Stephen L. Sinden

Genetic and environmental control of potato glycoalkaloids

Genetic and environmental factors that can cause potato tubers and processed products to have excessive glycoalkaloid levels (> 20 mg/100 g fresh wt) are reviewed and discussed. Measures that breeders, growers, processors, and distributors might take to maintain glycoalkaloid levels at their present low levels are suggested.ResumenSe revisan y se discuten los factures genéticos y ambientales que pueden producir niveles excesivos de glicoalcaloides (> 20 mg/100 g de peso fresco) en los tubérculos de papa y los productos procesados. Se sugieren medidas que puedan tomar los fitomejoradores, agricultores, técnicos en procesamiento y distribuidores para mantener bajos los niveles de glicoalcaloides.

Occurrence of the A2 mating type ofPhytophthora infestans in potato fields in the United States and Canada

Ten isolates ofP. infestans collected from blighted potato fields in the U.S. and Canada during the years 1983–1989 were examined for mating type on lima bean, oatmeal, and rye grain media. Two of the ten isolates produced oospores in less than 15 days when cultured in the presence of known A1 mating types from the USA, Mexico, and Europe, indicating they are A2 mating types. When the two A2 isolates (one from Pennsylvania and one from Vancouver, B.C.) were cultured singly or with known A2 isolates, no oospores formed after 6 weeks of culture. Pathogenicity tests showed that both isolates produced typical late blight symptoms on potato foliage and stems, and there appeared to be no difference in virulence between these two A2 and the eight A1 isolates. Inoculations with a mixture of A1 + A2 sporangia also produced oospores in host tissues. This is the first report of the presence of the A2 mating type ofP. infestans in the U.S. and Canada.CompendioDiez aislamientos deP. infestans obtenidos de campos de papa infectados en los EE.UU. y el Canadá durante los años 1983–1989, fueron examinados para determinar el tipo presente en el apareamiento sobre medios de habas, avena y granos de arroz. Dos de los diez aislamientos produjeron oosporas en menos de 15 días cuando se les cultivó en presencia de los ya conocidos tipos A1 de apareamiento de los EE.UU., México y Europa, indicando que ellos son tipos de apareamiento A2. Cuando los dos aislamientos A2 (uno de Pennsylvania y uno de Vancouver, B.C.) fueron cultivados independientemente o con aislamientos A2, no se formaron oosporas después de seis semanas de cultivo. Las pruebas de patogenicidad mostraron que ambos aislamientos producían síntomas típicos de tizón tardío sobre el follaje y tallos y pareció no existir diferencias en virulencia entre estos dos A2 y los ocho aislamientos A1. Inoculaciones con una mezcla de esporangios A1 + A2 produjeron también oosporas en los tejidos del hospedante. Este es el primer informe de la presencia del tipo A2 de apareamiento deP. infestans en los EE.UU y el Canadá.

Inheritance of potato glycoalkaloids

Significant differences in tuber glycoalkaloid (TGA) content were found among parents and among family means in a two year study of 10 tetraploid crosses. TGA contents of the parents ranged from 3.6–36 mg/100 g, with an average content of 10 mg/100 g.Offspring variations within families were generally continuous, indicating polygenic inheritance. Heritability (1-year—1-replicate base) ranged from 86–89% in the broad sense and from 66–84% in the narrow sense. It was concluded that TGA content is highly heritable.The use of parents with high TGA contents in a breeding program is discussed.

Glycoalkaloids and resistance to the Colorado potato beetle inSolanum chacoense Bitter

