排序方式： 共有10条查询结果，搜索用时 15 毫秒
1
1.
H.M.P.J.B. van Rheenen Rene G.A. Boot Marinus J.A. Werger Miguel Ulloa Ulloa 《Forest Ecology and Management》2004,200(1-3):39-48
For sustainable forest management, it is important to know the response of timber species to the change in environment caused by logging. We performed a 2-year study on germination, survival and growth of four timber species, Cedrela odorata, Swietenia macrophylla, Hymenaea courbaril, and Cariniana micrantha, and one non-commercial species Tachigali vasquezii. We sowed seeds of these species in five microenvironments: log landing, gap-crown and gap-trunk, skidder trail and understory, in a tropical lowland moist rain forest in northern Bolivia. We related seed and seedling performance to light availability, soil compaction, and plant competition. Germination did not differ significantly between microenvironments but survival of germinated seeds for most species was significantly higher (P < 0.05) in the log landing (46–100%) than in the understory (0–7%). After 2 years, the tallest plants were always found in the log landing (119–190 cm) and the smallest in the understory (12–26 cm) caused by a higher relative height growth rate (RHGR) in the log landing (0.003–0.004 cm cm−1 per day) compared to the understory (0.000–0.001 cm cm−1 per day). During the first year RHGR was positively related to canopy openness for all species and negatively to the number of overtopping competitors for three species. During the second year also water infiltration explained observed variation to RHGR. These results show that abandoned log landings and logging gaps are suitable environments for the regeneration of timber species studied. This finding suggests that the removal of competitors in log landings and logging gaps combined with leaving seed trees near these microenvironments or sowing seeds, will improve regeneration of timber species in tropical forests. 相似文献
2.
H. A. Van Rheenen 《Euphytica》1963,12(3):245-353
As the sweet potato, Ipomoea batatas
Poir, is propagated vegetatively its selection is comparatively simple. Choice of parents and selection procedures were carried out on the basis of yield capacity, resistance or tolerance to a fungus and virus disease, resistance to Cylas formicarius F. and the shape and size of tubers. Because insufficient data were available the protein content played no important role in the choice of parents. In the selection procedures, also this character could not yet be taken into account because the laboratory equipment was insufficient. This might have changed in the future.In the selection fields the new clones were planted by the side of a well-known test-clone, in such a way, that every new clone had a test on either side. At every selection cycle 25% of the new clones was kept for further research while the rest was rejected. On two generations the visible disease symptoms of new clones increased considerably while their production capacity decreased. For various characters a clear relation could be demonstrated between the phenotype of the parents and their offspring. 相似文献
3.
Summary The character of determinate plant growth has not been reported for chickpea and has not been observed in the world germplasm collection at ICRISAT, Patancheru, India. A determinate growth habit would be desirable where growing conditions often lead to excessive vegetative growth. We attempted to generate this trait by mutation breeding. Seeds of the cultivar ICCV 6 were exposed to varying irradiation treatments, M1 and M2 populations were raised, and in the latter one plant was detected that showed the determinate growth habit and female sterility. The character of determinate growth segregated in a postulated digenic epistatic 3:13 fashion in the F2 and confirmed its digenic mode of inheritance in the F3 and F4. The symbol cd is proposed for the allele conditioning for determinancy and Dt for the allele expressing the determinate trait. Continued mutation breeding with this and other material may result in identifying fully fertile, determinate plant types.Abbreviations DT -
determinate
- IDT -
indeterminate
ICRISAT Journal Article No. 1396. 相似文献
4.
J. Kort H. A. van Rheenen 《European journal of plant pathology / European Foundation for Plant Pathology》1959,65(4):147-157
Summary Some observations have been made on lucerne wilt disease during the growing season in 1957, and in experimental inoculation tests in a glasshouse in 1958. In the province of Zeeland the disease does harm to the crop and prevents many farmers from keeping their crops longer than two years.In a survey data have been collected on soil type, preceding crops, green manuring and manuring with stable dung, pH, structure and weeds. No correlations between these factors and the degree of attack by the disease could be proved, except that on heavy soils the disease was less severe than on lighter soils (as a mean of all observations).Development of the disease is facilitated by damage caused by mechanical equipment to the crop. Damage to the crown of the plants should be avoided as much as possible. The disease is distributed extensively after frequent mowing. On attacked leaves left behind on the mowed stalks, and on decayed leaves dropped to the soil, masses of spores ofVerticillium albo-atrum are produced, which form a potential source of infection in a weakened crop.It seems that the disease is more air-borne than soil-borne, since one year old crops are seldom attacked.From attacked lucerne plants in the field the following fungi have been isolated:Verticillium albo-atrum
Reinke & Berth.,Gliocladium roseum
Bain andFusarium avenaceum
(Fr.) Sacc. (table 1).Isolations have been made from 50 different species of weeds, out of which the following fungi were obtained:Verticillium albo-atrum
Reinke & Berth. fromCapsella bursa-pastoris
Med. andPlantago major L.,V. dahliae
Kleb. fromPrunella vulgaris L.,Capsella bursa-pastoris
Med. andThlaspi arvense L., andV. lecanii
(Zimm.) Viegas fromPlantago major L.In inoculation experiments with all these isolates, in roots, stalks and on cut plants of lucerne, onlyV. albo-atrum, both from lucerne and weeds, andV. lecanii proved to be able to cause wilting of leaves and stalks. WithGliocladium, Fusarium andVerticillium dahliae no such symptoms could be obtained. The results were the same whatever method of inoculation was used. 相似文献
5.
