Identification of Sources of Resistance in Sesame Against Leaf Webber and Capsule Borer (Antigastra Catalaunalis Dup.)

The 197 entries including two checks (SI-250 Resistance check and TC-25 Susceptible check) of sesame (Sesamum indicum L.) representing varied geographic and genetic diversity were tested at three diverse climatic locations of India viz., Jabalpur, Mandor and Vriddhachalam, against leaf webber and capsule. None of the screened entry was found to be free from infestation by leaf webber and capsule borer. The average plant, flower and capsule damage over the locations varied from 6.58 to 27.17, 7.80 to 23.71 and 3.33 to 15.43%, respectively. At vegetative stage, the entries SI-0018-B (6.33%) and IS-353-A (6.58%) at flowering, the entry KMR-7 (7.80%) and at capsule stage, the entries SI-0018-B (3.33%), MT-67-25 (3.65%) and RJS- 56-A (3.80%) were recorded the lowest damage. Further, the response of promising entries under artificial pest load conditions over the locations showed that the entry SI-271-B was superior to others with respect to lowest plant and flower damage while at capsule stage, the entry NIC-8510-B was superior. Under artificial pest load condition, the entries SI-271-B, NIC-9839 and MT-67-25 showed the lowest damage whereas under natural condition, the entries IS-178-C and SP-3267 were superior to others with respect to lowest damage. The feeding preference studies showed that the entries SI-271-B, IS-178-C, MT-67-25 and S-OO-17-B were least preferred by the leaf webber and capsule borer and recorded the lowest leaf area damage. Bangladesh J. Bot. 50(3): 565-575, 2021 (September)

An experimental investigation of costs of tolerance against leaf and floral herbivory in the herbaceous weed horsenettle (Solanum carolinense, Solanaceae)

Background and aims – A plant’s tolerance of herbivory depends on its ability to endure and compensate for damage so as to lessen the impact that herbivores have on the plant’s performance (e.g. its growth, reproduction, or fitness). While tolerance of herbivory is beneficial to plants, it is rarely complete, and individuals in plant populations tend to vary in their levels of tolerance. The goal of this study was to investigate potential costs associated with tolerance of leaf and floral herbivory in horsenettle (Solanum carolinense), a perennial herbaceous weed that is often subjected to high levels of damage from a diversity of herbivores. Material and methods – We exposed 96 potted individuals across eight genets of horsenettle to factorial treatments of leaf herbivory by lace bugs and simulated floral herbivory by weevils. We quantified tolerance for each plant genet for both types of herbivory in terms of the impact of damage on the number of flowers opened, number of seeds produced, and root biomass (i.e. paternal, maternal, and vegetative tolerance, respectively).Key results – Plant genets ranged widely in their ability to compensate for leaf and flower damage. While there was little evidence for tradeoffs in tolerance through the different routes, there was strong evidence of tradeoffs in genets’ abilities to tolerate herbivore damage to leaves and damage to flowers.Conclusion – Tolerance is a useful defence strategy to cope with damage caused by herbivores, but its evolution may be constrained by concomitant costs and tradeoffs. The evolutionary role of the tradeoffs identified in this study are likely to be greater the more species of herbivores a plant hosts, and the more that herbivore levels vary both spatially and temporally.

Incidence of Pink Bollworm Pectinophora gossypiella (Saunders) (Lepidoptera: Gelechiidae) on Flowers (Rosette) of Bt Cotton in Andhra Pradesh, India

The pink bollworm Pectinophora gossypiella (Saunders) (Lepidoptera: Gelechiidae) has recently emerged as a serious menace on Bt cotton in India. Extensive roving surveys were conducted in 12 locations of three major cotton growing districts of Andhra Pradesh, India, to assess the level of pink bollworm infestation in Bt cotton during 2018-19 and 2019-20. The dynamics and severity of flower damage due to pink bollworm during the 60-135 days’ crop period were evaluated based on a random sampling of flowers. Survey results revealed a widespread infestation of pink bollworm on Bt cotton flowers across the surveyed sites in a range of 11.8-19.50%. With the advancement of the crop season, a progressive increase in the flower damage was observed till 120 DAS then declined. Reasons for the enhanced flower damage and implications are discussed in this article.

How pollinator visits are affected by flower damage and ants presence in Ipomoea carnea subs. fistulosa (Martius and Choise) (Convolvulaceae)?

This study aimed to evaluate the effects of florivory and of the patrolling ants associated to EFNs-extrafloral nectaries, on the frequency of floral visitors, using the specie Ipomoea carnea subs. fistulosa (Martius and Choise) in Caatinga area. The floral attributes of the species were characterized. The effect of florivoria on the frequency of visitors and the influence of the presence of ants associated with the NEFs on the pollinator visit rate were evaluated. The rate of natural florivoria was recorded and collected floral visitors and ants over eight months. The damage on floral structure and the presence of ants foraging in the flowers causes a decrease in the number of total visits. The results may be justified by the fact that the floral damage consisted in the loss of important floral attributes. These effects for Ipomoea carnea subs. fistulosa can affect reproductive success, since it is a self-incompatible species and depends on the activity of the pollinators for their fertilization to occur.

Effect of configuration of calyx in cowpea flowers on infestation by spotted pod borer, Maruca vitrata (Fab.) (Lepidoptera: Crambidae)

Twenty cowpea accessions were evaluated for resistance to the spotted pod borer, Marucavitrata in the Department of Agricultural Entomology, College of Horticulture, KeralaAgricultural University, Thrissur. The calyxes of the flowers were examined and the accessionswere categorized into two groups, partially free (major portion of the sepals free, the basalportion tight) and semi tight (major portion of the sepals tight, only the tip free). Significantvariation was observed in terms of damage to cowpea flowers due to spotted pod borer. Thehighest extent of flower damage (50.39 %) was recorded in case of Bhagyalakshmy.Categorization of the different accessions on the basis of the configuration of calyx indicatedthat EC 100092, Palakkadanthandanpayar, TVX – 944, EC 300039, IC 20645 and IC 52110 hadsemi tight calyx characterized by tight sepals with tips alone being free. All these accessionshad consistently low levels of infestation ranging from zero to 3.16 per cent. The accessions C– 152, Kanakamony, PKM – 1, Anaswara, IC 20431, Sreya, Hridya, Mysore local, IC 52105,Kashikanchan, Vellayani Jyothika, Malika, Bhagyalakshmy and Lola had major portion ofsepals free with their basal portion tight. Hence, they were grouped as partially free. Freesepals would provide the first instar borer larvae some extent of concealment as well as enableit to bore into the flower more easily. Tight calyx, thus, could possibly have a deterrent effecton the first instar larvae entry.