Efeito do retardamento da secagem na qualidade fisiológica de sementes de milho

Corn seeds were harvested with 16% and 21% of moisture content and dryed for 0, 12, 24, 36, 48, 60, 72, 84, 96, 108, 120, 132, 144 and 156 hours after harvest to verify the effect of delaying desiccation on germination and vigor. The results pointed out that to obtain seed germination over 85%, seed drying may be retarded up to 84 hours when seeds were harvested with 21% of moisture content. The physiological quality of seeds decreased significantly when seed drying was retarded for more than 84 hours after harvesting seeds with high moisture content (21%). The physiological quality was not affected when seeds were harvested with low moisture content (16,0%) and desiccated up to 156 hours.Sementes de milho (Zea mays L.) híbrido, colhidas com 16% e 21% de umidade, foram submetidas ao retardamento da secagem, com o objetivo de verificar o seu efeito na qualidade fisiológica das sementes. A secagem da semente foi adiada por 0, 12, 24, 36, 48, 60, 72, 84, 96, 108, 120, 132, 144 e 156 horas, e a germinação e o vigor foram determinados imediatamente após a secagem. Os resultados indicam que as sementes colhidas com 21% de umidade podem ter sua secagem retardada até 84 horas. Acima de 84 horas foram observados decréscimos significativos na qualidade fisiológica da semente. Sementes colhidas com baixa umidade (16%) não foram afetadas em sua qualidade fisiológica quando secadas até 156 horas após a colheita

Efeito de diferentes graus de dano mecânico na qualidade fisiológica de sementes de sorgo

Twelve seed lots of sorghum (Sorghum bicolor L. Moench.), cultivar BR 303, with different degrees of mechanical damage were evaluated on germination and vigor test. The data of mechanical damage based upon fast green test, accelerating aging, cold test, speed of emergence and stand establishment. The experiment was conducted in Seed Laboratory Analysis of the Embrapa-Centro Nacional de Pesquisa de Milho e Sorgo (CNPMS), in Sete Lagoas, MG, Brazil. There were significantly decrease through regressions analysis on germination and vigor tests, when the seeds were damaged up to 5%; from 5% to 15% of damage the decrease was not significant. From 15% to 23% of damage, the germination and vigor declined 22.5% compared to the control. The immediate hazard effect of mechanical damages on physiological quality of sorghum seeds could be detected by several tests.Diversas amostras de sementes de sorgo (Sorghum bicolor L. Moench.), cultivar BR 303, com diferentes níveis de danos mecânicos, foram analisadas com o objetivo de determinar o efeito imediato de danos mecânicos sobre a qualidade fisiológica. Os percentuais de dano mecânico foram determinados pelo teste de verde rápido, e a qualidade fisiológica das sementes pelos testes degerminação, envelhecimento acelerado, teste de frio, índice de velocidade de emergência e população inicial de plântulas. O experimento foi conduzido no Laboratório de Análises de Sementes da Embrapa-Centro Nacional de Pesquisa de Milho e Sorgo (CNPMS), em Sete Lagoas, MG. Através da análise de regressão, verificou-se que houve redução significativa da germinação e do vigor quando as sementes apresentaram até 5% de dano; de 5% a 15% de dano a redução na qualidade fisiológica não foi significativa. Acima de 15% até 23% de dano a germinação e o vigor sofreram um decréscimo de 22,5%, em comparação com o controle. O efeito prejudicial imediato dos danos mecânicos sobre a qualidade fisiológica das sementes de sorgo pôde ser detectada pelos testes aplicados

Respostas heteróticas de acessos elites tropicais do Programa Latino Americano de Milho em cruzamento com testadores brasileiros

