PHENOTYPIC VARIATION IN MILICIA-EXCELSA TO ATTACK BY PHYTOLYMA-LATA (PSYLLIDAE)

A study was conducted to screen 21 half-sib Milicia excelsa progenies for pest resistance to the gall-forming psyllid Phytolyma lata. Result s of incidence of large galls indicate that there were significant dif ference among individual progenies. The mean percentage of large galls ranged from 15.4 to 99.6% and 39.5-99.9% for 1992 and 1993 respective ly. Four progenies (AA8, AA35, EA9 and EM1) appeared consistently resi stant while five others (BK3, EM2, AA24, EA7 and VH3) were consistentl y susceptible to P. lata. A highly significant relationship was shown between the incidence of dieback and relative abundance of large galls (R(2) = 0.82, d.f. = 2,18, F = 39.9, P = 0.001) and was described by a curvilinear model. Relationships among incidence of dieback and heig ht, number of leaves, girth and branches were also evaluated.