The presence of genotype × environment (GE) interactions in plant breeding experiments has led to the development of several stability parameters in the past few decades. The present study investigated the repeatability of these parameters for 16 chickpea (Cicer arietinum L.) genotypes by correlating their estimates obtained from extreme subsets of environments within a year and also over years. Based on the estimates of response and stability parameters within each trial, the ranking of genotypes in the low-yielding subset differed from that in the high-yielding subset. This indicates poor repeatability for response and stability parameters over the extreme environmental subsets. The estimates of mean yield and stability parameters represented by ecovalence, W2i, were consistent over years, whereas those of response parameters (bi, and S2i) showed poor repeatability. Our results suggest that single-year results for yield and stability can be used effectively for selecting cultivars with stable grain yield if tested in a wider range of environments. 相似文献
6.
H. A. Van Rheenen S. G. S. Muigai 《European journal of plant pathology / European Foundation for Plant Pathology》1984,90(3):85-94
The deployment of the dominant gene I for the control of bean common mosaic predisposes a bean crop to the risk of death by black root if one or more recessive genes to prevent the hypersensitive plant reaction are lacking. However, during 3 years of observation in Kenya black root occurred only exceptionally to more than 10%, and in such cases the yields from crops having the dominant gene I exceeded significantly those from mosaic-susceptible crops. The use of the dominant resistance factor in Kenya is therefore recommended, but continued caution and monitoring of the disease situation are required. Broadening the resistance basis by adding recessive genes to control black root is advisable.Samenvatting Het gebruik van het dominante gen I voor de bestrijding van de virusziekte bonerolmozaïek stelt een bonengewas bloot aan het gevaar van systemische necrose, als niet een of meer recessieve genen aanwezig zijn om deze overgevoeligheidsreactie van de planten te voorkomen. Gedurende een periode van drie jaar werden waarnemingen verricht om na te gaan hoe vaak deze necrose optrad. Slechts bij uitzondering bleek meer dan 10% van de planten te worden aangetast. In die gevallen werd de opbrengst toch aanmerkelijk verhoogd door de aanwezigheid van het dominante gen I. Het gebruik van dit gen ter bestrijding van het bonerolmozaïek wordt daarom voor Kenya aanbevolen. Voortdurend moet echter worden nagegaan in welke mate necrose-inducerende stammen van het virus voorkomen. Een verbreding van de erfelijke basis van de resistentie ter voorkoming van de necrotische reactie door introductie van recessieve resistentiegenen is raadzaam.
Résumé L'emploi du gène dominant I pour la lutte préventive contre la mosaïque commune du haricot, en I'absence d'un ou plusiers gènes récessifs pour éviter une réaction hypersensible de la plante, entraine un danger de mort de la plante par racines noires. Néanmoins, pendant les 3 ans d'observations au Kénya, les cas de racines noires ne sont apparus qu'exceptionnellement à un taux superieur à 10%, et, dans de tels cas, le rendement du végétal ayant le gène dominant I était, de façon significative, supérieur à celui des végétaux prédisposées à la mosaïque. L'utilisation au Kénya du facteur de résistance dominant est par conséquent recommendé mais une attention et une surveillance permanentes de I'évolution de la maladie sont nécessaires. On peut conseiller I'élargissement de la base de résistance par addition de gènes récessifs pour le contrôle de la maladie des racines noires.相似文献
7.
Summary Male sterile bean plants were discovered at Embu Agricultural Research Station, Kenya. The character is controlled by one recessive gene.The Grain Legume Project is a joint project of the Kenya Ministry of Agriculture and The Netherlands Ministry of Foreign Affairs. 相似文献
8.
H. A. Van Rheenen O. E. Hasselbach S. G. S. Muigai 《European journal of plant pathology / European Foundation for Plant Pathology》1981,87(5):193-199
Compared with mono-cultures, beans grown in association with maize showed generally less incidence of the following diseases and pests: halo blight, bean common mosaic, anthracnose, common blight, scab,Phoma, mildew, bolworm and to a lesser extent angular leaf spot. For white mold and the black beetleSystates the opposite was observed. Rust and aphilds were erratic in this respect. Apparently a kind of cultural control of the major bean diseases in Kenya is effected by growing beans in association with maize. 相似文献
9.
H. A. Van Rheenen 《Euphytica》1965,14(3):271-275
Flower formation of most sweet potato clones in the collection at Manokwari was poor and when seed for breeding purposes was desired flowering had to be stimulated accordingly.Of various methods applied to stimulate the flowering some proved to be satisfactory. Good results were obtained in training tendrils to racks and grafting on different species of the genus Ipomoea. 相似文献
10.
H. A. Van Rheenen 《Euphytica》1964,13(1):94-99
In the sweet potato fruit formation following artificial selfing, artifical cross pollination and natural pollination was investigated. Artificial self-pollination in one case gave a fruit formation of 21.2%; in five other cases no or hardly any fruit formation took place. Artificial cross-pollination produced a fruit formation varying from 0 to 52.9%. Natural fertilization did not occur in cases when the nearest flowering sweet potato clone stood at a distance of 80 m. When other flowering clones were in the direct vicinity the percentage of fruit formation through natural pollination differed from 0 to 25.2%.Pre-treatment of sweet potato seed with concentrated sulphuric acid applied during 10 or 20 minutes had a favourable effect on the speed of germination and the germination percentage, also when the seed after treatment was kept in store in or outside an exsiccator for one or two months. The method of scarifying the seed showed a reasonably good influence in this respect. Two different warm water treatments were not or practically not satisfactory. 相似文献
1