Principles of Plant Breeding

QTL analysis of kernel size and shape in two hexaploid wheat mapping populations

Durante o periodo de 1990/94, foi realizado um trabalho na area experimental do Departamento de Solos da Universidade Federal de Santa Maria (RS), num Argissolo Vermelho distrofico arenico, para avaliar o potencial de algumas plantas de cobertura de solo no fornecimento de N ao milho no sistema plantio direto. O delineamento experimental foi o de blocos ao acaso, com parcelas subdivididas e quatro repeticoes. Nas parcelas principais, foram utilizadas, em cada inverno, as leguminosas ervilhaca comum (Vicia sativa L.), ervilha forrageira (Pisum sativum var. arvense (L.) Poir), chicharo (Lathyrus sativus L.) e tremoco azul (Lupinus angustifolius L.), a graminea aveia preta (Avena strigosa Schieb.), alem de um tratamento com pousio invernal (plantas invasoras). Nas subparcelas, foram aplicadas as doses de 0, 80 e 160 kg ha-1 de N no milho, na forma de ureia. Na media dos quatro anos, as duas especies que produziram maior quantidade de materia seca pela parte aerea foram o tremoco azul (5.228 kg ha-1) e a aveia preta (4.417 kg ha-1), seguidas do chicharo (3.047 kg ha-1), ervilha forrageira (2.754 kg ha-1), ervilhaca comum (2.527 kg ha-1) e plantas invasoras do pousio invernal (1.197 kg ha-1). Dentre as leguminosas, a especie tremoco azul acumulou a maior quantidade de N na parte aerea (113,7 kg ha-1 de N). Os tratamentos que adicionaram menor quantidade de N ao solo pela fitomassa foram a aveia preta (41,7 kg ha-1 de N) e o pousio invernal (20,5 kg ha-1 de N). Aproximadamente, 60% do N acumulado na parte aerea das leguminosas foi liberado durante os primeiros 30 dias apos o seu manejo. Na ausencia de adubacao nitrogenada, o rendimento de graos de milho foi maior apos as leguminosas do que apos a aveia e o pousio invernal. As leguminosas diferiram entre si quanto ao potencial de fornecimento de N ao milho. Os maiores valores de equivalencia em N mineral (EqN) foram obtidos com a ervilhaca (137 kg ha-1 de N) e com o tremoco (122 kg ha-1 de N), evidenciando a possibilidade de reducao das quantidades de N mineral por aplicar no milho quando ele for cultivado em sucessao a estas duas leguminosas.

/pdf/plantas-de-cobertura-de-solo-como-fonte-de-nitrogenio-ao-2uorwro9fk.pdf

Plantas de cobertura de solo como fonte de nitrogênio ao milho

Rice is a model genome for cereal research, providing important information about genome structure and evolution. Retrotransposons are common components of grass genomes, showing activity at transcription, translation and integration levels. Their abundance and ability to transpose make them good potential markers. In this study, we used 2 multilocus PCR-based techniques that detect retrotransposon integration events in the genome: IRAP (inter-retrotransposon amplified polymorphism) and REMAP (retrotransposon-microsatellite amplified polymorphism). Markers derived fromTos17, a copia-like endogenous retrotransposon of rice, were used to identify genetic similarity among 51 rice cultivars (Oryza sativa L.). Genetic similarity analysis was performed by means of the Dice coefficient, and dendrograms were developed by using the average linkage distance method. A cophenetic correlation coefficient was also calculated. The clustering techniques revealed a good adjustment between matrices, with correlation coefficients of 0.74 and 0.80, or lower (0.21) but still significant, between IRAP and REMAP-based techniques. Consistent clusters were found for Japanese genotypes, while a subgroup clustered the irrigated Brazilian genotypes.

IRAP and REMAP assessments of genetic similarity in rice.

Maize (Zea mays L) is grown on 15 million ha in eastern and southern Africa Several diseases are of common occurrence in the region and regularly result in significant yield losses A collaborative regional disease nursery (REGNUR) project was initiated in 1998 to identify and increase access to disease resistant germplasm, generate and disseminate information on disease and insect resistance sources, and facilitate the development of resistant cultivars by project partners A diallel among 12 elite inbred lines was formed with the specific objective of evaluating the combining ability of these inbred lines for grain yield and resistance to seven diseases The trial was grown at six sites in 2001 Results showed that both general (GCA) and specific combining ability effects were significant for most diseases On the average, GCA accounted for 69% of resistance to diseases and only 37% of variation for grain yield Correlations between GCA effects for disease scores were generally non-significant, implying that it is possible to pyramid genes for disease resistance in inbred lines This underscores the need for screening for resistance to prevailing diseases using artificial inoculation or reliable hot-spots Based on GCA effects for grain yield and across diseases, P12 and P6 were the best inbred lines The crosses P4 × P9 (67 t ha−1) and P4 × P12 (69 t ha−1) were the best hybrids in the earlier maturity group, while P3 × P9 (83 t ha−1) and P2 × P8 (74 t ha−1) were the best hybrids in the late maturity group

Diallel analysis of grain yield and resistance to seven diseases of 12 African maize ( Zea mays L.) inbred lines

This study was aimed to characterize yield components and plant traits related to grain yield. Correlation and path analysis were carried out in wheat genotypes grown under irrigated and non-irrigated field conditions. In the path coefficient analysis, grain yield represented the dependent variable and the number of spikes m-2, number of grains spike-1, kernel weight, days to anthesis, above-ground biomass m-2 and plant height were the independent ones. In both years, periods without rain occurred from early milk to grain ripening and from flag leaf sheath opening to grain ripening for first and second sowing dates, respectively. Character associations were similar in both water regimes. Grain yield showed positive phenotypic correlation with above-ground biomass, number of spikes m-2 and number of grains per spike. Path analysis revealed positive direct effect and moderate correlation of number of spike m-2 and number of grains per spike with grain yield. These results indicated that the number of spikes m-2 and the number of grains per spike followed by the above-ground biomass were the traits related to higher grain yield, under irrigated and late season water stress conditions.

