Basic Information - Genetics, Genomics and Breeding of Crop Plants - page 34

H. strumosus , H . grosseserratus , H . maximiliani , H . nuttallii and H . divaricatus
appear to have stalk rot resistance (Jan et al. 2006a).
1.5.5.2 Viral and Bacterial Resistance
Bacterial foliar diseases, including apical chlorosis ( Pseudomonas syringae
pv. Tagetis ) and bacterial blight ( P . syringae pv. helianthi ), generally have little
economic impact on sunflower (Gulya 1982). Sunflower can be infected by
over 30 viruses, but viral diseases are generally of concern only in tropical
or subtropical climates, such as India, where tobacco streak virus is a
problem. In North America, sunflower mosaic virus and sunflower chlorotic
mottle virus are rarely seen on sunflower, with only sunflower mosaic virus
noted on wild sunflower in Texas. Sources of resistance are available from
wild H . annuus to produce resistant hybrids if necessary (Gulya et al. 2002).
Jan and Gulya (2006) have released three germplasms with sunflower mosaic
virus resistance, SuMV-1, SuMV-2, and SuMV-3.
1.5.5.3 Insects
Wild sunflowers are native to North America where their associated insect
herbivores and entomophages co-evolved in natural communities. This
provides the opportunity to search for insect resistance genes in the wild
species. North America has the largest losses due to insect pests. In the
major production area there are about 15 principal insect pests of cultivated
sunflower, and of this total, about six are considered important economic
pests from year to year (Charlet and Brewer 1997). Sunflower moth
( Homoeosoma electellum ) tolerance was observed in annual H . petiolaris , and
perennials H . maximiliani , H . ciliaris , H . strumosus , and H . tuberosus (Rogers
et al. 1984). Stem weevil ( Cylindrocopturus adspersus ) tolerance was found in
perennials H . grosseserratus , H . hirsutus , H . maximiliani , H . pauciflorus , H .
salicifolius , and H . tuberosus (Rogers and Seiler 1985). Sunflower beetle
( Zygogramma exclamationis ) tolerance was observed in annual, H . agrestis
and H . praecox , and perennials H . grosseserratus , H . pauciflorus , H . salicifolius ,
and H . tuberosus (Rogers and Thompson 1978, 1980). Charlet and Seiler
(1994) found indications of resistance to the red sunflower seed weevil
( Smicronyx fuluus ) in several native Helianthus species.
1.5.5.4 Oil and Oil Quality
Variability for oil concentration exists in the wild species. While oil
concentration is lower in the wild species than in cultivated sunflower,
backcrossing to cultivated lines quickly raises the oil concentration to an
acceptable level. Annual H . anomalus has the highest oil concentration of