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B.T. Scully, D.H. Wallace, and D.R. Viands

One-hundred-twelve common bean (Phaseolus vulgaris L.) lines of diverse origin were grown in three environments in 1986 and two environments in 1987. The purpose was to estimate broad-sense heritabilities of nine yield-related traits and the phenotypic, genetic, and environmental correlations among them. The traits and their heritabilities were seed yield (0.90), biomass (0.93), harvest index (0.92), days to maturity (0.96), days to flower (0.98), days of pod fill (0.94), biomass growth rate (biomass/days to maturity) (0.87), seed growth rate (seed yield/days of pod fill) (0.87), and economic growth rate (seed yield/days to maturity) (0.86). These high heritabilities were attributed to the broad genetic diversity and the comparatively small variances associated with the genotype × environment interactions. Genetic correlations of yield were: with biomass, 0.86; harvest index, 0.42; days to maturity, 0.40; days to flower, 0.33; days of pod fill, 0.24; biomass growth rate, 0.92; seed growth rate, 0.84; and the economic growth rate, 0.85. The concomitant phenotypic correlations were mostly equal to the genetic correlations for biomass and the three growth rates, but lower for the phonological traits (days to maturity, flower, and pod fill). Harvest index had the lowest correlations with yield. Correlations were also reported for the other 28 pairwise combinations among these nine traits. Indirect selection was explored with yield as the primary trait and the other eight as secondary traits. Estimates of relative selection efficiency (p) suggested that indirect selection was not a viable option for increasing common bean yields or identifying superior parents.

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B.T. Scully and D.H. Wallace

A diverse set of 112 common bean (Paseolus vulgaris L.) accessions were evaluated for variation in eight traits related to yield over a 2-year period. Days to flower, days of pod fill, and days to maturity ranged from 25 to 66, 44 to 83, and 70 to 133, respectively, in upstate New York: Yield and biomass ranged from 81 to 387 and 270 to 1087 g•m-2, respectively. Harvest index ranged from 12% to 65%. The biomass (biomass/days to maturity) and seed (yield/days of pod fill) growth rates ranged from 3.2 to 9.3 and 1.2 to 9.5 g•m-2 -day-1, respectively. The economic growth rate (yield/days to maturity) extended from 0.6 to 5.7 g•m-2 -day-1. The growth rates, biomass, and days of pod fill were linearly and positively related to yield. Biomass and the growth rates explained a large amount of the variation in yield, with r 2 values between 0.71 and 0.84; days of pod fill explained the least, with r 2 = 0.09. Yield followed a curvilinear relationship with days to flower and days to maturity; yield was maximized at 48.5 days to flower and 112.2 days to maturity. Yield was a quadratic function of harvest index and maximized at 57.2%. Among these three curvilinear traits, days to flower explained 80% of the variation in yield, while days to maturity and harvest index accounted for 25% and 12.5%, respectively. The “ideal” genotype for New York was defined at these maximum values for harvest index, days to maturity, days to flower, and at 63.7 days of pod fill. Additionally, a simple equation is proposed to aid breeders in the selection of common bean accessions with strong sink strength. It is defined as “relative sink strength”: RSS = seed growth rate/biomass growth rate. Values > 1.0 implied strong sink capacity in common beans.

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Martin P.N. Gent, Wade H. Elmer, Kranti Macherla, and Richard J. McAvoy

Can regulated deficit irrigation in an ebb and flow system alleviate the effects of salinity stress on poinsettia? Two cultivars of poinsettia (Euphorbia pulcherrima Willd ex Klotzsch) were grown under partial- or full-saturation irrigation using a standard fertilizer solution, with or without the addition of 0.5 g·L−1 NaCl. The volumetric water content of the medium averaged 0.25 and 0.33 L·L−1 before irrigation, and 0.5 and 0.67 L·L−1 following irrigation, for partial- or full-saturation regimes, respectively. Plants had lower fresh weight with partial than full saturation. Sodium concentrations in bract, leaf, and stem tissues were higher (P ≤ 0.05) in plants exposed to salinity, and these plants accumulated less K in stems and less P in bracts. Eight cultivars were grown in a second study with or without salinity of 1.2 g·L−1 NaCl under drip or ebb and flow watering. Cultivar and watering had effects on plant fresh weight, but salinity did not. Of the cultivars tested, ‘DaVinci’, ‘Premium Picasso’, and ‘Prestige Red’ had the highest sodium in bracts under salinity with drip irrigation, whereas ‘Snowcap’ had the least. ‘Ruby Frost’ had the most sodium in stems, whereas ‘Snowcap’ had the least. For all cultivars, added salinity resulted in lower K in leaves and stem. Snowcap was the cultivar with the least sodium in stems and bracts under saline irrigation, with either drip or ebb and flow. Our research demonstrates that regulated deficit irrigation resulting in partial saturation of the growing medium is an effective water management option, when control of plant height and overall crop growth are desirable, and it limits the accumulation of sodium when raw water contains elevated salinity.

