Pigeonpea improvement: An amalgam of breeding and genomic research

In the past five decades, constant research has been directed towards yield improvement in pigeonpea resulting in the deployment of several commercially acceptable cultivars in India. Though, the genesis of hybrid technology, the biggest breakthrough, enigma of stagnant productivity still remains unsolved. To sort this productivity disparity, genomic research along with conventional breeding was successfully initiated at ICRISAT. It endowed ample genomic resource providing insight in the pigeonpea genome combating production constraints in a precise and speedy manner. The availability of the draft genome sequence with a large‐scale marker resource, oriented the research towards trait mapping for flowering time, determinacy, fertility restoration, yield attributing traits and photo‐insensitivity. Defined core and mini‐core collection, still eased the pigeonpea breeding being accessible for existing genetic diversity and developing stress resistance. Modern genomic tools like next‐generation sequencing, genome‐wide selection helping in the appraisal of selection efficiency is leading towards next‐generation breeding, an awaited milestone in pigeonpea genetic enhancement. This paper emphasizes the ongoing genetic improvement in pigeonpea with an amalgam of conventional breeding as well as genomic research.     

Comparative analysis of diversity based on morpho-agronomic traits and microsatellite markers in common bean

Morpho-agronomic traits and microsatellite markers were used to survey genetic diversity in 115 common bean genotypes that included 70 Indian landraces, 24 released varieties and 21 exotic accessions. Twelve morpho-agronomic traits, namely, days to 50% flowering, leaflet length, leaflet width, pod length, pod width, number of pods per plant, days to maturity, seed length, seed width, number of seeds per pod, 100 seed weight and seed yield per plant were studied. Field data of two consecutive years were subjected to multivariate analysis as proposed by Mahalanobis’s D²-statistics, Tochers method of clustering and combined analysis of variance. Seventeen microsatellite markers were also used to examine genetic diversity at molecular level that showed polymorphic information content (PIC) in the range of 0.00–0.684. Dendrograms based on Euclidean distances and UPGMA analysis showed the presence of majority of released varieties into single cluster, which pointed toward their low genetic base in comparison to indigenous landraces and exotic germplasm. Significant correlation existed between morphological genetic distance and microsatellite genetic distance tested by Mantel test (r = 0.876).     

Suitability of mapped sequence tagged microsatellite site markers for establishing distinctness, uniformity and stability in aromatic rice

At present, testing for distinctness, uniformity and stability (DUS) of crop varieties relies on a set of morphological characters. These characters suffer fromthe limitations of number, interaction with the environment in which the variety grows and subjectivity in decision-making. The potential of DNA-based markers such as sequence tagged microsatellite site (STMS), for establishing DUS merits investigation. In the present study, a set of 55 mapped STMS markers, selected from 12 linkage groups of rice genome, was used to examine distinctness of 23 aromatic rice genotypes including the commercially important Basmati varieties. Forty-one of these markers (74.5%) showed polymorphism between the varieties. The number of alleles per locus ranged from 2–4 with an average of 2.3. The polymorphism information content (PIC) of the markers varied from 0.083 to 0.665 with an average of 0.338. All the varieties could be differentiated from each other at a low probability (0.07×10^-13) of identical match by chance. The marker-based clustering of the varieties corresponded with the known phenotypic classification, thereby providing confidence in the distinctness established by the mapped STMS markers. The utility of these markers to study uniformity and stability was analysed using a commercially important crossbred Basmati rice variety Pusa Basmati 1(IET-10364) that contributes about 40–50% of Basmati rice export from India. Genotyping of twenty individual plants, grown from the nucleus, breeder, foundation, certified and farmer's saved seed samples using all the 55 markers revealed no variation among the plants. These observations suggested that the set of mapped markers employed in this study could be further used for establishing distinctness of aromatic rice varieties and for studying DUS of the important commercial variety Pusa Basmati 1. This revised version was published online in July 2006 with corrections to the Cover Date.     

