Índices para avaliar o estado de nitrogênio da batata multiplicada por distintos materiais propagativos

Melhoria na eficiência de aplicação do N pode ser conseguida pela sincronização da demanda da planta com o suprimento de N durante o ciclo da batateira. O objetivo do trabalho foi determinar os valores ótimos de índices relacionados com o estado de nitrogênio ao longo do ciclo da batata cultivada em ambiente protegido, utilizando distintos materiais propagativos, tubérculo-semente, minitubérculo e broto, comuns na produção de tubérculo-semente básica. Os índices, determinados na quarta folha e na mais velha, foram intensidade da cor verde, avaliada pelo índice SPAD e pela tabela de cor, e características agronômicas: comprimento, largura, área e número de folíolos. Foram realizados três experimentos em vaso, em casa de vegetação na Universidade Federal de Viçosa. Em cada experimento, instalado no delineamento de blocos ao acaso, com quatro repetições, foram utilizadas seis doses de nitrogênio (0; 25; 50; 100; 200 e 400 mg dm-3). Os índices foram determinados a cada 10 dias iniciando-se aos 20 dias após a emergência. Com cada material de propagação, o índice SPAD medido tanto na QF quanto na FV respondeu de forma diferenciada ao incremento na dose de N e atingiu os valores ótimos de 41,3; 40,5; 37,0; 35,8; 36,0; 31,9 e 29,8 dos 20 aos 80 DAE, respectivamente, ao ser utilizado o tubérculo-semente básica. Com todos os materiais de propagação, a idade da planta influencia significativamente todas as variáveis, exceto o número de hastes ou o número de folhas, quando é utilizado broto ou minitubérculo, respectivamente. O valor ótimo dos índices relacionados com a intensidade da cor das folhas e das características agronômicas da planta foram estabelecidos e variam com o material de propagação e idade da planta de batata

Genetic analysis of iron chlorosis tolerance in Prunus rootstocks

39 Pags., 4 Tabls., 4 Figs. The definitive version is available at: http://link.springer.com/journal/11295The high economic losses caused by the occurrence of iron chlorosis in Prunus orchards in the Mediterranean area justifies the implementation of breeding programs to generate high-performance rootstocks for different edaphoclimatic area conditions. For that reason, the genetic control of iron chlorosis tolerance was studied in an F1 population derived from a three-way interspecific cross between a Myrobalan plum (P 2175) and an almond × peach hybrid (Felinem). Several phenotypic measurements were assessed to guarantee an accurate data set for genetic analysis. SPAD (Soil and Plant Analyzer Development) values, chlorophyll concentration, and visual diagnostic symptoms were highly correlated with leaf chlorosis in trees. SPAD value was the most reliable measure, since it was an objective, unbiased, and non-destructive method. Two significant quantitative trait loci (QTLs) involved in SPAD and chlorophyll concentration were identified for Felinem in linkage groups 4 and 6. Both QTLs were detected in four of the six consecutive years of the experiment. For P 2175, two of the three putative QTLs identified, pspad4.1 and chl4.1, were placed in linkage group 4. These QTLs were related to the SPAD values and chlorophyll concentration, respectively, and co-localized with QTLs detected in the Felinem map affecting the same traits. Candidate gene PFIT, related to iron metabolism, was localized within the confidence interval of the QTL in linkage group 4. This research suggests an association of this chromosome region with tolerance to iron chlorosis in Prunus, and it provides a first approach to localize candidate genes involved in tolerance to this abiotic stress.This research was funded by MICINN (Spanish Ministry of Science and Innovation, AGL 2008-00283) and co-funded with a FEDER project and Gobierno de Aragón (A44). M.J. Gonzalo was the beneficiary of an I3P-PC2006 contract from the CSIC-FSE.Peer reviewe

Leaf senescence and N uptake parameters as selection traits for nitrogen efficiency of oilseed rape cultivars

The cultivation of N-efficient oilseed rape cultivars could contribute to a reduction of the large N balance surpluses of this crop. To facilitate the breeding process of N-efficient cultivars, the identification of secondary plant traits correlating with N efficiency is necessary. The objectives of this study were to investigate leaf senescence and N uptake parameters of oilseed rape cultivars and doubled haploid (DH) lines with contrasting N efficiency in a short-term nutrient solution experiment and to relate these results to their performance in field experiments. In the nutrient solution experiment, genotypes differed in leaf senescence of fully expanded leaves and maximum N uptake rate per unit root length under low N supply. A high maximum N uptake rate seemed to have contributed to delayed leaf senescence by enhancing N accumulation in leaves. Also in the field experiments, genotypes differed in leaf senescence after flowering at limiting N supply. Additionally, the most N-efficient DH line was able to adapt leaf photosynthetic capacity to the low-light conditions in the canopy during flowering. N efficiency (grain yield at limiting N supply) was positively correlated with delayed leaf senescence both in nutrient solution and field experiments. It is concluded that important leaf and root traits of N-efficient cultivars are expressed in short-term nutrient solution experiments, which may facilitate the selection of N-efficient cultivars