R2R3-MYB Transcription Factor NtMYB330 Regulates Proanthocyanidin Biosynthesis and Seed Germination in Tobacco (Nicotiana tabacum L.)

Proanthocyanidins (PAs) are important phenolic compounds and PA biosynthesis is regulated by a ternary MBW complex consisting of a R2R3-MYB regulator, a bHLH factor and a WDR protein. In this study, a tobacco R2R3-MYB factor NtMYB330 was characterized as the PA-specific regulator in which the PA biosynthesis was promoted in the flowers of NtMYB330-overexpressing lines while decreased in the flowers of ntmyb330 mutants. NtMYB330 can interact with flavonoid-related bHLH partner NtAn1b and WDR protein NtAn11-1, and the NtMYB330-NtAn1b complex is required to achieve strong transcriptional activation of the PA-related structural genes NtDFR1, NtANS1, NtLAR1 and NtANR1. Our data reveal that NtMYB330 regulates PA biosynthesis in seeds and affects seed germination, in which NtMYB330-overexpressing lines showed higher PA accumulations in seed coats and inhibited germination, while ntmyb330 mutants had reduced seed coat PAs and improved germination. NtMYB330 affects seed germination possibly through two mechanisms: modulating seed coat PAs to affect coat-imposed dormancy. In addition, NtMYB330 regulates the expressions of abscisic acid (ABA) and gibberellin acid (GA) signaling-related genes, affecting ABA-GA crosstalk and seed germination. This study reveals that NtMYB330 specifically regulates PA biosynthesis via formation of the MBW complex in tobacco flowers and affects germination through adjustment of PA concentrations and ABA/GA signaling in tobacco seeds.

Signatures of selection in recently domesticated macadamia

Macadamia is a high value nut crop that is recently domesticated, ideal for testing the effect of artificial selection. Here, we sequence the genome of Hawaiian cultivar ‘Kau’ and assemble into 794 Mb in 14 pseudo-chromosomes with 37,728 genes. Genome analysis reveals a whole-genome duplication event, occurred 46.8 million years ago. Gene expansions occurred in gene families involves in fatty acid biosynthesis. Gene duplication of MADS-Box transcription factors in proanthocyanidin biosynthesis are relevant for seed coat development. Genome re-sequencing of 112 accessions reveals the origin of Hawaiian cultivars from Mount Bauple in southeast Queensland in Australia. Selective sweeps are detected in macadamia cultivars, including genes involved in fatty acid biosynthesis, seed coat development, and heat stress response. Such strong effects of artificial selection in few generations reveals the genomic basis for ‘one-step operation’ for clonal crop domestication. The knowledge gained could accelerate domestication of new crops from wild species.

Genetic and QTL Analysis for Hilum-Eye Types in Cowpea (Vigna Unguiculata L. Walp)

Cowpea is an important food legume widely grown in the semi-arid tropics and serves as a main source of dietary protein, minerals, and vitamins. However, varieties differ from region to region based on the consumer’s preference for seed types determined by seed size, seed coat texture, seed color, and hilum-eye types. The genetics of seed size, seed color, and seed coat texture have been well documented, but the hilum-eye types have not been studied well because they represent seven different types with complex interactions. We studied the genetic segregation for hilum-eye types and determined the number of genes involved in a recombinant inbred line (RIL) population derived from a cross between a small eye parent ‘GEC’ and a Watson eye parent ‘IT98K-476-8’. The results demonstrated a three-gene model, W (Watson), S (small), and R (large), for cowpea seed hilum-eye type pattern and the interaction of these three genes, W, S, and R, resulted in five phenotypes, viz. self, Watson, small, large, and ring hilum-eye types. Moreover, we also mapped the RILs for hilum-eye types, identified three quantitative trait loci (QTLs), and aligned to the cowpea reference genome as QTL qHilum7.1, qHilum9.1, and qHilum10.1, corresponding to these three genes, Ring type (R), Watson type (W), and Small type (S) hilum-eye type patterns, respectively. Therefore, there was a complete agreement between the genetic analysis and QTL mapping for the number of genes controlling the hilum types in cowpea.

Seed Breaking Dormancy Technique and Growth of Screw Tree (Helicteres isora Linn.) seedlings

Screw tree is a shrub from family Malvaceae that has many benefits in pharmacy. Screw tree seed has very hard seed coat, so the seed must be treated before germination. The aim of this research was to assess the characteristic of fruit and seeds, effect of seed breaking dormancy, and effect of NPK fertilizer dosage on the growth of screw tree (Helicteres isora) seedlings. The results indicated that screw tree fruits belong to dry fruits with capsule form and has 5 follicles that has different direction. Screw tree seed is orthodox type that has 9 ̶ 36 seeds in one follicle with triangle and square shape. Germination technique in laboratory with soaking the seeds in hot water 100oC until the water cool for 48 hours treatment produced the best germination amounting to 65.0%. Germination technique in green house with soaking the seeds in hot water 100oC until the water cool for 24 hours treatment was the best germination amounting to 77.0%. Seedlings fertilized with 1 g NPK doses increased screw tree growth in diameter parameter of 6.35 mm and shoot-root ratio parameter of 3.9 compared to control.