Fusarium wilt of chickpea: physiological specialization, genetics of resistance and resistance gene tagging

Chickpea wilt caused by Fusarium oxysporum f. sp. ciceris is one of the major yield limiting factors in chickpea. The disease causes 10–90% yield losses annually in chickpea. Eight physiological races of the pathogen (0, 1A, 1B/C, 2, 3, 4, 5 and 6) are reported so far whereas additional races are suspected from India. The distribution pattern of these races in different parts of the world indicates regional specificity for their occurrence leading to the perception that F. oxysporum f. sp. ciceris evolved independently in different regions. Pathogen isolates also exhibit differences in disease symptoms. Races 0 and 1B/C cause yellowing syndrome whereas 1A, 2, 3, 4, 5 and 6 lead to wilting syndrome. Genetics of resistance to two races (1B/C and 6) is yet to be determined, however, for other races resistance is governed either by monogenes or oligogenes. The individual genes of oligogenic resistance mechanism delay onset of disease symptoms, a phenomenon called as late wilting. Slow wilting, i.e., slow development of disease after onset of disease symptoms also occurs in reaction to pathogen; however, its genetics are not known. Mapping of wilt resistance genes in chickpea is difficult because of minimal polymorphism; however, it has been facilitated to great extent by the development of sequence tagged microsatellite site (STMS) markers that have revealed significant interspecific and intraspecific polymorphism. Markers linked to six genes governing resistance to six races (0, 1A, 2, 3, 4 and 5) of the pathogen have been identified and their position on chickpea linkage maps elucidated. These genes lie in two separate clusters on two different chickpea linkage groups. While the gene for resistance to race 0 is situated on LG 5 of Winter et al. (Theoretical and Applied Genetics 101:1155–1163, 2000) those governing resistance to races 1A, 2, 3, 4 and 5 spanned a region of 8.2 cM on LG 2. The cluster of five resistance genes was further subdivided into two sub clusters of 2.8 cM and 2.0 cM, respectively. Map-based cloning can be used to isolate the six genes mapped so far; however, the region containing these genes needs additional markers to facilitate their isolation. Cloning of wilt resistance genes is desirable to study their evolution, mechanisms of resistance and their exploitation in wilt resistance breeding and wilt management.     

Widening the gene pool of cultivated lentils through introgression of alien chromatin from wild Lens subspecies

Wild Lens species/subspecies are a potential source for increasing genetic diversity in cultivated lentil. Four intraspecific crosses were attempted between cultivated and wild lentils. Viable hybrids were produced between L. culinaris ssp. culinaris × L. culinaris ssp. orientalis and L. culinaris ssp. culinaris × L. culinaris ssp. odomensis. Normal meiosis and pollen fertility were observed in the first set of crosses, whereas chromosomal abnormalities and reduced pollen fertility were observed in the second set of crosses. These crosses were also studied for some quantitative traits. The range, mean and coefficient of variation were calculated in parents, F₁, F₂ and BC₁ generations to determine the extent of variability generated in the cultivated lentil through introgression of genes from wild lentil. The cultivated lentil × L. culinaris ssp. orientalis crosses showed substantially higher variability for all the traits than crosses involving cultivated lentil ×L. culinaris ssp. odomensis. The results of the present study indicated that these wild subspecies can be exploited for breeding purposes and their variation can easily be utilized to widen the genetic base of the cultivated lentil.     

Wild relatives of sorghum as sources of resistance to sorghum shoot fly, Atherigona soccata

The levels of resistance to shoot fly, Atherigona soccata in sorghum germplasm are low to moderate and therefore, we evaluated 17 wild relatives of sorghum under field and greenhouse conditions as an alternate source of genes for resistance to this pest. Thirty-two accessions belonging to Parasorghum , Stiposorghum and Heterosorghum did not suffer any shoot fly damage under multi-choice conditions in the field, while one accession each of Heterosorghum ( Sorghum laxiflorum ) and Chaetosorghum ( S. macrospermum ) suffered very low shoot fly damage. Accessions belonging to S. exstans (TRC 243601), S. stipoideum (TRC 243399) and S. matarankense (TRC 243576) showed absolute non-preference for oviposition under no-choice conditions. Accessions belonging to Heterosorghum , Parasorghum and Stiposorghum were preferred for oviposition, but suffered low deadheart formation. Manual infestation of seedlings with shoot fly eggs did not result in deadheart formation in some of the accessions belonging to S. exstans (TRC 243601), S. stipoideum (TRC 243399), S. matarankense (TRC 243576) and S. purpureosericeum (IS 18944). Larval mortality was recorded in main stems of the Parasorghums . Within section Sorghum , accessions belonging to S. bicolor ssp. verticilliflorum were highly susceptible to shoot fly, as were those of S. halepense . However, a few accessions such as IS 18226 (race arundinaceum ) and IS 14212 ( S. halepense ) resulted in reduced survival and fecundity. Wild relatives of sorghum exhibited very high levels of antibiosis to A. soccata , while only low levels of antibiosis have been observed in the cultivated germplasm. Therefore, wild relatives with different mechanisms of resistance can be used as a source of alternate genes to increase the levels and diversify the basis of resistance to shoot fly, A. soccata .     