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Guangyao Wang, Mathieu Ngouajio, Milton E. McGiffen Jr, and Chad M. Hutchinson

muskmelon planting. Management systems did not affect muskmelon leaf area and biomass growth. Table 3. Growth parameters of muskmelon affected by cover crops and management systems. z Muskmelon plants in all cover crop treatments had

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Sudeep Vyapari, S.M. Scheiber, and E.L. Thralls

Three root ball conditions—nonroot-bound (NRB), root-bound (RB), and root-bound sliced (RBS)—were evaluated for their effect on plant growth of plumbago (Plumbago auriculata) during establishment and postestablishment in the landscape. At transplant, NRB plants were smaller than other treatments. Canopy size, shoot dry weight, root dry weight, and total biomass growth rates were faster for NRB plants compared with RB or RBS. By 6 and 8 weeks after transplanting, respectively, biomass and canopy size were similar among treatments. Rootbound and RBS plants were similar indicating root ball slicing does not affect growth in the landscape.

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D.G. Mortley, C.K. Bonsi, P.A. Loretan, W.A. Hill, and C.E. Morris

Growth chamber experiments were conducted to study the physiological and growth response of sweetpotato [Ipomoea batatas (L.) Lam.] to either 50% or 85 % relative humidity (RH). Vine cuttings of T1-155 were grown using the nutrient film technique in a randomized complete-block design with two replications. Temperature regimes of 28/22C were maintained during the light/dark periods with irradiance at canopy level of 600 μmol·m-2·s-1 and a 14/10-hour photoperiod. High RH (85%) increased the number of storage roots per plant and significantly increased storage root fresh and dry weight, but produced lower foliage fresh and dry weight than plants grown at 50% RH. Edible biomass index and linear growth rate (in grams per square meter per day) were significantly higher for plants grown at 85 % than at 50% RH. Leaf photosynthesis and stomatal conductance were higher for plants at 85 % than at 50% RH. Thus, the principal effect of high RH on sweetpotato growth was the production of higher storage root yield, edible biomass, growth rate, and increased photosynthetic and stomatal activity.

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Sloane M. Scheiber, Richard C. Beeson Jr., and Sudeep Vyapari

Root ball slicing is often recommended for root-bound woody ornamentals to promote new root development during establishment in the landscape. It is a common practice among gardeners, but not necessarily landscapers, to disrupt root-bound annuals during transplant. However, little if any evidence exists for such practices. Therefore, this study evaluated the effect of root ball condition of annual bedding plants on landscape establishment and growth. Begoniasemperflorens were transplanted from 0.72-L (#1) containers into field plots in an open-sided clear polyethylene covered shelter and managed with Best Management Practices. Three root ball conditions were evaluated: non root-bound (6-week-old plants), root-bound (10-week-old plants), and root-bound with the bottom 1 cm of the root ball removed. Shoot and root dry masses and growth indices were collected weekly for 12 weeks and evaluated relative to root ball condition by linear regression analysis. Nonroot-bound plants had significantly greater biomass, growth indices, height, and root dry weights than the other treatments tested. No significant differences were found between root-bound and manipulated root-bound plants for any parameter examined. The data indicate that the practice of disrupting root-bound plants has no benefit on establishment or growth of annual bedding plants in the landscape.

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James A. Poss, Walter B. Russell, Stacy A. Bonos, and Catherine M. Grieve

Six cultivars or selections of kentucky bluegrass (Poa pratensis L.) were grown outdoors from vegetative clones in a gravelly sand medium from Apr. to Sept. 2005 in Riverside, CA, at soil water salinities ranging from 2 to 22 dS·m−1. Cultivars Baron, Brilliant, Cabernet, Eagleton, Midnight, and the selection A01-856, a ‘Texas’ × kentucky bluegrass hybrid (P.· arachnifera × P. pratensis), were evaluated for salt tolerance based on relative and absolute cumulative biomass production, growth rates, leaf chloride concentration, and hyperspectral ground-based remote sensing (RS) canopy reflectance measurements. Remotely sensed indices were linearly correlated with absolute biomass production. Three variations of a Normalized Difference Vegetation Index (NDVIred, NDVIprotein, and NDVIinfra) decreased with increasing salinity-induced changes in grass canopies. An index based on the red-edge inflection point increased (became less negative) with increasing salinity. A Floating Water Band Index decreased with decreased leaf moisture content related to increasing salinity but did not discriminate between cultivars. Shoot spreading rate and NDVIinfra were both related to shoot chloride concentration differences among the kentucky bluegrass (Poa pratensis L) (KBG) cultivars or selections. In theory, non-destructive RS monitoring of above-ground turf development, including NDVIinfra, coupled with measurement of leaf chloride concentrations could be useful in turf salt tolerance breeding programs. Salt tolerance rankings among the KBG cultivars varied depending on the evaluation methods and selection criteria used. Based on absolute and relative biomass, growth rate, and RS, cultivars Baron, Brilliant, and Eagleton were rated as more salt-tolerant than ‘Cabernet’, ‘Midnight’, and AO1-856.

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Ling Ma, Xingquan Rao, and Xiaoyang Chen

the experiment start date. The coexisting old- and new-leaves periods indicate that at least one old leaf and one new leaf coexisted. The no-leaf period indicates that no fully expanded leaves exist. Fresh biomass growth rate calculation. Five

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Pascal Nzokou and Bert M. Cregg

unit of foliar N). NUE: Whole plant nutrient use efficiency in grams of biomass/g of N per year. N/RW: Index of N availability (foliar N per unit root weight). RWR: Root weight ratio (grams of root/g of total biomass). Growth