EFFICACY OF TRANSMISSION OF FIRE BLIGHT RESISTANCE IN PYRUS

An efficient, reproducible seedling-screening procedure was devised that gave almost 100% infection yet differential levels of resistance to Erwinia amylovora. Seedling segregation for resistance to fire blight was studied for 48 separate progenies with segregation data based on 7,462 seedlings. Sources of high, intermediate or low resistance derived from P. ussuriensis, P. serotina or P. communis were compared for ability to transmit resistance to their offspring. P. communis selections that were most efficient in transmitting resistance to their progeny included: Magness, Purdue 80-51, Maxine and Mich. US 437. Similarly, the most efficient sources in the P. ussuriensis group included: Purdue 77-73, NJ 484338262 and NJ 487601174; and the most efficient in the P. serotina group included: Purdue 110-9 and Kieffer. The breeding value of the most efficient P. communis sources was considered to be superior to the other two species sources in view of the larger size and higher quality of fruit associated with ...