The past 25 years, 1686 potato accessions, representing 100 species in the genus Solanum L ., subgenus Potatoe, section Petota, were evaluated for field resistance to one or more of the following insect pests : green peach aphid, Myzus persicae (Sulzer) ; potato aphid, Macrosiphum euphorbiae (Thomas) ; Colorado potato beetle, Leptinotarsa decemlineata (Say) ; potato flea beetle, Epitrix cucumeris (Harris) ; and potato leafhopper, Empoasca fabae (Harris) . Accessions highly resistant to green peach aphid were identified within 36 species, to potato aphid within 24 species, to Colorado potato beetle within 10 species, to potato flea beetle within 25 species, and to potato leafhopper within 39 species . Resistance levels were characteristic within Solanum species . Insect resistance appears to be a primitive trait in wild potatoes . Susceptibility was most common in the primitive and cultivated Tuberosa . Insect resistance was also characteristic of the most advanced species . The glycoalkaloid tomatine was associated with field resistance to Colorado potato beetle and potato leafhopper . Other glycoalkaloids were not associated with field resistance at the species level .Dense hairs were associated with resistance to green peach aphid, potato flea beetle, and potato leafhopper .Glandular trichomes were associated with field resistance to Colorado potato beetle, potato flea beetle, and potato leafhopper . Significant correlations between insect score and altitude of original collection were observed in six of thirteen species . Species from hot and arid areas were associated with resistance to

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Cytological disturbances resulting in 2n pollen were examined in four clones of diploid (2x = 24) Solanum phureja Juz. and Buk.; two (148-17 and 127-14) were variable and two (154-1 and B2-11) were consistently high in 2n pollen production. Three types of abnormal spindle orientation were observed at the second meiotic division: fused, tripolar, and parallel spindles (fs, tps, and ps, respectively). All four genotypes had fs. Three had tps, and ps was least frequent, occuring in two genotypes only. Cross-sections of buds revealed that all three abnormalities can occur in adjacent cells of a locule. In all genotypes, fs predominated at high levels of expression of 2n gametes. At lower levels of expression (i.e. less than 60%, which occurred only in 148-17 and 127-14), however, the frequencies of tps and ps increased. In general, there was little evidence for localization of dyads (resulting from fs or ps) or tetrads (resulting from normal divisions) within cross sections of locules, but 52.4% of all tetrads which occurred in a single locule of genotype 127-14 were found in 25% of the locular area. Cross-sections of buds revealed variation in frequency of 2n gametes among anthers (61.7 vs. 5.6% in 148-17) and between locules of an anther (73.1 vs. 90.0% in B2-11). Implications of the anatomical study were applied to current genetic theory regarding the development of 2n gametes in potato species.

Frequency of unreduced pollen grains was estimated for five genotypes of Solanum phureja (2n=24) growing in three environments; (E1) cool (7.2-13.3°C) and (E2) warm (12.2-17.2°C) growth chambers and (E3) field conditions. Highly variable frequencies were found, with genotype, environment, and genotype x environment interaction as significant components of variance. The frequency of unreduced gametes for two additional genotypes was studied over time in two growth chamber environments (cool and warm). One genotype, characterized by mostly fused spindles at the second meiotic division, expressed a high frequency of big pollen (BP) in both environments, whereas the second, characterized by fused, parallel and tripolar second division spindless was found to increase in BP frequency over time in the cool chamber, but remained consistently low in the warm chamber. The identification of specific environmental components with general effect on the expression of un-reduced gametes is not possible because of the large genotype x environment interaction component of variance. A genetic hypothesis based on incomplete penetrance and variable expressivity of a dominant gene is presented as an alternative to the currently accepted theory of control of parallel spindles by a single recessive gene.

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