/pdf/correlation-and-path-analysis-of-yield-and-its-components-1796g3ijj1.pdf

Correlation and path analysis of yield and its components and plant traits in wheat

Genetic progress depends on germplasm quality and breeding methods. Twelve maize popu- lations and their crosses were evaluated to estimate combining ability and potential to be included as source populations in breeding programs. Plant height, point of insertion of the first ear, number of ears per plant, number of grains per ear, root and stalk lodging and grain yield were studied in two locations in Brazil, during the 1997/98 season. Genotype sum of squares was divided into general (GCA) and specific (SCA) combining ability. Results indicated the existence of genetic divergence for all traits analyzed, where additive effects were predominant. The high heterosis levels observed, mainly in Xanxere, suggested the environmental influence on the manifestation of this genetic phenomenon. Populations revealed potential to be used in breeding programs; however, those more intensively sub- mitted to selection could provide larger genetic progress, showing the importance of population im- provement for the increment of the heterosis in maize.

/pdf/combining-ability-of-twelve-maize-populations-1iarxsyjg3.pdf

Combining ability of twelve maize populations

The aim of the present study was to investigate the relationship between plant traits and yield per spike in wheat genotypes. The measured plant traits were: length of flag leaf blade, peduncle extrusion, peduncle, spike and sheath, culm diameter and plant height. Data were analyzed with correlation and path coefficient analysis. Yield per spike correlated positively with spike length and culm diameter. Path coefficient analysis indicated that, under irrigated condition, yield per spike had a positive direct effect and a positive correlation with spike length and culm diameter and, under non-irrigated condition, yield per spike showed a positive direct effect and a positive correlation with culm diameter, spike length and plant height. Culm diameter and spike length, under irrigated condition, and also plant height, under late season water stress condition, were the plant traits most related to higher grain yield per spike in wheat.

/pdf/plant-traits-to-complement-selection-based-on-yield-36buj7pepj.pdf

Plant traits to complement selection based on yield components in wheat

The oat (Avena sativa L.) cultivars cultivated in Southern Brazil up to the beginning of the 80's were introduced from Uruguay and Argentina. They presented adaptation problems to the new environment. Starting from the 70's, oat breeding programs began to produce their own segregant populations. These programs already released 35 cultivars. Aiming to estimate the genetic progress in oat breeding programs from southern Brazil, an experiment with 15 cultivars released in different times was conducted in two locations using four different cultural practices. The results indicated linear genetic progress for days to flowering, grain yield, grain weight and test weight. The non significance of quadratic effects suggested the possibility of additional gains through selection of new genotypes. The oat breeding programs in southern Brazil have been efficient in producing new cultivars with higher grain yield, good grain quality, and with superior agronomic traits. However, a maximum breeding plateau was not reached for this species.

/pdf/progresso-genetico-no-melhoramento-da-aveia-branca-no-sul-do-4x6q4xid61.pdf

Progresso genético no melhoramento da aveia-branca no Sul do Brasil

A selecao para tolerância ao aluminio e complicada pela desuniformidade natural dos solos e pela dificuldade de avaliar danos na raiz. Assim sendo, e importante desenvolver metodos eficientes de caracterizacao da tolerância ao aluminio em condicoes controladas de ambiente. O presente trabalho teve por objetivo adequar o metodo de solucao minima para a avaliacao da tolerância ao aluminio em genotipos de milho. O trabalho consistiu de dois experimentos. O primeiro foi feito para ajustar o metodo de avaliacao atraves do emprego de solucao minima, e o segundo, para avaliar um conjunto de 22 genotipos de milho fornecidos pela Empresa Agroeste Sementes Ltda. A avaliacao dos genotipos foi realizada com uma solucao que continha diferentes concentracoes de aluminio e calcio. As medias para todas as variaveis analisadas mostraram a diferenca entre os hibridos e entre as concentracoes de aluminio empregadas. As concentracoes de 6mg-1 de aluminio e 40mg-1 de calcio foram consideradas mais eficientes para a discriminacao da tolerância ao aluminio, sendo posteriormente empregadas para o trabalho com as linhagens. No segundo experimento, os resultados possibilitaram identificar linhagens com tolerância ao aluminio.

/pdf/tolerancia-ao-aluminio-em-plantulas-de-milho-3zd4ktv2pr.pdf

José Fernandes Barbosa Neto

Papers

Correlation and path analysis of yield and its components and plant traits in wheat

Combining ability of twelve maize populations

Plant traits to complement selection based on yield components in wheat

Progresso genético no melhoramento da aveia-branca no Sul do Brasil

Tolerância ao alumínio em plântulas de milho