棉 花 学 报 Cotton Science 2006，18(4)：228-32
A New Detection Method of Wilting Induction by Phytotoxin from V.dahliae on Cotton through Leaf Pricking and Spreading Abstract：A new method，measuring the extent of wilting by pricking on leaf surface and spreading on cotton ，has been developed. First，V.d. -toxin (phytotoxin of Verticillium dahliae) of V991 which is a severe defoliating virulence strain of Verticillium dahliae on cotton was purified partially with Sephacryl S-200 HR；next，cotyledon or euphyla of seedling of cotton was pricked 15-20 pinhole in 0.5cm2 area on the surface with small needle；then，V.d. -toxin was spreaded on it；and wilting symptom was recorded after 24h，taking water and BSA as the control. The extent of wilting could be divided into 5 classes from 0 to Ⅳ after 24 h. Apart from the purified V.d. -toxin，the filtrate (liquid culture medium filtered after culturing V.d. over 7 days) can be taken as this method yet. To validate the method above further，8 strains of V.d have been selected to do the repeat tests，which belong to severe wilting strains(V991，T9，V56 and V146)，weakness wilting，strains(V110，V246，V250) and medium wilting strain of V3-10-1. By pricking on leaf surface and spreading V.d. -toxin on cotton individually，the answers appears that their potential power of wilting can be easily measured and divided into corresponded groups，such as V120，V991 and T9 belong to the severely type after testing. This dividing way is as same as the ever measurement with traditional ways (such as soaking seedling method).To identify the most suitable stage and part of the leaf to treat on cotton plant ，we have tested to treat them both cotyledon and euphyla in seedling and euphyla in adult plant. As the result，this method can be utilized as early as in seedling stage，and cotyledon is better than euphyla since it is easy to prick but not to pore through. However，the extent of wilt has been appeared varying usually according to the temperature in environment，cotyledon or euphyla of seedling，and the concentration of V.d. -toxin. To identify the differential reaction of cultivars on cotton to V.d. -toxin with this method，we have chosen 4 cultivars of upland cotton which are Ejing-3，B99261，CCRI 12， Xingluzao-7. We have conducted different cultivar treatments with the same V.d. -toxin，and compared the coherence between V.d. -toxin soaking way to the way of pricking on leaf surface and spreading V.d. -toxin. The result indicated that both methods can get very similar results after repeating tests.
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