Genetic variation in the response of Pinus patula families to drought conditions

Abstract

A common garden trial with 18-month-old trees from 64 half-sib families of Pinus patula was established to identify genetic variation in growth and survival in response to drought for four months (November 25, 2020 to March 25, 2021, winter). A split-plot design with two moisture levels (Irrigation S₀ = 40 – 55 % and Drought S₁ = 20 – 39 % volumetric moisture) was used in large plots and families in small plots. At the beginning and end of the trial, the height (HT), diameter of the base (DB), and number of whorls and branches were determined, and the absolute (AGR) and relative (RGR) growth rates in HT and DB were calculated. Differences were found between the moisture levels during growth. Survival was 71 % in S₀ and 60 % in S₁. In S₁, AGR in HT and DB was affected by 52 and 38 %, and RGR by 46 and 32 %, respectively, with respect to S₀. In S₀, 31.4 % of the plants formed one whorl and 2.1 % two, in S₁ only 13.4 % and 0.2 % did. Genetic control was moderate in the joint environments with h²_i between 0.03 and 0.17 and h²_f between 0.15 and 0.53. The performance of the families between the two humidity conditions was stable (r_B from 0.71 to 1.0) in all variables, with greater genetic variation in S₀ than in S₁. Moderate genetic variability was observed in the growth of Pinus patula families under water restriction