Characterization of resistance in maize to shoot fly, Atherigona naqvii Steyskal
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Date
2019
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Punjab Agricultural University, Ludhiana
Abstract
Shoot fly, Atherigona naqvii Steyskal, is a major pest of spring sown maize in North India. Among different IPM components, host plant resistance is a promising alternative for insecticides to manage this pest. The characterization of maize inbreds, selected on the basis of their differential susceptibility to shoot fly, was carried out under epiphytotic conditions created by broadcasting moistened fish meal at seedling emergence. Eggs laid per plant by shoot fly varied non-significantly among the genotypes. So, the antixenosis for oviposition to A. naqvii was not exhibited by the inbreds. The genotypes were grouped into three classes on the basis of deadhearts incidence as well as susceptibility index which involves egg laying preference, antibiosis and tolerance mechanisms of resistance. The inbreds, SO1SHYQBBB13B, HK12–6–2–4, DMSC 28, Winpop 8, CM 143 and CML 420 were categorized as resistant; IIMRPPBT POOL, (CM 140 × LM 20)-1-1-1-2-1, (CM 140 × LM 20)-2-1-1-1-1, (CM 140 × LM 20)-1-2-2-1-1, IIMRSBT POOL, LM 20, (CM 140 × LM 20)-1-2-1-1-1 and CLQRCYQ 42 as moderately resistant; and (CM 140 × LM 20)-2-3-1-1-1, CM 140, S87P66QBBB 30, LM 16 and SE 563 as susceptible to shoot fly. Antibiosis and Tolerance mechanisms were found associated with resistance to shoot fly in test inbreds. Antibiosis was recorded in terms of significantly prolonged larval (by ~2.5 days) and pupal (by ~1.5 days) period; lower larval (52.23–61.43 %) and pupal (54.29–61.92 %) survival; and lower larval (3.00–3.56 mg) and female pupae (3.07–3.63 mg) weight, in resistant genotypes. Whereas, the susceptible checks, SE 563 and LM 16, displayed significantly higher larval (82.78–77.04 %) and pupal (72.47–69.13 %) survival; and higher larval (3.86–4.08 mg) and female pupae (4.03–4.42 mg) weight. Tolerance, in terms of less proportion of deadhearts out of shoot fly incidence, was higher in resistant inbreds (29.46–33.58 %) in comparison to the susceptible inbreds SE 563 and LM 16 (46.31–47.44 %). The plant characters like high seedling vigour, less leaf area and thin stem were associated with resistance to shoot fly. Among biochemical constituents, the susceptible inbreds exhibited higher contents of dietary elements like total soluble sugars, proteins and amino acids. Whereas, resistant inbreds exhibited higher contents of secondary metabolites like phenols and tannins; and activities of defense related enzymes like phenylalanine ammonia lyase (PAL) and polyphenol oxidase (PPO). A significant induction of these secondary metabolites, after shoot fly infestation, was also higher in resistant genotypes in comparison to the susceptible ones. Stepwise regression revealed that the deadhearts incidence was significantly influenced by seedling vigour (65.2 %), leaf area (7.5 %) and number of leaves per plant (2.8 %). The shoot fly survival and development were significantly influenced by PAL activity which explained 71.5, 82.9, 47.0, 29.8 and 39.9 per cent variation in larval period, per cent pupation, pupal weight female, pupal weight male and adult emergence, respectively. PPO activity significantly influenced the pupal period (R2= 59.7 %); and amino acids, proteins and total soluble sugars had significant impact on larval weight (R2= 74.9 %). These physico-chemical characters of the maize inbreds can be utilized as reliable markers traits in shoot fly resistance breeding programmes.
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