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Seed Loss (seed + loss)
Selected AbstractsPost-dispersal fate of seeds in the Monte desert of Argentina: patterns of germination in successive wet and dry yearsJOURNAL OF ECOLOGY, Issue 6 2000Luis Marone Summary 1,Patterns of seed germination of grass and forb species were studied in open Prosopis woodland of the central Monte desert (Argentina) during several years, to test the hypotheses that (i) seed germination is positively affected by both rainfall and protection afforded by vegetation cover (a facilitative effect), (ii) the number of surviving plants is positively influenced by rainfall but negatively affected by established vegetation (a competitive effect), and (iii) seed loss from soil banks owing to germination is lower than that caused by granivorous animals. 2,Forb species germinated during restricted periods, either in early autumn or in spring. Grasses, however, germinated throughout the growing season, but because seedlings could not be identified to species level, it was impossible to discern whether different species germinated in particular seasons, or if all grasses germinated in all seasons. Grass and forb germination were generally of similar magnitude, but grass germination increased by an order of magnitude during a summer of unusually abundant rainfall related to an El Niņo Southern Oscillation (ENSO) event. 3,Overall, the spatial distribution of neither germinating seeds nor surviving plants could be explained by interactions with established vegetation (facilitation and competition effects, respectively). An alternative explanation may be provided by the distribution of forb and grass seeds in the soil. 4,Seed loss owing to germination was low in both dry and rainy years. For forbs, such loss totalled <,1% of soil-seed reserves, and no forb species suffered losses >,4%. Total grass-seed loss to germination was usually <,0.5%, and the 5% reached in 1997,98 corresponded to an interruption of a prolonged drought by unusually abundant rainfall associated with a reduced seed bank. 5,Grass-seed loss caused by germination was one to two orders of magnitude lower than that reported due to autumn-winter granivory in the central Monte desert. [source] Identification of RAPD markers linked to recessive genes conferring siliqua shatter resistance in Brassica rapaPLANT BREEDING, Issue 6 2003O. Mongkolporn Abstract Shattering of siliquae causes significant seed loss in canola (Brassica napus) production worldwide. There is little genetic variation for resistance to shatter in canola and, hence, the trait has been studied in B. rapa. Previous studies have shown two randomly segregating recessive genes to be responsible for shatter resistance. Three random amplified polymorphic DNA markers were identified as being linked to shatter resistance using bulked segregant analysis in a F3B. rapa population. The population was derived from a cross between a shatter-susceptible Canadian cultivar and a shatter-resistant Indian line. Of the three markers, RAC-3900 and RX-71000 were linked to recessive sh1 and sh2 alleles, and SAC-201300 was linked to both dominant Sh1 and Sh2 alleles. The common marker for the dominant wild-type allele for the two loci was explained to have resulted from duplication of an original locus and the associated markers through chromosome duplication and rearrangements in the process of evolution of the modern B. rapa from its progenitor that had a lower number of chromosomes. Segregation data from double heterozygous F3 families, although limited, indicated the markers were not linked to each other and provided further evidence for the duplication hypothesis. [source] Farm-scale trials to compare the entomopathogenic fungus Beauveria bassiana with pirimiphos methyl + deltamethrin and essential oil of lemon grass for protection of stored cowpea against Callosobruchus maculatus (Coleoptera: Bruchidae)ANNALS OF APPLIED BIOLOGY, Issue 1 2007A.J. Cherry Abstract In trials conducted in Benin, conidia of Beauveria bassiana were evaluated as a control method against the cowpea weevil, Callosobruchus maculatus, in stored cowpea. In the first trial using a high artificial infestation of C. maculatus in 8-kg batches of cowpea in jerry cans under typical conditions, concentrations of 1 × 109 and 1 × 1011 conidia kg,1 were compared with lemon grass oil at 2 mL kg,1 and the synthetic pesticide mixture of 1.5% pirimiphos methyl + 0.05% deltamethrin at 0.5 g kg,1. After 2 months of storage, seed losses (SD) were 20.63 (5.3)% in the untreated control, 8.04 (3.2)% in the low-dose B. bassiana group, 3.12 (1.3)% in the high-dose B. bassiana group, 2.52 (0.4)% in the lemon grass oil group and 0% in the pirimiphos methyl + deltamethrin group. In a second trial with natural infestations in 50-kg batches of cowpea in 200-L drums, treatment with B. bassiana 1 × 1011 conidia kg,1 was compared with pirimiphos methyl + deltamethrin at 0.5 g kg,1. After 6 months of storage on six farms, losses reached 30.76 (1.5)% in the control, 1.28 (0.2)% in the pirimiphos methyl + deltamethrin group and 3.69 (0.6)% in the B. bassiana group. [source] | ||||||||||