Genes for reduced carotene content (white, yellow, and pale orange) and for anthocyanin pigmentation were identified in Daucus carota PI 173687 and in progeny derived from crosses of this Plant Introduction with orange-rooted inbred lines. Monogenic inheritance for each of these root color variants was examined. Mixed cell cultures of callus derived from white and orange roots indicated autonomy of carotene gene expression in carrot cell cultures. Strategies for incorporation of carrot genes conditioning pigment content will depend upon gene combinations sought.
M. Pooler and P.W. Simon
Despite its long history of obligate vegetative propagation, garlic (Allium sativum L.) exhibits a surprisingly large amount of variation between clones, as evidenced by both morphological and isozyme markers. As reported previously, several garlic clones which produce viable seed have been identified in the Wisconsin collection, and a possible correlation between clone fertility, morphology, and isozyme banding patterns was examined. The potential use of isozymes to analyze sexually-derived hybrid garlic lines, haploids, and interspecific hybridizations was also investigated.
Margaret Pooler and P.W. Simon
Garlic (Allium sativum L.) is an obligate apomict which reproduces almost exclusively by means of division of underground cloves or by propagation of topsets. The occurrence of viable, sexually-derived garlic seeds is rare. In order to assess the factors that limit garlic seed production, variables that affect flower initiation and development were studied. The effects on flowering of daylength, growing temperature, bulb and plant cold storage conditions, and cultivar were examined by observing flower development in plants grown under controlled greenhouse conditions. Correlations between isozyme markers and flowering, fertility, and morphological markers will be presented for a diverse collection of garlic clones, including six sexually-derived garlic plants.
John P. Navazio and Philipp W. Simon
Three orange-mesocarp derivatives of the xishuangbannan cucumber (Cucumis sativus L. var. xishuangbannanesis Qi et Yuan), P100, P101, and P104; and NPI (P105), an unrelated cucumber (Cucumis sativus L.) reported to have orange flesh, were selected as parents for a diallel experiment to evaluate inheritance of orange cucumber mesocarp pigment over 3 years. Visual color intensity and carotenoid content were closely related. A preponderance of additive genetic effects for cucumber mesocarp pigmentation was observed in grade size 2 fruit (immature fruit used for pickling). Both additive and nonadditive genetic effects were important in grade size 4 fruit (mature). Years and yea× genotype interactions were highly significant for pigmentation of size 2 fruit, indicating the importance of environment on the expression of pigmentation in this size class. In contrast, color development was stable among years for size 4 fruit. P104 exhibited high general combining ability (GCA) estimates for size 4 fruit pigmentation across years, while P101 had high GCA estimates for size 2 fruit. The diallel analysis illustrated high fruit carotene content of parents per se. However, most hybrid combinations of the diallel reduced carotenoid content relative to parents, indicating both dominance for low carotenoid content for both fruit sizes and lack of genetic complementation among parents to enhance fruit color. Genetic control of pigmentation in size 2 fruit appeared to be independent of that for size 4 fruit.
M.R. Pooler and P.W. Simon
The effects of cold storage, photoperiod, and growth temperature on flowering incidence in four clones of garlic (Allium sativum L.) were studied. While flowering percentage was influenced most by clone, interactions with photoperiod, growth temperature, and storage occurred. Clone R81 flowered equally well in all conditions, whereas flowering percentage of clones D129, D130, and PI485592 was reduced by cold (4C) storage of either bulbs or plants, long (16-h) photoperiod, and at 18C relative to 10C. The highest flowering percentage in all garlic clones was achieved by growing plants at 10C under short (9- to 10-h) photoperiod with no cold storage of bulbs before planting.
Philipp W. Simon and John P. Navazio
P.W. Simon, P.A. Roberts, and L.S. Boiteux
Nematodes impart significant damage to carrot production worldwide. Genetic resistance was studied for Meloidogyne javanica, one of the three major nematodes affecting carrots in warmer climates. F2, F3, and backcross families of `Brasilia' × B6274 were evaluated for resistance in inoculated seedlings. Resistance was conditioned by one, or two linked, dominant loci. Molecular markers were also evaluated with bulked segregant analysis. Three RAPD markers and AFLPs were associated with resistance loci.