Crown Morphology Relationships among Alfalfa Plant Introductions and Cultivars

Abstract

The alfalfa (Medicago sativa L.) crown is an important morphological structure because of its association with regrowth, yield, and persistence. The objectives of this research were to evaluate variability for crown morphological traits among 1067 plant introductions (P.I.s) and 110 North American cultivars, to determine the association between crown morphological traits and germplasm sources, and to compare the association between crown morphological traits and fall dormancy classes for North American alfalfa cultivars. The P.I.s and the cultivars were grown in separate field studies at Rosemount, MN, during 1989 and 1990, respectively. Plots consisted of one 3.5‐m‐long row for P.I.s, and one 1.8‐m‐long row for cultivars. They were seeded in May and the plants were dug in October. Plants were individually evaluated for crown depth, crown width, number of crown stems, crown stem width, and number of crown buds. Variation was observed among both P.I.s and North American cultivars for all crown traits. Discriminant analysis of crown traits was effective at separating germplasm sources from diverse geographic origins. The crown traits of germplasm sources from less diverse origins appeared similar. Discriminant analysis of crown traits separated highly dormant (fall dormancy = 1) cultivars more effectively than semi‐dormant and non‐dormant cultivars. Only number of crown buds had a meaningful correlation (−) with fall growth. Variation observed for crown traits among alfalfa germplasm sources indicated that selection for specific crown modifications could be effective.

Forage yield potential of alfalfa plants of varying crown size from old stands

“…When entries from both cultivars were analysed together, significant correlations were found in the second, third and total harvests of the clonal study (P < 0.01, P < 0.05 and P < 0.01, respectively; data not shown). However, even when correlation coefficients were significant, these values were of low magnitude (r < 0.7), making their biological significance doubtful (Smith et al 1991, Marquez-Ortiz et al 1996. A similar study involving alfalfa cultivar 'G636' (E. T. Bingham, unpublished data) did not find significant correlations between crown size and forage yield of clones.…”

“…The crown size of space-planted clones dug 16 months later showed a strong association (r > 0.7, P < 0.01) with DFY (Table 2). This is to be expected since crown width increases with an increase in crown size and, as a consequence, has the capacity to bear more shoots (Marquez-Ortiz et al 1996). However, the crown size of these clones could not be predicted based on the crown size of the parental plant from which they were derived, as these traits were poorly correlated (Table 2).…”

“…Therefore, the crown which gives rise to these shoots can play a major role in determining yield. In a study involving alfalfa plant introductions and cultivars, the highest positive correlation among crown characteristics was observed between crown width and the number of crown shoots (Marquez-Ortiz et al 1996). Busch and Davis (1969) evaluated crosses between creeping-rooted and noncreeping alfalfa and observed that crown and root weight were positively associated with most ofthe aerial charac-teristics.…”

Caracterização morfofisiológica de genótipos de cornichão (Lotus corniculatus L.)

“…Entre as populações do cv. São Gabriel, P37, P38, Alqueire e Corte mostraram hábito de crescimento mais prostrado que as demais, o que pode ser vantajoso sob pastejo, pois plantas mais prostradas apresentam suas gemas de crescimento próximas à superfície do solo e, portanto, estão mais protegidas da ação dos herbívoros (Nelson & Moser, 1994). A importância do hábito de crescimento para o cornichão foi confirmada no trabalho de Caroso et al (1981), por meio de avaliações sob cortes, no qual progênies e cultivares mais eretos foram menos persistentes.…”

“…Em cornichão, segundo Marquez-Ortiz et al (1996), alta produtividade e persistência podem estar associadas à morfologia da coroa, indicando maior ou menor vulnerabilidade a Tabela 2 -Estatura e hábito de crescimento de genótipos de Lotus corniculatus L. Tabela 4 -Características de folhas de genótipos de Lotus corniculatus L. Observou-se que todos os genótipos apresentaram hastes subterrâneas, que, apesar de não serem rizomas, são igualmente importantes para a persistência da planta, não como órgão armazenador de reservas, como os rizomas, mas como um local protegido, capaz de dar origem a novas hastes e, por fragmentação, a novos indivíduos. Essas hastes, por permanecerem abaixo da superfície do solo, mostraram-se aclorofiladas e deram origem a hastes aéreas, que diferiram dos rizomas, por serem mais delgadas e não possuírem folhas escamosas, razão pela qual não foram consideradas rizomas típicos.…”