A survey conducted in pepper-growing tracts of Karnataka State, covering 165 fields in 33 villages, revealed the occurrence of many pepper mosaic diseases. Based on reactions on selected test plants, the viruses were identified as pepper vein banding virus (PVBV), pepper veinal mottle virus, potato virus Y, cucumber mosaic virus, and tobacco mosaic virus. Among these, PVBV was the most prevalent. PVBV was purified from infected leaves of Capsicum annuum cv. California Wonder. Electron microscopy revealed flexuous rod-shaped particles in the purified preparations. The coat protein (CP) molecular weight was 35,000, which is similar to members of the Potyvirus group. As in other potyviruses, the CP underwent proteolytic degradation to a fragment with a molecular weight of 31,000. Both of these bands cross-reacted with antibodies against tobacco etch virus in Western blots. Polyclonal antibodies were produced against PVBV. Cross-reactivity studies with other potyviral antisera showed that PVBV is serologically closer to peanut mottle virus than to peanut stripe virus or sorghum potyvirus. N-terminal sequence analysis of the intact CP and trypsin-resistant core revealed that PVBV is a distinct member of the Potyvirus group.
Yellow mosaic disease (YMD) caused by mungbean yellow mosaic virus (MYMV) is one of the most destructive biotic production constraints in mungbean. Development and introduction of resistant cultivars are considered as the most economical and eco-friendly option to manage YMD, for which availability of stable sources of resistance is a pre-requisite. A set of 14 mungbean genotypes including a susceptible check were evaluated for responses to YMD under natural infection across three seasons and under challenged inoculation in glasshouse for one season. None of the genotypes were immune to YMD and produced different degrees of response to MYMV in terms of yellow mosaic symptoms (YMS). Based on the delayed appearance of initial YMS, and lower estimates of per cent disease index and area under disease progressive curve (AUDPC) in response to natural infection and challenged inoculation, five genotypes namely AVMU 1698, AVMU 1699, AVMU 16100, AVMU 16101 and KPS 2 were identified as resistant to YMD. Failure of detection of MYMV through polymerase chain reaction (PCR) using MYMV coat protein gene-specific primer and successful detection of the same through rolling circle amplification-PCR suggested latent infection of MYMV in resistant genotypes. The resistance response of the five genotypes could be attributed to enhanced activities of enzymes such as peroxidase, polyphenol oxidase and phenylalanine ammonia lyase and increased concentration of total phenols. These results are discussed in relation to strategies to breed mungbean for resistance to YMD.
A genotype is considered to be most adaptive / stable, when it registers high mean yield but show a minimum interaction with the environment. Knowledge of genotype × environment interaction and yield stability are important parameters in breeding new cultivars with improved adaptation to environmental constraints prevailing in the target environments. Therefore, an effort was made to know the genotype - environment interaction and to identify stable single cross hybrids across the environments. Eight newly synthesized single cross maize hybrids and 7 checks were evaluated in a Randomized Block Design with three replications during Rabi-2016 across three locations spread over different agro-climatic zones of Karnataka state, India. Different stability parameters as suggested by Eberhart and Russell [1] were estimated. Joint analysis of variance revealed significant differences among environments, hybrids and environments × hybrids interactions advocating the adequacy of stability analysis. Hybrids, viz., MAI 349×MAI 283, KDMI 16×BGUDI 118 were stable for days to anthesis and silking, respectively. Whereas, hybrids viz., KDMI 16×BGUDI 118, BGUDI 120×VL 109252 and MAI 283× KDMI 16 registered mean values lower than the overall mean with bi value nearer to unity and non significant S2di for anthesis silking interval. Hybrid, MAI 349×MAI 283 for plant height and cob length, KDMI 16×MAI 283 for cob length, number of kernel rows-1 and 100 grain weight, BGUDI 88×MAI 349 for cob diameter, MAI 394×BGUDI 88 for shelling % and KDMI 16×BGUDI 118 for grain yield plant-1 registered stable performance across the environments. Based on the positive and negative environmental indices, production environment at location 1 (K Block UAS, GKVK, Bengaluru), was most favorable for expression of majority of characters studied. Hybrid KDMI 16×MAI 283 was found stable across the environments for most of the characters studied.
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