Michener P M, Pataky J K, White D G
Department of Crop Sciences, University of Illinois, Urbana 61801.
Plant Dis. 2002 Feb;86(2):167-172. doi: 10.1094/PDIS.2002.86.2.167.
Stewart's wilt reactions of 98 food-grade, white corn hybrids, 3 yellow dent corn hybrids, and 23 sweet corn hybrids and infection of kernels by E. stewartii were evaluated in 1998, 1999, and 2000. Stewart's wilt symptoms were rated from 1 (no appreciable spread of symptoms) to 9 (dead plants) following inoculation. The mean Stewart's wilt ratings for the food-grade, white corn and yellow dent corn hybrids were 1.9, 2.4, and 2.9 in 1998, 1999, and 2000, respectively. The mean Stewart's wilt ratings for the sweet corn hybrids were 3.8, 4.2, and 4.6 in 1998, 1999, and 2000, respectively. Hybrids with ratings less than 3 were classified as resistant. Hybrids with ratings between 3 and 4.5 were classified as moderate. Hybrids with ratings greater than 4.5 were classified as susceptible. Ears harvested from each row in 1998 and 1999 were assayed for E. stewartii using an enzyme-linked immunosorbent assay (ELISA)-based seed health test. Kernels from 16 hybrids were positive for E. stewartii in 1998. Kernels from 11 hybrids were positive for E. stewartii in 1999. Kernel infection by E. stewartii was affected considerably by the level of host resistance (i.e., reactions of seed parent plants). For hybrids classified as resistant, estimates of kernel infection were 0.024 and 0.0007% in 1998 and 1999, respectively. For hybrids with moderate reactions to Stewart's wilt, estimates of kernel infection were 0.19 and 0.07% in 1998 and 1999, respectively. For hybrids with susceptible reactions to Stewart's wilt, estimates of kernel infection were 11.6 and 7.8% in 1998 and 1999, respectively. Based on high levels of Stewart's wilt resistance in food-grade, white corn hybrids, and low rates of kernel infection by E. stewartii in resistant and moderate hybrids, there is an exceedingly low probability of introducing E. stewartii to areas where it does not occur by transmitting the bacterium in grain of the food-grade, white corn hybrids evaluated in this study. Although all of the kernels harvested in these experiments were produced as grain on open-pollinated F1 hybrids, the rates of kernel infection observed for hybrids with resistant, moderate and susceptible reactions to Stewart's wilt are applicable to seed produced on inbred lines with equivalent Stewart's wilt reactions.
1998年、1999年和2000年对98个食品级白玉米杂交种、3个黄色马齿型玉米杂交种和23个甜玉米杂交种的斯图尔特萎蔫反应以及玉米细菌性枯萎病菌对籽粒的侵染情况进行了评估。接种后，斯图尔特萎蔫症状从1级（症状无明显扩散）到9级（植株死亡）进行评级。1998年、1999年和2000年，食品级白玉米和黄色马齿型玉米杂交种的斯图尔特萎蔫平均评级分别为1.9、2.4和2.9。1998年、1999年和2000年，甜玉米杂交种的斯图尔特萎蔫平均评级分别为3.8、4.2和4.6。评级小于3的杂交种被归类为抗病；评级在3至4.5之间的杂交种被归类为中度抗病；评级大于4.5的杂交种被归类为感病。1998年和1999年从每行收获的果穗使用基于酶联免疫吸附测定（ELISA）的种子健康测试法检测玉米细菌性枯萎病菌。1998年，16个杂交种的籽粒检测出玉米细菌性枯萎病菌呈阳性。1999年，11个杂交种的籽粒检测出玉米细菌性枯萎病菌呈阳性。玉米细菌性枯萎病菌对籽粒的侵染受寄主抗性水平（即种子亲本植株的反应）的影响很大。对于被归类为抗病的杂交种，1998年和1999年籽粒感染率估计分别为0.024%和0.0007%。对于对斯图尔特萎蔫反应为中度抗病的杂交种，1998年和1999年籽粒感染率估计分别为0.19%和0.07%。对于对斯图尔特萎蔫反应为感病的杂交种，1998年和1999年籽粒感染率估计分别为11.6%和7.8%。基于食品级白玉米杂交种对斯图尔特萎蔫的高抗性水平，以及抗病和中度抗病杂交种中玉米细菌性枯萎病菌对籽粒的低感染率，通过本研究评估的食品级白玉米杂交种的籽粒传播该细菌，将玉米细菌性枯萎病菌引入其未发生地区的可能性极低。尽管这些实验中收获的所有籽粒都是在开放授粉的F1杂交种上作为谷物生产的，但观察到的对斯图尔特萎蔫反应为抗病、中度抗病和感病的杂交种的籽粒感染率适用于具有同等斯图尔特萎蔫反应的自交系上生产的种子。