Effect of Pre-sowing Treatments on Vegetative Growth and Production of Graftable Rootstocks in Mango

The present investigations “Studies on the effect of pre-sowing treatment and time of wedge grafting on production of saleable grafts in mango” were carried out in the nursery block of Fruit Science Department. The study was conducted using wild mangoes seeds. The seeds were divided in two equal halves, one half of seeds were sown with intact seed coat (K1) while, in other half the mango kernels were extracted (K2), both type of seeds were then soaked in 6 different chemicals of varying concentrations viz. C1- KNO3 @ 0.5%, C2- KNO3 @ 1%, C3- KNO3 @ 1.5%, C4- BA @ 50 ppm, C5- BA @ 100 ppm, C6- GA3 @ 100 ppm, C7- GA3 @ 200 ppm, C8- beejaaumrit @ 2%, C9- beejaaumrit @ 3%, C10- panchgavya @ 2%, C11- panchgavya @ 3% for 12 hours and C12- Control. The germination and vegetative parameters were observed. The results of study revealed that the e×tracted kernels pre-soaked with GA3 @ 100 ppm produced earliest germination, 50 % germination, high rate of germination, germination percentage, number of leaves, maximum leaf area, highest seedling vigour index, while, on pre-soaking extracted kernel with KNO3 @ 0.5% produced maximum seedling diameter. The Seedling raised from extracted kernels pre-soaked in KNO3 @ 0.5% (C1K2) attained graftable diameter within 210 days of sowing. The present investigation was conducted during 2019-2020 at the nursery block of College of Horticulture and Forestry, Neri Hamirpur (H.P) to study the effect of pre-sowing treatments on germination, growth and production of graft-able seedlings.

Seed Breaking Dormancy Technique and Growth of Screw Tree (Helicteres isora Linn.) Seedlings

Screw tree is a shrub from family Malvaceae that has many benefits in pharmacy. Screw tree seed has very hard seed coat, so the seed must be treated before germination. The aim of this research was to assess the characteristic of fruit and seeds, effect of seed breaking dormancy, and effect of NPK fertilizer dosage on the growth of screw tree (Helicteres isora) seedlings. The results indicated that screw tree fruits belong to dry fruits with capsule form and has 5 follicles that has different direction. Screw tree seed is orthodox type that has 9 ̶ 36 seeds in one follicle with triangle and square shape. Germination technique in laboratory with soaking the seeds in hot water 100oC until the water cool for 48 hours treatment produced the best germination amounting to 65.0%. Germination technique in green house with soaking the seeds in hot water 100oC until the water cool for 24 hours treatment was the best germination amounting to 77.0%. Seedlings fertilized with 1 g NPK doses increased screw tree growth in diameter parameter of 6.35 mm and shoot-root ratio parameter of 3.9 compared to control.

Seed Micromorphology of Eleven Species of Pleione (Orchidaceae)

The micromorphological characteristics of the seeds of 11 species of Pleione have been studied, both qualitatively and quantitatively, to establish whether they are useful for systematic studies of the genus. The quantitative characteristics include seed length (0.237–0.626 μm), seed width (0.053–0.133 μm), seed length/width ratio (2.631–7.279), seed ridge thickness (1.4 E-3–4 E-3μm) and seed volume (1.88 E-4–3.06 E-3 μm3). The cluster analysis result agrees well with the results of previous systematic studies. The cluster analysis shows that: P. coronaria, P. forrestii and P. yunnanensis form a group, while the remaining eight species form a second group, with three subgroups, namely: P. limprichtii, P. pleionoides, P. formosana as group I; P. hookeriana and P. bulbocodioides as group II; and P. praecox, P. scopulorum and P. maculata for group III. All the Pleione species of Sect. Pleione and Sect. Humiles show the fusion of adjacent seed coat cells into a network. The shape of the seeds of P. praecox and P. maculata are very similar--being oval, and the mesh walls of their adjacent seed coat cells are not fused. Within these sections no clear pattern can be seen between the species, but the addition of further species might clarify the differences between Sect. Pleione and Sect. Humiles.

Seed-coat thickness explains contrasting germination responses to smoke and heat by Leucadendron species

Fire stimulates germination of most seeds in fire-prone vegetation. Fruits of Leucadendron (Proteaceae) are winged achenes or nutlets that correlate with their requirements for smoke and/or heat in promoting germination. We describe five possible smoke–heat dormancy-release/germination syndromes among plants, of which Leucadendron displays three (no response, smoke only, smoke and heat). As seed-coat thickness varies with seed-storage location (plant or soil) and morphology (winged or wingless), we tested its possible role in water uptake and germination. Species with winged seeds achieved 100% germination in the absence of smoke/heat, seed coats were an order of magnitude thinner, and their permeability greatly exceeded that of nutlets. As seed-coat thickness increased a) imbibitional water uptake declined at a decreasing rate, and b) the response to smoke, and to a lesser extent heat, increased linearly to reach levels of germination approaching those of winged seeds. For species responsive to smoke and heat, there was no additive effect when applied together, suggesting that they may have promoted the same physiological process. By what mechanisms a) the smoke response is greater the thicker the seed coat, and b) smoke chemicals could increase water permeability to explain the non-additive effect of smoke and heat, warrant further investigation.