Measurement Of Cell Membrane Thermo-Stability And Leaf Temperature For Heat Tolerance In Maize (Zea Mays L): Genotypic Variability And Inheritance Pattern

The rise in ambient temperature is intimidating sustainability of maize productions worldwide. To overcome heat stress effects, identification of potential genotypes and knowledge of inheritance pattern is necessary for developing thermo-tolerant cultivars. This investigation, consisted of four experiments, was conducted for assessing genetic variation followed by developing and evaluating breeding material in non-stressed and heat-stressed environments. The first experiment concerning reproductive stage heat tolerance comprised one hundred maize inbred lines, was conducted at mean day/night temperatures of 33 degrees C/19 degrees C (field) and 40 degrees C/23 degrees C (plastic tunnel), respectively. Variance analysis of absolute and relative data for leaf temperature and cell membrane thermostability revealed statistically significant (P <= 0.01) genotypic variations. In second and third experiments, one heat tolerant (ZL-11271) and one susceptible (R-2304-2) lines were selected and crossed in a generation mean fashion to develop non-segregating (P-1, P-2, F-1) and segregating (BC1, BC2, F-2) plant populations. The fourth experiment involved appraisal of six basic generations in a factorial randomized complete block design replicated thrice with mean day/night temperatures of 33 degrees C/20 degrees C and 39 degrees C/24 degrees C. Data on leaf temperature and cell membrane thermostability recorded at reproductive phase were analyzed in a nested block design which suggested involvement of digenic epistatic interactions in controlling inheritance of both these traits. Generation variance analysis, however, revealed predominance of additive genes supported by higher estimates [> 60%] of broad sense and narrow sense heritability (F-2 and F-infinity). Future progress in plummeting leaf temperature and cell membrane thermo-stability of plant material is achievable through hybridization and rigorous selections in succeeding generations.