Potential Sources of Resistance to Cucurbit Powdery Mildew in U.S. Plant Introductions of Bottle Gourd

Abstract

Powdery mildew (Podosphaera xanthii) can cause severe damage to cucurbit crops grown in open fields and greenhouses. In recent years, there has been an increased interest in the United States in grafting watermelon plants onto various cucurbit rootstocks. Bottle gourd plants (Lagenaria siceraria) are being used throughout the world as rootstocks for grafting watermelon. Although gourd plants are beneficial, they may still be susceptible hosts to various soilborne and foliar diseases. Bottle gourd plant introductions (PI) resistant to diseases and pests can be a valuable source of germplasm in rootstock breeding programs. We evaluated 234 U.S. PIs of L. siceraria for tolerance to powdery mildew in two greenhouse tests. Young seedlings were inoculated by dusting powdery mildew spores of melon race 1 on the cotyledons. Plants were rated 2 weeks after inoculation using a 1 to 9 scale of increasing disease severity. Although none of the L. siceraria PIs were immune to powdery mildew, several PIs had significantly lower levels of powdery mildew severity compared with susceptible watermelon cultivar Mickey Lee. The experiment was repeated with 26 select PIs on whole seedlings and cotyledon disks. Significant variability in the level of resistance to powdery mildew on plants within PI was observed. Moderate resistance in several PIs to powdery mildew was confirmed. PI 271353 had consistently lower ratings in the various tests and can be considered the most resistant to P. xanthii race 1 among the L. siceraria accessions evaluated in this study. A few other PIs with moderate resistance to powdery mildew included PI 271357, PI 381840, and PI 273663. These results suggest that novel sources of resistance could be developed by careful selection and screening of several of the PIs with moderate resistance described in our study.

Variation in Podosphaera xanthii on Cucurbits in Southern Italy

“…2004). Moreover, 18% of the isolates sampled in the Bari district remained undetermined using the set of eight differential melon genotypes, which suggests the presence of other races that may be identified using a more extensive set of differentials (Kousik et al. 2008).…”

“…All six races were found in the Bari district, where cultivation of different species and cultivar of cucurbits is more extensive than in other districts, and therefore, it is likely that P. xanthii populations are under a stronger selective pressure for specific virulence factors (Krˇı´st-kova´et al 2004). Moreover, 18% of the isolates sampled in the Bari district remained undetermined using the set of eight differential melon genotypes, which suggests the presence of other races that may be identified using a more extensive set of differentials (Kousik et al 2008).…”

The bottle gourd genome provides insights into Cucurbitaceae evolution and facilitates mapping of a Papaya ring‐spot virus resistance locus

“…Plant diseases are a major constraint in bottle gourd production (Mashilo et al ., ). Genetic sources of resistance to a number of economically important diseases have been identified in bottle gourd (Provvidenti, , ; Ling and Levi, ; Kousik et al ., ; Ling et al ., ; Sarao et al ., ), but their genetic inheritance of resistance and molecular markers useful for marker‐assisted selection remain largely unstudied. Among plant diseases, viral diseases are a major limiting factor in cucurbit crop productions.…”

Genetic diversity among Lagenaria siceraria accessions containing resistance to root-knot nematodes, whiteflies, ZYMV or powdery mildew

“…Indeed, in this study, L. siceraria PIs that belong to certain geographical regions (South Asia versus Africa or South America) showed different disease or pest resistance ( Fig. 1; group II) also have intermediate resistance to powdery mildew (Kousik et al, 2008). Edelstein et al (2000) indicated the potential of L. siceraria rootstocks in reducing infestation of the carmine spider mite on grafted watermelon scions.…”