Male Sterility Systems in Major Field Crops and Their Potential Role in Crop Improvement

Male sterility is a phenomenon where the male reproductive parts of the plants do not develop normally and fail to participate in sexual reproduction. The male sterility is of different kinds and can arise through a number of biological abnormalities. Among these, cytoplasmic nuclear male sterility has been extensively used by plant breeders to achieve breakthrough in the productivity of various field and horticultural crops through the development of hybrid cultivars. The impact of this technology is visible in crops like maize, rice, sorghum, pearl millet, etc., and this has helped in encountering the challenges of global food security. Among high-protein legumes, the world’s first hybrid was released recently with record 3–4 t/ ha of grain yield. This chapter briefly discusses the types of male sterility systems available in different crop species and their potential uses. Besides this, various methods of creating different male sterility systems are also described

Studies on Cytoplasmic Effects Using Iso-Nuclear Pigeonpea Lines

Two diverse cytoplasmic iso-nuclear pigeonpea lines, Pusa Ageti carrying cytoplasm of cultivated type Cajanus cajan cytoplasm, while ‘ICPA 2039’ carried the cytoplasm of a wild species Cajanus cajanifolius were used in the study. These were crossed as female parent with six known fertility restorers as male parents. The F1 hybrids were evaluated in replicated trials to study the effect of the two cytoplasm on yield and other traits. The data showed no significant effect on seed yield and other traits that could be attributed to the differences in the cytoplasm of the hybrids

Considerations for Breeding, Maintenance, and Utilization of TGMS Lines for a Two-Parent Hybrid System in Pigeonpea

Thermo-sensitive male sterility (TGMS) system has already proven its worth in rice. After China, it is now finding its roots in other rice growing countries. In pigeonpea, the first thermo-sensitive male sterility has now been reported, and this provides a good option to pigeonpea breeders for breeding high yielding hybrids. This will ease the process of seed production of male sterile (A-line) parent, because it will eliminate the need of maintainer (B-line) and more importantly, the pollinating insects. Besides this, for hybrid seed production it will not require the fertility restorer (R-line) also. To assist the pigeonpea breeders, this paper outlines salient feature of TGMS-based hybrid breeding technology (two parent hybrid breeding) such as breeding new hybrid parents, seed production, and identifying critical sterility and fertility points

Morpho-Biochemical Parameters Associated with Resistance to Pod Borer Complex of Pigeonpea

Host plant resistance is an important component for minimizing the losses due to the pod borer, Helicoverpa armigera and other pod borer complex. Among pod borer, which is the most devastating pest of pigeonpea. An understanding of different morphological and biochemical components of resistance is essential for developing strategies to breed for resistance to insect pests. morphological and biochemical components associated with expression of resistance to pod borer complex in Pigeonpea hybrids and cultivars to identify accessions with a diverse combination of characteristics associated with resistance to this pest. Among the genotypes ICPH 3461, ICPH 3762, BSMR 853, ICPL 332 WR, ICPH 2740, ENT 11 showed least preference for pod borer complex as compared to susceptible check ICPL 87. In context to morphological factors pod wall thickness, trichome density of type C and D on calyx and pod with correlation coefficient (r) (-0.508*), ( -0.717**, -0.748**), (-0.810**, -0.749**) exhibited a strong negative association with percent pod damage by pod borer complex. Among the biochemical factors protein, sugar content in pigeonpea seeds exhibited significant positive correlation with correlation coffecient (r) being (0.710**, 0.843**), respectively with percent pod damage by pod borer complex. Whereas, total phenols, tannins, total flavonoids present in seeds showed significant negative correlation with correlation coffecient (r) being (-0.729**, - 0.650**, -0.783**), respectively with percent pod damage by pod borer complex. Thus genotypes with maximum pod wall thickness, high non glandular trichome density and high phenol, tannins, flavonoids content in pigeonpea genotypes showed tolerance to pod borer complex

A Short-Cut Approach for Breeding Pigeonpea Hybrids With Tolerance to Biotic and Abiotic Stresses

Lack of stability associated with low productivity have remained key production constraints in pigeonpea for decades. In this paper, efforts have been made to address these two issues together by breeding high yielding pigeonpea hybrids carrying resistance/tolerance to some important biotic and abiotic stresses. In normal course, the selection of parental lines and breeding stress tolerant hybrids will take about 15 years. Therefore as an alternative, a short-cut hybrid breeding approach was designed and its salient features are discussed here. It is expected that by following this approach the crop losses caused by diseases, drought, and waterlogging can be reduced and at the same time, productivity can be enhanced through the exploitation of hybrid vigour

