SELECTION AND MAINTENANCE OF POPULATIONS. A PERSPECTIVE FOR in situ CONSERVATION OF MAIZE GENETIC DIVERSITY

Abstract

The maintenance of maize (Zea mays L.) populations on traditional agricultural systems is based on the empirical mass selection principles. Detasseling is a method used for seed production and for maintenance. The objective of this work was to analyze strategies for selection and maintenance of maize populations under a seed production scheme. On a maize population named ‘JAGUAN’ a seed production scheme was applied, using rows of detasseled (H) individuals female and rows of open pollinated male plants (M), through two generations (G₁ and G₂). In each generation and pollination method, mass selection was applied with farmer participation, resulting in six sub-populations: H and M in the first generation (G1), and the combinations HH, HM, MH and MM in the second (G₂). The agronomic evaluation of these sub-populations was carried out in 2008; the second generation sub-populations allowed analysis of population effects: Female (HH and HM) vs. Male (MM and MH), and production methods: Detasseling (HH and MH) vs. Open pollination (HM and MM). Results indicated differences (P ≤ 0.05) between H and M populations for grain yield in both generations with an increase of 6.3 and 6.4 % of M over the H population, respectively. Between production methods there was an average difference (P ≤ 0.01) of 7.8 % in grain yield of detasseling over open pollination. The highest grain yield of the male population in the two generations was attributed to selection effects when the first sub-populations were developed in the first generation, while in the production methods the difference was due to both selection and detasseling. Thus mass selection applied in populations obtained through seed production schemes (male and female rows) allows maintenance of population traits and increase of average grain yield in maize.