Establishment of a Standard Micropropagation Protocol for the Production of Uniform Planting Material in Musa Laterita (Section: Rhodochlamys).

Musa laterita is one of the dwarf statured, ornamental Musa species, which belongs to the section Rhodochlamys. It is immune to Sigatoka leaf spot and Fusarium wilt diseases and also exhibits tolerance to moisture deficit stress. Among the fungal diseases, fusarium wilt especially race TR4 is highly threatening the banana industry worldwide and hence the TR4 resistant gene should be identified on priority for use in banana improvement programmes. Though, it is a wild seeded type which can be easily propagated through seeds, the off springs are not genetically uniform making it unfit for any molecular analysis. In vitro micro propagation of ornamental banana including Musa laterita is limited due to poor multiplication rates compared to commercial cultivars. Therefore, the present study was undertaken to establish an in vitro protocol for plant regeneration from shoot tip explants. Efforts were made to enhance the multiplication efficiency using MS media fortified with BAP, TDZ, NAA, IAA and IBA in different combinations so as to obtain maximum numbers of plantlets in minimum duration. The plantlets produced would be used to study the molecular mechanism behind Fusarium wilt resistance (TR4), through transcriptome analysis.

Long-term Central Waikato summer-autumn rainfall and pasture growth trends. Are conditions for pasture growth changing over time?

Farmers in the upper North Island are concerned about the poor productivity of their perennial ryegrass pastures beyond 3 years and suggest this is linked to a trend towards drier conditions for pasture growth during summer and autumn. To explore how conditions for pasture growth and survival have changed, trends in rainfall (measured and interpolated; c. 1954 to 2020), frequency of soil moisture deficit stress on pasture growth (1972-2020), and pasture growth rates (simulated 1977-2020, and measured c. 1979-2020) were compiled for summer-autumn months (November to April) for two Waikato locations: DairyNZ Ruakura/Scott Farm near Hamilton; and a commercial farm at Paratu Road between Morrinsville and Matamata. Significant negative linear trends were observed for interpolated rainfall (Paratu Road only), total stress days (both sites) and simulated pasture growth (both sites). No significant trend in measured pasture growth was observed for either site, suggesting adaptive management has cushioned the physical effects of harsher climatic conditions. The suite of adaptive management practices adopted on the Paratu Road farm is described. Analysis of decadal patterns indicated greater variability in rainfall in the decade 2011-2020 (coefficient of variation ranging from 32% to 36% depending on site and data source, versus ~ 22% in earlier decades) and a significantly higher number of stress days in the decade 2011-2020 compared with the 1970s and 1980s at Paratu Road. Further adaptation strategies will be needed to mitigate these most-recent trends, should they continue as predicted by climate change forecasts.

Arbuscular Mycorrhizal Fungi Regulate Polyamine Homeostasis in Roots of Trifoliate Orange for Improved Adaptation to Soil Moisture Deficit Stress

Soil arbuscular mycorrhizal fungi (AMF) enhance the tolerance of plants against soil moisture deficit stress (SMDS), but the underlying mechanisms are still not fully understood. Polyamines (PAs) as low-molecular-weight, aliphatic polycations have strong roles in abiotic stress tolerance of plants. We aimed to investigate the effect of AMF (Funneliformis mosseae) inoculation on PAs, PA precursors, activities of PA synthases and degrading enzymes, and concentration of reactive oxygen species in the roots of trifoliate orange (Poncirus trifoliata) subjected to 15 days of SMDS. Leaf water potential and total chlorophyll levels were comparatively higher in AMF-inoculated than in non-AMF-treated plants exposed to SMDS. Mycorrhizal plants recorded a significantly higher concentration of precursors of PA synthesis such as L-ornithine, agmatine, and S-adenosyl methionine, besides higher putrescine and cadaverine and lower spermidine during the 15 days of SMDS. AMF colonization raised the PA synthase (arginine decarboxylase, ornithine decarboxylase, spermidine synthase, and spermine synthase) activities and PA-degrading enzymes (copper-containing diamine oxidase and FAD-containing polyamine oxidase) in response to SMDS. However, mycorrhizal plants showed a relatively lower degree of membrane lipid peroxidation, superoxide anion free radical, and hydrogen peroxide than non-mycorrhizal plants, whereas the difference between them increased linearly up to 15 days of SMDS. Our study concluded that AMF regulated PA homeostasis in roots of trifoliate orange to tolerate SMDS.

