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<p>Information on genetic diversity, homozygosity, drought stress and low N tolerance of maize inbred line are useful for parental selection in developing maize varieties tolerant to drought and low N. The objectives of this study were (a) selection for homozygoes lines and analysis of genetic diversity among 51 maize inbred lines applying simple sequence repeats (SSRs) using thirty six markers (b) selection for inbred lines (homozygosity over 80%) for drought and low nitrogen (N) tolerance. Experiment was conducted using split-split plots design with three replications. Water treatments were as the main plots (well-watered and drought stress conditions), subplots were nitrogen fertilization at rate of 75 and 150 kg N/ha and the sub-sub plots were 51 inbred lines. The results showed that there were broad ranges of genetic variability among inbred lines with genetic similarity coefficient values ranging from 0.22 to 0.87 and polymorphism information content average was 0.57. Thirty inbreds having homozygosity over 80% were spread into six heterotic groups. Drought tolerance inbreds were in heterotic groups C and F, namely DTPYC9-F46-3-9-1-1-B and 1044-30, the drought medium tolerance in heterotic group A and B, namely CML 161/NEI 9008 and MR 14. Inbred for low-N fertility tolerance was in the heterotic group D namely G20133077, while medium tolerance to low-N fertility inbreds were in heterotic group A, B, C, D, and F, and they were CML 161/NEI 9008, CY 11, CY 15, CY 6, CLRCY039, Nei9008, DTPYC9-F46-1-2-1-2-B, G2013627, G2013649, 1044-30. Inbreds tolerance to both medium drought and to low-N fertility were in heterotic group C and F they were DTPYC9-F46-1-2-1-2-B and 1044-30. Inbred lines of maize tolerant to drought and to low-N fertility can be used as parent to develop hybrid or synthetic varieties, posessing stress tolerances, by cross recombination between heterotic groups.</p>

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Salinity stress can reduce rice (Oryza sativa L.) productivity and cause crop failure. This problem needs a solution by development of tolerant varieties, and this development closely relates to the effectiveness of its screening. Screening at the phase of germination and seedling are the most common ones. However, the interactions between screenings based on the growth character selection index have not been widely reported, particularly with the principal component analysis (PCA). Therefore, the aim of this study was to determine the interaction between phases of rice salinity screening through a selection index based on PCA. This study consisted of two phases of salinity screening, namely growth phase of germination and seedlings. Both screenings were designed with a nested randomized complete block design, where replicates were nested in a selection environment. The selection environment consisted of two levels, normal (0 mM NaCl) and saline (120 mM NaCl). The genotypes consisted of eight varieties and was repeated three times. Observations were based on morphological and physiological characters, especially in seedling phase screening. Results showed that morphological character approach of the seedlings had a large distribution of salinity tolerances. The use of stress tolerance index and PCA were considered effective in the formation of the selection index on salinity screening. As for, the morphology index was formulated as 0.32 shoot height + 0.33 root fresh weight + 0.33 shoot fresh weight + 0.26 root length + 0.01 number of tillers, length + 0.34 total biomass fresh weight. Therefore, the use of this analytical concept is recommended in screening the tolerance of rice lines to salinity stress.