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Sierd Zijlstra, Coen Purimahua and Pim Lindhout

Crossing barriers between white- and purple-flowered species were examined. Four accessions of Capsicum annuum and three of C. pubescens were reciprocally crossed with one to four accessions of C. baccatum, C. cardenasii, C. chacoense, C. chinense, C. eximium, C. frutescens, C. galapagoense, and C. praetermissum. Capsicum chacoense is the only white-flowered species that inhibits C. annuum pollen tube growth but allows C. pubescens pollen tube penetration into the egg cell. Capsicum cardenasii and C. eximium exhibit similar crossabilities with C. annuum and C. pubescens: pollen tubes of C. cardenasii and of C. eximium can penetrate the egg cells of C. annuum but not vice versa, and pollen tubes of C. pubescens can penetrate the egg cells of C. cardenasii and of C. eximium but not vice versa.

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Steven P.C. Groot, Sierd Zijlstra and Johannes Jansen

Powdery mildew-resistant (PMR) cultivars of cucumber (Cucumis sativus L.) grown in greenhouses in the Netherlands during winter show chlorosis on the full-grown leaves of the main stem. The symptoms are yellowing and occasional necrosis between the main veins of the leaves, resembling symptoms of P toxicity. Severity of the chlorosis may vary from one winter to another. Variation is also observed in the severity of the symptoms between cultivars and individual plants of a cultivar. High P nutrition results in an increase of the severity of chlorosis and provides a better discriminating environment for the selection of PMR genotypes that are less susceptible for leaf chlorosis.