Citation: Purwanto; Baskorowati, L.; Sumantoro, P.; Hendrati, R.L.; Susanto, M.; Mashudi; Setiadi, D.; Nurtjahjaningsih, I.L.G.; Pudjiono, S.; Kurniawan, A.; et al. Evaluation of Aphid Resistance and Oleoresin Production in Indigenous Tropical Pine (Pinus merkusii Jungh. and de Vriese). Forests 2022, 13, 977. https:// doi.org/10.3390/f13070977 Academic Editor: Carol Loopstra Received: 10 May 2022 Accepted: 20 June 2022 Published: 22 June 2022 Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affil- iations. Copyright: © 2022 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https:// creativecommons.org/licenses/by/ 4.0/). Communication Evaluation of Aphid Resistance and Oleoresin Production in Indigenous Tropical Pine (Pinus merkusii Jungh. and de Vriese) Purwanto 1 , Liliana Baskorowati 2 , Pujo Sumantoro 1 , Rina Laksmi Hendrati 2 , Mudji Susanto 2 , Mashudi 2 , Dedi Setiadi 2 , Ida Luh Gede Nurtjahjaningsih 2 , Sugeng Pudjiono 2 , Agus Kurniawan 3 , Pandu Yudha Adi Putra Wirabuana 4, * and Sumardi 2 1 Department Research and Innovatiom, Perhutani Forest Institute, Cepu, Blora 58302, Indonesia; purwantopusbanghut@gmail.com (P.); pujosumantoro@gmail.com (P.S.) 2 Research Center for Plant Conservation, Botanic Garden and Forestry, National Research and Innovation Agency of Indonesia, Jl. Ir. H. Juanda No. 13, Cibinong 16122, Indonesia; liliana.baskorowati@gmail.com (L.B.); rina.l.hendrati@gmail.com (R.L.H.); mudjisusanto@yahoo.com (M.S.); masshudy64@gmail.com (M.); setiadi2009@yahoo.com (D.S.); iluh_nc@yahoo.com (I.L.G.N.); sg_pudjiono@yahoo.co.id (S.P.); sumardi_184@yahoo.com (S.) 3 Research Center for Ecology and Etnobiology, National Research and Innovation Agency of Indonesia, Jl. Raya Jakarta Bogor Km 45, Cibinong 16911, Indonesia; age_kurniawan@yahoo.com 4 Faculty of Forestry, Universitas Gadjah Mada, Yogyakarta 55182, Indonesia * Correspondence: pandu.yudha.a.p@ugm.ac.id; Tel.: +62-274-548815 Abstract: 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. Keywords: breeding strategy; phenotypic correlation; Pineus boerneri; progeny; tropical pine 1. Introduction As a pioneer species, Pinus merkusii Jungh. and de Vriese is the only one native pine species in Indonesia, called tusam, which is also found in several Southeast Asian countries [1]. This pine is grown as the second largest artificially regenerated forest after teak in Java for oleoresin production. Pinus merkusii has been genetically improved in Indonesia since 1977 [2]. Genetically improved traits include greater stemwood growth, reduced fox tailing, and increased oleoresin production [3–6]. There were minor evaluations of aphid resistance in this species, with the well-known aphid (Pineus boerneri Annand, 1928) having been recorded as damaging P. merkusii and other pine species globally, including P. kesiya Royle ex Gordon [7], P. tecunumanii Eguiluz and Perry, P. maximinoi H.E. Moore, P. oocarpa Schiede ex Schltdl [8], P. taeda L., P. elliottii Engelmann, and P. caribaea Morelet [7]. Forests 2022, 13, 977. https://doi.org/10.3390/f13070977 https://www.mdpi.com/journal/forests