Sixteen spring wheat genotypes were grown under hot, irrigated, low latitude conditions, during the 1990-1991 and 1991-1992 winter cropping cycles in Mexico, Egypt, India and the Sudan, and in the 1990 and 1991 winter cycles in Brazil. The genotypes were chosen to represent a range of genetlc diversity within modem wheat varieties. In addition to grain yield, in Mexico a number of morphological and physiological traits were measured throughout the growing season on two sowing dates (December and February), to evaluate their correlation with yield in the other countries. The morphological traits - above-ground biomass at maturity, grains m-2, days to anthesis and days to maturity - measured on both sowing dates in Mexico showed generally significant correlations with yields measured at the other sites. Moreover, ground-cover estimates early in establishment, and at anthesis, also showed some association with performance at these sites, but only when measured on the hotter, February sowing date in Mexico. Membrane thermostability (MT), measured on field-acclimated flag leaves showed generally significant correlations with performance at all sites, and with MT measurements made on heat- acclimated seedlings of the same genotypes grown in growth chambers. Flag-leaf photosynthesis measured at booting, anthesis and during grain filling on both sowing dates, was generally significantly correlated with grain yield at all sites, as was rate of loss of leaf chlorophyll content during grain filling. Stomatal conductance was also significantly correlated with performance at all three stages. Canopy temperature depression (CTD) measured with an infrared thermometer was significantly positively correlated with performance at the international sites when measured between 1200 and 1600 hours, after full canopy establishment. The correlation of CTD with yield was not affected by the irrigation status of the crop under well-watered conditions. The possible use of these traits in selection for yield under hot conditions is discussed.
Canopy temperature depression (CTD = air temperature [Ta] – canopy temperature [Tc]) has been used to estimate crop yield and to rank genotypes for tolerance to heat and drought, but when to measure CTD for breeding selection has seldom been addressed. Our objectives were to evaluate the suitability of CTD for the Texas High Plains environment and to determine optimal measurement times in relation to growth stage, time of day, and weather. Three years of CTD and weather data were used to assess regression models of grain yield in three wheat (Triticum aestivum L.) lines. Under dryland agriculture, long‐term mean CTD at noon and yield were correlated in 2000 and 2001. The relation of short‐term CTD readings to grain yield was highly variable. Poor correlation was associated with days of low solar irradiance, high wind speed, and rain events. Genotype effects on CTD were detected for all hours of day and night. Genotype × hour interaction was insignificant at night, suggesting that nighttime measurements may provide more stable conditions for CTD comparison among genotypes. In general, tree regression assessed grain yield from short‐term CTD measurements better than linear regression and suggested that the best times to measure CTD were 0900, 1300, and 1800 h. Tree regression models provided a heuristic interpretation of crop water status under different scenarios of soil water availability.
‘Bailey’ (Reg. No. CV‐111, PI 659502) is a large‐seeded virginia‐type peanut (Arachis hypogaea L. subsp. hypogaea var. hypogaea) with partial resistance to five diseases that occur commonly in the Virginia‐Carolina production area: early leaf spot (caused by Cercospora arachidicola Hori), late leaf spot [caused by Cercosporidium personatum (Berk. & M.A. Curtis) Deighton], Cylindrocladium black rot [caused by Cylindrocladium parasiticum Crous, M.J. Wingf. & Alfenas], Sclerotinia blight (caused by Sclerotinia minor Jagger), and tomato spotted wilt (caused by Tomato spotted wilt tospovirus). It also has partial resistance to southern stem rot (caused by Sclerotium rolfsii Sacc.). Bailey was developed as part of a program of selection for multiple‐disease resistance funded by growers, seedsmen, shellers, and processors. Bailey was tested under the experimental designation N03081T and was released by the North Carolina Agricultural Research Service (NCARS) in 2008. Bailey was tested by the NCARS, the Virginia Agricultural Experimental Station, and five other state agricultural experiment stations and the USDA‐ARS units participating in the Uniform Peanut Performance Tests. Bailey has an alternate branching pattern, an intermediate runner growth habit, medium green foliage, and high contents of fancy pods and medium virginia‐type seeds. It has approximately 34% jumbo and 46% fancy pods, seeds with tan testas and an average weight of 823 mg seed−1, and an extra large kernel content of approximately 42%. Bailey is named in honor of the late Dr. Jack E. Bailey, formerly the peanut breeding project's collaborating plant pathologist.
Wheat (Triticum aestivum L.) cultivars with high canopy temperature depression (CTD) tend to have higher grain yield under dry, hot conditions. Therefore, CTD has been used as a selection criterion to improve adaptation to drought and heat. The CTD is a result of the leaf's energy balance, which includes terms determined by environment and physiological traits. We hypothesized that one or more of several physiological traits contributed to consistent CTD differences among three closely‐related winter wheat lines grown under dryland conditions. For three years we measured several leaf traits, including CTD, leaf dimension, gas exchange rates, and carbon‐13 isotope discrimination (Δ). Soil water content was also monitored. Data showed that daytime CTD was related to the leaf size in these wheat lines. The most drought‐tolerant line, TX86A8072, had consistently smaller and narrower leaves than TX86A5606, the least drought tolerant. For TX86A8072, dryland and irrigated average noon CTD was −0.8°C, and average flag leaf area (LA) 11 cm2, for TX86A5606, values were −1.7°C and 12.5 cm2, respectively. However, TX86A8072 also had higher CTD (i.e., lower temperatures) than TX86A5606 at night, despite a theoretically greater sensible heat transfer coefficient, suggesting greater nighttime transpiration (T). Implications of these traits on nighttime leaf energy balance and possible adaptive roles of nighttime T are discussed.
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