Variation and Genetic Control of Vegetative Phenology in Teak (Tectona grandis L.f.) Clones Grown at Two Clonal Seed Orchards: Karka and Manchikere

Abstract

Vegetative phenology is an important component of adaptation in teak (Tectona grandis L.f.), but the relative contribution of genotype and environment to individual phenological traits may vary among growing sites. The present study evaluated variation and genetic control of vegetative phenology in eleven common teak clones at the Karka and Manchikere clonal seed orchards in Karnataka, India, during 2024–2025. Four traits, namely leaf shedding initiation, leafless period, leaf flushing initiation and leaf flushing duration, were recorded at 15-day intervals. Data were analysed using a two-factorial randomised block design, and genotypic and phenotypic coefficients of variation (GCV and PCV), broad-sense clonal heritability, genetic advance (GA) and genetic advance as a percentage of the mean (GAM) were estimated. Leaf shedding initiation ranged from 321 to 354 days at Manchikere and from 334 to 362 days at Karka, with location means of 333 and 341 days, respectively. The leafless period averaged 32 days at Manchikere and 40 days at Karka, while leaf flushing initiation averaged 56 and 68 days, respectively. Leaf flushing duration showed the largest location difference, averaging 50 days at Manchikere and 81 days at Karka. Among the pooled clone means, the magnitude of variation was 14 days for leaf shedding initiation, 7 days for the leafless period, 32 days for leaf flushing initiation and 28 days for leaf flushing duration. The genetic component was negligible for leaf shedding initiation and the leafless period, for which GCV, heritability, genetic advance and GAM were zero. In contrast, leaf flushing initiation and duration showed measurable but relatively low genetic control, with GCV values of 8.83% and 7.14%, heritability values of 0.21 and 0.17, genetic advances of 5.24 and 3.94 days, and GAM values of 8.41% and 6.01%, respectively. The substantially higher PCV than GCV for both flushing traits further indicated a considerable environmental contribution to their phenotypic expression. Overall, leaf flushing initiation and leaf flushing duration showed greater potential for genetic evaluation than leaf shedding initiation and the leafless period, although their relatively low heritability suggests that multi-environment and repeated-season evaluation is necessary for reliable identification of clones with stable vegetative phenology.