Luiz José Oliveira Tavares de Melo

Aplicação de técnicas multivariadas no estudo da divergência genética em cana-de-açúcar

Resumo - Estudos sobre divergencia genetica sao importantes na identificacao de genitores potenciais para a obtencao de novos individuos com maior efeito heterotico. Em cana-de-acucar esses estudos assumem fundamental importância, po is com o passar do tempo as variedades comerciais devem ser substituidas de suas areas de cultivo, devido a serios declinios agronomicos e industriais ocasionados pela degenerescencia varietal. Sendo assim, o objetivo deste trabalho foi avaliar a divergencia genetica em progenies de cana-de-acuca r, atraves de tecnicas multivariadas, com base em oito caracter es agroindustriais. O trabalho foi conduzido na area agricola da Usina Santa Tereza, municipio de Goiana (PE), durante o ano agricola 2007/2008. Foi utilizado o delineamento experimental casualizado em blocos completos com cinco repeticoes. As variaveis analisadas foram: toneladas de pol por hectare, toneladas de cana por hectare, fibra, pol % corrigida, pureza, teor de solidos soluveis, acucares redutores e acucar total recuperavel. Apos analise de variância e estimacao de parâ metros geneticos, a distância generalizada de Mahalanobis foi calculada para quantificar a dissimilaridad e. Foram utilizados o metodo hierarquico de ligacoes medias (UPGMA) e o metodo de otimizacao de Tocher. O coeficiente de herdabilidade media foi de alta magnitude para as variaveis TPH e TCH, indicando possibilidade de sucesso na selecao com base nesses caracteres. A metodologia aplicada permitiu a identificacao de progenies de maior divergencia genetica proporcionando ao fitomelhoramento canavieiro da RIDESA sugestao de cruzamentos a serem realizados futuramente. Palavras-chave - Cana-de-acucar. Hibridacao vegetal. Melhoramento genetico.This study aimed to evaluate the genetic diversity in progenies of sugar cane by means of multivariate techniques based on eight agroindustrial traits. The work was carried out in the agricultural area of Usina Santa Teresa, Goiana (PE), during the agricultural year 2007/2008. A complete randomized block design with five replications was used. The variables analyzed were: pol tons per hectare (PTH), sugarcane tons per hectare (STH), fiber (FB), corrected pol % (CPP), purity (PTY), content of soluble solids (BX), reducing sugar (RS) and total retrievable sugar (TRS). After analysis of variance and estimation of genetic parameters, the Mahalanobis distance was calculated for quantifying dissimilarity. We used average-linkage method (UPGMA) and the optimization method of Tocher. The average coefficient of heritability was high for the variables PTH and STH indicating the possibility of success in selection for these characters. The methodology allowed identification of progenies with greater genetic divergence providing information for RIDESA sugarcane plant breeding on crosses to be made in the future.

Desempenho agroindustrial de cultivares de cana-de-açúcar na zona da mata litoral sul de Pernambuco

The aim of this work was to evaluate the genetic variability of some characters of the plant and the agroindustrial performance of sugar cane cultivars. The experimental design was the complete randomized blocks with four replications and 16 cultivars, being four of them used as check varieties. The plots were formed by five furrows of 8.0 m length, spaced 1.0 m, characterizing a useful area of 40 m2. The variables evaluated were the tons of cane per hectare (TCH), tons of pol per hectare (TPH), pol in the cane (PC), % cane fiber (FIB), brix in the cane (BC) and purity in the cane (PUR). The TCH is the component most influenced by the harvest cycles of the sugar cane farming and the least expressive for the other studied characters. The variables TCH and TPH reflected most of the phenotypic variation observed due to genetic causes, indicating success in the selection for the improvement of these characters. The genotypes SP78-4764, SP86-0621, and SP86-127 demonstrated productive potential from the agroindustrial point of view. The effect of the cane cut cycle was highly significant, indicating specific behaviors among the cultivars during the cane harvest.

Avaliação agroindustrial e parâmetros genético de progênies de cana-de-açúcar em fase inicial na zona canavieira do Litoral Norte de Pernambuco

The objective of our research was to evaluate the agronomical, industrial performance and the magnitude of the genetic parameters of initial phase sugarcane progenies in the north coast of Pernambuco. Experimental works were developed during the agricultural year of 2006/2007 in the sugarcane plantation zone in the north coast of Pernambuco, in the district of Igarassu, in the area of the Sao Jose industrial plant. The experimental delineation was randomized blocks with five repetitions, using 24 genotypes as treatment (20 from the crossings and 4 standard varieties). The parcel was planted in three furrows of 6 m, spaced by 1.30 m with 10 seedlings per furrow (spaced by 0.6 m within the furrow), totalizing a total area of 23.4 m2. Harvest was done in the 10th month after the transplantation, where were evaluated the following variables: pol tons per hectare (PTH), sugarcane tons per hectare (STH), fiber (FB), corrected pol % (CPP), purity (PTY), brix (BX) and total retrievable sugar (TRS). The progenies of the crossings: RB855035 X RB72454; RB865230 X RB855035; Tuc71-7 X RB 72454 and RB 72454X Tuc71-7, overtopped for most of the studied variables. There is genetical variability among the progenies of the crossings for all the evaluated variables. The h2m estimations were expressive for the variables STH, PTH, CPP, FB, BX and TRS, indicating the possibility of success in the selection of these variables within the sugarcane plantation region of North Coast of Pernambuco.