Imposing a moderate level of nutrient deficiency may be an effective management strategy to limit vegetative growth and enhance maturity of Pima cotton (Gossypium barbadense L.). Whether such deficiency affects fiber quality of American Pima cotton, however, is not well known. A field study was conducted in 1991 and 1992 to determine the fiber quality responses of Pima cotton to nitrogen and phosphorus fertilization ranging between deficient and excess. Pima cotton cv. "S-7" was treated with nitrogen rates ranging between 0 and 269 kg ha(-1) in a factorial combination with phosphorus rates ranging between 0 and 44 kg ha(-1). Fiber property measurements included fiber length, strength, fineness, elongation, and color properties. Increasing rate of applied nitrogen significantly (P less than or equal to 0.05) increased fiber length, elongation, micronaire, and color characteristics and reduced fiber uniformity ratio in 1991. Increasing nitrogen rate significantly (P less than or equal to 0.10) increased fiber length, uniformity index, and yellowness in 1992, when the degree of nitrogen deficiency imposed by the lowest nitrogen rate was not as severe as the deficiency imposed by the same treatment in 1991. Phosphorus did not significantly (P less than or equal to 0.10) affect any of the important fiber properties-length, strength, or micronaire-in either cropping season. These results indicate moderate level of nitrogen or phosphorus deficiency does not affect Pima cotton fiber quality. Nitrogen or phosphorus deficiency severe enough to reduce fiber quality and affect marketing of Pima cotton is unlikely to be encountered under normal Pima cotton production practices.

The cotton crop is attacked by a number of insect pests, diseases, nematodes and weeds. Yield losses due to these pests range from 15 to 25 per cent. There are a number of problems encountered by the cotton growers in adoption of the recommendation of IPM practices. The study was conducted inHaryana on the total sample size of 180 respondents. The constraints were reported as serious to most serious level by majority of the respondents in case of technological; economical; service, supply and marketing and transfer oftechnology besides overall constraints perceived in the adoption of IPM practices by the cotton growers. Education, land holding, socio-economic- status, information sources, risk orientation, economic motivation, change proneness and management orientation were found to have negative and highly significant relationship with technological, economical, transfer oftechnology as well as overall constraints perceived in the adoption of IPM practices. Social participation had negative and highly significant correlation with only transfer of technology constraints. The service, supply and marketing constraints were found to have negative and highly significant relationship with land holding and economic motivation whereas, management orientation had shown negative and significant correlation.

The effect of root-knot nematode (RKN) (Meloidogyne incognita) on Verticillium dahliae and Fusarium oxysporum f.sp. vasinfectum in cotton (Gossypium hirsutum) was investigated. Two different inoculation methods were used, one in which inoculum was added to the soil, so that nematode and fungal inoculum were in close proximity; the other, inoculation into the stem, whereby the two inocula were spatially separated. Invasion of the roots by RKN enhanced disease severity, as measured by the height of vascular browning in the stem, following inoculation with either wilt pathogen. The effect of RKN on Fusarium wilt was more pronounced than that on Verticillium wilt. Nematode-enhanced infection by F. oxysporum is a well known effect but there are few reports of enhanced infection by Verticillium due to RKN. Relative resistance of a number of cotton cultivars to both wilt diseases, as measured by height of vascular browning, was similar to the known field performance of the cultivars. The use of vascular browning as an estimate of disease severity was therefore validated.

Estudo sobre o desenvolvimento de linhagens avançadas de algodoeiro (Gossypium hisrutum) com resistência múltipla a cinco doenças - murcha de Fusarium e de Verticillium, mancha-angular, ramulose e nematóides - revelou um processo acumulativo gerador de resultados expressivos, do ponto de vista agronômico, depois de decorridos 15 anos de trabalho. Baseado num esquema interativo compreendendo a eleição de linhagens apresentando resistência a uma ou mais dessas doenças e resseleção posterior dentro delas, o processo mostrou-se eficiente para aproveitar a variabilidade genética natural existente em genótipos estabilizados para outras características agronômicas e industriais. Tendência para estabelecimento de correlações positivas foi verificada apenas entre a resistência das plantas a nematóides e à mancha-angular. Por outro lado, a persistência de correlações negativas - principalmente entre a resistência a nematóides e à ramulose e entre esta e mancha-angular - mesmo nos materiais mais resistentes, indicou a possibilidade de perdas de resistência a algumas doenças se pressões excessivas de seleção forem realizadas para outras. | After 15 years of studies concerning the development of multiple resistance to five major diseases of cotton (Gossypium hirsutum) - Fusarium and Verticillium wilts, bacterial blight, ramulosis, and nematodes - in advanced lineages arising from the normal breeding program conduced in the State of Sao Paulo, Brazil, by Instituto Agronômico (IAC), it was revealed an accumulative process whose results were agronomically relevant. Based on an interactive scheme involving the selection of lineages exhibiting resistance to one or more of the considered diseases and posterior reselection within them, the process was shown to effectively exploit natural genetic variability existing in cotton genotypes stabilized for other agronomic and industrial traits. Tendency to the establishment of the positive correlation was observed only in the case of resistance to bacterial blight and nematodes. Otherwise, persistence of negative correlations, mainly resistance to nematodes x ramulosis and ramulosis x bacterial blight, even in the more resistant materials, indicated the possibility of resistance losses for certain diseases if excessive selection pressures are exerted for others.

