Marker Development for Differentiation of Fusarium oxysporum f. sp. Niveum Race 3 from Races 1 and 2

Fusarium wilt of watermelon, caused by Fusarium oxysporum f. sp. niveum (FON), is pathogenic only to watermelon and has become one of the main limiting factors in watermelon production internationally. Detection methods for this pathogen are limited, with few published molecular assays available to differentiate FON from other formae speciales of F. oxysporum. FON has four known races that vary in virulence but are difficult and costly to differentiate using traditional inoculation methods and only race 2 can be differentiated molecularly. In this study, genomic and chromosomal comparisons facilitated the development of a conventional polymerase chain reaction (PCR) assay that could differentiate race 3 from races 1 and 2, and by using two other published PCR markers in unison with the new marker, the three races could be differentiated. The new PCR marker, FNR3-F/FNR3-R, amplified a 511 bp region on the “pathogenicity chromosome” of the FON genome that is absent in race 3. FNR3-F/FNR3-R detected genomic DNA down to 2.0 pg/µL. This marker, along with two previously published FON markers, was successfully applied to test over 160 pathogenic FON isolates from Florida, Georgia, and South Carolina. Together, these three FON primer sets worked well for differentiating races 1, 2, and 3 of FON. For each marker, a greater proportion (60 to 90%) of molecular results agreed with the traditional bioassay method of race differentiation compared to those that did not. The new PCR marker should be useful to differentiate FON races and improve Fusarium wilt research.

Draft Genome Sequences of Three Fusarium oxysporum f. sp. niveum Isolates Used in Designing Markers for Race Differentiation

ABSTRACT Here, we report the draft genome sequences of three Fusarium oxysporum f. sp. niveum isolates that were used to design markers for molecular race differentiation. The isolates were collected from watermelon fields in Georgia (USA) and were determined to be different races of F. oxysporum f. sp. niveum using a traditional bioassay.

Reproductive incompatibility and fitness components in Neoleucinodes elegantalis races (Lepidoptera, Crambidae) from three Solanaceae hosts

Neoleucinodes elegantalis (Lepidoptera, Crambidae) is a Neotropical Solanaceae pest that has evolved into four host races due to host plant association. In this study, prezygotic and postzygotic isolation were evaluated in parental and F1 generations collected from Solanum lycopersicum (S. l), S. quitoense (S. q) and S. betaceum (S. b), representing medium size (S. l, S. q) and large size genitalia races (S. b). 617 adults were obtained in the laboratory and 106 copulated. One spermatophore per female was found in the bursa copulatrix, suggesting monoandry. Crosses between adults mostly occurred assortatively. A third of the female’s eggs laid occurred, but females from ♀S. b x ♂ S. l, ♀S. l x ♂S. b and S. l x S. l did not. In the cross, ♀S. l x ♂ S. q and its reciprocal F1 progeny developed into larvae. Reproductive success only occurred in three crosses: S. q x S. q, ♀ S. q x ♂ S. b and its reciprocal progeny. All the progeny from these crosses reached adulthood. The parental population showed differences in pupae and adult measurements according to host. The results on reproductive isolation obtained here suggest speciation in N. elegantalis due to host race differentiation which is relevant for the improvement of the management of this species, especially when the species has evolved reproductive isolation among races. We suggest that the use of their host plants in sympatry might reduce N. elegantalis densities in the field since hybrids between its races have low survival rates and to evaluate the possibility of pheromone composition differentiation among races given the results on assortative mating obtained here.

Nutrition as a Project

This conversation is part of a special issue on “Critical Nutrition” in which multiple authors weigh in on various themes related to the origins, character, and consequences of contemporary American nutrition discourses and practices, as well as how nutrition might be known and done differently. In this section authors discuss the aims and effects of nutrition interventions. In terms of aims, various authors emphasize how such interventions act as pedagogies of citizenship, governmentalize people as metric consumers, or reflect colonial practices. In terms of effects, authors discuss how the project of nutrition works in class/race differentiation, the disempowerment of mothers, or the interest of transnational corporations. All of the authors essentially challenge not only nutrition’s fundamental claims to neutrality and objectivity, but also its claims to benevolence.