IRRI upland rice ecosystem program: directions and achievements : directions and achievements

About 17 million hectares of upland rice are grown annually worldwide, with 10.5 million ha in Asia, 3.7 million ha in Latin America, and 2.8 million ha in Africa (IRRI 1993). Total upland production is about 20 million tons. Rice is a major staple crop for upland farmers in many parts of Asia, Africa, and Latin America. The total area supporting upland rice-based cropping is considerably larger because of rotation with fallow and other crops. The crop is grown alone or in diverse mixtures in shifting or permanent fields under a wide range of conditions of climate, slope, and soil type, often as a subsistence crop receiving few purchased inputs, although it is commonly a commercial crop receiving inputs in favourable areas such as Brazil, Indonesia, and the southern Philippines. Reported upland rice areas have remained stable or have increased in some countries, including the major Asian producers Bangladesh, India, and Indonesia, but have declined for others such as Thailand, the Philippines, and Myanmar (Table 1). Care needs to be taken, however, in interpreting upland rice area estimates, which can be unreliable. For example, the 1991 upland rice area in the Philippines was reported as 68,000 ha in the 1993 IRRI Rice Almanac (IRRI 1993), as 17 1,000 ha in the 1997 IRRI Rice Almanac (IRRI 1997), and as 126,000 ha by the Philippine Bureau of Agricultural Statistics (Pandey, unpublished 1997

Atração e penetração de Meloidogyne javanica e Heterodera glycines em raízes excisadas de soja Attraction and penetration of Meloidogyne javanica and Heterodera glycines in excised soybean roots

Com vista ao estudo de atração e penetração de Meloidogyne javanica (Treub) Chitwood e Heterodera glycines (Ichinoe) em soja (Glycine max L.), desenvolveu-se uma técnica empregando-se segmento de raiz com 2cm de comprimento. Nos segmentos de raiz de soja infectados, observou-se que a penetração de juvenis de segundo estádio (J2) de M. javanica ocorre pela coifa seguida de migração entre os feixes vasculares do cilindro central. Juvenis de H. glycines penetraram, aproximadamente, 15mm da coifa. A região seccionada da raiz de soja atraiu três vezes mais J2 de M. javanica do que a região da coifa, mas esta não foi tão atrativa para J2 de H. glycines. A obstrução conjunta da coifa e do local seccionado reduziu (83%) a penetração de J2, tanto de M. javanica quanto de H. glycines. Quando apenas um desses locais foi obstruído, a outra extremidade livre compensou o processo atrativo. Portanto, as substâncias atrativas são liberadas por essas extremidades. A penetração de J2 de M. javanica foi maior no segmento de raiz quando comparada com a plântula intacta de soja. Entretanto, os J2 de H. glycines penetraram menos em segmentos de raiz e em plântulas sem folhas, quando comparados com plântulas intactas e com as seccionadas no colo. Portanto, na cultivar de soja "Embrapa 20", a atração e os locais de penetração de J2 de H. glycines e M. javanica são diferenciados. Esta técnica poderá ser útil nos estudos de atração e penetração de outros nematoides endoparasitas.<br>To study the attraction and penetration of Meloidogyne javanica (Treub) Chitwood and Heterodera glycines (Ichinoe) in soybean (Glycine max L.), a technique using 2-cm long root segments was developed. In infected soybean root segments penetration of second stage juveniles (J2) of M. javanica occured through the root cap following migration between the vascular bundles of the central cylinder. Juveniles of H. glycines penetrated about 15mm from the root cap. The cut region of the soybean root attracted three times more J2 of M. javanica when compared to the root cap, but was not as attractive to H. glycines J2. Sealing both root cap and cut region reduced (83%) the J2 penetration of M. javanica and H. glycines. When only one of these penetration sites was sealed the open site compensated attractiveness. These results show that the attractive substances are released by these two penetration sites. The M. javanica J2 penetration was higher in root segments when compared to whole soybean plants. However, H. glycines J2 penetrated less in root segments and in roots of seedlings without leaves when compared to roots of whole soybean plants and roots of plants without the aerial part. In short, attraction and infection sites of H. glycines and M. javanica J2s in soybean cultivar "Embrapa 20" are different and this technique may be useful in studies of attraction and penetration of other endoparasitic nematodes

Three fragment sequential decay of heavy nuclei around 3 MeV/u excitation energy

A new method is proposed to identify the sequential decay of hot nuclei into large fragments. This method is based on a minimization procedure. It is illustrated for the Ar+Au reaction at 30 MeV/u. In this case, corresponding to about 3 MeV/u excitation energy, it is shown that the three fragment production can be explained by sequential binary splittings.SCOPUS: ar.jinfo:eu-repo/semantics/publishe

Decay of equilibrated very hot nuclei via multifragment emission

International audienceCoïncidences between at least 3 fragments emitted at large angle have been used to study central collisions in the Ar+Au reactions at 30 and 60 MeV/u incident energies. For both energies, the formation of equilibrated very hot nuclei is evidenced. Excitation energy as high as 1 GeV are reached in the reaction at 60 MeV/u

The decay of primary products in binary highly damped 208^{208}Pb +197^{197}Au collisions at 29 mev per nucleon

Expérience GANIL, Nautilu