Volatile metabolite profiling to detect and discriminate stem-end rot and anthracnose diseases of mango fruits

The volatile metabolites from the headspace gas of containerised mango ( Mangifera indica ) cv. Tommy Atkins fruits, surface wounded and inoculated with the two fungal anamorphic pathogens Colletotrichum gloeosporioides and Lasiodiplodia theobromae , or non-inoculated (controls), were profiled using a portable gas chromatograph/mass spectrometer to discriminate diseases of mango. Thirty-four compounds were detected relatively consistently among replicates. Several of these were disease/inoculation-discriminatory and were classified into three groups: (i) compounds unique to only one treatment; (ii) compounds common to two or more treatments, but not to all; and (iii) compounds common to all treatments, but varying in their abundance. Two compounds, 1-pentanol and ethyl boronate, were detected in L. theobromae- inoculated mangoes alone, while thujol was observed only in C. gloeosporioides- inoculated mangoes. Discriminant analysis models based on the abundance of significant mass ions and consistent compounds correctly classified diseases/inoculations in up to 100% of cases. The disease-discriminatory compounds and discriminant analysis models developed here have the potential to be used in the early detection of postharvest diseases of mango fruits after validation under commercial conditions.     

Enhanced grain yield in rice hybrids through complementation of fertility restoration by Rf3 and Rf4 genes as revealed by multilocation evaluation of tropical japonica derived rice (Oryza sativa) hybrids

Thirty-one tropical japonica derived Rf gene carrying rice hybrids were classified into three classes as Rf3, Rf4 and Rf3 + Rf4 hybrids. These hybrids were tested under three different mega-environments. Between Rf3 class and both the classes of hybrids possessing Rf4 genes, significant variation for spikelet and pollen fertility and grain yield was found. The pollen fertility was five times higher among Rf4 hybrids than that of hybrids carrying Rf3 alone. Likewise, spikelet fertility among Rf4 hybrids was two times higher than that of Rf3 hybrids. Parallel grain yield increase in Rf4 hybrids was 2.4 times than in Rf3 hybrids. However, Rf3 gene was found complementing Rf4 to truncate the range of pollen and spikelet fertility. Hybrids possessing Rf3 alone exhibited partial pollen and spikelet sterility, and significant negative standard heterosis for grain yield. The high yielding hybrid, “HYB36” carrying both the Rf genes was found to be widely adapted. The present study established that Rf4 gene is essential either alone or in combination with Rf3 for fertility restoration to achieve enhanced grain yield in WA-CMS based hybrids.     

Zooming in on microscopic flow by remotely detected MRI

Magnetic resonance imaging (MRI) can elucidate the interior structure of an optically opaque object in unparalleled detail but is ultimately limited by the need to enclose the object within a detection coil; acquiring the image with increasingly smaller pixels reduces the sensitivity, because each pixel occupies a proportionately smaller fraction of the detector's volume. We developed a technique that overcomes this limitation by means of remotely detected MRI. Images of fluids flowing in channel assemblies are encoded into the phase and intensity of the constituent molecules' nuclear magnetic resonance signals and then decoded by a volume-matched detector after the fluids flow out of the sample. In combination with compressive sampling, we thus obtain microscopic images of flow and velocity distributions ~10(6) times faster than is possible with conventional MRI on this hardware. Our results illustrate the facile integration of MRI with microfluidic assays and suggest generalizations to other systems involving microscopic flow.     

Characterization of released and elite genotypes of guar [Cyamopsis tetragonoloba (L.) Taub.] from India proves unrelated to geographical origin

Twenty-three released and elite genotypes of guar [Cyamopsis tetragonoloba (L.) Taub.] from different parts of India were subjected to morphological, biochemical and molecular characterization. The major objective was to study the extent of genetic variability amongst different genotypes of guar, their grouping and identification using combination of phenotypic, biochemical and molecular markers. Phenotypic characters revealed the presence of ample amount of variation in cotyledon size, root length, hypocotyl length, epicotyl length, pubescence, plant height, leaf margin, branching habit, growth habit, days to 50 % flowering, days to maturity, flower colour, pod size, number of pods per cluster and number of clusters per plant for all the 23 genotypes. Biochemical studies including peroxidase activity along with phenol, potassium hydroxide and gibberellic acid tests also produced significant variability among the genotypes. A total of 180 amplified bands were detected using 21 RAPD primers, out of which 178 were polymorphic. The genotypes revealed high genetic divergence with similarity indices ranged from 0.59 to 0.85. A clear relationship between genetic diversity and geographical location was not observed. Fingerprints generated in the present study, using morphological, biochemical and molecular markers, successfully categorize the different guar genotypes into various groups and also establish relatedness among them based on the genetic diversity. This work will help the breeders working in the country for crop improvement of guar in characterization, identification, determination of seed purity and parental selection.