Genetic Response of Some Groundnut (Arachis hypogaea L.) Genotypes to Severity of Early and Late Leaf Spot (Cercospora spp) Diseases in Southern Guinea Savannah of Nigeria

Abstract

A field experiment was conducted during the 2015 and 2016 cropping seasons to assess the genetic response of groundnut genotypes to the severity of early and late leaf spot diseases at the Teaching and Research Farm of the Federal University of Agriculture, Makurdi, Benue State, Nigeria. Thirteen treatments (groundnut genotypes) used in the disease assessment were Campalla, Samnut-10, Aloshi, Tisha-1, Benue AGR, Ijiwanda, Samnut-22, Borno Brown, Borno Red, Dan-Bomboyo, Samnut-21, Shar-nya, and Ex-Dakar. The treatments were laid out in a randomised complete block design (RCBD) and replicated four times on a 40 x 17 m area containing 52 subplots; each subplot measured 3 x 2 m. Two seeds were sown per hole on each of four ridges, and no synthetic chemical was used. The results revealed significant (P ≤ 0.05) differences among the groundnut genotypes in establishment count, disease severity, combined disease severity, leaf defoliation, fresh leaf yield (kg/ha), fresh pod yield, and 1000-seed weight in both cropping seasons. All treatments expressed different levels of early leaf spot disease severity from 50 to 57 DAS and late leaf spot disease severity from 64 to 71 DAS in both seasons. Combined disease severity showed that Borno Brown, Campalla, Samnut-10, Samnut-21, Samnut-22, and Tisha-1 were resistant (R) to early leaf spot disease; Ijiwanda was moderately susceptible (MS), whereas the remaining groundnut genotypes were moderately resistant (MR) at 57 DAS. Similarly, Aloshi, Benue AGR, Borno Red, Campalla, Dan-Bomboyo, Ex-Dakar, Ijiwanda, and Shar-nya were highly susceptible (HS) to late leaf spot disease; Borno Brown, Samnut-22, and Tisha-1 were very susceptible (VS); Samnut-10 was moderately resistant (MR); and Samnut-21 was moderately susceptible (MS) at 71 DAS. Samnut-21, Samnut-10, Tisha-1, and Samnut-22 had higher fresh leaf yields in 2015, while Tisha-1, Samnut-21, and Samnut-22 recorded higher fresh leaf yields in 2016. Samnut-21, Samnut-22, and Samnut-10 had higher fresh pod yields in 2015, while Samnut-21, Samnut-10, and Tisha-1 had higher fresh pod yields than the other genotypes in 2016. Samnut-21 and Campalla had higher 1000-seed weights than the other groundnut genotypes in both seasons. Hence, resistant and moderately resistant groundnut genotypes with high-yielding traits are recommended as a suitable alternative management option for groundnut leaf spot (Cercospora spp) diseases in this region because of their economic benefits compared with synthetic fungicides, which may be economically infeasible and may pose environmental and human health risks.