Field runoff plots, 70 x 10 m each, were established on a tropical Alifisol in southwestern Nigeria to monitor water runoff,
soil erosion and nutrient loss in water runoff. The non-agroforestry control treatment (A) was established at two levels:
plow-till and no-till systems of seedbed preparation. There were two agroforestry systems based on contour hedgerows of (B)
Leucaena leucocephala and (C) Gliricidia sepium established at 4-m and 2-m spacings. Field plots were established in 1982 and hydrological measurements were made for uniform
maize-cowpea rotation for 12 consecutive growing seasons from 1982 through 1987.
Once established hedgerows of Leucaena at 2-m spacing were extremely effective in reducing water runoff and controlling erosion. Runoff, erosion and nutrient losses
were generally more from maize grown in the first season than from cowpea grown in the second. Mean seasonal erosion from
maize was 4.3, 0.10, 0.57, 0.10, 0.64 and 0.60 t/ha for plow-till, no-till, Leucaena-4m, Leucaena-2m, Gliricidia-2m treatments, respectively. Mean runoff in the first season from treatments listed in the order above was 17.0, 1.3, 4.9,
3.3, 4.3, and 2.4 percent of the rainfall received. There were high losses of Ca and K in water runoff from the plow-till
treatment. In contrast to runoff and erosion, losses of bases in water runoff from agroforestry treatments were relatively
high, high concentration of bases in runoff was probably due to nutrient recycling by the deep-rooted perennials. 相似文献
Summary Inheritance of aphid resistance and allelic relationships among sources of resistance was studied in the parents, F1, F2, F3, and backcross populations of cowpea crosses. Each 4-day old seedling was infested with five fourthinstar aphids. Seedling reaction was recorded 14–16 days after infestation when the susceptible check was killed. The segregation data from eight crosses between resistant and susceptible cowpea cultivars indicated that aphid resistance was inherited as a monogenic dominant trait. Segregation data from crosses among eight resistant cultivars indicated that one or two loci and modifier(s) were involved in the expression of resistance to aphids. It was suggested that further studies on allelism among sources of resistance needed to be conducted in order to resolve this. 相似文献
Summary Nine cowpea (Vigna unguiculata (L.) Walp.) breeding lines were grown in 13 experiments under sole crop and intercrop management, with and without insecticide application, in Nigeria. Cowpea was intercropped with cassava (Manihot esculenta Cranz), maize (Zea mays L.) and maize-cassava in the forest zone and with sorghum (Sorghum bicolor Moench.) and millet (Pennisetum glaucum (L.) R.Br.) in the savanna zone. Line by cropping system interactions were significant in 5 of 13 experiments and line by insecticide treatment interactions were significant in 2 of 13 experiments. Cowpea yield was severely depressed in intercropped plots and in plots to which no insecticide was applied. Among-environment variation in cowpea yield was greater when no insecticide was applied. Within each management treatment, the yield performance and stability of the cowpea lines was examined. Stability was assessed both by examining among-environment coefficients of variation and by regression analysis. Several of the breeding lines evaluated appeared promising under different levels of management and in a diversity of environments. 相似文献
Summary Twenty-one genotypes of cowpea (Vigna unguiculata), comprising landraces and varieties, were grown in 22 photothermal environments in Nigeria and Niger, West Africa, and a stability analysis of days from sowing to flowering (f) was carried out. Cowpeas are rarely insensitive to photoperiod; they are typically quantitative shortday plants wherein f is delayed when photoperiod (P) is longer than the critical photoperiod (Pc). Therefore, in order to quantify genotypic variation in temperature sensitivity, genotype f was regressed against the mean trial f in circumstances where P
c
(i.e. approximately 13 hd-1) and mean temperature (T) was between 19° and 28° C. Correspondingly, in order to assess genotypic variation in photoperiod sensitivity, trials where T was near optimal (25°–28° C) but where P ranged from 10–14.5 hd-1 were used. These stability analyses detected no significant differences (P>0.05) between genotypes 9n temperature sensitivity but revealed significant differences (P<0.001) in photoperiod sensitivity. Regression coefficients from the stability analysis were strongly correlated (r=0.94, 19df) with a photoperiod sensitivity constant, c, determined from a photothermal flowering model. A stability analysis of f from field trials can therefore identify and quantify genotypic variation in response to temperature and photoperiod in cowpea.Abbreviations
f
days from sowing to flowering
- P
mean photoperiod
- Pc
critical photoperiod
- Pce
ceiling photoperiod
- T
mean temperature
- Tb
base temperature
- To
optimum temperature
- SDP
short-day plant 相似文献
Summary Linkage among loci controlling various morphological traits in cowpea were determined using F2 progenies. Data were collected on individual plants of four crosses segregating for several loci. Recombination estimates between the following pairs of loci were as follows: Sw (swollen vs normal stem base)-Fbc (cream vs green flower buds) (41±4.8%), Pus(purple vs green stems)-Cbr (cocoa-brown vs straw-yellow dry pods) (31±5.7%), Pup(purple vs green immature pods)-Cbr (30±5.7%), Pus-Pup (4±1.5%), Ndt (non-determinate vs determinate)-Pd (peduncle colour) (26±2.8%), Ndt-Hg (semi-erect vs erect plant type) (26±2.8%), Pt(purple vs green pod tips)-Bk (greyish-black vs straw-yellow dry pods) (19±2.4%) and Hg-Bpd (normal vs branching peduncle (24±9.5%). Four linkage groups (LG) were identified in these studies. The proposed LG I contained loci Sw and Fbc; LG II loci Pus, Pup, and Cbr; LG III loci Pd, Ndt, Gh, and Bpd; and LG IV loci Ptand Bk. 相似文献
Summary Physiological and morphological characteristics of the two wild and three domesticated subspecies of cowpeas are compared. The wild accessions are alike in having small, hard seeds borne in dehiscent pods, but differ in other characteristics. We suggest that the wild subsp. dekindtiana, from the seasonally-arid tropics, is more likely to have been the progenitor of modern cowpeas than the other wild subspecies (subsp. mensensis), but that subsp. dekindtiana was first cultivated in the humid tropics where its pods are slow to dehisce. Domestication has been associated with changes in the structure of pod valves and seed coats which reduce pod dehiscence and seed hardness. Pods and seeds have increased in size, mainly by increases in the rate of dry weight accumulation, and their increase has been only partly paralleled by increase in the area of subtending leaves. There has been no increase in the maximum photosynthetic rate of leaves, but the duration of their photosynthetic activity has increased. Domesticates are less sensitive than are wild plants to some environmental controls, such as in the response of germination to temperature, but in their flowering responses to daylength both wild and cultivated forms retain sensitivity under conditions where this is of adaptive value. 相似文献
An in vitro growth system was used to determine the virulence of two samples of Striga gesnerioides from Zakpota in southern Benin. Cowpea variety B301, previously considered resistant to all races of S. gesnerioides, was susceptible to both samples of the parasite. Two other cowpea varieties, 58–57 and IT81D-994, were totally resistant. Resistance in 58–57 was associated with a hypersensitive necrosis of infected roots, whilst IT81D-994 supported production of small S. gesnerioides tubercles with stems which failed to develop. Striga gesnerioides from southern Benin is the fourth race of the parasite to be identified, and the first with virulence on variety B301. The implications for breeding cowpeas with resistance to S. gesnerioides are discussed.Abbreviations IITA
International Institute of Tropical Agriculture
- LARS
Long Ashton Research Station
- SAFGRAD
Semi-Arid Food Grain Research and Development 相似文献