The native tropical pine (Pinus merkusii Jungh. and de Vriese) has been genetically improved in Indonesia since 1977; nevertheless, minor evaluations of aphid resistance have been conducted since 2004. As a result, a progeny test for aphid resistance was established in 2010 in Lawu, Central Java, Indonesia. Subjects in the trial were attacked significantly at the rate of 30.7% after 4 years, but surprisingly, some individuals were found to be healthy without any aphid attack. The observed a 7-year progeny trial comprised 34 families with 4 trees per unitary plot and replicated in 10 blocks. At 7 years, observations during 9 months (April–December) showed that there were differences in the range of resistance across families. The stem diameter, oleoresin production, and resistance to aphid attack were evaluated, and all traits were distinct among families except for oleoresin exudation from the western side of the stem. Five families performed above average for all three traits, while three other families had high diameter and maintained good oleoresin production. These eight families can be included in a forward selection strategy. Cluster analysis revealed that the eight best families were grouped into two of the eight clusters. Phenotypic correlations revealed that all pairs of traits were significantly related, with the highest correlation registered between stem diameter and resistance to aphid attack (0.99). Forward selection ensures the simultaneous improvement of the three traits.

Pinus merkusii, a natural tropical pine species of Indonesia, is cultivated as the second most important artificial forest for the industry in Java, after teak, to produce oleoresin. Its genetic improvement began in 1977 because of its critical role in raising community incomes. Meanwhile, the effort for genetic improvement in aphid (Pineus boerneri) resistance has just recently started since its spread was only found broadly in Java by 2004. The second-generation progeny trial for this purpose was established in 2010, with materials from the best growing 34 families of the first generation. This study aimed to obtain the best pine genotypes through screening the existing natural variations found on important characters. The reported incidence of the trigger was when the experiment was attacked significantly at 30.7% after four years, while some 67 individuals were unexpectedly still performing well after six years. The results show that blocks affect differences for all traits of diameter, aphid resistance, and oleoresin productions, and all families differ except for the west-side yield of oleoresin production. Furthermore, heritability values at individual and family levels were moderate for the diameter (h2i = 0.16; h2f = 0.53) and eastern oleoresin (h2i = 0.14; h2f = 0.42). The gain is 4.3% when 30% of families with the best diameters are retained, while the genetic gain reaches 11% for oleoresin production. As one of the important traits in the breeding program, aphid resistance has a weakly inherited trait (h2i =0.07; h2f =0.29). Interestingly, this trait shows positive moderate genetic correlations with the two essential economic values of diameter (rg = 0.66) and oleoresin production (rg = 0.40). Therefore, the selection of the diameter and oleoresin production will not substantially affect the resistance.