Pear Breeding for Scab and Psylla Resistance

Sprays of chemical pesticides raise numerous ecological problems; in addition, growers now have to comply with new legislation mostly aimed at minimizing chemical residue levels which has resulted in the banning of several pesticide molecules. Pear breeding for resistance to diseases and pests is now a priority combined with fruit quality. The new programme developed at INRA in Angers puts emphasis on pear scab and pear psylla resistance. The programme on scab resistance relies on a better knowledge of Venturia pirina pathogenecity and the selection of durable sources of resistance. Progenies of several pear cultivars were inoculated in a greenhouse and the results show different potential sources of resistance from simple major gene ('Navara') to more complex inheritance ('Delice d'Avril'). Results are discussed and notes made that the differences in the degree of resistance could be due to differential races and/or environmental influences. The programme on pear psylla resistance is mostly based on the resistant selection 'NY 10355'. The progeny 'Angelys' x 'NY 10551 and the progenitors 'Doyenne d'Hiver', 'Doyenne du Comice' and 'Bartlett', have been inoculated in the greenhouse; growing plants were infested with young adults from a laboratory colony developing on the susceptible variety 'Bartlett'. Results show segregation for resistance according to different criteria such as amount of 1(st) to 3(rd) instar nymphs or presence of secreted honeydew. Genetic mapping of the major resistance gene identified in 'Navara' (scab) and putative QTL(s) from 'NY 10355' (pear psylla) is in progress.