 to February 1990 was examined with four differential bean cultivars. The three races recovered were race 2 (52.5%), race 1 (45.0%), and race 3 (2.5%) Some strains of race 2, designated as 2P, produced a brown, diffusible pigment on agar media. Some race 2P strains grew at 34 C, whereas the non-pigment-producing strains of race 2 and of races 1 and 3 failed to grow at this temperature (.)

In tests in northern Tanzania, populations of Pseudomonas syringae pv. phaseolicola on and in bean (Phaseolus vulgaris) foliage were higher, severity of halo blight on foliage and pods was greater, and incidence of seed infection was higher when beans were intercropped with maize (Zea mays) than when beans were grown alone. Maize leaves did not support high populations of the pathogen and thus did not seem to provide additional inoculum for the bean crop when the two were grown in association. However, bean leaves in the intercrop system took longer to dry after rainfall and were wetter than those in the monoculture (.)

Bean seeds (Phaseolus vulgaris), either noninfested or internally infested with Xanthomonas campestris pv. phaseoli, were immersed in solutions of polyethylene glycol (PEG) or glycerol as well as in solutions of these materials containing streptomycin, tetracycline, and chlorotetracycline. Immersion in either 25% PEG or 60% glycerol solutions did not diminish germination while seedling vigor was slightly reduced. PEG solutions were more effective than glycerol solutions for introduction of antibiotics into seeds (.)

The yield data of 39 cultivars of diverse commercial classes of beans (Phaseolus vulgaris L.) planted in seven locations in Michigan were subjected to cluster and canonical variate analyses. The essential findings and conclusions can be summarized as follows: (1) Cluster analysis classified the cultivars into sub-sets or clusters almost identically coinciding with their commercial class designation. Canonical variate analysis completely confirmed the sub-groupings. Within class similarities were attributed to a narrow genetic base resulting from a common genetic relationship, or at least sharing of a common gene pool. (2) It was found that two clusters could possess almost identical mean (cluster mean) yields, and deviate in opposite directions over the same range of environments. (3) When total genotype × environmental interaction variance was partitioned into between and within clusters, the cluster × environment portion constituted 80% of the total. (4) These results imply that if the behavior of a given cultivar across a series of environments is known, the behavior of all other members of the class across a similar range of environments would be predictable.

Five cultivars and one breeding line of field bean (Phaseolus vulgaris L.) were evaluated for their differential reactions to beta, gamma, and delta races of anthraenose (Collectotrichum lindemuthianum [Sacc. and Magn.] Scrib.). Parental, F1 and F2 plants from 10 crosses involving anthraenose resistant and susceptible parents were inoculated with the 3 races. Inoculated plants were maintained in a mist chamber for 8 to 10 days until plants could be classified into resistant and susceptible groups on the basis of their reactions to the pathogen. The F2 segregation patterns suggested that independent and complementary gene action at 1 or 2 different loci produced a resistant reaction to all races of the pathogen. In addition, an allelomorphic series of three alleles was assumed to be controlling resistance to the beta race. A breeding scheme, involving alternate generations of back-crossing to the recurrent parent and selfing is an effective method to develop resistant cultivars.

The potential induction of phytoalexin production by stress following exposure to ozone, sulfur dioxide and several herbicides was evaluated in bean (Phaseolus vulgaris L.) cultivars and lines varying in sensitivity to ozone injury. The isoflavonoids, coumestrol and several other coumestans were extracted from leaf tissue after various periods of exposure to ozone, sulfur dioxide or application of various herbicides. Elicitation of isoflavonoid production varied with lines and cultivars, but generally increased with increased plant injury caused by ozone, sulfur dioxide or herbicide.

Antioxidants are compounds used to prevent the reactions of organic materials with molecular oxygen. Antioxidants are used to protect foods and other products from discoloration and spoilage, thus sodium benzoate is added to bread to prolong its shelf life. Other antioxidants such as piperonyl butoxide (..cap alpha..-(2-(2-butoxyethoxy)ethoxy)-4,5-methylenedioxy-2-propyltoluene) and sesamex (a component of sesame oil) are used as insecticide synergists. Both of these compounds are potent microsomal mixed function oxidase (m.f.o.) inhibitors and when applied in combination with certain insecticides increase the insecticide's potency by decreasing the rate at which insects can detoxify the insecticides. In plants, EDU (N-(2-(2-oxo-1-imidazolidiny)ethyl)-N-phenylurea has been reported to protect pinto beans (Phaseolus vulgaris L.) and piperonyl butoxide to protect tobacco (Nicotiana tabacum L.) from ozone injury. The purpose of this study was to a) evaluate the antioxidants EDU, piperonyl butoxide, and n-propyl gallate, as protectants against ozone injury in navy bean, and b) to determine if these antioxidants could function as herbicide synergists just as piperonyl butoxide functions as an insecticide synergist.

WELLER, D. M., and A. W.. SAETTLER. 1978. Rifampin-resistant Xanthomonas phaseoli \ar. hiiscans and Xanthomonas phaseoli: Tools for field study of bean blight bacteria. Phytopathology 68: 778-781. Rifampin-resistant mutants of Xanthomonas phaseoli rifampin-resistance marker permitted selective isolation of (Xp) and X. phaseoli var. fuscans (Xpf) were screened for RIO and Ra from field-grown inoculated bean leaves; growth. similarity to wild-type isolates and their utility as tools for of all phyllosphere bacteria was inhibited on media with field study of bean blight bacteria. A mutant (R I0) isolate of rifampin (50 uig/ ml). Addition of cycloheximide at 25 Ag/ ml Xpf and one (Ra) of Xp were similar to wild types in reduced growth of resident yeasts and fungi. The rifampin numerous bacteriological tests, grew at rates identical to, and resistance marker was stable when the bacteria were grown in were as virulent as the wild types in bean leaves. The doubling culture or beans; no reversions to rifampin sensitivity have time for R 10 and Ra was about 11% longer than that for the been detected. wild types in buffered yeast-extract liquid medium. The