Very few studies have investigated interactions at the plant surface and cellular levels for infection of Brassica napus by Sclerotinia sclerotiorum. Garg et al. demonstrate for the first time that resistance results from retardation of pathogen development on and within host tissues, and the mechanisms include impeded fungal growth, suppressed formation of appresoria and infection cushions, extrusion of hyphal protoplast, reduced calcium oxalate and starch deposits, and a hypersensitive reaction.
The Phytophactor has a post on the appeal of Botany, and it’s something that needs saying. Plants are interesting, but your typical school student has little way of finding that out. He does point to a solution though, using plants in class to explore basic biology. In an era when Health & Safety and litigation are important factors in class planning, plants offer an opportunity to do science, rather than just watch someone else do it.
Previous phylogenetics studies of the monocot order Asparagales, although extensive and generally well supported, have left several sets of taxa unclearly placed and have not addressed all relationships within certain clades thoroughly. Kim et al. collect a totally new set of data for a large sampling of species and find that the results are highly similar to those of previous studies with sparser sampling. The data provide a robust framework for further studies on the family Ruscaceae (or subfamily Nolinoideae of Asparagaceae s.l.), which have been the subject of several recent controversies.
The exchange of photosynthetic intermediates between Kranz mesophyll and bundle sheath cells in C4 plants may be affected by low temperatures. Bilska and Sowiński study chilling-tolerant and chilling-sensitive varieties of Zea mays and find that low temperatures result in changes in the ultrastructure of plasmodesmata, which inhibit transfer of photosynthate to the phloem and hence export from the leaf. Closure of plasmodesmata appears to be related to the action of calreticulin; however, callose deposition is found to be a secondary effect of chilling.
Rice bean (Vigna umbellata) was domesticated in Southeast Asia and is a scientifically neglected crop with under-exploited potential. Isemura et al. compare its domestication QTLs with those of azuki bean (V. angularis) of East Asian origin. The inheritance of domestication-related traits is found to be so simple that a few major QTLs explain the phenotypic variation between cultivated and wild rice bean. Interchange of major QTLs between rice bean and azuki bean might be useful for broadening the genetic variation of both species.
The distribution of cytotypes on different spatial scales provides valuable insights into evolutionary processes of a polyploid complex. Sonnleitner et al. determine ploidy levels of more than 5000 individuals of Senecio carniolicus (Asteraceae) in the Eastern Alps and show that the three main cytotypes are either distributed allopatrically, probably resulting from Pleistocene range shifts, or, if co-occurring in mixed populations (44 of 100 populations studied), they are segregated spatially (altitude) and ecologically (exposition, vegetation cover).
I’m just writing a quick post here to point to another blog post at Vaviblog by Jeremy Cherfas on the recent paper Did backcrossing contribute to the origin of hybrid edible bananas?. Banana domestication revisited is well worth your time because the post connects de Langhe’s banana research to other domestication. In particular he connects it to research research in cassava published in New Phytologist as well as hooking it into older puzzles in banana domestication.
There’s been reaction in the blogosphere to an editorial in another journal by someone who has an aversion to bloggers. This post is a simple an elegant example of why we at Annals of Botany think science blogging matters. It adds context that we missed. Twice in my case, because my banana blog post didn’t reference the cassava research either.
Most genetic studies on the effects of water and salt stresses on seed germination have used conditions that are more extreme than those found in nature. Vallejo et al. apply relatively mild stresses to seeds of Arabidopsis thaliana accessions and find two loci associated with the salt sensitivity response and four associated with the osmotic sensitivity response, one of which only appears to act under mild stress. The regulation of germination under moderate salt and osmotic stresses involves the action of independent major loci, revealing the existence of loci specifically associated with the toxic component of salt and not just its osmotic effect.
Richard Mabey has a piece for his new book on weeds in the BBC’s Magazine. Mabey argues that weeds show the reslience of nature. Is Japanese Knotweed just “a plant whose virtues have not yet been discovered”.
Bananas and plantains (Musa spp.) provide a staple food for many millions of people living in the humid tropics. The genomic constitution of the diploids has been classified as AB, and that of the triploids as AAB or ABB; however, the morphology of many accessions is biased towards either the A or B phenotype and does not conform to predictions based on these genomic formulae. On the basis of published cytotypes, De Langhe et al. hypothesize that the evolution under domestication of cultivated banana hybrids is likely to have passed through an intermediate hybrid, which was then involved in a variety of backcrossing events. Such a complex origin of the cultivated banana hybrids would imply a reconsideration of current breeding strategies.