N. Vorasoot

Effect of end of season water deficit on phenolic compounds in peanut genotypes with different levels of resistance to drought

Terminal drought reduces pod yield and affected the phenolic content of leaves, stems and seed of peanut (Arachis hypogaea L.). The aim of this study was to investigate the effects of end of season water deficit on phenolic content in drought tolerant and sensitive genotypes of peanuts. Five peanut genotypes were planted under two water regimes, field capacity and 1/3 available water. Phenolic content was analyzed in seeds, leaves, and stems. The results revealed that terminal drought decreased phenolic content in seeds of both tolerant and sensitive genotypes. Phenolic content in leaves and stems increased under terminal drought stress in both years. This study provides basic information on changes in phenolic content in several parts of peanut plants when subjected to drought stress. Future studies to define the effect of terminal drought stress on specific phenolic compounds and antioxidant properties in peanut are warranted.

Variability of arginine content and yield components in Valencia peanut germplasm

Peanut seeds are rich in arginine, an amino acid that has several positive effects on human health. Establishing the genetic variability of arginine content in peanut will be useful for breeding programs that have high arginine as one of their goals. The objective of this study was to evaluate the variation of arginine content, pods/plant, seeds/pod, seed weight, and yield in Valencia peanut germplasm. One hundred and thirty peanut genotypes were grown under field condition for two years. A randomized complete block design with three replications was used for this study. Arginine content was analyzed in peanut seeds at harvest using spectrophotometry. Yield and yield components were recorded for each genotype. Significant differences in arginine content and yield components were found in the tested Valencia peanut germplasm. Arginine content ranged from 8.68–23.35 μg/g seed. Kremena was the best overall genotype of high arginine content, number of pods/plant, 100 seed weight and pod yield.

Seasonal variation in photosynthesis performance of cassava at two different growth stages under irrigated and rain-fed conditions in a tropical savanna climate

Seasonal variations in photosynthesis of cassava cv. Rayong 9 (RY9) under irrigated and rain-fed conditions were evaluated at the age of three and six months after planting (MAP). Photosynthetic light-response (PN/I) curves revealed that cassava leaves attained the highest maximum net photosynthetic rates (PNmax) in the rainy season, followed by the hot one, while the lowest PNmax was found in the cool season. Photosynthetic potential of the 3-month-old plants was mostly higher than that of the 6-month-old plants, and the seasonal variation in photosynthetic capacity was also more apparent in the younger plants. PN/I curves were used to predict daily net photosynthetic rate (PN) for each season based on daily average solar radiation data. The predicted PN were considerably lower than the PNmax values. This indicated that solar radiation is a limiting factor for photosynthesis, particularly in the rainy season. The data provided basic information for breeding cassava genotypes with enhanced photosynthesis during the period of unfavorable environment. Furthermore, the data are potentially useful in modeling photosynthesis and crop growth as affected by environmental factors.

Simple sequence repeat (SSR)-based genetic variability among peanut genotypes different in specific leaf weight and relative water content

The objective of this study was to compare if simple sequence repeat (SSR) markers could correctly identify peanut genotypes with difference in specific leaf weight (SLW) and relative water content (RWC). Four peanut genotypes and two water regimes (FC and 1/3 available water; 1/3 AW) were arranged in factorial randomized complete block design with six replications. The data were recorded for specific leaf weight (SLW) and relative water content (RWC), and 256 SSR markers were used to detect genetic difference. 89 SSR markers could detect polymorphism among peanut genotypes (48.9%). The numbers of alleles ranged from 1 to 6 with a mean of 2.7 alleles per locus. The polymorphic information content (PIC) values varied from 0.38 to 0.75 with a mean of 0.48. The genetics relationship among peanut genotypes was estimated. KK 4 was clustered distinct from the others genotypes, whereas ICGV 98324 and ICGV 98303 were grouped in the same cluster furthest from the KK 4. The results from this study could be useful as a source of variation for development of mapping population for drought tolerance in peanut breeding program. Keywords : Drought, water regime, polymorphism, genetic relationship, SSR markers African Journal of Biotechnology Vol. 12(26), pp. 4053-4064, 26 June, 2013