Resistance of 20 F2Solarium chacoense Bitter clones to the Colorado potato beetle,Leptinotarsa decemlineata (Say), was measured in a field test. Levels of total glycoalkaloids (TGA) and composición of the glycoalkaloid mixtures in foliage of the clones were also determined. Clones with either commersonine or dehydrocommersonine as the major foliar glycoalkaloid were significantly more resistant (lower damage ratings, fewer larvae and adult insects) than clones with solanine and chaconine. Damage ratings were negatively correlated (r = -0.67, p = 0.01) with foliar TGA levels. The results indicate that the types of glycoalkaloids present in the foliage ofS. chacoense may be as important as the level of TGA in limiting damage and numbers of insects.ResumenResistencia de 20 clones F2 deSolarium chacoense Bitter, al “Colorado potato beetle”,Leptinotarsa decemlineata (Say), se evaluó en una prueba de campo. Asimismo, se determinó niveles de glicoalcaloides totales (TGA) y composición de mezclas de glicoalcaloides en el follaje. Clones con cualquiera de los dos commersonine o dehydrocommersonine como el mayor componente de glicoalcaloide en el follaje fueron significativamente mas resistentes (lecturas bajas de daños, pocas larvas e insectos adultos) que clones con solanine y chaconine. Las lecturas de daño mostraron correlación negativa (r = -0.67, p = 0.01) con los niveles de glicoalcaloides totales en el follaje (GA). Los resultados indicaron que los tipos de glicoalcaloides presentes en el follaje deS. chacoense puede ser tan importante como el nivel de glicoalcaloides totales en la limitación del daño y número de los insectos.

Effect of variety and location on the glycoalkaloid content of potatoes

Significant differences in tuber glycoalkaloid (TGA) content were found among five commercial varieties and B5141-6 grown at 39 different locations in 28 states. Line B5141-6 had the highest average TGA content, 29.3 mg/100 g in 1970 and 28.1 mg/100 g in 1971. Average TGA contents in 1970 of Kennebec, Russet Burbank, Katahdin, Irish Cobbler, and Red Pontiac were 9.7, 7.9, 7.9, 6.2, and 4.3 mg/100g, respectively. There were also significant location effects. Possible causes of high TGA levels are discussed.

Glandular pubescence, glycoalkaloid composition, and resistance to the green peach aphid, potato leafhopper, and potato fleabeetle inSolanum berthaultii

Fifteen accessions ofSolarium berthaultii Hawkes andS. berthaultii xS. tarijense Hawkes were assessed for resistance to field infestations of the green peach aphid,Myzus persicae (Sulzer), potato leafhopper,Empoasca fabae (Harris), and potato fleabeetle,Epitrix cucumeris (Harris). Accessions bearing both Type A and Type B glandular trichomes were much more resistant to the green peach aphid and potato leafhopper than accessions bearing Type A hairs alone. All accessions had significantly smaller populations of these 3 pests than S.tuberosum cultivars. Total glycoalkaloid (TGA) content of foliage and tubers was not correlated with insect populations. Foliar TGA levels of field-grown plants varied among accessions, ranging from < 2–240 mg/100 g fresh wt. Solasonine and solamargine were the major foliar glycoalkaloids while solamarines predominated in tubers.ResumenBajo condiciones de campo e infestaciones naturales, quince entradas deSolatium berthaultii Hawkes yS. berthaultii x S. tarijense Hawkes fueron evaluadas para determinar su resistencia al áfido verde del melocotonero,Myzus persicae (Sulzer), cigarrita de la papa,Empoasca fabae (Harris) y pulguilla de la papa,Epitrix cucumeris (Harris). Las entradas que poseían ambos tipos de tricomas glandulares, tipo A y tipo B, fueron mucho más resistentes al áfido verde del melocotonero y a la cigarrita de la papa que las entradas que poseían solamente el tipo A de pelos. Todas las entradas tuvieron poblaciones significativamente menores de estas tres pestes que los cultivares deS. tuberosum. El contenido total de glycoalcaloides (TGA) en follaje y tubérculos no tuvo correlación con las poblaciones de insectos. Los niveles de TGA en el follaje de plantas desarrolladas en el campo variaron entre las entradas, desde < 2–240 mg/100 g peso fresco. Solasonine y solamargine fueron los alcaloides de follaje en major cantidad mientras que solamarines predominó en los tubérculos.

Activity of cecropin SB37 against protoplasts from several plant species and their bacterial pathogens

Abstract The lethal concentration of cecropin SB37 was determined for protoplasts from 11 plant cultivars or experimental lines representing 7 plant species and for 9 bacterial species that are pathogens of these plants. Lethal concentrations ranged from 4.5 μM for tomato ( Lycopersicon esculentum cv Red Cherry) to 41 μM for sugarbeet ( Beta vulgaris REL 1). Cecropin SB37 exhibited potent antibacterial activity against all of the bacterial pathogens tested. Lethal concentrations ranged from 0.1–4.5 μM. The difference between the lethal concentrations of cecropin SB37 for protoplasts from certain plants and their respective bacterial pathogens suggests it may be feasible to protect against these pathogens by introducing a modified cecropin gene into the plant.

