Screening the Cucumber Germplasm Collection for Resistance to Gummy Stem Blight in North Carolina Field Tests

Abstract

<jats:p>Gummy stem blight (Didymella blight<jats:italic>)</jats:italic>, caused by <jats:italic>Didymella bryoniae</jats:italic> (Auersw.) Rehm and its anamorph <jats:italic>Phoma cucurbitacearum</jats:italic> (Fr.:Fr.) Sacc., is the second most important disease of cucumber (<jats:italic>Cucumis sativus</jats:italic> L.) in North Carolina after root knot nematodes <jats:italic>Meloidogyne</jats:italic> <jats:italic>sp</jats:italic>. Both <jats:italic>Didymella blight</jats:italic> and Phoma blight, caused by <jats:italic>Phoma exigua</jats:italic> Desm.<jats:italic>,</jats:italic> have similar symptoms and control practices, and are generally referred to as gummy stem blight. In order to determine whether resistance existed to North Carolina isolates of <jats:italic>D. bryoniae</jats:italic>, 851 cultigens [cultivars, breeding lines, and plant introduction (PI) lines] were evaluated in the field. Plants were inoculated with one selected isolate (highly pathogenic in preliminary greenhouse tests) at the vine tip-over stage. They were rated for foliage lesion size and number on a 0 to 9 visual scale (0 = no disease, 9 = plant killed) and average ratings for 10 plants per plot were analyzed. The ratings ranged from 2.0 (highly resistant) to 8.5 (highly susceptible) with a mean of 6.2. The most resistant breeding lines and PI accessions were PI 200815, PI 390243, `LJ 90430', PI 279469, and PI 432855. The most resistant cultivars were `Homegreen #2', `Little John', `Transamerica', and `Poinsett 76'. The most susceptible cultigens in the study were PI 288238, PI 357843, PI 357865, and PI 167134. Two popular cultivars in North Carolina, `Calypso' and `Dasher II', were moderately resistant.</jats:p>

Inheritance of Resistance to Gummy Stem Blight in Watermelon

“…Gummy stem blight has shown significant variability for resistance in cucurbits (Boyhan et al, 1994;Wehner and Shetty, 2000). For example, plant-to-plant variability in four replications of two plants each was 4-8 for 'Charleston Gray' compared with a 2-4 rating for PI 482276 on a 0 to 9 scale .…”

Ornamental Cabbage and Kale Cultivar Comparison Study: Growth Characteristics and Response to Daminozide and Uniconazole Foliar Sprays

“…Classifying ornamental cabbage and kale cultivars by growth habit assists growers in determining what type of fertilizer to use, the type and concentration of PGR, and wholesale shipping capacities (Whipker et al, 1998). The growth habit categories, which were based on mean heights of the nontreated controls, were separated into five groups using the range/LSD technique (Wehner and Shetty, 2000). EXPERIMENT 2.…”

“…Plant height varied by cultivar, with the height of the plants increasing (shortest to tallest) from the curly leaf kale cultivars to the ornamental cabbage and notched kale cultivars (Table 1). Using the range/ LSD technique (Wehner and Shetty, 2000), cultivars were classified into groups which characterized their growth habit by the mean height. Cultivars with mean heights 13.8 inches (35.0 cm) or higher were classified as vigorous growers, ≥11.8 to <13.8 inches (30.0 to 35.0 cm) as tall, ≥9.8 to <11.8 inches (25 to 30.0 cm) as medium, ≥7.9 to <9.8 inches (20 to 25.0 cm) as short, and <7.9 inches (20.0 cm) as dwarf (Table 1).…”

Screening the Watermelon Germplasm Collection for Resistance to Gummy Stem Blight

“…Seedling screening methods are the most commonly used among breeders to test new cultivars and lines for resistance to gummy stem blight in cucurbits (Zhang et al, 1995;Dias et al, 1996;Zhang et al, 1997;Wehner and Shetty, 2000). Tests involve spraying seedlings with a water suspension of spores collected from in vitro cultures of the pathogen.…”