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- Author or Editor: Ajmer S. Bhagsari x
Field experiments were conducted from 1980-1983 to evaluate sweetpotato [Ipomoea batatas (L.) Lam.] germplasm for photosynthetic efficiency, harvest index [HI; (storage root dry matter/total plant dry matter) × 100], and yield. Most genotypes maintained leaf area index (LAI) above five until final harvest, 164 days after planting (DAP). The higher LAI (> 8) for PI 318859, PI 344134, and PI 308205 compared to the other genotypes was maintained at the expense of the storage root development. Single leaf net photosynthesis (Pn) of the genotypes ranged from 0.61 to 1.09 mg CO2/m2 per sec during 1980. Canopy photosynthesis on a ground area (CPn-Ga) basis ranged from 0.95 to 1.56 and 1.04 to 1.30 mg CO2/m2 per sec during July and August 1983, respectively. Canopy photosynthesis expressed on leaf dry-weight (CPn-Dwt) basis was higher for PI 344122 than the other genotypes, except PI 344138, indicating its superior photosynthetic efficiency. Photosynthetic efficiency and stomatal conductance were not related to yield. Stomatal conductance and CPn-Ga were significantly correlated. Harvest index differed significantly at each sampling and ranged from 14.0% to 75.5% at final harvest. Fresh storage root yield for 1983 and 4-year mean yield ranged from 8.6 to 60.1 and 14.1 to 42.2 t·ha-1 respectively. At final harvest, HI correlated significantly with fresh-(r = 0.91) and dry-matter storage root yield (r = 0.95). Despite significant photosynthetic variations among the genotypes, sweetpotato yield was influenced more by HI and storage root sink strength than by photosynthetic efficiency.
Significant differences were observed in yield, net photosynthetic rates (Pn), percent leaf nitrogen, chlorophyll content, stomatal density and specific leaf weight in various genotypes of sweet potato (Ipomoea batatas (L.) Lam.) but these characters were not correlated with root yield.
Field experiments with 15 sweet potato [Ipomoea batatas L. (Lam.)] genotypes were conducted to study the physiological basis of yield in 1981 and 1982. The leaf area index differed significantly among the sweet potato genotypes during early and late phases of growth, hut showed an inconsistent relationship with yield. Single leaf net photosynthesis ranged from 0.74 to 1.12 mg CO2/m' per sec. Canopy photosynthesis for sweet potato genotypes differed significantly in 1981, but not in 1982. It ranged from 0.81 to 1.16 mg CO2/m2 per sec in Aug. 1981. and from 0.63 to 0.88 mg CO2/m2 per sec in 1982. Four hours after “C-labeling, 14C-assimilate translocation from the treated leaf ranged from 21% to 46%, but did not differ significantly among the genotypes. At final harvest, harvest index [HI, defined as (storage root yield/total biological yield) × 100] of the genotypes varied from 43% to 77% and 31% to 75% for 1981 and 1982, respectively. Canopy photosynthesis during September was significantly correlated with storage root dry matter yield (r = 0.54*) in 1981 and with phytomass (above-ground biomass plus storage roots) (r = 0.60*) in 1982. Both phytomass and HI were significantly correlated with storage root matter yield. Canopy photosynthetic evaluation of sweet potato germplasm may be-more relevant when the storage root sinks are at an advanced stage of development. Our study suggests that yield is poorly predicted by Pn, particularly when the genotypes have different leaf sizes.
In Asian countries and among the oriental populations in the United States, vegetable soybeans are consumed much the same way as green peas are consumed. A need exists for developing soybean cultivars adapted to the U.S. environments to take advantage of the economic potential of vegetable soybeans for both domestic and international markets. During 1997, 12 vegetable soybean genotypes of exotic origin and two local U.S. soybean cultivars were evaluated for their agronomic performance in a randomized complete block, with four replications, at the Agric. Res. Stn. FVSU, Ga. At the R6 stage (when the seeds are of full size and still immature), plants from a half-meter-row length were sampled from each plot to estimate green pod and seed yield, and determine the nutritional quality of green beans. Significant differences were observed among genotypes for the agronomic and biochemical parameters studied. The green seed yield ranged from 7.1 (cv. Ware) to 14.0 Mg·ha–1 (cv. Tanbagura). Three cultivars, Tomahamare, Mian Yan, and Tousan-122, produced green seed yields in excess of 12 Mg·ha–1. The number of green pods varied between 1518 (Tanbagura) and 3526/m2 (cv. Hutcheson). The green bean oil and protein contents, ranged from 53.1 to 105.4 and from 354.2 and 418.3 g·kg–1, respectively. Thus, the green seeds contained only 30% of oil, but 50% to 80% of protein normally found in mature soybean seed. The glucose content was between 4.1% and 7.0%, while the phytate content varied between 0.93% and 1.3%. T he green seed yield was significantly correlated with number of green pods, number of green seeds, and green pod weight. This study showed that some exotic vegetable soybean genotypes may be suitable for production in the southeastern U.S.