Efficiency of Endophytic bacterial culture on yield and yield attributes of groundnut

Field experiments were carried out for three consecutive years conducted during 2016, 2018 and 2019 during kharif season at Zonal Agricultural and Horticultural Research Station, Babbur farm, Hiriyur, Karnataka, India to study the alleviation of moisture-deficit stress in groundnut by application of endophytic bacteria under rainfed conditions. The experiment was laid out in randomized block design with three replication and eight treatments. The pooled results of three years revealed that treatment having DGREB-3 culture with intercultural operations significantly recorded higher pod yield (1022 kg ha-1) as compared to control (693 kg ha-1) and it is on par with any DGREB culture (T2) with two intercultural operations (909 kg ha-1). Any DGREB culture with two intercultural operations significantly recorded highest nodulations at 30 and 60 days (50.2 and 57.8) as compared to control (20.6 and 33.7). In case of higher gross returns (Rs. 46,565), net returns (Rs. 16,997) were recorded with DGREB-3 culture with intercultural operations. Whereas highest B:C (1.66) was recorded with any DGREB culture with two intercultural operations.

Mapping genomic regions of moisture deficit stress tolerance using backcross inbred lines in wheat (Triticum aestivum L.)

Identification of markers associated with major physiological and yield component traits under moisture deficit stress conditions in preferred donor lines paves the way for marker-assisted selection (MAS). In the present study, a set of 183 backcross inbred lines (BILs) derived from the cross HD2733/2*C306 were genotyped using 35K Axiom genotyping array and SSR markers. The multi-trait, multi-location field phenotyping of BILs was done at three locations covering two major wheat growing zones of India, north-western plains zone (NWPZ) and central zone (CZ) under varying moisture regimes. A linkage map was constructed using 705 SNPs and 86 SSR polymorphic markers. A total of 43 genomic regions and QTL × QTL epistatic interactions were identified for 14 physiological and yield component traits, including NDVI, chlorophyll content, CT, CL, PH, GWPS, TGW and GY. Chromosomes 2A, 5D, 5A and 4B harbors greater number of QTLs for these traits. Seven Stable QTLs were identified across environment for DH (QDh.iari_6D), GWPS (QGWPS.iari_5B), PH (QPh.iari_4B-2, QPh.iari_4B-3) and NDVI (QNdvi1.iari_5D, QNdvi3.iari_5A). Nine genomic regions identified carrying major QTLs for CL, NDVI, RWC, FLA, PH, TGW and biomass explaining 10.32–28.35% of the phenotypic variance. The co-segregation of QTLs of physiological traits with yield component traits indicate the pleiotropic effects and their usefulness in the breeding programme. Our findings will be useful in dissecting genetic nature and marker-assisted selection for moisture deficit stress tolerance in wheat.

Physiological traits reveal potential for identification of drought tolerant mungbean [Vigna radiata (L.) Wilczek] genotypes under moderate soil-moisture deficit

Canopy temperature is an important physiological trait used for screening drought tolerance in several crop plants. Mungbean being often exposed to post-flowering drought,we evaluated a set of 48 genotypes for variability in post-flowering canopy temperature and its association with root traits and other physiological parameters contributing to drought tolerance under soil-moisture deficit stress conditions. Overall, canopy temperature depression revealed significant association with seed yield. Root traits like number of lateral branches and dry root weight exhibited significant negative correlation with canopy temperature. Leaf SPAD readings were positively associated with grain yield and most of the high SPAD genotypes maintained hot canopies under drought. Some genotypes with contrasting variation in SPAD levels (DMG-1050 and SML-1628) maintained their photosystem PSII health at par. Moreover, cool canopy was no guarantee for better PSII health or vice versa. This study identified some cool canopy genotypes (VC-6173-C, IC-325770 and ML-2082) and a genotype (DMG-1050) with novel trait combinations like high SPAD and better PSII health despite high canopy temperature which can be used as donors in mungbean breeding programs. Present study explores genetic variation in these adaptation traits contributing to plant performance under soil-moisture deficit stress conditions and potential of physiological breeding approaches for genetic enhancement of this legume crop.