Little emphasis has been placed on identifying new sources of tropical maize germplasm that can be used in breeding programs. Additional information on the performance and heterotic classification of tropical germplasm is needed. This study was conducted to identify elite maize accessions from Latin America that could contribute to increase the level of heterosis with the best heterotic patterns of Brazil. Seventy-two elite accessions from the Latin American Maize Project (LAMP) were crossed with the testers BR 105 (flint kernel Suwan background) and BR 106 (dent kernel Tuxpeño background). The 72 crosses plus 9 checks were evaluated using a simple 9 × 9 lattice in four locations that represent one tropical region. The combined analysis showed highly significant differences among treatments for ear weight and the interaction treatment × location was also significant. With both testers better crosses for ear weight were identified in relation to the double cross BR 201 (commercial check). With the tester BR 105, the high parent heterosis ranged from --28% to 26%, the accessions SE 032 and PE 001 were selected for further work. With the tester BR 106, the high parent heterosis ranged from --35% to 17% and the accessions PE 011 and Pasco 14 were selected for further work. The selected accessions will be improved through recurrent selection schemes to increase yield and improve agronomic traits. Afterwards they can be exploited, within and between heterotic groups, to produce highly productive hybrid combinations, or used per se as improved maize varieties.Pouca ênfase tem sido dada na identificação de novas fontes de germoplama tropical que podem ser usadas em programas de melhoramento de milho. São necessárias informações adicionais sobre a performance e classificação heterótica de germoplasmas tropicais. O objetivo deste estudo foi identificar acessos elite originados do Programa Latino Americano de Milho (LAMP) que poderiam contribuir para aumentar o nível de heterose com padrões heteróticos do Brasil. Setenta e dois acessos elites do LAMP foram cruzados com os testadores BR 105 (padrão heterótico flint) e BR 106 (padrão heterótico dentado). Os setenta e dois testcrosses, resultantes de cada cruzamento, e nove testemunhas foram avaliados em quatro locais. Utilizou-se o delineamento em látice simples 9 × 9. A análise combinada mostrou diferença significativa entre tratamentos para o caráter peso de espigas sendo também significativa a interação tratamentos × locais. Foram identificados, com ambos os testadores, cruzamentos mais produtivos que o híbrido duplo BR 201 (testemunha comercial). Com a variedade BR 105, a heterose em relação ao pai superior variou de --28% a 26% e os acessos SE 032 e PE 001 foram selecionados para melhoramento. Com a variedade BR 106, a heterose em relação ao pai superior variou de --35% a 17% e os acesses PE 011 e Pasco 14 foram selecionados para posteriores trabalhos de melhoramento. Os acessos selecionados serão melhorados através de esquemas de seleção recorrente para produção e características agronômicas. Estes acessos podem ser explorados, dentro e entre os grupos heteróticos, para produzir combinações híbridas ou para serem usados como variedades melhoradas de milho

Pervasive gaps in Amazonian ecological research

Biodiversity loss is one of the main challenges of our time,1,2 and attempts to address it require a clear un derstanding of how ecological communities respond to environmental change across time and space.3,4 While the increasing availability of global databases on ecological communities has advanced our knowledge of biodiversity sensitivity to environmental changes,5–7 vast areas of the tropics remain understudied.8–11 In the American tropics, Amazonia stands out as the world’s most diverse rainforest and the primary source of Neotropical biodiversity,12 but it remains among the least known forests in America and is often underrepre sented in biodiversity databases.13–15 To worsen this situation, human-induced modifications16,17 may elim inate pieces of the Amazon’s biodiversity puzzle before we can use them to understand how ecological com munities are responding. To increase generalization and applicability of biodiversity knowledge,18,19 it is thus crucial to reduce biases in ecological research, particularly in regions projected to face the most pronounced environmental changes. We integrate ecological community metadata of 7,694 sampling sites for multiple or ganism groups in a machine learning model framework to map the research probability across the Brazilian Amazonia, while identifying the region’s vulnerability to environmental change. 15%–18% of the most ne glected areas in ecological research are expected to experience severe climate or land use changes by 2050. This means that unless we take immediate action, we will not be able to establish their current status, much less monitor how it is changing and what is being lostinfo:eu-repo/semantics/publishedVersio