Segregation of leptines and other glycoalkaloids inSolanum tuberosum (4x) ×S. chacoense (4x) crosses

A clone, 8380-1, selected fromSolanum chacoense (PI 458310) for its high foliage content of the leptine glycoalkaloids, a factor in resistance to Colorado potato beetle, was doubled in chromosome number from 2n=2x=24 to 2n=4x=48. Three 4x clones were crossed with sixS. tuberosum (4x) clones. Foliage glycoalkaloid contents were measured for 452 F1 hybrids from 15 crosses. The 4xchacoense parental clones were not different in respect to glycoalkaloid contents and were similar to the original 2x clone. All F1 hybrids synthesized foliage leptines ranging from 9 to 369 mg/100 g fresh weight (fw) with a mean content of 113 mg/100 g fw. The proportion of leptines in the total glycoalkaloid content ranged from 1% to 62% with a mean of 25%. The 4xchacoense parent mean leptine content was 1482 mg/ 100 g fw which was 90% of the total glycoalkaloid content. Tubers from 136 hybrids and the threechacoense parental clones were tested for glycoalkaloid contents. The tuber solanine + chaconine contents of the 136 hybrids ranged from 30 to 180 mg/100 g fw with a mean of 79. The mean tuber content of the threechacoense parental clones was 157 mg/100 g fw. Leptines were not found in any of the tubers.

Evaluation of wild tuber-bearingSolanum accessions for foliar glycoalkaloid level and composition

Six hundred forty-five accessions of 70Solanum species and six natural hybrids were screened for foliar glycoalkaloids. Total foliar glycoalkaloid (TFGA) level and glycoalkaloid composition of one or more accessions of each species were determined by TLC and GLC analyses. Of the more than 12 different glycoalkaloids found in the wild species in this survey, solanine and chaconine account for more than 60% of the TFGA found in the foliage of these plants. There was wide variation in the total glycoalkaloid levels among the species.S. neocardenasii had the highest average TFGA value of the 70 species, 222 mg/100 g fresh wt (222 mg %) and an accession ofS. chacoense had the highest TFGA value recorded in the survey, 486 mg %. Of the 70 species, only 11 had average TFGA levels of more than 100 mg %. However, one or more accessions in 27 of the species synthesized more than 100 mg %. Forty-five species synthesized an average level of less than 50 mg %. The level usually found in the foliage of commercial potato cultivars is about 50 mg %. Therefore, most of theSolanum species in the potato germplasm collection can be considered low glycoalkaloid species.CompendioSe evaluaron y seleccionaron 645 entradas de 70 especies deSolanum y seis híbridos naturales para glicoalcaloides foliares. Se determinaron el nivel de glicoalcaloides totales (TFGA) y la compositión de una o más entradas de cada especie por medio de análisis TLC y GLC. De más de 12 glicoalcaloides diferentes encontrados en las especies silvestres en este estudio, la solanina y la chaconina representan más de 60% del TFGA encontrado en el follaje de estas plantas. Hubo una gran variatión, entre las especies, en los niveles de glicoalcaloides totales.S. neocardenasii tuvo el valor promedio más alto de TFGA de las 70 especies, 222 mg/100 g de peso fresco (222 mg %) y una entrada de S. chacoense tuvo el valor más alto de TFGA registrado en el estudio, 486 mg %. De las 70 especies, sólo 11 tuvieron niveles promedio de TFGA de más de 100 mg %. Sin embargo, una o más entradas en 27 de las especies sintetizaron más de 100 mg % g. Cuarenta y cinco especies sintetizaron un nivel promedio menor de 50 mg %. El nivel encontrado generalmente en el follaje de cultivares comerciales de papa es más o menos de 50 mg %. Por consiguiente, la mayoría de las especies de Solanum en la colección de germoplasma de papa pueden considerarse especies de bajo contenido de glicoalcaloides.

Commersonine, a new glycoalkaloid from two Solanum species

Abstract Selected plant introduction lines of S. chacoense and S. commersonii contain two major glycoalkaloids, demissine and a new compound called commersonine. In contrast, other plant introduction lines of S. chacoense contain only solanine and chaconine as the major glycoalkaloids. The isolation and characterization of the new glycoalkaloid is described.