TUMOR-FORMATION AND BETA-GLUCURONIDASE EXPRESSION IN PHASEOLUS-VULGARIS INOCULATED WITH AGROBACTERIUM-TUMEFACIENS

Ten common bean (Phaseolus vulgaris L,.) lines-including cultivars, br eeding lines, and one wild line-were evaluated for susceptibility to A grobacterium tumefaciens strain C58 by stab-inoculating intact shoot t ips of germinating seeds. Significant differences for tumor frequency and size were found on the resulting 3-week-old seedlings. UW 325, a w ild bean, had the highest rate of tumorigenesis; 'Olathe', a dry bean cultivar, had the lowest. Uninoculated excised shoot tips cultured in media with BA or BA plus NAA exhibited differences in phytohormone sen sitivity, as evidenced by callusing and root initiation. The cultivar Montcalm seemed to be highly sensitive, while 'Olathe' was relatively insensitive. Fluorometric GUS assays of shoot tips from germinating se eds inoculated with the disarmed GUS-containing A. tumefaciens strain C58C1(pGV3850/pKIWI105) showed that UW 325 had the highest level of GU S activity. 'Montcalm' had a high rate of tumorigenesis but a low leve l of GUS activity this anomaly was attributed to its high phytohormone sensitivity. The use of the virulence-inducing compound acetosyringon e in the inoculum culture medium did not alter genotypic differences ( ranks) in susceptibility. Histochemical GUS assays. of inoculated UW 3 25 shoot tips showed that 60% of the apexes exhibited' one or;more tra nsformation events. Chemical names used: beta-glucuronidase (GUS); alp ha-naphthaleneacetic acid (NAA); N-(phenylmethyl)-1H-purin-6-amine (BA ).