Pervasive gaps in Amazonian ecological research

Biodiversity loss is one of the main challenges of our time,1,2 and attempts to address it require a clear understanding of how ecological communities respond to environmental change across time and space.3,4 While the increasing availability of global databases on ecological communities has advanced our knowledge of biodiversity sensitivity to environmental changes,5,6,7 vast areas of the tropics remain understudied.8,9,10,11 In the American tropics, Amazonia stands out as the world's most diverse rainforest and the primary source of Neotropical biodiversity,12 but it remains among the least known forests in America and is often underrepresented in biodiversity databases.13,14,15 To worsen this situation, human-induced modifications16,17 may eliminate pieces of the Amazon's biodiversity puzzle before we can use them to understand how ecological communities are responding. To increase generalization and applicability of biodiversity knowledge,18,19 it is thus crucial to reduce biases in ecological research, particularly in regions projected to face the most pronounced environmental changes. We integrate ecological community metadata of 7,694 sampling sites for multiple organism groups in a machine learning model framework to map the research probability across the Brazilian Amazonia, while identifying the region's vulnerability to environmental change. 15%–18% of the most neglected areas in ecological research are expected to experience severe climate or land use changes by 2050. This means that unless we take immediate action, we will not be able to establish their current status, much less monitor how it is changing and what is being lost

EVALUATION OF MAIZE LAND RACES ACCESSION COLLECTED IN THE CENTRAL REGION OF BRAZIL

The Brazilian maize germplasm collection is one of the greatest in the worldwith 3,816 accessions preserved in the Active Maize Germplasm Bank of Embrapa Maize andSorghum Research Center in Sete Lagoas, Minas Gerais, Brazil. One of the main reasons that difficult its use is the lack of information about this germplasm . To increase the amount and thequality of germplasm information, the Embrapa Maize and Sorghum Research Center has beendoing a continuous work to characterize and evaluate this maize collection. Within this scope,in 1984, it was published the first catalogue of maize germplasm with 26 descriptors of 282accessions. In 1986 it was initiated of the program “Latin American of Maize” ( LAMP ) tocharacterize and evaluate the maize germplasm. At that time, 1,715 accessions from Brazilwere characterized and evaluated using three geographic regions which resulted in the publicationof a catalogue. In 1996, a new LAMP program began ( LAMP II) with the objective ofcharacterizing and evaluating other maize germplasm not considered in the first stage. So , inthe 1988/89 season year was established in Sete Lagoas, Minas Gerais, one experiment using324 accessions of land race germplasm, mostly collected in central Brazil. The experimentaldesign was a 9x9 lattice with four trials and one check within blocks with two replications. Thehomogeneous groups were classified according to their endosperm type ( sweet, floury, pop,dent, semident, flint and semiflint). The dissimilarities among groups were determined using theEuclidean average distance method , according to the characteristics of male and femaleflowering, plant height, ear height, stalk and root lodging, final stand, prolificity, ear weight, andgrain weight. The results showed high phenotipic variation among accessions for all characteristics,and based on that, it was possible to select accessions to improve intrapopulation varieties andcomposites formation

AGRONOMICAL AND MOLECULAR EVALUATION OF ACCESSIONS FROM MAIZE CORE COLLECTION, SUBGROUP FLINT ENDOSPERM

The utilization efficiency of maize germplasm accessions that consist of a core collection can be incremented using molecular and morpho-agronomical characteristics, getting more detailed descriptions about these accessions. The objective of this work was to valorize maize core collection, sub-group endosperm flint of the Brazilian Agricultural Research Corporation (Embrapa), through the use of morphological descriptors and AFLP molecular markers. Fifty-eight accessions from the core collection were used, thirty-two morphoagronomical descriptors considered, and six AFLP primers combinations were tested to obtain the genetic patterns. The most contributions of morpho-agronomical variables for core collection genetic divergence were grain thousand weight (31.0%), ear height (21.7%) and ear weight (16.4%). The core collection principal component analysis was done with 14 morphoagronomical variables and indicated that variance accumulated by the first three components was 70.57%. The six primers AFLP combinations used in 58 accessions generated 207 bands, with 32.8 polymorphic bands average. Dendrograms of core collection showed similar general structure and did not indicate homogeneous group formation. The observed allele number average was 1.95, allele effective number average was 1.47 and the heterosigosity (h), (Nei’s index of genetic diversity) used for polymorphic information content evaluation was 0.28. Molecular characterization allowed valorization of each accession, indicating new information on the core collection genetic structure, and confirming high variability among accessions