This study was carried out to optimize conditions for plant regeneration of sweetpotato [Ipomoea batatas (L.) Lam] using shoot tips, petioles, and leaves of Selection 75-96-1 as explants in Murashige and Skoog (MS) with several growth regulators at different levels. Callus initiation and callus proliferation media were 9.0 μm 2,4-dichlorophenoxyacetic acid (2,4-D) and 9.0 μm 2,4-D + 1.1 μm N 6-benzyladenine (6-BA) in protocol I; 8.1 μm α-naphthaleneacetic acid (NAA) + 1.2 μm kinetin (KIN) and 5.4 μm NAA + 4.6 μm KIN in protocol II; 0.9 μm 2,4-D, and 0.9 μm 2,4-D + 1.2 μm N-isopenylamino purine (2iP) in protocol III; NAA (8.1 μm) + KIN (1.2 μm) and 2,4-D (0.9 μm) + 2ip (1.2 μm) in protocol IV, respectively. In protocol I and II, shoot tip, petiole, and leaf were used, but only petiole and leaf in protocol III and IV. In the protocol I and II, somatic embryos were obtained only from shoot tip explants; in protocol III and IV, only from petioles. The frequencies of somatic embryo development were 33.3% in protocol I, 42.1% in protocol II, 21.2% in protocol III, and 10.3% in protocol IV, respectively. The leaf explants failed to produce somatic embryos in all the experiments. In protocol I, somatic embryogenesis occurred through the well-known sequence of globular-, heart-shaped-, torpedo-, and cotyledon-type embryos. However, in protocol II, the structures resembling plumule and radicle were observed before the emergence of torpedo/cotyledon type embryo clusters. The somatic embryogenesis in protocol III and IV was similar to that in protocol I. Growth regulators influenced somatic embryo development. Further, this study showed that explant resource and growth regulators affected the frequency of plant regeneration in sweetpotato.
Field experiments were conducted during 1979 and 1980 growing seasons with sweet potato [Ipomoea batatas (L.) Lam.] genotypes at different stages of growth to determine leaf net photosynthetic rates (Pn) and photosynthate partitioning patterns. Net photosynthesis was measured in an open system with an infrared analyzer on the youngest and the fully expanded leaves still attached to the plant. Photosynthesis rates differed significantly in both years. Photosynthesis varied from 19.1 to 32.4 mg CO2dm−2hr−1 in 1979 and from 25.8 to 36.9 mg CO2dm−1hr−1 in 1980. A new selection, 75-96-1, averaged highest both years. Percentages of photosynthate partitioning to storage roots also differed significantly. About 45 days after planting, ‘Centennial’ and ‘Georgia Jet’ diverted the highest percentage, about 28%, of the total dry matter to the storage roots. But ‘Georgia Red’ diverted the highest percentages of photosynthate (51.0 and 56.4) to the storage roots 75 and 90 days after planting, respectively. Photosynthate partitioning to storage roots ranged from 11.2 to 56.4%, 90 days after planting. Final root yield correlated significantly (r = 0.69 to 0.87) with photosynthate partitioning at all stages of growth. During 1980, Pn and total dry matter yield also were significantly correlated. Harvest index was significantly correlated (r = 0.89) with final storage root yield. But Pn did not significantly correlate with either storage root yield or photosynthate partitioned to roots. Stomatal density was 2 to 3 times more on the abaxial than the adaxial surface of the leaves. Percentages of neither leaf nitrogen nor chlorophyll content of leaves differed significantly. High-yielding genotypes generally initiated storage root formation earlier and also partitioned more photosynthate to storage roots than low-yielding genotypes.