Traits that confer post-flowering drought tolerance in short duration pigeonpea

Pigeonpea (Cajanus cajan) is one of the most important legume crop, ranking fifth in importance among edible legumes globally. It is adversely affected by intermittent and terminal droughts. As grain yield under drought is heavily influenced by genotype × environment interactions, a trait-based selection had been considered more beneficial in drought tolerance breeding. The objective of this study is to identify putative traits that confer yield advantages under post-flowering drought stress. Fifteen super early and early genotypes including breeding and germplasm lines, as a subset of greater number of test genotypes were field evaluated for pre and post-harvest physiological and agronomical traits. Significant variation was observed, among the genotypes, for the traits normalized difference vegetation index (NDVI) and SPAD chlorophyll meter reading, measured at different days after sowing at the reproductive phase, shoot biomass productivity, and yield components. Genotype × drought treatment interactions were found to be meager, especially in super early lines. Grain yield under drought was closely associated with NDVI measured at podfilling stage (r=0.86***), shoot biomass at maturity, harvest index (HI) and yield components. Though the genotypic variation in SPAD chlorophyll reading was large, its correlation with grain yield under drought was not significant. NDVI, a high throughput measure, was found to be significantly correlated with the other putative traits such as shoot biomass (r=0.91***), HI, pod number m-2 and seed number m-2 and therefore, can be used as a proxy in identifying better drought tolerant lines in crop improvement for early and super early pigeonpea

Hybrid pigeonpea: Research to reality

Cytoplasmic and genetic male sterility based hybrids in field crops led to tremendous increase in productivity by exploiting the genetic principles of heterosis. Pigeonpea is an often-cross pollinated important grain legume in rainfed cropping systems, globally cultivated in 5 million hectares. The productivity in the crop is hovering around 800 kg/ha for the past 6 decades which is unacceptably low. The phenomenon of hybrid vigor was successfully exploited in the crop by identifying sources of male sterility from the wild relatives. It took three decades of research efforts to develop stable maintainers, complete restorers and heterotic hybrid combinations. The hybrids ICPH 2671, ICPH 2740 and ICPH 3762 were released for general cultivation by the farmers in different agroecoregions of India and a number of other hybrids are in the pipeline. Yield advantage of 30 to 40% (rainfed) and 50 to 60% (irrigated) was realized in farmers’ fields over the local varieties. Seed production technology was standardized by exploiting male sterility and entomophily thereby appreciable amounts of hybrid seeds were harvested from the seed parent. Conventional and genomic approaches are underway to identify candidate genes responsible for fertility restoration, elite parents with resistance to fusarium wilt and sterility mosaic disease and heterotic gene pools to breed adaptive hybrids for different niches across the globe

Multiomics approach unravels fertility transition in a pigeonpea line for a two‐line hybrid system

Pigeonpea [Cajanus cajan (L.) Millsp.] is a pulse crop cultivated in the semi-arid regions of Asia and Africa. It is a rich source of protein and capable of alleviating malnutrition, improving soil health and the livelihoods of small-holder farmers. Hybrid breeding has provided remarkable improvements for pigeonpea productivity, but owing to a tedious and costly seed production system, an alternative two-line hybrid technology is being explored. In this regard, an environmentsensitive male sterile line has been characterized as a thermosensitive male sterile line in pigeonpea precisely responding to day temperature. The male sterile and fertile anthers from five developmental stages were studied by integrating transcriptomics, proteomics and metabolomics supported by precise phenotyping and scanning electron microscopic study. Spatio-temporal analysis of anther\ud transcriptome and proteome revealed 17 repressed DEGs/DEPs in sterile anthers that play a critical role in normal cell wall morphogenesis and tapetal cell development. The male fertility to sterility transitionwasmainly due to a perturbation in auxin homeostasis, leading to impaired cellwallmodification and sugar transport. Limited nutrient utilization thus leads to microspore starvation in response to moderately elevated day temperature which could be restored with auxin-treatment in the male sterile line. Our findings outline a molecular mechanism that underpins fertility transition responses thereby providing a process-oriented two-line hybrid breeding framework for pigeonpea

Genetic Variability for Yield, Physiological and Quality Traits in Novel Super-Early Pigeonpea (Cajanus cajan (L.) Millsp.)

Super-early pigeonpea are novel genotypes that are reported to be photoperiod insensitive making it possible to grow it in non-traditional regions. Estimation of genetic parameters would be useful in developing appropriate selection and breeding strategies. A study was conducted to evaluate 37 super-early pigeonpea genotypes to access the magnitude of variability and to study heritable component of variation present in the yield, physiological and quality traits. The results revealed that traits leaf area duration between 60 DAS & maturity followed by leaf area & leaf area index at maturity, net assimilation between 60 DAS & maturity, leaf area index & leaf area at 60 DAS, leaf area duration between 60 DAS & maturity and plant height had high had higher PCV and GCV values. In general, phenotypic coefficients of variation (PCV) estimates were higher than genotypic coefficients of variation (GCV) estimates for all the characters under study, but the difference was relatively small indicating that these characters were less influenced by the environment and selection to improve those traits might be effective. High heritability combined with high genetic advance as a percent of mean was noted for all the traits except protein content conveying the governance of additive gene on trait expression. Anticipating these traits as selection index reaps competent improvement in yield, physiological and quality traits in early maturing pigeonpea