Search Results
You are looking at 1 - 4 of 4 items for :
- Author or Editor: Christopher S. Cramer x
- HortTechnology x
Determination of ploidy is an essential plant breeding technique. Laboratory exercises for teaching students how to determine ploidy in plant tissues using various techniques are described for geranium and onion. The different methods include root tip squashes, pollen mother cell squashes, pollen grain size and germinal pore counts, stomata size and density determination, and gross morphology.
Eighteen hybrid onion and 23 open-pollinated (OP) varieties were tested in southern New Mexico for plant characteristics, disease resistance, and bulb yield in order to determine if hybrid varieties outperformed OP varieties. Varieties were short- to intermediate-day in their bulbing response and were planted in the fall seasons of 1997 and 1998 and harvested the following May or June. Varieties were grouped based upon their relative maturity for fall-planted onions grown in southern New Mexico (early, intermediate, late). They were planted two (1998) or four (1997) rows per plot with plots being 8 ft (2.5 m) long and 22 inches (56 cm) wide. Plant stand per plot, plant height of seven plants, and leaf number of seven plants were measured 164 d after planting. Plots were harvested when 80% of the plant tops had fallen across all four replications of a single population. At harvest, number of seedstalks, number of bulbs, pink root incidence, and total bulb weight per plot were recorded. After removing culls, the percentage of marketable bulbs, marketable bulb yield, and average bulb size were determined. Hybrid varieties outperformed OP varieties for plant height, and leaf number but not for percentage of seedstalks, pink root incidence, percentage marketable yield, bulb size, and marketable bulb yield. In this study, most OP varieties perform as well or better than most of the hybrid varieties.
Fusarium basal rot (FBR), caused by Fusarium oxysporum f.sp. cepae, is a soilborne fungal disease that affects bulb onions (Allium cepa) worldwide. Winter-sown onion cultivars that are resistant to FBR are lacking. The goal of this project was to screen winter-sown onion germplasm for FBR resistance using a mature-bulb field screening at harvest and after 4 weeks in storage. The project was conducted for 2 years, and in each year, 22 winter-sown onion lines were grown in a field known to produce a high incidence of FBR-infected bulbs. At maturity, the basal plates of 20 randomly selected bulbs were cut transversely and each plate was scored for disease severity on a scale of 1 (no diseased tissue) to 9 (70% or more diseased tissue). Bulbs were stored and scored again at 4 weeks after harvest. Severity and incidence increased in storage for both years. NMSU 99-30, `NuMex Arthur', and `NuMex Jose Fernandez' showed the lowest disease severities and incidences in both years. For fields that produce a high incidence of FBR-infected bulbs, these cultivars could be grown with less loss to FBR at harvest and after storage than more FBR-susceptible cultivars. When developing FBR-resistant cultivars, breeding lines should be evaluated over multiple years and bulbs should be stored for 4 weeks before being screened.
Black mold, caused by the fungus Aspergillus niger, is one of the major postharvest onion (Allium cepa) diseases causing qualitative and quantitative losses. To screen autumn-sown onion cultivars for black mold resistance, 12 cultivars were sown in 2004 and 2005 in Las Cruces, NM. Percent sporulated area, disease severity, and disease incidence were recorded after 2 and 4 weeks of storage. ‘Texas Early White’ exhibited less disease symptoms than other cultivars tested. For all cultivars, disease symptoms in terms of severity and incidence increased as bulbs were stored for longer periods of time.