agronomy Review An Overview of the Bionomics, Host Plant Resistance and Molecular Perspectives of Sesamia inferens Walker in Cereals and Millets Niranjanadevi Jeevanandham 1, Nalini Ramiah 2, Vanniarajan Chockalingam 3 and Ramalingam Jegadeesan 1,* 1 Department of Biotechnology, Center for Excellence in Innovations, Agricultural College & Research Institute, Tamil Nadu Agricultural University, Madurai 625 104, India; [email protected] 2 Department of Agricultural Entomology, Agricultural College & Research Institute, Tamil Nadu Agricultural University, Kudumiyanmalai 622 104, India; [email protected] 3 Department of Plant Breeding and Genetics, Agricultural College & Research Institute, Tamil Nadu Agricultural University, Madurai 625 104, India; [email protected] * Correspondence: [email protected] Received: 16 July 2020; Accepted: 25 August 2020; Published: 4 November 2020 Abstract: There is an urgent need to enhance agricultural production as well as productivity to meet the food demand of the growing population, estimated to be 10 billion by 2050, using a holistic and sustainable approach. The daily food sources for almost three-fourth of the global population, cereals and millets, are prone to several biotic factors and abiotic pressures. In particular, cereals and millet cultivation are limited by the polyphagous pink stem borer, Sesamia inferens Walker (Lepidoptera:Noctuidae) gaining national importance, since its larvae and pupae are concealed within the stem, none of the management measures have been found effective in controlling the menace. However, host plant resistance (HPR) is a reasonable and ecologically safe method wherein resistance mechanisms of crops could lower the stem borer infestation. The foremost challenge in understanding the mechanism would be to detecting the genes of interest in the crop using novel biotechnological approaches. The fundamental criterion for developing insect-resistant lines relies on recognizing the mechanism of plant resistance. The entire life cycle of this group of borers is completed or hidden within the stem, posing a hurdle in their management. Thus, molecular markers and Quantitative Trait Locus (QTL) mapping offer a more efficient approach to entomologists and plant breeders wherein they can work with traits like QTLs for stem borer resistance. In this review, an attempt has been made to provide an extensive summary of the host range and crop losses due to this borer, besides its taxonomic position, geographic distribution, bionomics, genetics of resistance, and molecular perspectives. Keywords: S. inferens; cereals; millets; host plant resistance; molecular perspectives 1. Introduction Plants with resistance coexisted with vulnerable insects for several decades until the domestication era. Consequently, challenging crops continued with the law of inheritance and natural assortment, which led to the evolution of host plant resistance. Investigation and improvement in research are pre-requisites to explore the host-plant relations and avail effective control measures against pests [1]. The crop improvement via plant resistance to insects includes plants transformed with insect resistance genes, termed as “substantial crop development.” The most notable attribute of Host Plant Resistance (HPR) is that it offers a farmer-friendly mechanism without specific knowledge and additional Agronomy 2020, 10, 1705; doi:10.3390/agronomy10111705 www.mdpi.com/journal/agronomy Agronomy 2020, 10, 1705 2 of 18 investment. Thus, having the potential to reduce pesticide usage, slow down the development rate of resistance to insecticides, increase the activity of beneficial organisms, and ultimately reduce pesticide residue in agricultural produce. Host-plant resistance has the potential to be the most viable and sustainable method of pest control, and a variety resistant to such menacing pests would be most enviable [2,3]. Subsistence farmers in Europe, Asia and African countries mainly cultivate and consume small millets which contain high nutrients [4]. One of the chief producers of millets throughout the world is India [5], with 6–19 percent losses attributed to insect-pests [6]. Among all the insect-pests, stem borers are the most destructive assemblages infesting the millets [7–10]. The dominant stem borer species in India are the ragi pink stem borer, Sesamia inferens [Wlk] (Noctuidae); sorghum stem borer, Chilo partellus [Swinhoe] (Pyralidae) and the white stem borer, Saluria inficita [Wlk] (Pyralidae) [11]. S. inferens Walker (Noctuidae, Lepidoptera), also called Asian pink stem borer, gramineous pink stem borer, and ragi pink stem borer are highly polyphagous pests of all cereals and millets at different stages, causing severe yield loss. It is also referred to as “Goolabi tanna chhedak” and “khod kid” in North Indian states and Maharashtra, respectively [12] while in Gujarat, it is known vernacularly as “Gulabi gaabhmarani eyal” [13]. Sesamia inferens is a major insect pest of small millets, especially the pearl millet Pennisetum glaucum, (Poales: Poaceae) however, it has shifted its infestation to other crops like barnyard millet. S. inferens occurrence was reported 30–35 percent in barnyard millet [14]. In India, the incidence of this group of pests has been documented in the states of Odisha, Karnataka, Andhra Pradesh, and Tamil Nadu. The larvae bore into the stem that causes a dead heart symptom in the early stage, promoting profused side-tillering with unproductive spikes. In later stages, peduncle and spike are damaged, leading to white ear symptoms [15]. Pesticides are a reliable tool to curtail the yield losses caused by stem borers and maintain sustainable production and productivity. However, stem borers are challenging to manage as the entire immature stages (larvae and pupae) hide inside the stem, besides the nocturnal nature of the adult moths. Climatic change with modern crop cultivation practices has hustled S. inferens to the status of major pests of millets in India [16]. Conventional breeding methods are time-consuming and labor-intensive, requiring skills for accurate evaluation and proficient selection of parents. DNA markers are used to overcome these issues by developing improved genotypes with specific traits. DNA markers and continuous improvement in molecular assays resulted in a successful molecular marker-assisted breeding (MAB) [17] program. This program is a superior breeding method as compared to traditional cum conventional methods [18]. In the early 1980s and 1990s, different types of DNA markers were developed for plants in molecular biotechnology. Moreover, DNA markers were also used in multiple fields of life sciences viz., evaluation of germplasm traits, gene mapping, QTL gene innovation and description of individual quality, biotic stress traits, abiotic stress performance, and up-gradation of the crop. Molecular studies have been developed as a dominant and consistent tool for the genetic exploitation of essential and defense traits in different plants. Identification and utilization of resistant cultivars are the cheapest, practicable, and environmentally friendly way to combat the insect pest problems. The identified resistant genetic resources can thus be utilized in a molecular breeding program with the aid of DNA markers. Improving the defense mechanism against insects and exploration of resistance genes is the only way to manage the stem borers using transgenic approaches [19]. Therefore, the development of stem borer resistant genotypes using molecular approaches to increase agricultural production is gaining importance. In subsequent sections, the host plant resistance mechanisms and molecular features of S. inferens like the mitochondrial genome, molecular categorization of heat shock proteins and Quantitative Real-Time PCR Analysis are summarized, which could help the researchers in planning future research. Agronomy 2020, 10, x FOR PEER REVIEW 3 of 18 Agronomy 2020, 10, 1705 3 of 18 1.1. Historical Perspectives 1.1. Historical Perspectives Foremost damage of the pink stem borer was observed in maize during 1914 by Fletcher in India.Foremost Afterwards damage it moved of the pinkto finger stem borermillet, was rice observed and wheat. in maize Later during on, the 1914 pink by Fletcherstem borer in India. was Afterwardsconfounded it as moved a rigorous to finger pest millet, in many rice andcrops. wheat. The historical Later on, theperspective pink stem of borer this waspest confounded is depicted asin aFigure rigorous 1. pest in many crops. The historical perspective of this pest is depicted in Figure1. Figure 1.1. Historical perspectives of S. inferens. 1.2. Pink Stem Borer—Host Range and Crop Losses 1.2. Pink Stem Borer—Host Range and Crop Losses In South India, the pink stem borer has a broad host range that includes wheat, maize, sorghum, In South India, the pink stem borer has a broad host range that includes wheat, maize, sorghum, ragi, rice, sugarcane [20], and citronella grass in Bengal [21]. Besides, it has also been reported to infest ragi, rice, sugarcane, [20] and citronella grass in Bengal [21]. Besides, it has also been reported to sorghum in Gujarat [22]. In addition, the infestation was also reported [23,24] in rice, oats, barley, infest sorghum in Gujarat [22]. In addition, the infestation was also reported [23,24] in rice, oats, sugarcane, and some grasses, while Deole et al. [25] reported damage in maize crops in Chhattisgarh barley, sugarcane, and some grasses, while Deole et al. [25] reported damage