Developmental abnormalities in the ovule and embryo sac of ulluco (Ullucus tuberosus) and their effect on seed set

Abstract

Ulluco (Ullucus tuberosus) is a vegetatively propagated crop plant that flowers abundantly but sets only few seeds . We examined if the low seed/ovule ratio can be explained by morphological abnormalities in ovules, embryo sacs or embryos . In 35 clones growing in the actual area of cultivation in Ecuador and in 5 clones grown in Finland flowers were analysed by clearing technique . About half of all analysed clones contained ovules and embryo sacs whose development was arrested, in two clones there were embryo sacs whose cell patterns were abnormal and in four clones there were double embryo sacs . There were both normal and abnormal ovules and embryo sacs in the same plant . Genetic load is suggested to be one of the causes for the low sexual fertility found in ulluco . It may be incapable of maintaining homeostasis of development of the ovule and embryo sac in a varying environment . The occurrence of developmental abnormalities should be studied in each clone intended for inclusion in traditional breeding programmes . 31

Fertilisation assessment and postzygotic development in several intra- and interspecific Prunus hybrids

“…Booth (Palser et al ., 1992) and Cunninghamia lanceolata (Liang & Herr, 1994) to describe the period from anthesis to fertilisation . While the technique has proven to be useful in different species (Pietila & Jokela, 1994 ;Tavoletti, 1994), the protocol has to be adapted to suit the peculiarities of each species. Another problem is that tannin deposits appear earlier than starch during ovule development in most angiosperms, starting in the chalazal end and spreading towards the micropylar end (Palser et al ., 1992) .…”

Genetic Diversity of Andean Tuber Crop Species in the in situ Microcenter of Huanuco, Peru

“…Furthermore, seed production in oca remains naturally limited because of a trimorphic system of genetic incompatibility in the case of oca (Gibbs, 1976; Trognitz et al, 1998). In the case of ulluco, morphological abnormalities in the ovules and embryo sacs, combined with genetic loads (somatic mutations, especially those affecting sexual reproduction, may have appeared and be maintained during hundreds generations of vegetative reproduction) are responsible for the low seed number (Pietilä and Jokela, 1994). Grau et al (2003) reported on mashua's capacity to exhibit both allo‐ and autogamy and a great botanical seed production has been reported for this species (Popenoe, 1989).…”

“…They are cultivated for their edible tubers in Andean farming systems of high altitudes (from 2500 to 4000 m above sea level; Cárdenas, 1989; Cadima Fuentes, 2006). Regarding the reproductive systems, fruit and seed production are marginal for oca and ulluco (Gibbs, 1976; Trognitz et al, 1998; Pietilä and Jokela, 1994), whereas mashua flowers profusely and sets many viable seeds with high germination rates (Grau et al, 2003). But under farming conditions, propagation of these three species is exclusively made through tubers, and botanical seed propagation by farmers has never been observed (Hernández Bermejo and León, 1992).…”