Tolerance of precocious dwarf cashew clones to salt stress during rootstock formation stage

Abstract

This study was conducted to evaluate the tolerance of precocious dwarf cashew clones to irrigation with waters of different salinity levels during rootstock formation. The experimental design consisted of randomized blocks, arranged in a 5 x 3 factorial scheme, corresponding to five levels of electrical conductivity of irrigation water (0.4; 1.2; 2.0; 2.8 and 3.6 dS m-1) and three clones of precocious dwarf cashew (Faga 11, Embrapa 51, CCP 76), with three replicates. Water salinity above 0.4 dS m-1 inhibited chlorophyll synthesis and growth, but led to cashew seedlings with the Dickson Quality Index (DQI) higher than the acceptable limit. Based on the relative yield of the total dry mass, the clones Faga 11, Embrapa 51 and CCP 76, at the highest salinity level studied, were classified as moderately sensitive, sensitive and moderately tolerant, respectively. There was interaction between water salinity and precocious dwarf cashew clones for chlorophyll a content, chlorophyll b content and DQI at 75 days after sowing.

Salinity-tolerant dwarf cashew rootstock has better ionic homeostasis and morphophysiological performance of seedlings

“…The decrease in the dry matter production of cashew seedlings under salinity probably occurs due to the reduction in soil water availability and/or the excessive accumulation of toxic ions in plant tissues. Under these conditions, the loss of plant leaves under salt stress is due to early senescence caused by the toxic effects of the salts (Silva et al, 2011), as also observed for early dwarf cashew (Silva et al, 2018, Lima et al, 2020, Alencar et al, 2021, in addition to other fruit seedlings treated with saline water (Oliveira et al, 2018).…”

“…Under saline conditions, the maintenance or increase of RWC indicated osmotic adjustment, in which salt stress did not affect the hydration of the leaves, and the excess of accumulated ions contributed to the retention of water in the tissues (Sanwal et al, 2022), increasing leaf succulence (Lima et al, 2020). Thus, higher RWC in seedlings under salinity conditions demonstrates greater adjustment to stress, suggesting that the self-graft CCP 76 combination had high NaCl, observed at 30 days after beginning of the salt stress Means followed by the same lowercase letters in Figure 2A do not differ statistically by the Tukey test (p ≤ 0.05).…”

“…High concentrations of ions in the root region of plants, mainly Na + and Cl -, trigger stress that causes ionic and osmotic effects, as it inhibits the absorption of K + and Ca +2 , because Na + competes with K + and Ca +2 for absorption sites on the cell membrane, causing nutritional disorders (Silva et al, 2022), inhibits water absorption, reduces leaf turgidity, plant growth and biomass production, and increases cell membrane degradation (Oliveira et al, 2018;Lima et al, 2020;Santana Júnior et al, 2020).…”

“…Thus, studies with grafted and contrasting materials in salinity tolerance can improve the understanding of morphophysiological mechanisms involved between scion and rootstock and interactions under salt stress (Ferreira-Silva et al, 2010), selecting more tolerant rootstocks, which results in more productive orchards (Lima et al, 2020). The hypothesis is that the use of tolerant rootstock promotes better morphophysiological performance of grafted seedlings.…”