ISSN 2348-313X (Print) International Journal of Life Sciences Research ISSN 2348-3148 (online) Vol. 9, Issue 2, pp: (55-70), Month: April - June 2021, Available at: www.researchpublish.com
Effect of Phytophthora cinnamomi inoculation on chlorophyll concentration and chlorophyll fluorescence parameters of four avocado (Persea americana Mill.) rootstocks seedlings grown under water logging conditions. Shiranda M. A.1, Musyimi D. M. 2, Mmayi M. P.3 1
Department of Botany, School of Biological and Physical Sciences, Maseno University, Private Bag, Maseno, Kenya.
2
Department of Botany, School of Biological and Physical Sciences, Maseno University, Private Bag, Maseno, Kenya.
3
Department of Botany, School of Biological and Physical Sciences, Maseno University, Private Bag, Maseno, Kenya. Corresponding Author; maryshiranda@gmail.com
Abstract: Avocado plant`s fruits have high amounts of fats, proteins and fibre. Phytophthora cinnamomi fungal causes avocado root rot that is devastating to growth. The pathogen combined with flooding leads to asphyxiation, root decay and eventually death. Several studies have evaluated the tolerance of different avocado rootstocks to Phytophthora cinnamomi, there are few studies in Kenya that characterized the pathogen and evaluated the effect of the pathogen on the physiology of avocado rootstocks under flooding. The objectives of this study therefore were to determine physiological responses of avocado rootstocks to the fungus under water logging conditions. Rootstocks; Puebla, Fuerte, Booth7 and Pinkerton were obtained from orchards in Maseno, Nyando, Kisumu East and Budalangi of Western Kenya. The fungus was isolated from the soil by planting on selective medium and by baiting methods. Avocado rootstocks were planted in 10 litre plastic pots containing sand - soil mixture of ratio 1:2 for 3 months, inoculated under flooded and non-flooded conditions. Experiment was laid in a CRD within greenhouse. Data on chlorophyll concentration and chlorophyll fluorescence were collected then subjected to analysis of variance. Means separation and comparison was done using LSD at 0.05. Flooding and inoculation significantly (p≤0.05) reduced chlorophyll a, b, total chlorophyll concentration and, reduced Fv/Fm, ΦPSII and ETR of rootstocks. This was an indication that photosynthetic apparatus were affected. This contributed to the reduction in overall avocado growth. Interactions between treatments and avocado rootstocks were significantly different for the parameters. Puebla rootstocks responded better to flooding and P. cinnamomi inoculation, and were therefore recommended for growing in flood affected regions of Kenya where P. cinnamomi infestation is also a common problem. Keywords: Avocado rootstocks, Flooding, Phytophthora cinnamomi, Physiological response, Chlorophyll fluorescence.
1. INTRODUCTION In many countries seed propagated avocado rootstock are still chosen according to availability and nursery performance rather than as to orchard performance (Allen et al., 1980). After a new rootstock clonal propagation method was developed in California, USA, it was spread to Israel where green ovacado cutting mist spray was developed. Unfortunately the methods never became commercial (Baum and Pinkas, 1988). Avocado is highly susceptible to P.
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