Avaliação da resistência à antracnose em germoplasma de Lupinus spp.

Abstract

R E S U M OUma das principais limitações à cultura de tremoceiros (pertencentes a várias espécies de Lupinus) em diversas partes do mundo resulta da sua suscetibilidade à antracnose, uma doença causada pelo fungo Colletotrichum lupini. Ao afetar o caule principal, esta doença pode causar a morte da planta, levando a perdas de produção frequentemente elevadas. A doença foi reportada apenas recentemente e a reduzida variabilidade genética do seu agente causal sugere uma origem recente do fungo. Pelo contrário, a grande riqueza genética encontrada no germoplasma de diversas espécies de Lupinus, algumas das quais tendo o território português como parte significativa da sua área de distribuição natural, impele estudos com vista à caracterização do grau de resistência a esta doença em acessos desse germoplasma. Após análise duma coleção de germoplasma contendo 51 acessos de Lupinus albus, 46 de L. angustifolius, 19 de L. luteus e 10 de L. mutabilis, através de inoculações em condições artificiais, foi identificado germoplasma de L. albus e de L. angustifolius com níveis promissores de resistência, respetivamente em variedades tradicionais e em germoplasma espontâneo português. O estudo do efeito da doença nos componentes da produção, em condições de campo, revelou que o número de vagens por infrutescência foi o componente da produção mais afetado, ilustrando um elevado aborto floral atribuído à doença. Estes resultados permitem uma utilização mais informada do germoplasma das espécies de Lupinus estudadas nos respetivos programas de melhoramento de plantas. Palavras-chave: tremoceiro; Lupinus; Colletotrichum lupini; Colletotrichum acutatum; antracnose. A B S T R A C TAnthracnose, caused by the fungus Colletotrichum lupini, is one of the main limitations to the cultivation of several lupin species in different parts of the world. Affecting the main stem, this disease may cause plant death, leading to frequently high yield losses. This disease was reported only recently and the narrow genetic diversity of its pathogen suggests a recent origin for this fungus. On the contrary, the vast genetic richness found in the germplasm of diverse Lupinus species, some of them having the Portuguese territory as important component of their natural distribution areas, call for the study targeting the characterisation of disease resistance in such germplasm accessions. The analysis of a germplasm collection comprising 51 Lupinus albus, 46 L. angustifolius, 19 L. luteus and 10 L. mutabilis accessions using artificial inoculation conditions pointed out L. albus and L. angustifolius accessions with promising levels of resistance, on Portuguese landraces and wild germplasm respectively. Under field conditions, the effect of the disease on yield components affected mostly the number of pods per pod set, suggesting a high flower abortion due to the disease. These results enable a more informed use of the germplasm of these Lupinus species on the respective breeding programmes.

Response to Anthracnose in a Tarwi (Lupinus mutabilis) Collection Is Influenced by Anthocyanin Pigmentation

“…According to our scale used to classify severity, several L. mutabilis accessions presented significantly lower disease levels that other accessions. Present results differ from previous studies [2,18,19], where L. mutabilis accessions were generally found as susceptible. These differences are clearly related with anthocyanin pigmentation, criterion used to define the accessions to be integrated in the assays.…”

“…Ten Lupinus mutabilis accessions were evaluated for anthracnose response using six L. albus accessions as reference [2]. All accessions were inoculated with Colletotricum lupini and the first symptoms appeared from seven days after inoculation.…”

“…Typical disease symptoms include twisting of stems, petioles and pods with necroses, in the centre Plants 2020, 9, 583 2 of 12 of which arise acervuli. When ripe, acervuli produce conidia aggregates in mucilaginous masses of orange colour [2]. Tissues above the infection area may thus collapse, leading to plant death if the infection occurs on the main stem in early stages of the plant life cycle, compromising the crop.…”

“…Besides the narrow genetic diversity typical of a recently domesticated species with no known wild specimens [4,5], the main challenges for selecting genotypes suitable for cultivation in different parts of the world are yield, yield stability and growth habit adaptable to the climatic conditions in each region [6]. Tarwi is generally regarded as susceptible to anthracnose [2] and anthracnose is considered the most important disease of this crop [7].…”

“…Anthocyanin present in rice increased the resistance against the rice blast pathogen, Magnaporthe grisea [14]. In Lupinus, cases of resistance to Colletotrichum lupini were identified in some genotypes of Lupinus angustifolius and L. albus [2,15]. Thenceforth, these materials have been used as a source of resistance in breeding programs for these species.…”