Russet Burbank potato plants have been genetically improved to resist insect attack and damage by Colorado potato beetles (Leptinotarsa decemlineata (Say)) by the insertion of a cryIIIA gene encoding the insect control protein of Bacillus thuringiensis var. tenebrionis. A modified gene that dramatically improved plant expression of this protein was utilized. Its expression in Russet Burbank potato plants resulted in protection from damage by all insect stages in the laboratory and in dramatic levels of protection at multiple field locations. Analysis of these genetically modified potatoes indicated that they conform to the standards for Russet Burbank potatoes in terms of agronomic and quality characteristics including taste.

The European corn borer [ECB; Ostrinia nubilalis (Hübner)] is an economically significant pest of corn (Zea mays L.). The ability to routinely transform corn has broadened the control options available to include the introduction of resistance genes from sexually incompatible species. In this study, microprojectile bombardment was used to introduce synthetic versions of cryIA insecticidal protein genes from Bacillus thuringiensis subsp, kurstaki (Btk) into embryogenitcis sue of the Hi‐II] (A188/B73 derivative) genotype of corn. Of 715 independent transgenic calli produced, 314 (44%) had insecticidal activity against tobacco hornworm (Manduca sexta L.) larvae. Plants were regenerated, self‐pollinated when possible, and crossed to B73. First‐generation progeny of 173 independent Btk‐protein expressing calli were evaluated under field conditions with artificial ECB infestations in 1992 or 1993. Approximately half (89/173) segregated in single‐gene manner for resistance to first‐generation ECB leaf‐feeding damage. All of the 89 lines evaluated in 1992 or 1993 for resistance to second‐generation ECB exhibited less stalk tunneling damage than the non‐transgenic controls. In 1993, 44% (34177) of the lines tested had ≤2.5 cm of tunneling, compared to severe damage (mean = 45.7 cm) in the B73 × Hi‐II controls. Experiments are in progress to evaluate the effect of the introduced genes on yield and other agronomic properties.

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Colorimetry was evaluated as a method to assess pod disease in peanuts (Arachis hypogaea L.) caused primarily by Pythium myriotylum Drechs., Sclerotium rolfsii Sacc., and Rhizodoniu solani Kuhn. Data analyzed were from nineteen replicated tests conducted from 1982 to 1987, exclusive of 1985, in three South Texas locations. Each plot was scored for pod disease colonmetrically and visually. A negative linear relationship (R2>96%) was found between Hunter color values (L and b) and percent infection measured visually for samples hand selected to approximate eleven disease levels varying from 0-100%. Variability among readings was less at extremes of infection. Correlation both between visual ratings and between visual and colorimetric ratings was affected by soil differences, pathogens infecting the pods, pod genotype, and level of infection present. Correlation among visual raters was generally higher than that between color value ratings. Two-thirds 'Contribution from the Texas Agri. Exp. Stn., Texas A&M Univ., College Station, TA No. 24440. Mention of a trademark or proprietary product does not constitute a guarantee or warranty of the product and does not imply its approval to the exclusion of other products that may be suitable. This publication was partially supported by the Peanut CRSP, USAID grant number DAN4048-C-SS-2065-00. Recommendations do not represent an official position or policy of USAID.* A part of this improvement program has included attempts to improve disease assessment methodologies for evaluating resistance ofbreedmg material to the three pathogens (1,4). Our procedure has been to use two or three experienced raters, the mean ofwhose visual estimate ofpod disease was used as the criterion for selection. Beginning in 1982, a colorimeter was used in addtion to multiple visual ratings to evaluate levels of infection in samples. The potential advantages in pod rot evaluation were objective comparisons, improved accuracy and/or repeatability, reduction in time per evaluation, utilization of less skilled labor, and automation of data entry. The objective of this study was to examine the efficacy of colorimetry to assess pod disease in breeding material with reference to the more traditional visual methods. Materials and Methods Experimental MaterialData In the other three tests, only runner entries and the two runner checks were grown. Florunner and Tamnut 74 were considered susceptible to pod disease, while TxAG-3 and Toalson were considered resistant.Plots were harvested at maturity by dgging and invertingwith a two-row commercial digger-inverter followed by bagging whole plants in burlap bags. Hot-air dryers were used for drymg to approximately 10% seed moisture. Plants were threshed with a stationary small-plot thresher. Pod samples were cleaned by hand and with a Hobb's stemmer. Random samples for disease determination were collected using a riffle divider.From one to three people (designated R1, R2, R3) independently rated each plot sample for percentage of pod tissue dncolored by p...

Transgenic and nontransformed seed potatoes were planted on 20 May at the Michigan State University, Montcalm Potato Research Station, Entrican, MI. Treatment rows were 10 ft long, 12 in. within the row and 34 in. between rows, and were bordered by a row of commercial 'Russet Burbank' potatoes and a blank row. Treatments included four Btt transformed minitubers, a nontransformed minituber, commercial 'Russet Burbank' seed, and commercial 'Russet Burbank' seed yielding plants that were treated with Asana XL and PBO (0.05 lb Al/acre and 8.0 oz/acre, respectively) weekly from 6 Jun, through 8 Aug. Treatment effectiveness was determined by counting the total number of insects found on the center six plants of each treatment twice weekly from 19 Jun through 9 Aug. Plants were visually assessed for defoliation and given a damage rating on 8 Jul.