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Title: Root distribution of drought-resistant peanut genotypes in response to drought

item SONGSRI, P - Khon Kaen University
item JOGLOY, S - Khon Kaen University
item VORASOOT, N - Khon Kaen University
item AKKASAENG, C - Khon Kaen University
item PATANOTHAI, A - Khon Kaen University
item Holbrook, Carl - Corley

Submitted to: Journal of Agronomy and Crop Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/25/2009
Publication Date: 11/20/2009
Citation: Songsri, P., Jogloy, S., Vorasoot, N., Akkasaeng, C., Patanothai, A., Holbrook Jr, C.C. 2009. Root distribution of drought-resistant peanut genotypes in response to drought. Journal of Agronomy and Crop Science. 194:92-103.

Interpretive Summary: The ability of a plant to modify its root distribution to exploit deeper stored soil water may be an important mechanism to avoid drought stress. Our objective was to examine the root growth of some drought tolerance peanut lines when grown under different levels of drought stress. Eleven peanut lines were grown in three soil moisture levels for two years. Root length was determined using a scanner and computer soft ware at three sampling dates. Pod yield was also recorded at harvest. Five of the peanut lines responded to increasing drought stress by increase rooting at deeper soil levels. Information on the ability of drought resistant peanut lines to alter root systems contributing to high yield under drought conditions might reveal avoidance mechanisms and could result in the development of improved breeding strategies for developing drought resistance in peanut.

Technical Abstract: The ability of a plant to modify its root distribution to exploit deeper stored soil water may be an important mechanism to avoid drought. This study aimed at assessing root distributions, variations in root length density (RLD) and percentage of root distribution, and the relevance of root traits for yield of drought-resistant peanut genotypes under different available soil water levels. The experiment was conducted in the dry season during the years 2003/04 and 2004/05. Eleven peanut genotypes (ICVG 98300, ICGV 98303, ICGV 98305, ICGV 98308, ICGV 98324, ICGV 98330, ICGV 98348, ICGV 98353, Tainan 9, KK 60-3, and Tifton 8) and three soil moisture levles [field capacity (FC), 2/3 available soil water (AW) and 1/3 AWW] were laid out in a split-plot design with four replications. Roots were sampled by a core sampler at 37, 67 and 97 days after sowing (DAS). Root length was determined by a scanner and the WINRHIZO Pro 2004a software. RLD was calculated as the ratio of root length (cm) and soil volume (cm3). Graphical illustration of root distribution was constructed by merging RLD in the first and second soil layer (0-40 cm) as upper roots and pooling RLD at the third, fourth and fifth layers (40-100 cm) as lower roots. Pod yield, biomass and harvest index (HI) were recorded at harvest. A drought tolerance index (DTI) was calculated for each parameter as the ratio of the parameter under stress treatment to that under well-watered conditions. Variations in RLD in 40 to 100 cm layer (RLD40 to 100 cm) were found under well-watered conditions, and the peanut genotypes could be readily identified as high, intermediate and low for this trait. Changes in RLD in the 40 to 100 cm soil layer were found at 2/3 AW and were more evident at 1/3 AW. ICGV 98300, ICGV 98303, ICGV 98305, ICGV 98308 and KK 60-3 were classified as drought responsive as they increased RLD in the deeper subsoil level in response to drought. In general, RLD under drought conditions was not related to biomass production. The ability to maintain the percentage of RLD (DTI for % RLD) was related to pod yield, DTI for pod yield and DTI for HI. ICGV 98300, ICGV 98303, ICGV 98305 exhibited high DTI (RLD40 to 100 cm) which may explain their high pod yield, DTI (PY) and DTI (HI). Based on these observations we classified them as drought-avoiding genotypes.