Weed competition decreases cotton yield by more than 70; in Sudan. An experiment was carried out at Gezira Research Station Farm in 2002-03 season to evaluate the efficacy and selectiviy of Hadaf 24EC, Oxyfen 24EC and Eradicool 24EC (new formulations of Oxyfluorfen) and Proud (new formulation of Pendimethalin) for preemergence weed control in cotton. Cultivar Barac 67B was sown on ridges 80 cm apart and at interrow spacing of 50cm between holes. Hadaf, Oxyfen, Eradicool and Goal as standard, each at 0.12kg a.i./ fed and Proud and Stomp as standard, each at 0.6kg a.i./fed, weedwd and unweeded treatments were arranged in a randomized complete block design with 4 replicates. All products were tank mixed with Diuron at 0.2kg a.i./fed. Some herbicide treated plots were supplemented by hand weeding 4weeks after sowing. Weeded control given three hand weedings. Effect of treatments were assessed by counting total and individual weed species. Percent weed ground cover; man-hours required for supplementary weeding, weed biomass/m**, crop stand and yield were determined. All Oxyfluorfen formulations, irrespective of supplementary weeding, gave excellent control of grasses and good to poor control of broadleaved weeds. Proud and stomp displayed excellent control of grasses and satisfactory to poor control of broadleaved weeds. All products reduced weed ground cover, man-hours required for supplementary weeding and weed biomass. All herbicides out yielded, significantly, the unweeded control by over 54; and resulted in yield comparable to that of the weeded control and their standards Goal and stomp. The Pests and Diseases Committee recommended the following herbicides for control of pre-emergence weed in cotton:1- Hadaf 24 EC + Diuron 80 WP at (0.5 L + 0.25 kg/fed (0.12 + 0.2kg a.i./fed), 2- Oxyfen 24 EC + Diuron 80 WP at (0.5 L + 0.25 kg/fed (0.12 + 0.2kg a.i./fed), 3- Eradicool 24 EC + Diuron 80 WP at (0.5 L + 0.25 kg/fed (0.12 + 0.2kg a.i./fed), 4- Proud 50 EC + Diuron 80 WP at (0.6 + 0.2kg a.i./fed)

Transgenic plants are produced via Agrobacterium mediated transformation and other direct DNA transfer methods. A number of transgenes conferring resistance to insects, diseases and herbicide tolerance have been transferred into crop plants from a wide range of plant and bacterial systems. In the majority of the cases, the genes showing expression in transgenic plants are stably inherited into the progeny without detrimental effects on the recipient plant. More interestingly, transgenic plants under field conditions have also maintained increased levels of insect resistance. Now, transgenic crops occupy 44.2 million hectares on global basis. During the last 15 years, transformations have been produced in more than 100 plant species; notable examples include maize, wheat, soybean, tomato, potato, cotton, rice, etc. Amongst these herbicide tolerant and insect tolerant cotton, maize and soybean carrying Bacillus thuringiensis (Bt) genes are grown on a commercial scale. Genetic transformation and gene transfer are routine in many laboratories. However, isolation of useful genes and their expression to the desired level to control insect pests still involves considerable experimentation and resources. Developing pest resistant varieties by insertion of a few or single specific gene(s) is becoming an important component of breeding. Use of endotoxin genes such as Bt and plant derived genes (proteinase inhibitors) to the desired levels offers new opportunities to control insects and strategies involving combination of genes. Transgenic technology should be integrated in a total system approach for ecologically friendly and sustainable pest management. Issues related to Intellectual property rights, regulatory concerns, and public perceptions for release of transgenics need to be considered. Providing wealth of information on gene expression in higher plants by switching the gene on and off as and when required, makes gene manipulation a more direct process for genetic improvement of crops.

Using primary data from a survey of expert opinion, this paper identifies key successes emerging in African agriculture. Among these, major commodity-specific successes identified include breakthroughs in maize breeding across Africa, sustained gains in cassava breeding and successful combat of its disease and pests, control of the rinderpest livestock disease, booming horticultural and flower exports in East and Southern Africa and increased cotton production and exports in West Africa. Using a dynamic analytical framework, the paper attempts to identify key ingredients that appear necessary for building on these individual cases and expanding them into broad-based agricultural growth.Insights for the dynamics of successful change include:Private actors farmers and trading firms are central to the process of change. Changes in the internal asset base of private actors and in the external environment are equally important. From the multiplicity of responses, one can conclude that neither type of intervention is sufficient in isolation. Thus, farmers cannot benefit from improved market opportunities if they do not have the means to access knowledge about improved practices, or seeds, or other inputs. Conversely, farmers cannot benefit from greater resources for production without injections of technology and outlets for their surplus. The role of the public sector, as well as that of civil society and collective actors, in influencing the changes in both internal and external environments is critically important.Science-based technology, particularly productivity-enhancing, is a key driver of Africa.s agricultural growth. Certainly the success stories reviewed here overwhelmingly point to improved technology as the lynchpin of increased farm production and incomes. For this reason, recent declines in the funding for agricultural research by both African governments and donors threaten to stall agricultural advance. These success stories highlight the highly dynamic environment within which farmers, traders and agricultural policy makers operate. Rapidly mutating diseases, ever-adapting pests, climatic shocks, changing world market conditions and policy environments all contribute to continuously evolving pulsations, surges and shocks to Africa’s agricultural systems.These insights suggest that, where there is participation and individual motivation, where incentives are aligned with improved means to respond to incentives, and where technology plays a pivotal role, success may follow.