Fusarium wilt on watermelons. Image courtesy
New Form of Fusarium Wilt Could Pose Threat to
By Erin Peabody
August 14, 2006
Its too bad that one of
summers most enjoyed simple pleasures--the watermelon--can be such a bear
to grow. Melon growers are beset by numerous problems related to disease,
weather, pests and the quest for fruit uniformity. But now, unfortunately, a
new threat has emerged--one that may cause growers to wince even more.
In separate studies, scientists with the Agricultural Research Service (ARS) in Lane, Okla., and at the University
of Maryland (UM) in
have identified a new, more aggressive race of the fungus that causes Fusarium
wilt in watermelon.
This disease is one that all melon farmers dread seeing. It can attack
plants at any stage of growth, leaving young seedlings lifeless, or mature
plants fruitless with nothing to show but shriveled and yellowing leaves.
Watermelon grafted onto Cucurbita
rootstock. The resulting watermelon plant will gain resistance to Fusarium wilt
and enhanced fruit quality from the graft. Click the image for more
information about it.
Fish, together with UMs Xin-Gen Zhou and Kathryne Everts, discovered
a new race of the fungus Fusarium oxysporum that causes Fusarium wilt.
Their findings were presented last week at the joint meeting of the
American Phytopathology Society and
Mycological Society of America, in
Quebec City, Canada.
Bruton and Fish, who work at the ARS
Central Agricultural Research Laboratory in Lane, found the new race,
dubbed Race 3, while monitoring watermelon plants in fields near
their Oklahoma laboratory. Bruton saw that a new, differently-acting fungus was
plaguing plants thought to be resistant to Fusarium.
Three distinct races of Fusarium are known to cause wilt in melons.
Plant breeders have developed watermelon varieties that can fend off Races 0
and 1 fairly well. And, luckily, Race 2--for which there are no resistant
commercial cultivars--isnt competitive in the soil environment.
According to Bruton, the same is likely true for the new, more virulent Race
3. But hes got a solution. He and colleagues have found that grafting
watermelon onto sturdy squash or gourd rootstock is an effective way of
controlling Fusarium wilt. Those rootstocks are resistant to the
Fusarium races that attack watermelon.
ARS is the U.S. Department of
Agricultures chief scientific research agency.