Background: This study aimed to determine the effects of different waterlogging duration imposed at the V2 leaf stage and assess the impact of waterlogging on maize growth during the recovery period, identify susceptible and tolerant lines and traits conferring tolerance to waterlogging at the early seedling stage. Methods: The study was arranged in a Split-plot RCBD and replicated three times. Intercharacter and waterlogging durations to maize growth parameters were correlated to determine the degree of the linear relationship using Pearson’s product moments correlation and simple linear regression analysis. Result: The result shows that the different waterlogging durations negatively influenced the maize growth parameters regarding plant height and root length. These parameters became shorter and did not recover after waterlogging stress was removed. Therefore, plant height and root length are traits sensitive to waterlogging stress. The USM Var 10, BRK and T. Monkayo obtained a high degree of leaf greenness, heaviest shoot and root dry matter compared to other evaluated maize lines. Maize with greener leaves, taller plant height, longer root length and high total dry matter accumulation could be a good criterion in selecting a parent material in the maize waterlogging breeding program.

Oryza rufipogon Griff. or ‘Rufi’ is the wild progenitor of the cultivated rice, Oryza sativa L. In the Philippines, Rufi was previously known to be found only in Lake Apo, Bukidnon. However, a new population was identified in Lake Napalit in the same province. Based on previous morphological diversity assessment, both populations are unique for at least three characters, i.e., leaf, culm, and awn lengths. Environmental parameters such as rainfall and air temperature also differed between the two lakes. With these, an assessment of Rufi’s genetic diversity at the molecular level is beneficial to further ascertain its usefulness in rice breeding and gain insights on its conservation status. Thus, this study estimated the degree of genetic diversity and determined the population structure of 41 samples of natural Rufi populations in the Philippines using SSR markers. A total of 98 genome wide polymorphic SSR markers were selected to examine the genetic diversity and structure of Rufi populations, along with seven rice cultivars for comparison. Results showed that Philippine Rufi populations have lower genetic diversity compared to cultivated rice accessions and other Rufi populations in Southeast Asia and China. This low genetic diversity suggested that Rufi populations might be in a genetic bottleneck, perhaps due to observed unsustainable farming practices near their habitat and lack of awareness of their importance. A significant population structure and differentiation were determined using the STRUCTURE and phylogenetic analyses. Population differentiation might be due to geographic isolation which prevented gene flow between the two populations and the unique climatic conditions between the two lakes.