Status and consolidated list of threatened medicinal plants of India

A wide array of medicinal plants in India, primarily used by locals for health care, have found wide acceptance and adoption globally (either directly or processed) due to distinct advantages of good results, low or no side-effects and ease of access to general public. Indigenous and traditional systems of medicine in practice since historical times have shown potential (direct or indirect as immune-boosters) against many dreaded ailments including the recent global pandemic of COVID-19. With prediction of sixth mass extinction, there is worldwide concern as majority of these plants, collected from natural stands, are also facing threat of extinction. Since 1990s concerted efforts have been directed towards assessment of threat status, the basic requirement for prioritizing conservation activity to various species of plants and animals. In literature there is staggered information regarding list of threatened plants, including medicinal plants of India, compiled at either state level or national or international level. Analysis of these publications led to collation of a consolidated list of 84 species and the same is presented here. A brief account of conservation efforts in India at national level and supportive policy framework is also included. This compilation is aimed to serve as a comprehensive reference especially for beginners, researchers, conservationists, foresters, pharmaceutical professionals as well as policy makers.

     

Comparison of two ground-based active-optical sensors for in-season estimation of corn (Zea mays,L.) yield

Thirty field experiments were conducted in North Dakota during 2011 and 2012 to compare two ground-based active-optical sensors for their relationship between sensor readings and INSEY (in-season estimate of yield). The experimental design at each site was a randomized complete block with four replications and six nitrogen (N) rate treatments: control, 45, 90, 134, 179, and 224 kg ha^?1 applied pre-plant as ammonium nitrate within five days of planting. The two sensors, GreenSeeker® (Trimble, Sunnydale, CA, USA) (GS) and Crop Circle ACS 470® sensor (Holland Scientific, Lincoln, NE, USA) (CC) were used to scan over the top of the corn at V6 and V12 growth stages. The GS INSEY and the CC INSEY were similarly related to corn yield at V6. The CC using the red-edge lens option improved the INSEY relationship to corn yield compared to the GS or the CC using the red lens option at V12.     

Amendment of Sugar Mill Wastewater Irrigation on Soil Biohydrological Properties and Yield of Vigna umguiculata L. Walp in Two Seasons

A field experiment was conducted to study the biohydrological properties of soil and yield of Vigna unguiculata L. Walp irrigated with five concentrations of sugar mill wastewater (SMW) during the Kharif and Zaid seasons. Among various concentrations of SMW, irrigation with 100% SMW significantly (P < 0.001) increased zinc (Zn), copper (Cu), cadmium (C), nickel (Ni), chromium (Cr), and iron (Fe) of the soil, while decreased total bacteria, fungi, actinomycetes, yeast, and rhizobia of the soil in both the cultivated seasons. However, the values of these metals were below the recommended permissible limit except Cd. Enrichment factor (Ef) of various heavy metals for soil was in the order Ni > Cr > Cd > Zn > Cu after irrigation with SMW. The crop yield of V. unguiculata was found to be inversely proportional to concentrations of SMW, with the best results being obtained at 50% SMW concentrations after 90 days of irrigation in both the cultivated seasons.     

Influence of staggered sown Spring sunflower (Helianthus Annuus L.) at varying intra–row spacing and applied–N on pre– and post–anthesis N dynamics and dry matter partitioning in Indo–Gangetic Plains Region

In current study, dry–matter accumulation (DMA), pre– and post–anthesis nitrogen (N) accumulation, N translocation (NT) and dry–matter partitioning by sunflower seeds was investigated under three sowing dates (January 20, February 10 & March 2), two intra–row spacings (30 & 24 cm) and four nitrogen doses (0, 45, 60 & 75 kg ha^–1) in two alluvial soils. Early sowing resulted in higher DMA and NT; leading to higher nitrogen use efficiency (NUE) that could be associated with higher pre–anthesis N accumulation. The closer intra–row spacing resulted in higher DMA by all plant parts except seed. Each graded N dose improved DMA, but improvement in dry–matter partitioning to seed was significant up to 60 and 75 kg N ha^–1 during 2014 and 2015, respectively owing to higher NT under respective treatments. NUE was highest at 60 kg N ha^–1 during both years.