Late maturity and high grain moisture content at harvest have been major limitations to the use of tropical maize (Zea mays L.) germplasm in temperate regions. The objective of this study was to determine if selection for reduced grain moisture content at harvest in a tropical maize population indirectly influenced grain yield potential. Two hundred sixteen temperately‐adapted S4 lines were derived in 1991 at Raleigh, NC, from Cycle 9 of recurrent phenotypic selection for reduced grain moisture at harvest in the tropical maize population TROPHY, and these were testcrossed in 1992 at Raleigh, NC, to the temperate hybrid B73Ht × Mo17Ht. Selected subsets of these testcrosses were evaluated for their agronomic potential in seven environments over two years, and their performance was compared with that of Cycle 0 S0 testcrosses as well as three public and three commercial F1 hybrids. Selected Cycle 9 S4 testcrosses had higher mean grain yield (7.14 Mg ha‒1) and lower mean grain moisture at harvest (184 g kg−1) than the Cycle 0 So testcrosses (6.77 Mg ha−1, and 189 g kg−1 respectively). The highest yielding Cycle 9 S4 testcrosses were comparable to the commercial hybrid LH132 × LH51. This study supported the conclusion that ergonomically competitive inbred lines with acceptable grain moisture content at harvest can be derived from 100% tropical germplasm.

Hydrogen sulfide-producing strains of salmonellae, Escherichia coli, Citrobacter freundii, and Proteus mirabilis were isolated from fresh pork sausage. All the strains produced black-centered colonies on Hektoen enteric agar (HE). On xylose lysine deoxycholate agar (XLD), C. freundii produced yellow colonies, and the strains of the other three genera formed black-centered colonies. The selectivity of HE and XLD for salmonellae was improved by the addition of novobiocin to both media. With increasing concentrations of novobiocin, the degree of growth inhibition for the four genera was less on HE than on XLD. Novobiocin concentrations of 80 jug/ml in HE and 5 ,ug/ml in XLD did not affect the growth or colonial morphology of salmonellae. When 80 ,ug of novobiocin per ml was incorporated into HE, P. mirabilis strains were not recovered, 40% of C. freundii strains failed to form black-centered colonies, and growth of E. coli strains was not affected but colonies were altered without eliminating the black centers. When novobiocin at 5 ,tg/ml was incorporated into XLD, colonies ofP. mirabilis strains were not recovered, C. freundii formed yellow colonies, and the colonies of the H2S-producing E. coli strains were unaffected.

A collaborative study was conducted in 15 laboratories to evaluate 2 different techniques for enumerating Bacillus cereus in foods. A direct plating technique using mannitol-egg yolk-polymyxin agar and a most probable number (MPN) technique using trypticase-soy-polymyxin broth were compared for the enumeration of high and low populations of B. cereus in mashed potatoes. The collaborative results showed that the overall mean recovery obtained with the low population level was essentially the same by both techniques. However, the overall mean recovery was significantly higher by the direct plating technique at the high population level. A statistical evaluation of the data also showed that the direct plating technique had better repeatability and reproducibility than did the MFN technique at both the high and low population levels. These results suggest that the MPN technique is suitable for examining foods containing low populations of B. cereus, but that the direct plating technique is preferable for foods that contain a high population of this organism. The confirmatory technique used in the proposed method is reliable for presumptive identification of isolates as B. cereus. The method has been adopted as official first action.

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Antibiotic susceptibility patterns for Yersinia enterocolitica strains involving 10 different serotypes were analyzed and compared. All Y. enterocolitica were susceptible to colistin, gentamicin, kanamycin, neomycin and doxycycline, whereas all isolates displayed resistance to penicillin G, methicillin (derivative of penicillin), novobiocin, and clindamycin. The antibiograms for the Y. enterocolitica isolates were in some instances related to the somatic serotypes, especially serotype 0:8 for which the antimicrobial susceptibility pattern displayed the greatest disparity. By eliminating the antibiograms for the four serotype 0:8 strains, antimicrobial susceptibility patterns for atypical and typical strains were similar.